commit d9ba9f91d25210f10f740d243899dbe99f8acb60 Author: Nick Mathewson nickm@torproject.org Date: Mon May 7 12:44:34 2012 -0400

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

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 --- changes/bug5786_nocrash | 7 +++++++ src/or/dirvote.c | 6 +++--- 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/changes/bug5786_nocrash b/changes/bug5786_nocrash new file mode 100644 index 0000000..ec6c5d8 --- /dev/null +++ b/changes/bug5786_nocrash @@ -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. + diff --git a/src/or/dirvote.c b/src/or/dirvote.c index 4848917..20dc8c2 100644 --- a/src/or/dirvote.c +++ b/src/or/dirvote.c @@ -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",