krb5 commit: Improve pointer hygiene around gss_display_name

[Greg Hudson]

https://github.com/krb5/krb5/commit/0bf18fd4363f9f1244688daac224bd456bf52e7f
commit 0bf18fd4363f9f1244688daac224bd456bf52e7f
Author: Greg Hudson <ghudson at mit.edu>
Date:   Wed May 21 12:03:00 2014 -0400

    Improve pointer hygiene around gss_display_name
    
    GSSAPI functions are responsible for setting their output parameters
    on failure.  Take greater care to do so in krb5_gss_display_name.
    
    The mechglue is generally defensive about initializing variables used
    as outputs, and not assuming that mechs will set them on failure.
    Make gssint_convert_name_to_union_name initialize
    union_name->external_name before calling mech->gss_display_name, so
    that if the mech's gss_display_name doesn't touch it, we don't free an
    uninitialized pointer.
    
    Either one of these changes prevents an unlikely memory bug which
    could occur if krb5_gss_init_context fails within
    krb5_gss_display_name when called from
    gssint_convert_name_to_union_name.
    
    ticket: 7915 (new)
    target_version: 1.12.2

 src/lib/gssapi/krb5/disp_name.c  |    8 +++++---
 src/lib/gssapi/mechglue/g_glue.c |    2 ++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/lib/gssapi/krb5/disp_name.c b/src/lib/gssapi/krb5/disp_name.c
index 6ff2543..b097bf0 100644
--- a/src/lib/gssapi/krb5/disp_name.c
+++ b/src/lib/gssapi/krb5/disp_name.c
@@ -37,15 +37,17 @@ krb5_gss_display_name(minor_status, input_name, output_name_buffer,
     krb5_gss_name_t k5name = (krb5_gss_name_t) input_name;
     gss_OID nametype = (gss_OID) gss_nt_krb5_name;
 
+    output_name_buffer->length = 0;
+    output_name_buffer->value = NULL;
+    if (output_name_type)
+        *output_name_type = GSS_C_NO_OID;
+
     code = krb5_gss_init_context(&context);
     if (code) {
         *minor_status = code;
         return GSS_S_FAILURE;
     }
 
-    output_name_buffer->length = 0;
-    output_name_buffer->value = NULL;
-
     if (krb5_princ_type(context, k5name->princ) == KRB5_NT_WELLKNOWN) {
         if (krb5_principal_compare(context, k5name->princ,
                                    krb5_anonymous_principal()))
diff --git a/src/lib/gssapi/mechglue/g_glue.c b/src/lib/gssapi/mechglue/g_glue.c
index e438a03..4aa3591 100644
--- a/src/lib/gssapi/mechglue/g_glue.c
+++ b/src/lib/gssapi/mechglue/g_glue.c
@@ -647,6 +647,8 @@ OM_uint32 gssint_convert_name_to_union_name(minor_status, mech,
 	    major_status = GSS_S_FAILURE;
 	    goto allocation_failure;
     }
+    union_name->external_name->length = 0;
+    union_name->external_name->value = NULL;
 
     major_status = mech->gss_display_name(minor_status,
 					  internal_name,