krb5 commit [krb5-1.14]: Revisit inquire_attrs_for_mech on old mechs

[Tom Yu]

https://github.com/krb5/krb5/commit/9e26436f2acb5fcd450f5cc1ac1f81ccbb0aa6ac
commit 9e26436f2acb5fcd450f5cc1ac1f81ccbb0aa6ac
Author: Greg Hudson <ghudson at mit.edu>
Date:   Tue Mar 15 17:45:26 2016 -0400

    Revisit inquire_attrs_for_mech on old mechs
    
    In gss_inquire_attrs_for_mech(), if the mech does not implement RFC
    5587, return success with empty mech_attrs and known_mech_attrs sets
    to indicate a lack of knowledge for all attributes.  The previous
    behavior of returning an error caused gss_indicate_mechs_by_attr() to
    fail out in the presence of an old mechanism, in turn causing
    gss_acquire_cred() and SPNEGO to break.
    
    (cherry picked from commit 89683d1f135765e91041f3a239af865b11aaf86b)
    
    ticket: 8358
    version_fixed: 1.14.2
    status: resolved
    tags: -pullup

 src/lib/gssapi/mechglue/g_mechattr.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/lib/gssapi/mechglue/g_mechattr.c b/src/lib/gssapi/mechglue/g_mechattr.c
index 08a6008..e49651e 100644
--- a/src/lib/gssapi/mechglue/g_mechattr.c
+++ b/src/lib/gssapi/mechglue/g_mechattr.c
@@ -181,8 +181,12 @@ gss_inquire_attrs_for_mech(
     mech = gssint_get_mechanism(selected_mech);
     if (mech == NULL)
         return GSS_S_BAD_MECH;
-    else if (mech->gss_inquire_attrs_for_mech == NULL)
-        return GSS_S_UNAVAILABLE;
+
+    /* If the mech does not implement RFC 5587, return success with an empty
+     * mech_attrs and known_mech_attrs. */
+    if (mech->gss_inquire_attrs_for_mech == NULL)
+        return GSS_S_COMPLETE;
+
     public_mech = gssint_get_public_oid(selected_mech);
     status = mech->gss_inquire_attrs_for_mech(minor, public_mech, mech_attrs,
                                               known_mech_attrs);