Allow arbitrary-length PAM messages

The PAM standard allows for messages of any length to be returned
to the client. We were discarding all messages of length greater
than 255. This patch dynamically allocates the message buffers so
we can pass the complete message.

This resolves https://fedorahosted.org/sssd/ticket/432

2 files changed, 7 insertions, 20 deletions

diff --git a/src/providers/krb5/krb5_auth.c b/src/providers/krb5/krb5_auth.c
index ce3aacd8..880930a1 100644
--- a/src/providers/krb5/krb5_auth.c
+++ b/src/providers/krb5/krb5_auth.c
@@ -1091,7 +1091,7 @@ static void krb5_child_done(struct tevent_req *req)
                                                 *msg_len));
 
     if ((p + *msg_len) != len) {
-        DEBUG(1, ("message format error.\n"));
+        DEBUG(1, ("message format error [%d] != [%d].\n", p+*msg_len, len));
         goto done;
     }
 
diff --git a/src/providers/krb5/krb5_child.c b/src/providers/krb5/krb5_child.c
index 86242ef3..620e4d14 100644
--- a/src/providers/krb5/krb5_child.c
+++ b/src/providers/krb5/krb5_child.c
@@ -247,27 +247,15 @@ done:
     return kerr;
 }
 
-static struct response *init_response(TALLOC_CTX *mem_ctx) {
-    struct response *r;
-    r = talloc(mem_ctx, struct response);
-    r->buf = talloc_size(mem_ctx, MAX_CHILD_MSG_SIZE);
-    if (r->buf == NULL) {
-        DEBUG(1, ("talloc_size failed.\n"));
-        return NULL;
-    }
-    r->max_size = MAX_CHILD_MSG_SIZE;
-    r->size = 0;
-
-    return r;
-}
-
 static errno_t pack_response_packet(struct response *resp, int status, int type,
                                     size_t len, const uint8_t *data)
 {
     size_t p = 0;
 
-    if ((3*sizeof(int32_t) + len +1) > resp->max_size) {
-        DEBUG(1, ("response message too big.\n"));
+    resp->buf = talloc_array(resp, uint8_t,
+                             3*sizeof(int32_t) + len);
+    if (!resp->buf) {
+        DEBUG(1, ("Insufficient memory to create message.\n"));
         return ENOMEM;
     }
 
@@ -293,9 +281,9 @@ static struct response *prepare_response_message(struct krb5_req *kr,
     size_t user_resp_len;
     uint8_t *user_resp;
 
-    resp = init_response(kr);
+    resp = talloc_zero(kr, struct response);
     if (resp == NULL) {
-        DEBUG(1, ("init_response failed.\n"));
+        DEBUG(1, ("Initializing response failed.\n"));
         return NULL;
     }
 
@@ -321,7 +309,6 @@ static struct response *prepare_response_message(struct krb5_req *kr,
             talloc_zfree(msg);
         }
     } else {
-
         if (user_error_message != NULL) {
             ret = pack_user_info_chpass_error(kr, user_error_message,
                                               &user_resp_len, &user_resp);