prop250: Add a valid flag to sr_commit_t

We assert on it using the ASSERT_COMMIT_VALID() macro in critical places
where we use them expecting a commit to be valid.

Signed-off-by: David Goulet <dgoulet@torproject.org>

src/or/shared_random.c

@@ -700,6 +700,8 @@ save_commit_to_state(sr_commit_t *commit)
 {
   sr_phase_t phase = sr_state_get_phase();
 
+  ASSERT_COMMIT_VALID(commit);
+
   switch (phase) {
   case SR_PHASE_COMMIT:
     /* During commit phase, just save any new authoritative commit */
@@ -914,6 +916,8 @@ sr_generate_our_commit(time_t timestamp, const authority_cert_t *my_rsa_cert)
 
   log_debug(LD_DIR, "SR: Generated our commitment:");
   commit_log(commit);
+  /* Our commit better be valid :). */
+  commit->valid = 1;
   return commit;
 
  error:
@@ -942,6 +946,8 @@ sr_compute_srv(void)
   /* We must make a list of commit ordered by authority fingerprint in
    * ascending order as specified by proposal 250. */
   DIGESTMAP_FOREACH(state_commits, key, sr_commit_t *, c) {
+    /* Extra safety net, make sure we have valid commit before using it. */
+    ASSERT_COMMIT_VALID(c);
     smartlist_add(commits, c);
   } DIGESTMAP_FOREACH_END;
   smartlist_sort(commits, compare_reveal_);
@@ -1130,6 +1136,9 @@ sr_handle_received_commits(smartlist_t *commits, crypto_pk_t *voter_key)
       sr_commit_free(commit);
       continue;
     }
+    /* Ok, we have a valid commit now that we are about to put in our state.
+     * so flag it valid from now on. */
+    commit->valid = 1;
     /* Everything lines up: save this commit to state then! */
     save_commit_to_state(commit);
   } SMARTLIST_FOREACH_END(commit);

src/or/shared_random.h

@@ -48,6 +48,9 @@
 #define SR_SRV_VALUE_BASE64_LEN \
   (((DIGEST256_LEN - 1) / 3) * 4 + 4)
 
+/* Assert if commit valid flag is not set. */
+#define ASSERT_COMMIT_VALID(c) tor_assert((c)->valid)
+
 /* Protocol phase. */
 typedef enum {
   /* Commitment phase */
@@ -68,6 +71,8 @@ typedef struct sr_srv_t {
 typedef struct sr_commit_t {
   /* Hashing algorithm used. */
   digest_algorithm_t alg;
+  /* Indicate if this commit has been verified thus valid. */
+  unsigned int valid:1;
 
   /* Commit owner info */
 

src/or/shared_random_state.c

@@ -410,6 +410,9 @@ disk_state_parse_commits(sr_state_t *state,
        * fingerprint that we don't know about so it shouldn't be used. */
       continue;
     }
+    /* We consider parseable commit from our disk state to be valid because
+     * they need to be in the first place to get in there. */
+    commit->valid = 1;
     /* Add commit to our state pointer. */
     commit_add_to_state(commit, state);