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Diffstat (limited to 'hostfile.c')
| -rw-r--r-- | hostfile.c | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/hostfile.c b/hostfile.c new file mode 100644 index 000000000000..2cceb352a1fe --- /dev/null +++ b/hostfile.c @@ -0,0 +1,353 @@ +/* $OpenBSD: hostfile.c,v 1.45 2006/08/03 03:34:42 deraadt Exp $ */ +/* + * Author: Tatu Ylonen <ylo@cs.hut.fi> + * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland + * All rights reserved + * Functions for manipulating the known hosts files. + * + * As far as I am concerned, the code I have written for this software + * can be used freely for any purpose. Any derived versions of this + * software must be clearly marked as such, and if the derived work is + * incompatible with the protocol description in the RFC file, it must be + * called by a name other than "ssh" or "Secure Shell". + * + * + * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. + * Copyright (c) 1999 Niels Provos. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#include <sys/types.h> + +#include <netinet/in.h> + +#include <openssl/hmac.h> +#include <openssl/sha.h> + +#include <resolv.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include "xmalloc.h" +#include "match.h" +#include "key.h" +#include "hostfile.h" +#include "log.h" + +static int +extract_salt(const char *s, u_int l, char *salt, size_t salt_len) +{ + char *p, *b64salt; + u_int b64len; + int ret; + + if (l < sizeof(HASH_MAGIC) - 1) { + debug2("extract_salt: string too short"); + return (-1); + } + if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { + debug2("extract_salt: invalid magic identifier"); + return (-1); + } + s += sizeof(HASH_MAGIC) - 1; + l -= sizeof(HASH_MAGIC) - 1; + if ((p = memchr(s, HASH_DELIM, l)) == NULL) { + debug2("extract_salt: missing salt termination character"); + return (-1); + } + + b64len = p - s; + /* Sanity check */ + if (b64len == 0 || b64len > 1024) { + debug2("extract_salt: bad encoded salt length %u", b64len); + return (-1); + } + b64salt = xmalloc(1 + b64len); + memcpy(b64salt, s, b64len); + b64salt[b64len] = '\0'; + + ret = __b64_pton(b64salt, salt, salt_len); + xfree(b64salt); + if (ret == -1) { + debug2("extract_salt: salt decode error"); + return (-1); + } + if (ret != SHA_DIGEST_LENGTH) { + debug2("extract_salt: expected salt len %d, got %d", + SHA_DIGEST_LENGTH, ret); + return (-1); + } + + return (0); +} + +char * +host_hash(const char *host, const char *name_from_hostfile, u_int src_len) +{ + const EVP_MD *md = EVP_sha1(); + HMAC_CTX mac_ctx; + char salt[256], result[256], uu_salt[512], uu_result[512]; + static char encoded[1024]; + u_int i, len; + + len = EVP_MD_size(md); + + if (name_from_hostfile == NULL) { + /* Create new salt */ + for (i = 0; i < len; i++) + salt[i] = arc4random(); + } else { + /* Extract salt from known host entry */ + if (extract_salt(name_from_hostfile, src_len, salt, + sizeof(salt)) == -1) + return (NULL); + } + + HMAC_Init(&mac_ctx, salt, len, md); + HMAC_Update(&mac_ctx, host, strlen(host)); + HMAC_Final(&mac_ctx, result, NULL); + HMAC_cleanup(&mac_ctx); + + if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || + __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) + fatal("host_hash: __b64_ntop failed"); + + snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, + HASH_DELIM, uu_result); + + return (encoded); +} + +/* + * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the + * pointer over the key. Skips any whitespace at the beginning and at end. + */ + +int +hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) +{ + char *cp; + + /* Skip leading whitespace. */ + for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) + ; + + if (key_read(ret, &cp) != 1) + return 0; + + /* Skip trailing whitespace. */ + for (; *cp == ' ' || *cp == '\t'; cp++) + ; + + /* Return results. */ + *cpp = cp; + *bitsp = key_size(ret); + return 1; +} + +static int +hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum) +{ + if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) + return 1; + if (bits != BN_num_bits(key->rsa->n)) { + logit("Warning: %s, line %d: keysize mismatch for host %s: " + "actual %d vs. announced %d.", + filename, linenum, host, BN_num_bits(key->rsa->n), bits); + logit("Warning: replace %d with %d in %s, line %d.", + bits, BN_num_bits(key->rsa->n), filename, linenum); + } + return 1; +} + +/* + * Checks whether the given host (which must be in all lowercase) is already + * in the list of our known hosts. Returns HOST_OK if the host is known and + * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED + * if the host is known but used to have a different host key. + * + * If no 'key' has been specified and a key of type 'keytype' is known + * for the specified host, then HOST_FOUND is returned. + */ + +static HostStatus +check_host_in_hostfile_by_key_or_type(const char *filename, + const char *host, const Key *key, int keytype, Key *found, int *numret) +{ + FILE *f; + char line[8192]; + int linenum = 0; + u_int kbits; + char *cp, *cp2, *hashed_host; + HostStatus end_return; + + debug3("check_host_in_hostfile: filename %s", filename); + + /* Open the file containing the list of known hosts. */ + f = fopen(filename, "r"); + if (!f) + return HOST_NEW; + + /* + * Return value when the loop terminates. This is set to + * HOST_CHANGED if we have seen a different key for the host and have + * not found the proper one. + */ + end_return = HOST_NEW; + + /* Go through the file. */ + while (fgets(line, sizeof(line), f)) { + cp = line; + linenum++; + + /* Skip any leading whitespace, comments and empty lines. */ + for (; *cp == ' ' || *cp == '\t'; cp++) + ; + if (!*cp || *cp == '#' || *cp == '\n') + continue; + + /* Find the end of the host name portion. */ + for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) + ; + + /* Check if the host name matches. */ + if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { + if (*cp != HASH_DELIM) + continue; + hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); + if (hashed_host == NULL) { + debug("Invalid hashed host line %d of %s", + linenum, filename); + continue; + } + if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) + continue; + } + + /* Got a match. Skip host name. */ + cp = cp2; + + /* + * Extract the key from the line. This will skip any leading + * whitespace. Ignore badly formatted lines. + */ + if (!hostfile_read_key(&cp, &kbits, found)) + continue; + + if (numret != NULL) + *numret = linenum; + + if (key == NULL) { + /* we found a key of the requested type */ + if (found->type == keytype) { + fclose(f); + return HOST_FOUND; + } + continue; + } + + if (!hostfile_check_key(kbits, found, host, filename, linenum)) + continue; + + /* Check if the current key is the same as the given key. */ + if (key_equal(key, found)) { + /* Ok, they match. */ + debug3("check_host_in_hostfile: match line %d", linenum); + fclose(f); + return HOST_OK; + } + /* + * They do not match. We will continue to go through the + * file; however, we note that we will not return that it is + * new. + */ + end_return = HOST_CHANGED; + } + /* Clear variables and close the file. */ + fclose(f); + + /* + * Return either HOST_NEW or HOST_CHANGED, depending on whether we + * saw a different key for the host. + */ + return end_return; +} + +HostStatus +check_host_in_hostfile(const char *filename, const char *host, const Key *key, + Key *found, int *numret) +{ + if (key == NULL) + fatal("no key to look up"); + return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0, + found, numret)); +} + +int +lookup_key_in_hostfile_by_type(const char *filename, const char *host, + int keytype, Key *found, int *numret) +{ + return (check_host_in_hostfile_by_key_or_type(filename, host, NULL, + keytype, found, numret) == HOST_FOUND); +} + +/* + * Appends an entry to the host file. Returns false if the entry could not + * be appended. + */ + +int +add_host_to_hostfile(const char *filename, const char *host, const Key *key, + int store_hash) +{ + FILE *f; + int success = 0; + char *hashed_host = NULL; + + if (key == NULL) + return 1; /* XXX ? */ + f = fopen(filename, "a"); + if (!f) + return 0; + + if (store_hash) { + if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { + error("add_host_to_hostfile: host_hash failed"); + fclose(f); + return 0; + } + } + fprintf(f, "%s ", store_hash ? hashed_host : host); + + if (key_write(key, f)) { + success = 1; + } else { + error("add_host_to_hostfile: saving key in %s failed", filename); + } + fprintf(f, "\n"); + fclose(f); + return success; +} |