s3-gse: Don't release the mech OID from gss_accept_security_context

This is constant data according to the man pages I find for this
fucntion, and causes a segfault to free() when linked to Heimdal.  I
am advised that while it is constant for gss_mech_krb5, it may not be
for other mechanisms, so an assert will ensure this is dealt with by
the programmer who extends this code in future.

Andrew Bartlett

3 files changed, 33 insertions, 5 deletions

diff --git a/source3/configure.in b/source3/configure.in
index 883f0b1df0..a463aa910d 100644
--- a/source3/configure.in
+++ b/source3/configure.in
@@ -3870,6 +3870,7 @@ if test x"$with_ads_support" != x"no"; then
   AC_CHECK_FUNC_EXT(krb5_free_host_realm, $KRB5_LIBS)
   AC_CHECK_FUNC_EXT(gss_krb5_import_cred, $KRB5_LIBS)
   AC_CHECK_FUNC_EXT(gss_get_name_attribute, $KRB5_LIBS)
+  AC_CHECK_FUNC_EXT(gss_oid_equal, $KRB5_LIBS)
 
   # MIT krb5 1.8 does not expose this call (yet)
   AC_CHECK_DECLS(krb5_get_credentials_for_user, [], [], [#include <krb5.h>])
diff --git a/source3/librpc/crypto/gse.c b/source3/librpc/crypto/gse.c
index 42e9c942a9..22b940a1f3 100644
--- a/source3/librpc/crypto/gse.c
+++ b/source3/librpc/crypto/gse.c
@@ -85,6 +85,24 @@ struct gse_context {
 	bool authenticated;
 };
 
+#ifndef HAVE_GSS_OID_EQUAL
+
+static bool gss_oid_equal(const gss_OID o1, const gss_OID o2)
+{
+	if (o1 == o2) {
+		return true;
+	}
+	if ((o1 == NULL && o2 != NULL) || (o1 != NULL && o2 == NULL)) {
+		return false;
+	}
+	if (o1->length != o2->length) {
+		return false;
+	}
+	return memcmp(o1->elements, o2->elements, o1->length) == false;
+}
+
+#endif
+
 /* free non talloc dependent contexts */
 static int gse_context_destructor(void *ptr)
 {
@@ -125,10 +143,19 @@ static int gse_context_destructor(void *ptr)
 		gss_maj = gss_release_cred(&gss_min,
 					   &gse_ctx->delegated_creds);
 	}
-	if (gse_ctx->ret_mech) {
-		gss_maj = gss_release_oid(&gss_min,
-					  &gse_ctx->ret_mech);
-	}
+
+	/* MIT and Heimdal differ as to if you can call
+	 * gss_release_oid() on this OID, generated by
+	 * gss_{accept,init}_sec_context().  However, as long as the
+	 * oid is gss_mech_krb5 (which it always is at the moment),
+	 * then this is a moot point, as both declare this particular
+	 * OID static, and so no memory is lost.  This assert is in
+	 * place to ensure that the programmer who wishes to extend
+	 * this code to EAP or other GSS mechanisms determines an
+	 * implementation-dependent way of releasing any dynamically
+	 * allocated OID */
+	SMB_ASSERT(gss_oid_equal(&gse_ctx->gss_mech, GSS_C_NO_OID) || gss_oid_equal(&gse_ctx->gss_mech, gss_mech_krb5));
+
 	return 0;
 }
 
diff --git a/source3/wscript b/source3/wscript
index 6081ac9d4d..cdafc1683a 100644
--- a/source3/wscript
+++ b/source3/wscript
@@ -632,7 +632,7 @@ msg.msg_acctrightslen = sizeof(fd);
         if conf.CHECK_FUNCS_IN('gss_display_status', 'gssapi') or \
            conf.CHECK_FUNCS_IN('gss_display_status', 'gssapi_krb5'):
             have_gssapi=True
-        conf.CHECK_FUNCS_IN('gss_wrap_iov gss_krb5_import_cred gss_get_name_attribute', 'gssapi gssapi_krb5 krb5')
+        conf.CHECK_FUNCS_IN('gss_wrap_iov gss_krb5_import_cred gss_get_name_attribute gss_oid_equal', 'gssapi gssapi_krb5 krb5')
         conf.CHECK_FUNCS_IN('krb5_mk_req_extended krb5_kt_compare', 'krb5')
         conf.CHECK_FUNCS('''
 krb5_set_real_time krb5_set_default_in_tkt_etypes krb5_set_default_tgs_enctypes