krb5 commit [krb5-1.17]: Fix handling of invalid CAMMAC service verifier

https://github.com/krb5/krb5/commit/ad105209b4701d51437d1ffcc75ee3aa1e45f5ad
commit ad105209b4701d51437d1ffcc75ee3aa1e45f5ad
Author: Jeffrey Arbuckle <[email protected]>
Date:   Sat Dec 21 22:59:20 2019 -0500

    Fix handling of invalid CAMMAC service verifier
    
    In extract_cammacs(), avoid a null dereference if the CAMMAC service
    verifier is invalid or the CAMMAC is empty.
    
    (cherry picked from commit 8451ff6ed57361de585a35f35a39c54dc48172c7)
    
    ticket: 8856
    version_fixed: 1.17.2

 src/lib/krb5/krb/authdata.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/src/lib/krb5/krb/authdata.c b/src/lib/krb5/krb/authdata.c
index 7fbcfab..12ac92d 100644
--- a/src/lib/krb5/krb/authdata.c
+++ b/src/lib/krb5/krb/authdata.c
@@ -557,6 +557,8 @@ extract_cammacs(krb5_context kcontext, krb5_authdata **cammacs,
         if (ret && ret != KRB5KRB_AP_ERR_BAD_INTEGRITY)
             goto cleanup;
         ret = 0;
+        if (elements == NULL)
+            continue;
 
         /* Add the verified elements to list and free the container array. */
         for (n_elements = 0; elements[n_elements] != NULL; n_elements++);