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chg: dev: Harden GSS-API context establishment in TKEY negotiation

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Implement RFC 3645 Section 3.1.1 client-side check for REPLAY, MUTUAL, and INTEG flags after gss_init_sec_context() completes.  Add server-side INTEG flag check after gss_accept_sec_context().  Also fixes an uninitialized gss_name_t on the error path in dst_gssapi_initctx().

Merge branch 'ondrej/harden-gssapi-integration' into 'security-main'

See merge request isc-private/bind9!978
This commit is contained in:
Ondřej Surý 2026-05-01 08:51:33 +02:00 committed by Michał Kępień
commit 9212e1ac50
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1 changed files with 36 additions and 6 deletions
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42
lib/dns/gssapictx.c
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@ -296,7 +296,7 @@ dst_gssapi_initctx(const dns_name_t *name, isc_buffer_t *intoken,
isc_mem_t *mctx, char **err_message) {
isc_region_t r;
isc_buffer_t namebuf;
gss_name_t gname;
gss_name_t gname = NULL;
OM_uint32 gret, minor, ret_flags, flags;
gss_buffer_desc gintoken, *gintokenp, gouttoken = GSS_C_EMPTY_BUFFER;
isc_result_t result;
@ -356,9 +356,22 @@ dst_gssapi_initctx(const dns_name_t *name, isc_buffer_t *intoken,
}
/*
* XXXSRA Not handled yet: RFC 3645 3.1.1: check ret_flags
* MUTUAL and INTEG flags, fail if either not set.
* RFC 3645 Section 3.1.1: verify that replay detection, mutual
* authentication and integrity are supported. The RFC mandates
* checking replay_det_state and mutual_state; integ_avail is
* also verified because GSS-TSIG cannot function without it.
*/
if (gret == GSS_S_COMPLETE &&
(ret_flags &
(GSS_C_REPLAY_FLAG | GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG)) !=
(GSS_C_REPLAY_FLAG | GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG))
{
gss_log(3,
"GSS-API context lacks required REPLAY, MUTUAL, "
"or INTEG flags (ret_flags=0x%x)",
(unsigned int)ret_flags);
CLEANUP(ISC_R_FAILURE);
}
/*
* RFC 2744 states the a valid output token has a non-zero length.
@ -372,7 +385,9 @@ cleanup:
if (gouttoken.length != 0U) {
(void)gss_release_buffer(&minor, &gouttoken);
}
(void)gss_release_name(&minor, &gname);
if (gname != NULL) {
(void)gss_release_name(&minor, &gname);
}
return result;
}
@ -429,15 +444,30 @@ dst_gssapi_acceptctx(const char *gssapi_keytab, isc_region_t *intoken,
#endif
}
OM_uint32 ret_flags = 0;
gret = gss_accept_sec_context(&minor, &context, GSS_C_NO_CREDENTIAL,
&gintoken, GSS_C_NO_CHANNEL_BINDINGS,
&gname, NULL, &gouttoken, NULL, NULL,
NULL);
&gname, NULL, &gouttoken, &ret_flags,
NULL, NULL);
result = ISC_R_FAILURE;
switch (gret) {
case GSS_S_COMPLETE:
/*
* RFC 2743 Section 1.2.2: verify that the negotiated
* context provides integrity protection.
*/
if ((ret_flags & GSS_C_INTEG_FLAG) == 0) {
gss_log(3,
"GSS-API context lacks required INTEG "
"flag (ret_flags=0x%x)",
(unsigned int)ret_flags);
(void)gss_delete_sec_context(&minor, &context, NULL);
result = DNS_R_INVALIDTKEY;
goto cleanup;
}
break;
/*
* RFC 3645 4.1.3: we don't handle GSS_S_CONTINUE_NEEDED