commit b82717b27378a0f8048da9d865a8bd3c6dfedd6f Author: Nick Mathewson nickm@torproject.org Date: Fri Dec 14 14:07:00 2018 -0500

Stop re-checking our hardcoded dh parameters on every startup

Closes ticket 28851. --- changes/ticket28851 | 4 ++++ src/lib/crypt_ops/crypto_dh_openssl.c | 6 ++++++ 2 files changed, 10 insertions(+)

diff --git a/changes/ticket28851 b/changes/ticket28851 new file mode 100644 index 000000000..bab031866 --- /dev/null +++ b/changes/ticket28851 @@ -0,0 +1,4 @@ + o Minor features (performance): + - Stop re-validating our hardcoded Diffie-Hellman parameters on every + startup. Doing this wasted time and cycles, especially on low-powered + devices. Closes ticket 28851. diff --git a/src/lib/crypt_ops/crypto_dh_openssl.c b/src/lib/crypt_ops/crypto_dh_openssl.c index 54946458d..0d9bd513c 100644 --- a/src/lib/crypt_ops/crypto_dh_openssl.c +++ b/src/lib/crypt_ops/crypto_dh_openssl.c @@ -45,6 +45,8 @@ static BIGNUM *dh_param_p_tls = NULL; /** Shared G parameter for our DH key exchanges. */ static BIGNUM *dh_param_g = NULL;

+/* This function is disabled unless we change the DH parameters. */ +#if 0 /** Validate a given set of Diffie-Hellman parameters. This is moderately * computationally expensive (milliseconds), so should only be called when * the DH parameters change. Returns 0 on success, * -1 on failure. @@ -98,6 +100,7 @@ crypto_validate_dh_params(const BIGNUM *p, const BIGNUM *g) DH_free(dh); return ret; } +#endif

/** * Helper: convert <b>hex<b> to a bignum, and return it. Assert that the @@ -151,8 +154,11 @@ crypto_dh_init_openssl(void) dh_param_p = bignum_from_hex(OAKLEY_PRIME_2); dh_param_p_tls = bignum_from_hex(TLS_DH_PRIME);

+ /* Checks below are disabled unless we change the hardcoded DH parameters. */ +#if 0 tor_assert(0 == crypto_validate_dh_params(dh_param_p, dh_param_g)); tor_assert(0 == crypto_validate_dh_params(dh_param_p_tls, dh_param_g)); +#endif }

/** Number of bits to use when choosing the x or y value in a Diffie-Hellman