diff options
| author | Mark Johnston <markj@FreeBSD.org> | 2026-03-24 02:12:42 +0000 |
|---|---|---|
| committer | Gordon Tetlow <gordon@FreeBSD.org> | 2026-03-26 01:11:54 +0000 |
| commit | 143293c14f8de00c6d3de88cd23fc224e7014206 (patch) | |
| tree | 9c3672cf4c2c7263c948d1abc01d445df588bd15 | |
| parent | 6b2d6ccad2552e46a5c9c3ba70b2d0ed27c70ca8 (diff) | |
rpcsec_gss: Fix a stack overflow in svc_rpc_gss_validate()
svc_rpc_gss_validate() copies the input message into a stack buffer
without ensuring that the buffer is large enough. Sure enough,
oa_length may be up to 400 bytes, much larger than the provided space.
This enables an unauthenticated user to trigger an overflow and obtain
remote code execution.
Add a runtime check which verifies that the copy won't overflow.
Approved by: so
Security: FreeBSD-SA-26:08.rpcsec_gss
Security: CVE-2026-4747
Reported by: Nicholas Carlini <npc@anthropic.com>
Reviewed by: rmacklem
Fixes: a9148abd9da5d
| -rw-r--r-- | lib/librpcsec_gss/svc_rpcsec_gss.c | 9 | ||||
| -rw-r--r-- | sys/rpc/rpcsec_gss/svc_rpcsec_gss.c | 10 |
2 files changed, 17 insertions, 2 deletions
diff --git a/lib/librpcsec_gss/svc_rpcsec_gss.c b/lib/librpcsec_gss/svc_rpcsec_gss.c index e9d39a813f86..73b92371e6d0 100644 --- a/lib/librpcsec_gss/svc_rpcsec_gss.c +++ b/lib/librpcsec_gss/svc_rpcsec_gss.c @@ -758,6 +758,14 @@ svc_rpc_gss_validate(struct svc_rpc_gss_client *client, struct rpc_msg *msg, memset(rpchdr, 0, sizeof(rpchdr)); + oa = &msg->rm_call.cb_cred; + + if (oa->oa_length > sizeof(rpchdr) - 8 * BYTES_PER_XDR_UNIT) { + log_debug("auth length %d exceeds maximum", oa->oa_length); + client->cl_state = CLIENT_STALE; + return (FALSE); + } + /* Reconstruct RPC header for signing (from xdr_callmsg). */ buf = rpchdr; IXDR_PUT_LONG(buf, msg->rm_xid); @@ -766,7 +774,6 @@ svc_rpc_gss_validate(struct svc_rpc_gss_client *client, struct rpc_msg *msg, IXDR_PUT_LONG(buf, msg->rm_call.cb_prog); IXDR_PUT_LONG(buf, msg->rm_call.cb_vers); IXDR_PUT_LONG(buf, msg->rm_call.cb_proc); - oa = &msg->rm_call.cb_cred; IXDR_PUT_ENUM(buf, oa->oa_flavor); IXDR_PUT_LONG(buf, oa->oa_length); if (oa->oa_length) { diff --git a/sys/rpc/rpcsec_gss/svc_rpcsec_gss.c b/sys/rpc/rpcsec_gss/svc_rpcsec_gss.c index 35c904560836..528112d5642a 100644 --- a/sys/rpc/rpcsec_gss/svc_rpcsec_gss.c +++ b/sys/rpc/rpcsec_gss/svc_rpcsec_gss.c @@ -1170,6 +1170,15 @@ svc_rpc_gss_validate(struct svc_rpc_gss_client *client, struct rpc_msg *msg, memset(rpchdr, 0, sizeof(rpchdr)); + oa = &msg->rm_call.cb_cred; + + if (oa->oa_length > sizeof(rpchdr) - 8 * BYTES_PER_XDR_UNIT) { + rpc_gss_log_debug("auth length %d exceeds maximum", + oa->oa_length); + client->cl_state = CLIENT_STALE; + return (FALSE); + } + /* Reconstruct RPC header for signing (from xdr_callmsg). */ buf = rpchdr; IXDR_PUT_LONG(buf, msg->rm_xid); @@ -1178,7 +1187,6 @@ svc_rpc_gss_validate(struct svc_rpc_gss_client *client, struct rpc_msg *msg, IXDR_PUT_LONG(buf, msg->rm_call.cb_prog); IXDR_PUT_LONG(buf, msg->rm_call.cb_vers); IXDR_PUT_LONG(buf, msg->rm_call.cb_proc); - oa = &msg->rm_call.cb_cred; IXDR_PUT_ENUM(buf, oa->oa_flavor); IXDR_PUT_LONG(buf, oa->oa_length); if (oa->oa_length) { |