diff options
| -rw-r--r-- | ChangeLog | 7 | ||||
| -rw-r--r-- | src/common/crypto.c | 38 | ||||
| -rw-r--r-- | src/common/crypto.h | 2 | ||||
| -rw-r--r-- | src/or/main.c | 4 |
4 files changed, 34 insertions, 17 deletions
@@ -24,6 +24,13 @@ Changes in version 0.2.1.1-alpha - 2008-??-?? - Add a couple of extra warnings to --enable-gcc-warnings for GCC 4.3, and stop using a warning that had become unfixably verbose under GCC 4.3. + - Start using OpenSSL's RAND_poll() for better (and more portable) + cross-platform entropy collection again. We used to use it, then + stopped using it because of a bug that could crash systems that called + RAND_poll when they had a lot of fds open. It looks like the bug got + fixed in late 2006. Our new behavior is to call RAND_poll() at + startup, and to call RAND_poll() when we reseed later only if we + have a non-buggy OpenSSL version. o Code simplifications and refactoring: - Refactor code using connection_ap_handshake_attach_circuit() to diff --git a/src/common/crypto.c b/src/common/crypto.c index ea70aad4ab..44fa3b2b40 100644 --- a/src/common/crypto.c +++ b/src/common/crypto.c @@ -1667,19 +1667,29 @@ crypto_dh_free(crypto_dh_env_t *dh) /* Use RAND_poll if openssl is 0.9.6 release or later. (The "f" means "release".) */ -//#define USE_RAND_POLL (OPENSSL_VERSION_NUMBER >= 0x0090600fl) -#define USE_RAND_POLL 0 -/* XXX Somehow setting USE_RAND_POLL on causes stack smashes. We're - * not sure where. This was the big bug with Tor 0.1.1.9-alpha. */ +#define HAVE_RAND_POLL (OPENSSL_VERSION_NUMBER >= 0x0090600fl) -/** Seed OpenSSL's random number generator with bytes from the - * operating system. Return 0 on success, -1 on failure. +/* Versions of openssl prior to 0.9.7k and 0.9.8c had a bug where RAND_poll + * would allocate an fd_set on the stack, open a new file, and try to FD_SET + * that fd without checking whether it fit in the fd_set. Thus, if the + * system has not just been started up, it is unsafe to call */ +#define RAND_POLL_IS_SAFE \ + ((OPENSSL_VERSION_NUMBER >= 0x009070afl && \ + OPENSSL_VERSION_NUMBER <= 0x00907fffl) || \ + (OPENSSL_VERSION_NUMBER >= 0x0090803fl)) + +/* We could actually get away with calling RAND_poll */ +#define USE_RAND_POLL (HAVE_RAND_POLL && RAND_POLL_IS_SAFE) + +/** Seed OpenSSL's random number generator with bytes from the operating + * system. <b>startup</b> should be true iff we have just started Tor and + * have not yet allocated a bunch of fds. Return 0 on success, -1 on failure. */ int -crypto_seed_rng(void) +crypto_seed_rng(int startup) { char buf[ADD_ENTROPY]; - int rand_poll_status; + int rand_poll_status = 0; /* local variables */ #ifdef MS_WINDOWS @@ -1693,15 +1703,15 @@ crypto_seed_rng(void) size_t n; #endif -#if USE_RAND_POLL +#if HAVE_RAND_POLL /* OpenSSL 0.9.6 adds a RAND_poll function that knows about more kinds of * entropy than we do. We'll try calling that, *and* calling our own entropy * functions. If one succeeds, we'll accept the RNG as seeded. */ - rand_poll_status = RAND_poll(); - if (rand_poll_status == 0) - log_warn(LD_CRYPTO, "RAND_poll() failed."); -#else - rand_poll_status = 0; + if (startup || RAND_POLL_IS_SAFE) { + rand_poll_status = RAND_poll(); + if (rand_poll_status == 0) + log_warn(LD_CRYPTO, "RAND_poll() failed."); + } #endif #ifdef MS_WINDOWS diff --git a/src/common/crypto.h b/src/common/crypto.h index e51c0777a9..2627335113 100644 --- a/src/common/crypto.h +++ b/src/common/crypto.h @@ -166,7 +166,7 @@ int crypto_expand_key_material(const char *key_in, size_t in_len, char *key_out, size_t key_out_len); /* random numbers */ -int crypto_seed_rng(void); +int crypto_seed_rng(int startup); int crypto_rand(char *to, size_t n); int crypto_rand_int(unsigned int max); uint64_t crypto_rand_uint64(uint64_t max); diff --git a/src/or/main.c b/src/or/main.c index 396b6f3b91..5630f4efe8 100644 --- a/src/or/main.c +++ b/src/or/main.c @@ -900,7 +900,7 @@ run_scheduled_events(time_t now) if (time_to_add_entropy < now) { if (time_to_add_entropy) { /* We already seeded once, so don't die on failure. */ - crypto_seed_rng(); + crypto_seed_rng(0); } /** How often do we add more entropy to OpenSSL's RNG pool? */ #define ENTROPY_INTERVAL (60*60) @@ -1810,7 +1810,7 @@ tor_init(int argc, char *argv[]) #endif crypto_global_init(get_options()->HardwareAccel); - if (crypto_seed_rng()) { + if (crypto_seed_rng(1)) { log_err(LD_BUG, "Unable to seed random number generator. Exiting."); return -1; } |