[tor-commits] [tor/master] Implement consensus method 12 (proposal 178)
nickm at torproject.org
nickm at torproject.org
Sun Nov 27 14:33:11 UTC 2011
commit e5e4bfd167425699a559a3a1545c0a3d6946f82e
Author: Sebastian Hahn <sebastian at torproject.org>
Date: Sun Feb 20 21:05:17 2011 -0500
Implement consensus method 12 (proposal 178)
---
changes/proposal178 | 6 ++++
src/or/dirvote.c | 32 ++++++++++++++++-----
src/or/dirvote.h | 3 +-
src/test/test_dir.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++---
4 files changed, 104 insertions(+), 13 deletions(-)
diff --git a/changes/proposal178 b/changes/proposal178
new file mode 100644
index 0000000..ee70695
--- /dev/null
+++ b/changes/proposal178
@@ -0,0 +1,6 @@
+ o Major features:
+ - Implement a more secure consensus parameter voting algorithm that
+ ensures that at least three directory authorities or a majority of
+ them voted on a given parameter before including it in the
+ consensus. Implements proposal 178.
+
diff --git a/src/or/dirvote.c b/src/or/dirvote.c
index bf34c62..01e2358 100644
--- a/src/or/dirvote.c
+++ b/src/or/dirvote.c
@@ -50,7 +50,7 @@ static int dirvote_publish_consensus(void);
static char *make_consensus_method_list(int low, int high, const char *sep);
/** The highest consensus method that we currently support. */
-#define MAX_SUPPORTED_CONSENSUS_METHOD 11
+#define MAX_SUPPORTED_CONSENSUS_METHOD 12
/** Lowest consensus method that contains a 'directory-footer' marker */
#define MIN_METHOD_FOR_FOOTER 9
@@ -64,6 +64,10 @@ static char *make_consensus_method_list(int low, int high, const char *sep);
/** Lowest consensus method that generates microdescriptors */
#define MIN_METHOD_FOR_MICRODESC 8
+/** Lowest consensus method that ensures a majority of authorities voted
+ * for a param. */
+#define MIN_METHOD_FOR_MAJORITY_PARAMS 12
+
/* =====
* Voting
* =====*/
@@ -608,11 +612,16 @@ compute_consensus_versions_list(smartlist_t *lst, int n_versioning)
return result;
}
+/** Minimum number of directory authorities voting for a parameter to
+ * include it in the consensus, if consensus method 12 or later is to be
+ * used. See proposal 178 for details. */
+#define MIN_VOTES_FOR_PARAM 3
+
/** Helper: given a list of valid networkstatus_t, return a new string
* containing the contents of the consensus network parameter set.
*/
/* private */ char *
-dirvote_compute_params(smartlist_t *votes)
+dirvote_compute_params(smartlist_t *votes, int method, int total_authorities)
{
int i;
int32_t *vals;
@@ -669,11 +678,17 @@ dirvote_compute_params(smartlist_t *votes)
next_param = smartlist_get(param_list, param_sl_idx+1);
if (!next_param || strncmp(next_param, param, cur_param_len)) {
/* We've reached the end of a series. */
- int32_t median = median_int32(vals, i);
- char *out_string = tor_malloc(64+cur_param_len);
- memcpy(out_string, param, cur_param_len);
- tor_snprintf(out_string+cur_param_len,64, "%ld", (long)median);
- smartlist_add(output, out_string);
+ /* Make sure enough authorities voted on this param, unless the
+ * the consensus method we use is too old for that. */
+ if (method < MIN_METHOD_FOR_MAJORITY_PARAMS ||
+ i > total_authorities/2 ||
+ i >= MIN_VOTES_FOR_PARAM) {
+ int32_t median = median_int32(vals, i);
+ char *out_string = tor_malloc(64+cur_param_len);
+ memcpy(out_string, param, cur_param_len);
+ tor_snprintf(out_string+cur_param_len,64, "%ld", (long)median);
+ smartlist_add(output, out_string);
+ }
i = 0;
if (next_param) {
@@ -1496,7 +1511,8 @@ networkstatus_compute_consensus(smartlist_t *votes,
}
if (consensus_method >= MIN_METHOD_FOR_PARAMS) {
- params = dirvote_compute_params(votes);
+ params = dirvote_compute_params(votes, consensus_method,
+ total_authorities);
if (params) {
smartlist_add(chunks, tor_strdup("params "));
smartlist_add(chunks, params);
diff --git a/src/or/dirvote.h b/src/or/dirvote.h
index d196351..1f4dc36 100644
--- a/src/or/dirvote.h
+++ b/src/or/dirvote.h
@@ -84,7 +84,8 @@ document_signature_t *voter_get_sig_by_algorithm(
#ifdef DIRVOTE_PRIVATE
char *format_networkstatus_vote(crypto_pk_env_t *private_key,
networkstatus_t *v3_ns);
-char *dirvote_compute_params(smartlist_t *votes);
+char *dirvote_compute_params(smartlist_t *votes, int method,
+ int total_authorities);
#endif
#endif
diff --git a/src/test/test_dir.c b/src/test/test_dir.c
index 205d7b5..5b7ce5c 100644
--- a/src/test/test_dir.c
+++ b/src/test/test_dir.c
@@ -620,13 +620,81 @@ test_dir_param_voting(void)
test_eq(0, networkstatus_get_param(&vote4, "foobar", 0, -100, 8));
smartlist_add(votes, &vote1);
+
+ /* Do the first tests without adding all the other votes, for
+ * networks without many dirauths. */
+
+ res = dirvote_compute_params(votes, 11, 6);
+ test_streq(res, "ab=90 abcd=20 cw=50 x-yz=-99");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 2);
+ test_streq(res, "");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 1);
+ test_streq(res, "ab=90 abcd=20 cw=50 x-yz=-99");
+ tor_free(res);
+
smartlist_add(votes, &vote2);
+
+ res = dirvote_compute_params(votes, 11, 2);
+ test_streq(res, "ab=27 abcd=20 cw=5 x-yz=-99");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 2);
+ test_streq(res, "ab=27 cw=5 x-yz=-99");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 3);
+ test_streq(res, "ab=27 cw=5 x-yz=-99");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 6);
+ test_streq(res, "");
+ tor_free(res);
+
smartlist_add(votes, &vote3);
+
+ res = dirvote_compute_params(votes, 11, 3);
+ test_streq(res, "ab=27 abcd=20 c=60 cw=50 x-yz=-9 zzzzz=101");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 3);
+ test_streq(res, "ab=27 abcd=20 cw=50 x-yz=-9");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 5);
+ test_streq(res, "cw=50 x-yz=-9");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 9);
+ test_streq(res, "cw=50 x-yz=-9");
+ tor_free(res);
+
smartlist_add(votes, &vote4);
- res = dirvote_compute_params(votes);
- test_streq(res,
- "ab=90 abcd=20 c=1 cw=50 x-yz=-9 zzzzz=101");
+ res = dirvote_compute_params(votes, 11, 4);
+ test_streq(res, "ab=90 abcd=20 c=1 cw=50 x-yz=-9 zzzzz=101");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 4);
+ test_streq(res, "ab=90 abcd=20 cw=50 x-yz=-9");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 5);
+ test_streq(res, "ab=90 abcd=20 cw=50 x-yz=-9");
+ tor_free(res);
+
+ /* Test that the special-cased "at least three dirauths voted for
+ * this param" logic works as expected. */
+ res = dirvote_compute_params(votes, 12, 6);
+ test_streq(res, "ab=90 abcd=20 cw=50 x-yz=-9");
+ tor_free(res);
+
+ res = dirvote_compute_params(votes, 12, 10);
+ test_streq(res, "ab=90 abcd=20 cw=50 x-yz=-9");
+ tor_free(res);
done:
tor_free(res);
@@ -1049,7 +1117,7 @@ test_dir_v3_networkstatus(void)
"Running:Stable:V2Dir:Valid");
tor_free(cp);
cp = smartlist_join_strings(con->net_params, ":", 0, NULL);
- test_streq(cp, "bar=2000000000:circuitwindow=80:foo=660");
+ test_streq(cp, "circuitwindow=80:foo=660");
tor_free(cp);
test_eq(4, smartlist_len(con->voters)); /*3 voters, 1 legacy key.*/
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