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diff --git a/crypto/krb5/doc/html/appdev/gssapi.html b/crypto/krb5/doc/html/appdev/gssapi.html new file mode 100644 index 000000000000..39de34df4865 --- /dev/null +++ b/crypto/krb5/doc/html/appdev/gssapi.html @@ -0,0 +1,827 @@ +<!DOCTYPE html> + +<html lang="en" data-content_root="../"> + <head> + <meta charset="utf-8" /> + <meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" /> + + <title>Developing with GSSAPI — MIT Kerberos Documentation</title> + <link rel="stylesheet" type="text/css" href="../_static/pygments.css?v=fa44fd50" /> + <link rel="stylesheet" type="text/css" href="../_static/agogo.css?v=879f3c71" /> + <link rel="stylesheet" type="text/css" href="../_static/kerb.css?v=6a0b3979" /> + <script src="../_static/documentation_options.js?v=236fef3b"></script> + <script src="../_static/doctools.js?v=888ff710"></script> + <script src="../_static/sphinx_highlight.js?v=dc90522c"></script> + <link rel="author" title="About these documents" href="../about.html" /> + <link rel="index" title="Index" href="../genindex.html" /> + <link rel="search" title="Search" href="../search.html" /> + <link rel="copyright" title="Copyright" href="../copyright.html" /> + <link rel="next" title="Year 2038 considerations for uses of krb5_timestamp" href="y2038.html" /> + <link rel="prev" title="For application developers" href="index.html" /> + </head><body> + <div class="header-wrapper"> + <div class="header"> + + + <h1><a href="../index.html">MIT Kerberos Documentation</a></h1> + + <div class="rel"> + + <a href="../index.html" title="Full Table of Contents" + accesskey="C">Contents</a> | + <a href="index.html" title="For application developers" + accesskey="P">previous</a> | + <a href="y2038.html" title="Year 2038 considerations for uses of krb5_timestamp" + accesskey="N">next</a> | + <a href="../genindex.html" title="General Index" + accesskey="I">index</a> | + <a href="../search.html" title="Enter search criteria" + accesskey="S">Search</a> | + <a href="mailto:krb5-bugs@mit.edu?subject=Documentation__Developing with GSSAPI">feedback</a> + </div> + </div> + </div> + + <div class="content-wrapper"> + <div class="content"> + <div class="document"> + + <div class="documentwrapper"> + <div class="bodywrapper"> + <div class="body" role="main"> + + <section id="developing-with-gssapi"> +<h1>Developing with GSSAPI<a class="headerlink" href="#developing-with-gssapi" title="Link to this heading">¶</a></h1> +<p>The GSSAPI (Generic Security Services API) allows applications to +communicate securely using Kerberos 5 or other security mechanisms. +We recommend using the GSSAPI (or a higher-level framework which +encompasses GSSAPI, such as SASL) for secure network communication +over using the libkrb5 API directly.</p> +<p>GSSAPIv2 is specified in <span class="target" id="index-0"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc2743.html"><strong>RFC 2743</strong></a> and <span class="target" id="index-1"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc2744.html"><strong>RFC 2744</strong></a>. Also see +<span class="target" id="index-2"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc7546.html"><strong>RFC 7546</strong></a> for a description of how to use the GSSAPI in a client or +server program.</p> +<p>This documentation will describe how various ways of using the +GSSAPI will behave with the krb5 mechanism as implemented in MIT krb5, +as well as krb5-specific extensions to the GSSAPI.</p> +<section id="name-types"> +<h2>Name types<a class="headerlink" href="#name-types" title="Link to this heading">¶</a></h2> +<p>A GSSAPI application can name a local or remote entity by calling +<a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.16">gss_import_name</a>, specifying a name type and a value. The following +name types are supported by the krb5 mechanism:</p> +<ul class="simple"> +<li><p><strong>GSS_C_NT_HOSTBASED_SERVICE</strong>: The value should be a string of the +form <code class="docutils literal notranslate"><span class="pre">service</span></code> or <code class="docutils literal notranslate"><span class="pre">service@hostname</span></code>. This is the most common +way to name target services when initiating a security context, and +is the most likely name type to work across multiple mechanisms.</p></li> +<li><p><strong>GSS_KRB5_NT_PRINCIPAL_NAME</strong>: The value should be a principal name +string. This name type only works with the krb5 mechanism, and is +defined in the <code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_krb5.h></span></code> header.</p></li> +<li><p><strong>GSS_C_NT_USER_NAME</strong> or <strong>GSS_C_NULL_OID</strong>: The value is treated +as an unparsed principal name string, as above. These name types +may work with mechanisms other than krb5, but will have different +interpretations in those mechanisms. <strong>GSS_C_NT_USER_NAME</strong> is +intended to be used with a local username, which will parse into a +single-component principal in the default realm.</p></li> +<li><p><strong>GSS_C_NT_ANONYMOUS</strong>: The value is ignored. The anonymous +principal is used, allowing a client to authenticate to a server +without asserting a particular identity (which may or may not be +allowed by a particular server or Kerberos realm).</p></li> +<li><p><strong>GSS_C_NT_MACHINE_UID_NAME</strong>: The value is uid_t object. On +Unix-like systems, the username of the uid is looked up in the +system user database and the resulting username is parsed as a +principal name.</p></li> +<li><p><strong>GSS_C_NT_STRING_UID_NAME</strong>: As above, but the value is a decimal +string representation of the uid.</p></li> +<li><p><strong>GSS_C_NT_EXPORT_NAME</strong>: The value must be the result of a +<a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.13">gss_export_name</a> call.</p></li> +<li><p><strong>GSS_KRB5_NT_ENTERPRISE_NAME</strong>: The value should be a krb5 +enterprise name string (see <span class="target" id="index-3"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc6806.html"><strong>RFC 6806</strong></a> section 5), in the form +<code class="docutils literal notranslate"><span class="pre">user@suffix</span></code>. This name type is used to convey alias names, and +is defined in the <code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_krb5.h></span></code> header. (New in +release 1.17.)</p></li> +<li><p><strong>GSS_KRB5_NT_X509_CERT</strong>: The value should be an X.509 certificate +encoded according to <span class="target" id="index-4"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc5280.html"><strong>RFC 5280</strong></a>. This name form can be used for +the desired_name parameter of gss_acquire_cred_impersonate_name(), +to identify the S4U2Self user by certificate. (New in release +1.19.)</p></li> +</ul> +</section> +<section id="initiator-credentials"> +<h2>Initiator credentials<a class="headerlink" href="#initiator-credentials" title="Link to this heading">¶</a></h2> +<p>A GSSAPI client application uses <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.19">gss_init_sec_context</a> to establish a +security context. The <em>initiator_cred_handle</em> parameter determines +what tickets are used to establish the connection. An application can +either pass <strong>GSS_C_NO_CREDENTIAL</strong> to use the default client +credential, or it can use <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.2">gss_acquire_cred</a> beforehand to acquire an +initiator credential. The call to <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.2">gss_acquire_cred</a> may include a +<em>desired_name</em> parameter, or it may pass <strong>GSS_C_NO_NAME</strong> if it does +not have a specific name preference.</p> +<p>If the desired name for a krb5 initiator credential is a host-based +name, it is converted to a principal name of the form +<code class="docutils literal notranslate"><span class="pre">service/hostname</span></code> in the local realm, where <em>hostname</em> is the local +hostname if not specified. The hostname will be canonicalized using +forward name resolution, and possibly also using reverse name +resolution depending on the value of the <strong>rdns</strong> variable in +<a class="reference internal" href="../admin/conf_files/krb5_conf.html#libdefaults"><span class="std std-ref">[libdefaults]</span></a>.</p> +<p>If a desired name is specified in the call to <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.2">gss_acquire_cred</a>, the +krb5 mechanism will attempt to find existing tickets for that client +principal name in the default credential cache or collection. If the +default cache type does not support a collection, and the default +cache contains credentials for a different principal than the desired +name, a <strong>GSS_S_CRED_UNAVAIL</strong> error will be returned with a minor +code indicating a mismatch.</p> +<p>If no existing tickets are available for the desired name, but the +name has an entry in the default client <a class="reference internal" href="../basic/keytab_def.html#keytab-definition"><span class="std std-ref">keytab</span></a>, the +krb5 mechanism will acquire initial tickets for the name using the +default client keytab.</p> +<p>If no desired name is specified, credential acquisition will be +deferred until the credential is used in a call to +<a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.19">gss_init_sec_context</a> or <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.21">gss_inquire_cred</a>. If the call is to +<a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.19">gss_init_sec_context</a>, the target name will be used to choose a client +principal name using the credential cache selection facility. (This +facility might, for instance, try to choose existing tickets for a +client principal in the same realm as the target service). If there +are no existing tickets for the chosen principal, but it is present in +the default client keytab, the krb5 mechanism will acquire initial +tickets using the keytab.</p> +<p>If the target name cannot be used to select a client principal +(because the credentials are used in a call to <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.21">gss_inquire_cred</a>), or +if the credential cache selection facility cannot choose a principal +for it, the default credential cache will be selected if it exists and +contains tickets.</p> +<p>If the default credential cache does not exist, but the default client +keytab does, the krb5 mechanism will try to acquire initial tickets +for the first principal in the default client keytab.</p> +<p>If the krb5 mechanism acquires initial tickets using the default +client keytab, the resulting tickets will be stored in the default +cache or collection, and will be refreshed by future calls to +<a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.2">gss_acquire_cred</a> as they approach their expire time.</p> +</section> +<section id="acceptor-names"> +<h2>Acceptor names<a class="headerlink" href="#acceptor-names" title="Link to this heading">¶</a></h2> +<p>A GSSAPI server application uses <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.1">gss_accept_sec_context</a> to establish +a security context based on tokens provided by the client. The +<em>acceptor_cred_handle</em> parameter determines what +<a class="reference internal" href="../basic/keytab_def.html#keytab-definition"><span class="std std-ref">keytab</span></a> entries may be authenticated to by the +client, if the krb5 mechanism is used.</p> +<p>The simplest choice is to pass <strong>GSS_C_NO_CREDENTIAL</strong> as the acceptor +credential. In this case, clients may authenticate to any service +principal in the default keytab (typically <a class="reference internal" href="../mitK5defaults.html#paths"><span class="std std-ref">DEFKTNAME</span></a>, or the value of +the <strong>KRB5_KTNAME</strong> environment variable). This is the recommended +approach if the server application has no specific requirements to the +contrary.</p> +<p>A server may acquire an acceptor credential with <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.2">gss_acquire_cred</a> and +a <em>cred_usage</em> of <strong>GSS_C_ACCEPT</strong> or <strong>GSS_C_BOTH</strong>. If the +<em>desired_name</em> parameter is <strong>GSS_C_NO_NAME</strong>, then clients will be +allowed to authenticate to any service principal in the default +keytab, just as if no acceptor credential was supplied.</p> +<p>If a server wishes to specify a <em>desired_name</em> to <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.2">gss_acquire_cred</a>, +the most common choice is a host-based name. If the host-based +<em>desired_name</em> contains just a <em>service</em>, then clients will be allowed +to authenticate to any host-based service principal (that is, a +principal of the form <code class="docutils literal notranslate"><span class="pre">service/hostname@REALM</span></code>) for the named +service, regardless of hostname or realm, as long as it is present in +the default keytab. If the input name contains both a <em>service</em> and a +<em>hostname</em>, clients will be allowed to authenticate to any host-based +principal for the named service and hostname, regardless of realm.</p> +<div class="admonition note"> +<p class="admonition-title">Note</p> +<p>If a <em>hostname</em> is specified, it will be canonicalized +using forward name resolution, and possibly also using +reverse name resolution depending on the value of the +<strong>rdns</strong> variable in <a class="reference internal" href="../admin/conf_files/krb5_conf.html#libdefaults"><span class="std std-ref">[libdefaults]</span></a>.</p> +</div> +<div class="admonition note"> +<p class="admonition-title">Note</p> +<p>If the <strong>ignore_acceptor_hostname</strong> variable in +<a class="reference internal" href="../admin/conf_files/krb5_conf.html#libdefaults"><span class="std std-ref">[libdefaults]</span></a> is enabled, then <em>hostname</em> will be +ignored even if one is specified in the input name.</p> +</div> +<div class="admonition note"> +<p class="admonition-title">Note</p> +<p>In MIT krb5 versions prior to 1.10, and in Heimdal’s +implementation of the krb5 mechanism, an input name with +just a <em>service</em> is treated like an input name of +<code class="docutils literal notranslate"><span class="pre">service@localhostname</span></code>, where <em>localhostname</em> is the +string returned by gethostname().</p> +</div> +<p>If the <em>desired_name</em> is a krb5 principal name or a local system name +type which is mapped to a krb5 principal name, clients will only be +allowed to authenticate to that principal in the default keytab.</p> +</section> +<section id="name-attributes"> +<h2>Name Attributes<a class="headerlink" href="#name-attributes" title="Link to this heading">¶</a></h2> +<p>In release 1.8 or later, the <a class="reference external" href="https://tools.ietf.org/html/rfc6680.txt#section-7.4">gss_inquire_name</a> and +<a class="reference external" href="https://tools.ietf.org/html/6680.html#section-7.5">gss_get_name_attribute</a> functions, specified in <span class="target" id="index-5"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc6680.html"><strong>RFC 6680</strong></a>, can be +used to retrieve name attributes from the <em>src_name</em> returned by +<a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.1">gss_accept_sec_context</a>. The following attributes are defined when +the krb5 mechanism is used:</p> +<ul class="simple" id="gssapi-authind-attr"> +<li><p>“auth-indicators” attribute:</p></li> +</ul> +<p>This attribute will be included in the <a class="reference external" href="https://tools.ietf.org/html/rfc6680.txt#section-7.4">gss_inquire_name</a> output if the +ticket contains <a class="reference internal" href="../admin/auth_indicator.html#auth-indicator"><span class="std std-ref">authentication indicators</span></a>. +One indicator is returned per invocation of <a class="reference external" href="https://tools.ietf.org/html/6680.html#section-7.5">gss_get_name_attribute</a>, +so multiple invocations may be necessary to retrieve all of the +indicators from the ticket. (New in release 1.15.)</p> +</section> +<section id="credential-store-extensions"> +<h2>Credential store extensions<a class="headerlink" href="#credential-store-extensions" title="Link to this heading">¶</a></h2> +<p>Beginning with release 1.11, the following GSSAPI extensions declared +in <code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_ext.h></span></code> can be used to specify how credentials +are acquired or stored:</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">struct</span> <span class="n">gss_key_value_element_struct</span> <span class="p">{</span> + <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">key</span><span class="p">;</span> + <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">value</span><span class="p">;</span> +<span class="p">};</span> +<span class="n">typedef</span> <span class="n">struct</span> <span class="n">gss_key_value_element_struct</span> <span class="n">gss_key_value_element_desc</span><span class="p">;</span> + +<span class="n">struct</span> <span class="n">gss_key_value_set_struct</span> <span class="p">{</span> + <span class="n">OM_uint32</span> <span class="n">count</span><span class="p">;</span> + <span class="n">gss_key_value_element_desc</span> <span class="o">*</span><span class="n">elements</span><span class="p">;</span> +<span class="p">};</span> +<span class="n">typedef</span> <span class="n">const</span> <span class="n">struct</span> <span class="n">gss_key_value_set_struct</span> <span class="n">gss_key_value_set_desc</span><span class="p">;</span> +<span class="n">typedef</span> <span class="n">const</span> <span class="n">gss_key_value_set_desc</span> <span class="o">*</span><span class="n">gss_const_key_value_set_t</span><span class="p">;</span> + +<span class="n">OM_uint32</span> <span class="n">gss_acquire_cred_from</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">const</span> <span class="n">gss_name_t</span> <span class="n">desired_name</span><span class="p">,</span> + <span class="n">OM_uint32</span> <span class="n">time_req</span><span class="p">,</span> + <span class="n">const</span> <span class="n">gss_OID_set</span> <span class="n">desired_mechs</span><span class="p">,</span> + <span class="n">gss_cred_usage_t</span> <span class="n">cred_usage</span><span class="p">,</span> + <span class="n">gss_const_key_value_set_t</span> <span class="n">cred_store</span><span class="p">,</span> + <span class="n">gss_cred_id_t</span> <span class="o">*</span><span class="n">output_cred_handle</span><span class="p">,</span> + <span class="n">gss_OID_set</span> <span class="o">*</span><span class="n">actual_mechs</span><span class="p">,</span> + <span class="n">OM_uint32</span> <span class="o">*</span><span class="n">time_rec</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_store_cred_into</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_cred_id_t</span> <span class="n">input_cred_handle</span><span class="p">,</span> + <span class="n">gss_cred_usage_t</span> <span class="n">cred_usage</span><span class="p">,</span> + <span class="n">const</span> <span class="n">gss_OID</span> <span class="n">desired_mech</span><span class="p">,</span> + <span class="n">OM_uint32</span> <span class="n">overwrite_cred</span><span class="p">,</span> + <span class="n">OM_uint32</span> <span class="n">default_cred</span><span class="p">,</span> + <span class="n">gss_const_key_value_set_t</span> <span class="n">cred_store</span><span class="p">,</span> + <span class="n">gss_OID_set</span> <span class="o">*</span><span class="n">elements_stored</span><span class="p">,</span> + <span class="n">gss_cred_usage_t</span> <span class="o">*</span><span class="n">cred_usage_stored</span><span class="p">);</span> +</pre></div> +</div> +<p>The additional <em>cred_store</em> parameter allows the caller to specify +information about how the credentials should be obtained and stored. +The following options are supported by the krb5 mechanism:</p> +<ul class="simple"> +<li><p><strong>ccache</strong>: For acquiring initiator credentials, the name of the +<a class="reference internal" href="../basic/ccache_def.html#ccache-definition"><span class="std std-ref">credential cache</span></a> to which the handle will +refer. For storing credentials, the name of the cache or collection +where the credentials will be stored (see below).</p></li> +<li><p><strong>client_keytab</strong>: For acquiring initiator credentials, the name of +the <a class="reference internal" href="../basic/keytab_def.html#keytab-definition"><span class="std std-ref">keytab</span></a> which will be used, if +necessary, to refresh the credentials in the cache.</p></li> +<li><p><strong>keytab</strong>: For acquiring acceptor credentials, the name of the +<a class="reference internal" href="../basic/keytab_def.html#keytab-definition"><span class="std std-ref">keytab</span></a> to which the handle will refer. +In release 1.19 and later, this option also determines the keytab to +be used for verification when initiator credentials are acquired +using a password and verified.</p></li> +<li><p><strong>password</strong>: For acquiring initiator credentials, this option +instructs the mechanism to acquire fresh credentials into a unique +memory credential cache. This option may not be used with the +<strong>ccache</strong> or <strong>client_keytab</strong> options, and a <em>desired_name</em> must +be specified. (New in release 1.19.)</p></li> +<li><p><strong>rcache</strong>: For acquiring acceptor credentials, the name of the +<a class="reference internal" href="../basic/rcache_def.html#rcache-definition"><span class="std std-ref">replay cache</span></a> to be used when processing +the initiator tokens. (New in release 1.13.)</p></li> +<li><p><strong>verify</strong>: For acquiring initiator credentials, this option +instructs the mechanism to verify the credentials by obtaining a +ticket to a service with a known key. The service key is obtained +from the keytab specified with the <strong>keytab</strong> option or the default +keytab. The value may be the name of a principal in the keytab, or +the empty string. If the empty string is given, any <code class="docutils literal notranslate"><span class="pre">host</span></code> +service principal in the keytab may be used. (New in release 1.19.)</p></li> +</ul> +<p>In release 1.20 or later, if a collection name is specified for +<strong>cache</strong> in a call to gss_store_cred_into(), an existing cache for +the client principal within the collection will be selected, or a new +cache will be created within the collection. If <em>overwrite_cred</em> is +false and the selected credential cache already exists, a +<strong>GSS_S_DUPLICATE_ELEMENT</strong> error will be returned. If <em>default_cred</em> +is true, the primary cache of the collection will be switched to the +selected cache.</p> +</section> +<section id="importing-and-exporting-credentials"> +<h2>Importing and exporting credentials<a class="headerlink" href="#importing-and-exporting-credentials" title="Link to this heading">¶</a></h2> +<p>The following GSSAPI extensions can be used to import and export +credentials (declared in <code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_ext.h></span></code>):</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">gss_export_cred</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_cred_id_t</span> <span class="n">cred_handle</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">token</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_import_cred</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">token</span><span class="p">,</span> + <span class="n">gss_cred_id_t</span> <span class="o">*</span><span class="n">cred_handle</span><span class="p">);</span> +</pre></div> +</div> +<p>The first function serializes a GSSAPI credential handle into a +buffer; the second unseralizes a buffer into a GSSAPI credential +handle. Serializing a credential does not destroy it. If any of the +mechanisms used in <em>cred_handle</em> do not support serialization, +gss_export_cred will return <strong>GSS_S_UNAVAILABLE</strong>. As with other +GSSAPI serialization functions, these extensions are only intended to +work with a matching implementation on the other side; they do not +serialize credentials in a standardized format.</p> +<p>A serialized credential may contain secret information such as ticket +session keys. The serialization format does not protect this +information from eavesdropping or tampering. The calling application +must take care to protect the serialized credential when communicating +it over an insecure channel or to an untrusted party.</p> +<p>A krb5 GSSAPI credential may contain references to a credential cache, +a client keytab, an acceptor keytab, and a replay cache. These +resources are normally serialized as references to their external +locations (such as the filename of the credential cache). Because of +this, a serialized krb5 credential can only be imported by a process +with similar privileges to the exporter. A serialized credential +should not be trusted if it originates from a source with lower +privileges than the importer, as it may contain references to external +credential cache, keytab, or replay cache resources not accessible to +the originator.</p> +<p>An exception to the above rule applies when a krb5 GSSAPI credential +refers to a memory credential cache, as is normally the case for +delegated credentials received by <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.1">gss_accept_sec_context</a>. In this +case, the contents of the credential cache are serialized, so that the +resulting token may be imported even if the original memory credential +cache no longer exists.</p> +</section> +<section id="constrained-delegation-s4u"> +<h2>Constrained delegation (S4U)<a class="headerlink" href="#constrained-delegation-s4u" title="Link to this heading">¶</a></h2> +<p>The Microsoft S4U2Self and S4U2Proxy Kerberos protocol extensions +allow an intermediate service to acquire credentials from a client to +a target service without requiring the client to delegate a +ticket-granting ticket, if the KDC is configured to allow it.</p> +<p>To perform a constrained delegation operation, the intermediate +service must submit to the KDC an “evidence ticket” from the client to +the intermediate service. An evidence ticket can be acquired when the +client authenticates to the intermediate service with Kerberos, or +with an S4U2Self request if the KDC allows it. The MIT krb5 GSSAPI +library represents an evidence ticket using a “proxy credential”, +which is a special kind of gss_cred_id_t object whose underlying +credential cache contains the evidence ticket and a krbtgt ticket for +the intermediate service.</p> +<p>To acquire a proxy credential during client authentication, the +service should first create an acceptor credential using the +<strong>GSS_C_BOTH</strong> usage. The application should then pass this +credential as the <em>acceptor_cred_handle</em> to <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.1">gss_accept_sec_context</a>, +and also pass a <em>delegated_cred_handle</em> output parameter to receive a +proxy credential containing the evidence ticket. The output value of +<em>delegated_cred_handle</em> may be a delegated ticket-granting ticket if +the client sent one, or a proxy credential if not. If the library can +determine that the client’s ticket is not a valid evidence ticket, it +will place <strong>GSS_C_NO_CREDENTIAL</strong> in <em>delegated_cred_handle</em>.</p> +<p>To acquire a proxy credential using an S4U2Self request, the service +can use the following GSSAPI extension:</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">gss_acquire_cred_impersonate_name</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_cred_id_t</span> <span class="n">icred</span><span class="p">,</span> + <span class="n">gss_name_t</span> <span class="n">desired_name</span><span class="p">,</span> + <span class="n">OM_uint32</span> <span class="n">time_req</span><span class="p">,</span> + <span class="n">gss_OID_set</span> <span class="n">desired_mechs</span><span class="p">,</span> + <span class="n">gss_cred_usage_t</span> <span class="n">cred_usage</span><span class="p">,</span> + <span class="n">gss_cred_id_t</span> <span class="o">*</span><span class="n">output_cred</span><span class="p">,</span> + <span class="n">gss_OID_set</span> <span class="o">*</span><span class="n">actual_mechs</span><span class="p">,</span> + <span class="n">OM_uint32</span> <span class="o">*</span><span class="n">time_rec</span><span class="p">);</span> +</pre></div> +</div> +<p>The parameters to this function are similar to those of +<a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.2">gss_acquire_cred</a>, except that <em>icred</em> is used to make an S4U2Self +request to the KDC for a ticket from <em>desired_name</em> to the +intermediate service. Both <em>icred</em> and <em>desired_name</em> are required +for this function; passing <strong>GSS_C_NO_CREDENTIAL</strong> or +<strong>GSS_C_NO_NAME</strong> will cause the call to fail. <em>icred</em> must contain a +krbtgt ticket for the intermediate service. The result of this +operation is a proxy credential. (Prior to release 1.18, the result +of this operation may be a regular credential for <em>desired_name</em>, if +the KDC issues a non-forwardable ticket.)</p> +<p>Once the intermediate service has a proxy credential, it can simply +pass it to <a class="reference external" href="https://tools.ietf.org/html/rfc2744.html#section-5.19">gss_init_sec_context</a> as the <em>initiator_cred_handle</em> +parameter, and the desired service as the <em>target_name</em> parameter. +The GSSAPI library will present the krbtgt ticket and evidence ticket +in the proxy credential to the KDC in an S4U2Proxy request; if the +intermediate service has the appropriate permissions, the KDC will +issue a ticket from the client to the target service. The GSSAPI +library will then use this ticket to authenticate to the target +service.</p> +<p>If an application needs to find out whether a credential it holds is a +proxy credential and the name of the intermediate service, it can +query the credential with the <strong>GSS_KRB5_GET_CRED_IMPERSONATOR</strong> OID +(new in release 1.16, declared in <code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_krb5.h></span></code>) using +the gss_inquire_cred_by_oid extension (declared in +<code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_ext.h></span></code>):</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">gss_inquire_cred_by_oid</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">const</span> <span class="n">gss_cred_id_t</span> <span class="n">cred_handle</span><span class="p">,</span> + <span class="n">gss_OID</span> <span class="n">desired_object</span><span class="p">,</span> + <span class="n">gss_buffer_set_t</span> <span class="o">*</span><span class="n">data_set</span><span class="p">);</span> +</pre></div> +</div> +<p>If the call succeeds and <em>cred_handle</em> is a proxy credential, +<em>data_set</em> will be set to a single-element buffer set containing the +unparsed principal name of the intermediate service. If <em>cred_handle</em> +is not a proxy credential, <em>data_set</em> will be set to an empty buffer +set. If the library does not support the query, +gss_inquire_cred_by_oid will return <strong>GSS_S_UNAVAILABLE</strong>.</p> +</section> +<section id="channel-binding-behavior-and-gss-c-channel-bound-flag"> +<h2>Channel binding behavior and GSS_C_CHANNEL_BOUND_FLAG<a class="headerlink" href="#channel-binding-behavior-and-gss-c-channel-bound-flag" title="Link to this heading">¶</a></h2> +<p>GSSAPI channel bindings can be used to limit the scope of a context +establishment token to a particular protected channel or endpoint, +such as a TLS channel or server certificate. Channel bindings can be +supplied via the <em>input_chan_bindings</em> parameter to either +gss_init_sec_context() or gss_accept_sec_context().</p> +<p>If both the initiator and acceptor of a GSSAPI exchange supply +matching channel bindings, <strong>GSS_C_CHANNEL_BOUND_FLAG</strong> will be +included in the gss_accept_sec_context() <em>ret_flags</em> result. If +either the initiator or acceptor (or both) do not supply channel +bindings, the exchange will succeed, but <strong>GSS_C_CHANNEL_BOUND_FLAG</strong> +will not be included in the return flags. If the acceptor and +initiator both inlude channel bindings but they do not match, the +exchange will fail.</p> +<p>If <strong>GSS_C_CHANNEL_BOUND_FLAG</strong> is included in the <em>req_flags</em> +parameter of gss_init_sec_context(), the initiator will add the +Microsoft KERB_AP_OPTIONS_CBT extension to the Kerberos authenticator. +This extension requests that the acceptor strictly enforce channel +bindings, causing the exchange to fail if the acceptor supplies +channel bindings and the initiator does not. The KERB_AP_OPTIONS_CBT +extension will also be included if the +<strong>client_aware_channel_bindings</strong> variable is set to <code class="docutils literal notranslate"><span class="pre">true</span></code> in +<a class="reference internal" href="../admin/conf_files/krb5_conf.html#libdefaults"><span class="std std-ref">[libdefaults]</span></a>.</p> +<p>Prior to release 1.19, <strong>GSS_C_CHANNEL_BOUND_FLAG</strong> is not +implemented, and the exchange will fail if the acceptor supply channel +bindings and the initiator does not (but not vice versa). Between +releases 1.19 and 1.21, <strong>GSS_C_CHANNEL_BOUND_FLAG</strong> is not recognized +as an initiator flag, so <strong>client_aware_channel_bindings</strong> is the only +way to cause KERB_AP_OPTIONS_CBT to be included.</p> +</section> +<section id="aead-message-wrapping"> +<h2>AEAD message wrapping<a class="headerlink" href="#aead-message-wrapping" title="Link to this heading">¶</a></h2> +<p>The following GSSAPI extensions (declared in +<code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_ext.h></span></code>) can be used to wrap and unwrap messages +with additional “associated data” which is integrity-checked but is +not included in the output buffer:</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">gss_wrap_aead</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="nb">int</span> <span class="n">conf_req_flag</span><span class="p">,</span> <span class="n">gss_qop_t</span> <span class="n">qop_req</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">input_assoc_buffer</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">input_payload_buffer</span><span class="p">,</span> + <span class="nb">int</span> <span class="o">*</span><span class="n">conf_state</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">output_message_buffer</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_unwrap_aead</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">input_message_buffer</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">input_assoc_buffer</span><span class="p">,</span> + <span class="n">gss_buffer_t</span> <span class="n">output_payload_buffer</span><span class="p">,</span> + <span class="nb">int</span> <span class="o">*</span><span class="n">conf_state</span><span class="p">,</span> + <span class="n">gss_qop_t</span> <span class="o">*</span><span class="n">qop_state</span><span class="p">);</span> +</pre></div> +</div> +<p>Wrap tokens created with gss_wrap_aead will successfully unwrap only +if the same <em>input_assoc_buffer</em> contents are presented to +gss_unwrap_aead.</p> +</section> +<section id="iov-message-wrapping"> +<h2>IOV message wrapping<a class="headerlink" href="#iov-message-wrapping" title="Link to this heading">¶</a></h2> +<p>The following extensions (declared in <code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_ext.h></span></code>) can +be used for in-place encryption, fine-grained control over wrap token +layout, and for constructing wrap tokens compatible with Microsoft DCE +RPC:</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">typedef</span> <span class="n">struct</span> <span class="n">gss_iov_buffer_desc_struct</span> <span class="p">{</span> + <span class="n">OM_uint32</span> <span class="nb">type</span><span class="p">;</span> + <span class="n">gss_buffer_desc</span> <span class="n">buffer</span><span class="p">;</span> +<span class="p">}</span> <span class="n">gss_iov_buffer_desc</span><span class="p">,</span> <span class="o">*</span><span class="n">gss_iov_buffer_t</span><span class="p">;</span> + +<span class="n">OM_uint32</span> <span class="n">gss_wrap_iov</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="nb">int</span> <span class="n">conf_req_flag</span><span class="p">,</span> <span class="n">gss_qop_t</span> <span class="n">qop_req</span><span class="p">,</span> + <span class="nb">int</span> <span class="o">*</span><span class="n">conf_state</span><span class="p">,</span> + <span class="n">gss_iov_buffer_desc</span> <span class="o">*</span><span class="n">iov</span><span class="p">,</span> <span class="nb">int</span> <span class="n">iov_count</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_unwrap_iov</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="nb">int</span> <span class="o">*</span><span class="n">conf_state</span><span class="p">,</span> <span class="n">gss_qop_t</span> <span class="o">*</span><span class="n">qop_state</span><span class="p">,</span> + <span class="n">gss_iov_buffer_desc</span> <span class="o">*</span><span class="n">iov</span><span class="p">,</span> <span class="nb">int</span> <span class="n">iov_count</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_wrap_iov_length</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="nb">int</span> <span class="n">conf_req_flag</span><span class="p">,</span> + <span class="n">gss_qop_t</span> <span class="n">qop_req</span><span class="p">,</span> <span class="nb">int</span> <span class="o">*</span><span class="n">conf_state</span><span class="p">,</span> + <span class="n">gss_iov_buffer_desc</span> <span class="o">*</span><span class="n">iov</span><span class="p">,</span> + <span class="nb">int</span> <span class="n">iov_count</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_release_iov_buffer</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_iov_buffer_desc</span> <span class="o">*</span><span class="n">iov</span><span class="p">,</span> + <span class="nb">int</span> <span class="n">iov_count</span><span class="p">);</span> +</pre></div> +</div> +<p>The caller of gss_wrap_iov provides an array of gss_iov_buffer_desc +structures, each containing a type and a gss_buffer_desc structure. +Valid types include:</p> +<ul class="simple"> +<li><p><strong>GSS_C_BUFFER_TYPE_DATA</strong>: A data buffer to be included in the +token, and to be encrypted or decrypted in-place if the token is +confidentiality-protected.</p></li> +<li><p><strong>GSS_C_BUFFER_TYPE_HEADER</strong>: The GSSAPI wrap token header and +underlying cryptographic header.</p></li> +<li><p><strong>GSS_C_BUFFER_TYPE_TRAILER</strong>: The cryptographic trailer, if one is +required.</p></li> +<li><p><strong>GSS_C_BUFFER_TYPE_PADDING</strong>: Padding to be combined with the data +during encryption and decryption. (The implementation may choose to +place padding in the trailer buffer, in which case it will set the +padding buffer length to 0.)</p></li> +<li><p><strong>GSS_C_BUFFER_TYPE_STREAM</strong>: For unwrapping only, a buffer +containing a complete wrap token in standard format to be unwrapped.</p></li> +<li><p><strong>GSS_C_BUFFER_TYPE_SIGN_ONLY</strong>: A buffer to be included in the +token’s integrity protection checksum, but not to be encrypted or +included in the token itself.</p></li> +</ul> +<p>For gss_wrap_iov, the IOV list should contain one HEADER buffer, +followed by zero or more SIGN_ONLY buffers, followed by one or more +DATA buffers, followed by a TRAILER buffer. The memory pointed to by +the buffers is not required to be contiguous or in any particular +order. If <em>conf_req_flag</em> is true, DATA buffers will be encrypted +in-place, while SIGN_ONLY buffers will not be modified.</p> +<p>The type of an output buffer may be combined with +<strong>GSS_C_BUFFER_FLAG_ALLOCATE</strong> to request that gss_wrap_iov allocate +the buffer contents. If gss_wrap_iov allocates a buffer, it sets the +<strong>GSS_C_BUFFER_FLAG_ALLOCATED</strong> flag on the buffer type. +gss_release_iov_buffer can be used to release all allocated buffers +within an iov list and unset their allocated flags. Here is an +example of how gss_wrap_iov can be used with allocation requested +(<em>ctx</em> is assumed to be a previously established gss_ctx_id_t):</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">;</span> +<span class="n">gss_iov_buffer_desc</span> <span class="n">iov</span><span class="p">[</span><span class="mi">4</span><span class="p">];</span> +<span class="n">char</span> <span class="nb">str</span><span class="p">[]</span> <span class="o">=</span> <span class="s2">"message"</span><span class="p">;</span> + +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_HEADER</span> <span class="o">|</span> <span class="n">GSS_IOV_BUFFER_FLAG_ALLOCATE</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_DATA</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="nb">str</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">=</span> <span class="n">strlen</span><span class="p">(</span><span class="nb">str</span><span class="p">);</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_PADDING</span> <span class="o">|</span> <span class="n">GSS_IOV_BUFFER_FLAG_ALLOCATE</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_TRAILER</span> <span class="o">|</span> <span class="n">GSS_IOV_BUFFER_FLAG_ALLOCATE</span><span class="p">;</span> + +<span class="n">major</span> <span class="o">=</span> <span class="n">gss_wrap_iov</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">GSS_C_QOP_DEFAULT</span><span class="p">,</span> <span class="n">NULL</span><span class="p">,</span> + <span class="n">iov</span><span class="p">,</span> <span class="mi">4</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">GSS_ERROR</span><span class="p">(</span><span class="n">major</span><span class="p">))</span> + <span class="n">handle_error</span><span class="p">(</span><span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">);</span> + +<span class="o">/*</span> <span class="n">Transmit</span> <span class="ow">or</span> <span class="n">otherwise</span> <span class="n">use</span> <span class="n">resulting</span> <span class="n">buffers</span><span class="o">.</span> <span class="o">*/</span> + +<span class="p">(</span><span class="n">void</span><span class="p">)</span><span class="n">gss_release_iov_buffer</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">iov</span><span class="p">,</span> <span class="mi">4</span><span class="p">);</span> +</pre></div> +</div> +<p>If the caller does not choose to request buffer allocation by +gss_wrap_iov, it should first call gss_wrap_iov_length to query the +lengths of the HEADER, PADDING, and TRAILER buffers. DATA buffers +must be provided in the iov list so that padding length can be +computed correctly, but the output buffers need not be initialized. +Here is an example of using gss_wrap_iov_length and gss_wrap_iov:</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">;</span> +<span class="n">gss_iov_buffer_desc</span> <span class="n">iov</span><span class="p">[</span><span class="mi">4</span><span class="p">];</span> +<span class="n">char</span> <span class="nb">str</span><span class="p">[</span><span class="mi">1024</span><span class="p">]</span> <span class="o">=</span> <span class="s2">"message"</span><span class="p">,</span> <span class="o">*</span><span class="n">ptr</span><span class="p">;</span> + +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_HEADER</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_DATA</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="nb">str</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">=</span> <span class="n">strlen</span><span class="p">(</span><span class="nb">str</span><span class="p">);</span> + +<span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_PADDING</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_TRAILER</span><span class="p">;</span> + +<span class="n">major</span> <span class="o">=</span> <span class="n">gss_wrap_iov_length</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">GSS_C_QOP_DEFAULT</span><span class="p">,</span> + <span class="n">NULL</span><span class="p">,</span> <span class="n">iov</span><span class="p">,</span> <span class="mi">4</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">GSS_ERROR</span><span class="p">(</span><span class="n">major</span><span class="p">))</span> + <span class="n">handle_error</span><span class="p">(</span><span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">strlen</span><span class="p">(</span><span class="nb">str</span><span class="p">)</span> <span class="o">+</span> <span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">+</span> <span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">+</span> + <span class="n">iov</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">></span> <span class="n">sizeof</span><span class="p">(</span><span class="nb">str</span><span class="p">))</span> + <span class="n">handle_out_of_space_error</span><span class="p">();</span> +<span class="n">ptr</span> <span class="o">=</span> <span class="nb">str</span> <span class="o">+</span> <span class="n">strlen</span><span class="p">(</span><span class="nb">str</span><span class="p">);</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">ptr</span><span class="p">;</span> +<span class="n">ptr</span> <span class="o">+=</span> <span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">ptr</span><span class="p">;</span> +<span class="n">ptr</span> <span class="o">+=</span> <span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">ptr</span><span class="p">;</span> + +<span class="n">major</span> <span class="o">=</span> <span class="n">gss_wrap_iov</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">GSS_C_QOP_DEFAULT</span><span class="p">,</span> <span class="n">NULL</span><span class="p">,</span> + <span class="n">iov</span><span class="p">,</span> <span class="mi">4</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">GSS_ERROR</span><span class="p">(</span><span class="n">major</span><span class="p">))</span> + <span class="n">handle_error</span><span class="p">(</span><span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">);</span> +</pre></div> +</div> +<p>If the context was established using the <strong>GSS_C_DCE_STYLE</strong> flag +(described in <span class="target" id="index-6"></span><a class="rfc reference external" href="https://datatracker.ietf.org/doc/html/rfc4757.html"><strong>RFC 4757</strong></a>), wrap tokens compatible with Microsoft DCE +RPC can be constructed. In this case, the IOV list must include a +SIGN_ONLY buffer, a DATA buffer, a second SIGN_ONLY buffer, and a +HEADER buffer in that order (the order of the buffer contents remains +arbitrary). The application must pad the DATA buffer to a multiple of +16 bytes as no padding or trailer buffer is used.</p> +<p>gss_unwrap_iov may be called with an IOV list just like one which +would be provided to gss_wrap_iov. DATA buffers will be decrypted +in-place if they were encrypted, and SIGN_ONLY buffers will not be +modified.</p> +<p>Alternatively, gss_unwrap_iov may be called with a single STREAM +buffer, zero or more SIGN_ONLY buffers, and a single DATA buffer. The +STREAM buffer is interpreted as a complete wrap token. The STREAM +buffer will be modified in-place to decrypt its contents. The DATA +buffer will be initialized to point to the decrypted data within the +STREAM buffer, unless it has the <strong>GSS_C_BUFFER_FLAG_ALLOCATE</strong> flag +set, in which case it will be initialized with a copy of the decrypted +data. Here is an example (<em>token</em> and <em>token_len</em> are assumed to be a +pre-existing pointer and length for a modifiable region of data):</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">;</span> +<span class="n">gss_iov_buffer_desc</span> <span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span> + +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_STREAM</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">token</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">=</span> <span class="n">token_len</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_DATA</span><span class="p">;</span> +<span class="n">major</span> <span class="o">=</span> <span class="n">gss_unwrap_iov</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">NULL</span><span class="p">,</span> <span class="n">NULL</span><span class="p">,</span> <span class="n">iov</span><span class="p">,</span> <span class="mi">2</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">GSS_ERROR</span><span class="p">(</span><span class="n">major</span><span class="p">))</span> + <span class="n">handle_error</span><span class="p">(</span><span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">);</span> + +<span class="o">/*</span> <span class="n">Decrypted</span> <span class="n">data</span> <span class="ow">is</span> <span class="ow">in</span> <span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="p">,</span> <span class="n">pointing</span> <span class="n">to</span> <span class="n">a</span> <span class="n">subregion</span> <span class="n">of</span> + <span class="o">*</span> <span class="n">token</span><span class="o">.</span> <span class="o">*/</span> +</pre></div> +</div> +</section> +<section id="iov-mic-tokens"> +<span id="gssapi-mic-token"></span><h2>IOV MIC tokens<a class="headerlink" href="#iov-mic-tokens" title="Link to this heading">¶</a></h2> +<p>The following extensions (declared in <code class="docutils literal notranslate"><span class="pre"><gssapi/gssapi_ext.h></span></code>) can +be used in release 1.12 or later to construct and verify MIC tokens +using an IOV list:</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">gss_get_mic_iov</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="n">gss_qop_t</span> <span class="n">qop_req</span><span class="p">,</span> + <span class="n">gss_iov_buffer_desc</span> <span class="o">*</span><span class="n">iov</span><span class="p">,</span> + <span class="nb">int</span> <span class="n">iov_count</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_get_mic_iov_length</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="n">gss_qop_t</span> <span class="n">qop_req</span><span class="p">,</span> + <span class="n">gss_iov_buffer_desc</span> <span class="o">*</span><span class="n">iov</span><span class="p">,</span> + <span class="n">iov_count</span><span class="p">);</span> + +<span class="n">OM_uint32</span> <span class="n">gss_verify_mic_iov</span><span class="p">(</span><span class="n">OM_uint32</span> <span class="o">*</span><span class="n">minor_status</span><span class="p">,</span> + <span class="n">gss_ctx_id_t</span> <span class="n">context_handle</span><span class="p">,</span> + <span class="n">gss_qop_t</span> <span class="o">*</span><span class="n">qop_state</span><span class="p">,</span> + <span class="n">gss_iov_buffer_desc</span> <span class="o">*</span><span class="n">iov</span><span class="p">,</span> + <span class="nb">int</span> <span class="n">iov_count</span><span class="p">);</span> +</pre></div> +</div> +<p>The caller of gss_get_mic_iov provides an array of gss_iov_buffer_desc +structures, each containing a type and a gss_buffer_desc structure. +Valid types include:</p> +<ul class="simple"> +<li><p><strong>GSS_C_BUFFER_TYPE_DATA</strong> and <strong>GSS_C_BUFFER_TYPE_SIGN_ONLY</strong>: The +corresponding buffer for each of these types will be signed for the +MIC token, in the order provided.</p></li> +<li><p><strong>GSS_C_BUFFER_TYPE_MIC_TOKEN</strong>: The GSSAPI MIC token.</p></li> +</ul> +<p>The type of the MIC_TOKEN buffer may be combined with +<strong>GSS_C_BUFFER_FLAG_ALLOCATE</strong> to request that gss_get_mic_iov +allocate the buffer contents. If gss_get_mic_iov allocates the +buffer, it sets the <strong>GSS_C_BUFFER_FLAG_ALLOCATED</strong> flag on the buffer +type. gss_release_iov_buffer can be used to release all allocated +buffers within an iov list and unset their allocated flags. Here is +an example of how gss_get_mic_iov can be used with allocation +requested (<em>ctx</em> is assumed to be a previously established +gss_ctx_id_t):</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">;</span> +<span class="n">gss_iov_buffer_desc</span> <span class="n">iov</span><span class="p">[</span><span class="mi">3</span><span class="p">];</span> + +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_DATA</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="s2">"sign1"</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">=</span> <span class="mi">5</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_SIGN_ONLY</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="s2">"sign2"</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">=</span> <span class="mi">5</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_MIC_TOKEN</span> <span class="o">|</span> <span class="n">GSS_IOV_BUFFER_FLAG_ALLOCATE</span><span class="p">;</span> + +<span class="n">major</span> <span class="o">=</span> <span class="n">gss_get_mic_iov</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">GSS_C_QOP_DEFAULT</span><span class="p">,</span> <span class="n">iov</span><span class="p">,</span> <span class="mi">3</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">GSS_ERROR</span><span class="p">(</span><span class="n">major</span><span class="p">))</span> + <span class="n">handle_error</span><span class="p">(</span><span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">);</span> + +<span class="o">/*</span> <span class="n">Transmit</span> <span class="ow">or</span> <span class="n">otherwise</span> <span class="n">use</span> <span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span> <span class="o">*/</span> + +<span class="p">(</span><span class="n">void</span><span class="p">)</span><span class="n">gss_release_iov_buffer</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">iov</span><span class="p">,</span> <span class="mi">3</span><span class="p">);</span> +</pre></div> +</div> +<p>If the caller does not choose to request buffer allocation by +gss_get_mic_iov, it should first call gss_get_mic_iov_length to query +the length of the MIC_TOKEN buffer. Here is an example of using +gss_get_mic_iov_length and gss_get_mic_iov:</p> +<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">OM_uint32</span> <span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">;</span> +<span class="n">gss_iov_buffer_desc</span> <span class="n">iov</span><span class="p">[</span><span class="mi">2</span><span class="p">];</span> +<span class="n">char</span> <span class="n">data</span><span class="p">[</span><span class="mi">1024</span><span class="p">];</span> + +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_MIC_TOKEN</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">type</span> <span class="o">=</span> <span class="n">GSS_IOV_BUFFER_TYPE_DATA</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="s2">"message"</span><span class="p">;</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">=</span> <span class="mi">7</span><span class="p">;</span> + +<span class="n">major</span> <span class="o">=</span> <span class="n">gss_get_mic_iov_length</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">GSS_C_QOP_DEFAULT</span><span class="p">,</span> <span class="n">iov</span><span class="p">,</span> <span class="mi">2</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">GSS_ERROR</span><span class="p">(</span><span class="n">major</span><span class="p">))</span> + <span class="n">handle_error</span><span class="p">(</span><span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">length</span> <span class="o">></span> <span class="n">sizeof</span><span class="p">(</span><span class="n">data</span><span class="p">))</span> + <span class="n">handle_out_of_space_error</span><span class="p">();</span> +<span class="n">iov</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">buffer</span><span class="o">.</span><span class="n">value</span> <span class="o">=</span> <span class="n">data</span><span class="p">;</span> + +<span class="n">major</span> <span class="o">=</span> <span class="n">gss_get_mic_iov</span><span class="p">(</span><span class="o">&</span><span class="n">minor</span><span class="p">,</span> <span class="n">ctx</span><span class="p">,</span> <span class="n">GSS_C_QOP_DEFAULT</span><span class="p">,</span> <span class="n">iov</span><span class="p">,</span> <span class="mi">2</span><span class="p">);</span> +<span class="k">if</span> <span class="p">(</span><span class="n">GSS_ERROR</span><span class="p">(</span><span class="n">major</span><span class="p">))</span> + <span class="n">handle_error</span><span class="p">(</span><span class="n">major</span><span class="p">,</span> <span class="n">minor</span><span class="p">);</span> +</pre></div> +</div> +</section> +</section> + + + <div class="clearer"></div> + </div> + </div> + </div> + </div> + <div class="sidebar"> + + <h2>On this page</h2> + <ul> +<li><a class="reference internal" href="#">Developing with GSSAPI</a><ul> +<li><a class="reference internal" href="#name-types">Name types</a></li> +<li><a class="reference internal" href="#initiator-credentials">Initiator credentials</a></li> +<li><a class="reference internal" href="#acceptor-names">Acceptor names</a></li> +<li><a class="reference internal" href="#name-attributes">Name Attributes</a></li> +<li><a class="reference internal" href="#credential-store-extensions">Credential store extensions</a></li> +<li><a class="reference internal" href="#importing-and-exporting-credentials">Importing and exporting credentials</a></li> +<li><a class="reference internal" href="#constrained-delegation-s4u">Constrained delegation (S4U)</a></li> +<li><a class="reference internal" href="#channel-binding-behavior-and-gss-c-channel-bound-flag">Channel binding behavior and 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