Check GSS_C_REPLAY_FLAG in client-side ret_flags validation

RFC 3645 Section 3.1.1 mandates that the client MUST abandon the
algorithm if replay_det_state is FALSE after GSS_Init_sec_context
completes.  The previous commit checked MUTUAL and INTEG but missed
REPLAY, even though it was already requested in the input flags.

Add GSS_C_REPLAY_FLAG to the ret_flags bitmask check so all three
required properties (replay detection, mutual authentication, and
integrity) are verified.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

diff --git a/lib/dns/gssapictx.c b/lib/dns/gssapictx.c
index 8f4c1c56c92d1ae5ce89dd272eab5d5f4ddda749..9e025b1a3b3751227b531c325a0f59310d4a1d47 100644 (file)
--- a/lib/dns/gssapictx.c
+++ b/lib/dns/gssapictx.c
@@ -356,17 +356,19 @@ dst_gssapi_initctx(const dns_name_t *name, isc_buffer_t *intoken,
        }
 
        /*
-        * RFC 3645 Section 3.1.1: verify that mutual authentication
-        * and integrity are supported.  If either is missing, the
-        * security context does not meet the protocol requirements.
+        * 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_MUTUAL_FLAG | GSS_C_INTEG_FLAG)) !=
-                   (GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG))
+           (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 MUTUAL or "
-                       "INTEG flags (ret_flags=0x%x)",
+                       "GSS-API context lacks required REPLAY, MUTUAL, "
+                       "or INTEG flags (ret_flags=0x%x)",
                        (unsigned int)ret_flags);
                CLEANUP(ISC_R_FAILURE);
        }