krb5 commit [krb5-1.12]: Fix S4U2Self against non-FAST KDCs

[Tom Yu]

https://github.com/krb5/krb5/commit/590b690483e7924186a5bd4b8cd40267bc6e6795
commit 590b690483e7924186a5bd4b8cd40267bc6e6795
Author: Greg Hudson <ghudson at mit.edu>
Date:   Thu Dec 5 20:32:05 2013 -0500

    Fix S4U2Self against non-FAST KDCs
    
    When we added FAST TGS support in 1.11, we broke S4U2Self against KDCs
    which don't support FAST, because the S4U2Self padata is only present
    within the FAST request.  For now, duplicate that padata in the outer
    request so that both FAST and non-FAST KDCs can see it.
    
    (cherry picked from commit 55c3a5f69919c2b5435bac0cb48ab09b11be869c)
    
    ticket: 7791
    version_fixed: 1.12.1
    status: resolved

 src/lib/krb5/krb/fast.c |   39 ++++++++++++++++++++++++++++++++++-----
 1 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/src/lib/krb5/krb/fast.c b/src/lib/krb5/krb/fast.c
index 84eaca4..56e61a6 100644
--- a/src/lib/krb5/krb/fast.c
+++ b/src/lib/krb5/krb/fast.c
@@ -225,6 +225,32 @@ krb5int_fast_as_armor(krb5_context context,
     return retval;
 }
 
+/*
+ * Construct a list of outer request padata for a TGS request.  Since we do
+ * FAST TGS even when we don't have reason to believe the KDC supports FAST,
+ * the outer padata has to contain duplicates of the inner padata (such as
+ * S4U2Self padata) as well as the PA-TGS-REQ and PA-FX-FAST padata.  The
+ * caller must free *out_padata with free() as it is not a deep copy.
+ */
+static krb5_error_code
+make_tgs_outer_padata(krb5_pa_data *tgs, krb5_pa_data *fast,
+                      krb5_pa_data **other, krb5_pa_data ***out_padata)
+{
+    krb5_pa_data **pa_list;
+    size_t i;
+
+    *out_padata = NULL;
+    for (i = 0; other[i] != NULL; i++);
+    pa_list = calloc(i + 3, sizeof(*pa_list));
+    if (pa_list == NULL)
+        return ENOMEM;
+    pa_list[0] = tgs;
+    pa_list[1] = fast;
+    for (i = 0; other[i] != NULL; i++)
+        pa_list[i + 2] = other[i];
+    *out_padata = pa_list;
+    return 0;
+}
 
 krb5_error_code
 krb5int_fast_prep_req(krb5_context context,
@@ -235,7 +261,7 @@ krb5int_fast_prep_req(krb5_context context,
                       krb5_data **encoded_request)
 {
     krb5_error_code retval = 0;
-    krb5_pa_data *pa_array[3];
+    krb5_pa_data *pa_array[2], **pa_tgs_array = NULL;
     krb5_pa_data pa[2];
     krb5_fast_req fast_req;
     krb5_pa_data *tgs = NULL;
@@ -299,12 +325,14 @@ krb5int_fast_prep_req(krb5_context context,
         pa[0].contents = (unsigned char *) encoded_armored_req->data;
         pa[0].length = encoded_armored_req->length;
         if (tgs) {
-            pa_array[0] = tgs;
-            pa_array[1] = &pa[0];
-        } else
+            retval = make_tgs_outer_padata(tgs, pa, request->padata,
+                                           &pa_tgs_array);
+            state->fast_outer_request.padata = pa_tgs_array;
+        } else {
             pa_array[0] = &pa[0];
+            state->fast_outer_request.padata = pa_array;
+        }
     }
-    state->fast_outer_request.padata = pa_array;
     if (retval == 0)
         retval = encoder(&state->fast_outer_request, &local_encoded_result);
     if (retval == 0) {
@@ -326,6 +354,7 @@ krb5int_fast_prep_req(krb5_context context,
         free(tgs);
     }
     state->fast_outer_request.padata = NULL;
+    free(pa_tgs_array);
     return retval;
 }