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Detect out-of-bounds bwweightscale values early in the voting process

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If the authorities agreed on a sufficiently bad bwweightscale value
(<=0 or == INT32_MAX), the bandwidth algorithm could make the voters
assert while computing the consensus.

Fix for bug5786; bugfix on 0.2.2.17-alpha
This commit is contained in:
Nick Mathewson
2012-05-07 12:44:34 -04:00
parent c8a0cceae2
commit d9ba9f91d2
2 changed files with 10 additions and 3 deletions
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changes/bug5786_nocrash
+7
View File
@@ -0,0 +1,7 @@
o Major bugfixes (directory authorties):
- When computing weight parameters, behave more robustly in the
presence of a bad bwweightscale value. Previously, the
authorities would crash if they agreed on a sufficiently browken
weight_scale value: now, they use a reasonable default and carry
on. Partial fix for 5786; bugfix on 0.2.2.17-alpha.
src/or/dirvote.c
+3 -3
View File
@@ -1005,7 +1005,7 @@ networkstatus_compute_bw_weights_v10(smartlist_t *chunks, int64_t G,
/* We cast down the weights to 32 bit ints on the assumption that
* weight_scale is ~= 10000. We need to ensure a rogue authority
* doesn't break this assumption to rig our weights */
tor_assert(0 < weight_scale && weight_scale < INT32_MAX);
tor_assert(0 < weight_scale && weight_scale <= INT32_MAX);
/*
* Provide Wgm=Wgg, Wmm=1, Wem=Wee, Weg=Wed. May later determine
@@ -1233,7 +1233,7 @@ networkstatus_compute_bw_weights_v9(smartlist_t *chunks, int64_t G, int64_t M,
/* We cast down the weights to 32 bit ints on the assumption that
* weight_scale is ~= 10000. We need to ensure a rogue authority
* doesn't break this assumption to rig our weights */
tor_assert(0 < weight_scale && weight_scale < INT32_MAX);
tor_assert(0 < weight_scale && weight_scale <= INT32_MAX);
if (Wgg < 0 || Wgg > weight_scale) {
log_warn(LD_DIR, "Bw %s: Wgg="I64_FORMAT"! G="I64_FORMAT
@@ -2019,7 +2019,7 @@ networkstatus_compute_consensus(smartlist_t *votes,
int ok=0;
char *eq = strchr(bw_weight_param, '=');
if (eq) {
weight_scale = tor_parse_long(eq+1, 10, INT32_MIN, INT32_MAX, &ok,
weight_scale = tor_parse_long(eq+1, 10, 1, INT32_MAX, &ok,
NULL);
if (!ok) {
log_warn(LD_DIR, "Bad element '%s' in bw weight param",