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Extract the OpenSSL DH functionality to a new file.
This commit is contained in:
Nick Mathewson
parent
99beed152e
commit
60a5b78480
@ -7,6 +7,8 @@
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/**
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* \file crypto_dh.c
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* \brief Block of functions related with DH utilities and operations.
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* over Z_p. We aren't using this for any new crypto -- EC is more
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* efficient.
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**/
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#include "lib/crypt_ops/compat_openssl.h"
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@ -17,495 +19,26 @@
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#include "lib/log/log.h"
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#include "lib/log/util_bug.h"
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DISABLE_GCC_WARNING(redundant-decls)
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#include <openssl/dh.h>
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ENABLE_GCC_WARNING(redundant-decls)
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#include <openssl/bn.h>
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#include <string.h>
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/** A structure to hold the first half (x, g^x) of a Diffie-Hellman handshake
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* while we're waiting for the second.*/
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struct crypto_dh_t {
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DH *dh; /**< The openssl DH object */
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};
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static int tor_check_dh_key(int severity, const BIGNUM *bn);
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/** Used by tortls.c: Get the DH* from a crypto_dh_t.
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*/
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DH *
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crypto_dh_get_dh_(crypto_dh_t *dh)
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{
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return dh->dh;
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}
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/** Our DH 'g' parameter */
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#define DH_GENERATOR 2
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/** Shared P parameter for our circuit-crypto DH key exchanges. */
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static BIGNUM *dh_param_p = NULL;
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/** Shared P parameter for our TLS DH key exchanges. */
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static BIGNUM *dh_param_p_tls = NULL;
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/** Shared G parameter for our DH key exchanges. */
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static BIGNUM *dh_param_g = NULL;
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/** Validate a given set of Diffie-Hellman parameters. This is moderately
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* computationally expensive (milliseconds), so should only be called when
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* the DH parameters change. Returns 0 on success, * -1 on failure.
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const unsigned DH_GENERATOR = 2;
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/** This is the 1024-bit safe prime that Apache uses for its DH stuff; see
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* modules/ssl/ssl_engine_dh.c; Apache also uses a generator of 2 with this
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* prime.
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*/
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static int
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crypto_validate_dh_params(const BIGNUM *p, const BIGNUM *g)
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{
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DH *dh = NULL;
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int ret = -1;
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/* Copy into a temporary DH object, just so that DH_check() can be called. */
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if (!(dh = DH_new()))
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goto out;
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#ifdef OPENSSL_1_1_API
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BIGNUM *dh_p, *dh_g;
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if (!(dh_p = BN_dup(p)))
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goto out;
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if (!(dh_g = BN_dup(g)))
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goto out;
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if (!DH_set0_pqg(dh, dh_p, NULL, dh_g))
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goto out;
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#else /* !(defined(OPENSSL_1_1_API)) */
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if (!(dh->p = BN_dup(p)))
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goto out;
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if (!(dh->g = BN_dup(g)))
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goto out;
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#endif /* defined(OPENSSL_1_1_API) */
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/* Perform the validation. */
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int codes = 0;
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if (!DH_check(dh, &codes))
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goto out;
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if (BN_is_word(g, DH_GENERATOR_2)) {
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/* Per https://wiki.openssl.org/index.php/Diffie-Hellman_parameters
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*
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* OpenSSL checks the prime is congruent to 11 when g = 2; while the
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* IETF's primes are congruent to 23 when g = 2.
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*/
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BN_ULONG residue = BN_mod_word(p, 24);
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if (residue == 11 || residue == 23)
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codes &= ~DH_NOT_SUITABLE_GENERATOR;
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}
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if (codes != 0) /* Specifics on why the params suck is irrelevant. */
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goto out;
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/* Things are probably not evil. */
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ret = 0;
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out:
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if (dh)
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DH_free(dh);
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return ret;
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}
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/** Set the global Diffie-Hellman generator, used for both TLS and internal
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* DH stuff.
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const char TLS_DH_PRIME[] =
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"D67DE440CBBBDC1936D693D34AFD0AD50C84D239A45F520BB88174CB98"
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"BCE951849F912E639C72FB13B4B4D7177E16D55AC179BA420B2A29FE324A"
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"467A635E81FF5901377BEDDCFD33168A461AAD3B72DAE8860078045B07A7"
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"DBCA7874087D1510EA9FCC9DDD330507DD62DB88AEAA747DE0F4D6E2BD68"
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"B0E7393E0F24218EB3";
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/**
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* This is from rfc2409, section 6.2. It's a safe prime, and
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* supposedly it equals:
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* 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
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*/
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static void
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crypto_set_dh_generator(void)
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{
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BIGNUM *generator;
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int r;
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if (dh_param_g)
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return;
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generator = BN_new();
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tor_assert(generator);
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r = BN_set_word(generator, DH_GENERATOR);
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tor_assert(r);
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dh_param_g = generator;
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}
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/** Set the global TLS Diffie-Hellman modulus. Use the Apache mod_ssl DH
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* modulus. */
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void
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crypto_set_tls_dh_prime(void)
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{
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BIGNUM *tls_prime = NULL;
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int r;
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/* If the space is occupied, free the previous TLS DH prime */
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if (BUG(dh_param_p_tls)) {
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/* LCOV_EXCL_START
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*
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* We shouldn't be calling this twice.
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*/
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BN_clear_free(dh_param_p_tls);
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dh_param_p_tls = NULL;
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/* LCOV_EXCL_STOP */
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}
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tls_prime = BN_new();
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tor_assert(tls_prime);
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/* This is the 1024-bit safe prime that Apache uses for its DH stuff; see
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* modules/ssl/ssl_engine_dh.c; Apache also uses a generator of 2 with this
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* prime.
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*/
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r = BN_hex2bn(&tls_prime,
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"D67DE440CBBBDC1936D693D34AFD0AD50C84D239A45F520BB88174CB98"
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"BCE951849F912E639C72FB13B4B4D7177E16D55AC179BA420B2A29FE324A"
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"467A635E81FF5901377BEDDCFD33168A461AAD3B72DAE8860078045B07A7"
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"DBCA7874087D1510EA9FCC9DDD330507DD62DB88AEAA747DE0F4D6E2BD68"
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"B0E7393E0F24218EB3");
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tor_assert(r);
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tor_assert(tls_prime);
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dh_param_p_tls = tls_prime;
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crypto_set_dh_generator();
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tor_assert(0 == crypto_validate_dh_params(dh_param_p_tls, dh_param_g));
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}
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/** Initialize dh_param_p and dh_param_g if they are not already
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* set. */
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static void
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init_dh_param(void)
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{
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BIGNUM *circuit_dh_prime;
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int r;
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if (BUG(dh_param_p && dh_param_g))
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return; // LCOV_EXCL_LINE This function isn't supposed to be called twice.
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circuit_dh_prime = BN_new();
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tor_assert(circuit_dh_prime);
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/* This is from rfc2409, section 6.2. It's a safe prime, and
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supposedly it equals:
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2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
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*/
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r = BN_hex2bn(&circuit_dh_prime,
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"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08"
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"8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B"
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"302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9"
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"A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6"
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"49286651ECE65381FFFFFFFFFFFFFFFF");
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tor_assert(r);
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/* Set the new values as the global DH parameters. */
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dh_param_p = circuit_dh_prime;
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crypto_set_dh_generator();
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tor_assert(0 == crypto_validate_dh_params(dh_param_p, dh_param_g));
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if (!dh_param_p_tls) {
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crypto_set_tls_dh_prime();
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}
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}
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/** Number of bits to use when choosing the x or y value in a Diffie-Hellman
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* handshake. Since we exponentiate by this value, choosing a smaller one
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* lets our handhake go faster.
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*/
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#define DH_PRIVATE_KEY_BITS 320
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/** Allocate and return a new DH object for a key exchange. Returns NULL on
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* failure.
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*/
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crypto_dh_t *
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crypto_dh_new(int dh_type)
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{
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crypto_dh_t *res = tor_malloc_zero(sizeof(crypto_dh_t));
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tor_assert(dh_type == DH_TYPE_CIRCUIT || dh_type == DH_TYPE_TLS ||
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dh_type == DH_TYPE_REND);
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if (!dh_param_p)
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init_dh_param();
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if (!(res->dh = DH_new()))
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goto err;
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#ifdef OPENSSL_1_1_API
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BIGNUM *dh_p = NULL, *dh_g = NULL;
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if (dh_type == DH_TYPE_TLS) {
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dh_p = BN_dup(dh_param_p_tls);
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} else {
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dh_p = BN_dup(dh_param_p);
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}
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if (!dh_p)
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goto err;
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dh_g = BN_dup(dh_param_g);
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if (!dh_g) {
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BN_free(dh_p);
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goto err;
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}
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if (!DH_set0_pqg(res->dh, dh_p, NULL, dh_g)) {
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goto err;
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}
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if (!DH_set_length(res->dh, DH_PRIVATE_KEY_BITS))
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goto err;
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#else /* !(defined(OPENSSL_1_1_API)) */
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if (dh_type == DH_TYPE_TLS) {
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if (!(res->dh->p = BN_dup(dh_param_p_tls)))
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goto err;
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} else {
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if (!(res->dh->p = BN_dup(dh_param_p)))
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goto err;
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}
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if (!(res->dh->g = BN_dup(dh_param_g)))
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goto err;
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res->dh->length = DH_PRIVATE_KEY_BITS;
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#endif /* defined(OPENSSL_1_1_API) */
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return res;
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/* LCOV_EXCL_START
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* This error condition is only reached when an allocation fails */
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err:
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crypto_openssl_log_errors(LOG_WARN, "creating DH object");
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if (res->dh) DH_free(res->dh); /* frees p and g too */
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tor_free(res);
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return NULL;
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/* LCOV_EXCL_STOP */
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}
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/** Return a copy of <b>dh</b>, sharing its internal state. */
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crypto_dh_t *
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crypto_dh_dup(const crypto_dh_t *dh)
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{
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crypto_dh_t *dh_new = tor_malloc_zero(sizeof(crypto_dh_t));
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tor_assert(dh);
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tor_assert(dh->dh);
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dh_new->dh = dh->dh;
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DH_up_ref(dh->dh);
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return dh_new;
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}
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/** Return the length of the DH key in <b>dh</b>, in bytes.
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*/
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int
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crypto_dh_get_bytes(crypto_dh_t *dh)
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{
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tor_assert(dh);
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return DH_size(dh->dh);
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}
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/** Generate \<x,g^x\> for our part of the key exchange. Return 0 on
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* success, -1 on failure.
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*/
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int
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crypto_dh_generate_public(crypto_dh_t *dh)
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{
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#ifndef OPENSSL_1_1_API
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again:
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#endif
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if (!DH_generate_key(dh->dh)) {
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/* LCOV_EXCL_START
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* To test this we would need some way to tell openssl to break DH. */
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crypto_openssl_log_errors(LOG_WARN, "generating DH key");
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return -1;
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/* LCOV_EXCL_STOP */
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}
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#ifdef OPENSSL_1_1_API
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/* OpenSSL 1.1.x doesn't appear to let you regenerate a DH key, without
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* recreating the DH object. I have no idea what sort of aliasing madness
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* can occur here, so do the check, and just bail on failure.
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*/
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const BIGNUM *pub_key, *priv_key;
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DH_get0_key(dh->dh, &pub_key, &priv_key);
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if (tor_check_dh_key(LOG_WARN, pub_key)<0) {
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log_warn(LD_CRYPTO, "Weird! Our own DH key was invalid. I guess once-in-"
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"the-universe chances really do happen. Treating as a failure.");
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return -1;
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}
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#else /* !(defined(OPENSSL_1_1_API)) */
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if (tor_check_dh_key(LOG_WARN, dh->dh->pub_key)<0) {
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/* LCOV_EXCL_START
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* If this happens, then openssl's DH implementation is busted. */
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log_warn(LD_CRYPTO, "Weird! Our own DH key was invalid. I guess once-in-"
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"the-universe chances really do happen. Trying again.");
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/* Free and clear the keys, so OpenSSL will actually try again. */
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BN_clear_free(dh->dh->pub_key);
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BN_clear_free(dh->dh->priv_key);
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dh->dh->pub_key = dh->dh->priv_key = NULL;
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goto again;
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/* LCOV_EXCL_STOP */
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}
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#endif /* defined(OPENSSL_1_1_API) */
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return 0;
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}
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/** Generate g^x as necessary, and write the g^x for the key exchange
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* as a <b>pubkey_len</b>-byte value into <b>pubkey</b>. Return 0 on
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* success, -1 on failure. <b>pubkey_len</b> must be \>= DH1024_KEY_LEN.
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*/
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int
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crypto_dh_get_public(crypto_dh_t *dh, char *pubkey, size_t pubkey_len)
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{
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int bytes;
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tor_assert(dh);
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const BIGNUM *dh_pub;
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#ifdef OPENSSL_1_1_API
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const BIGNUM *dh_priv;
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DH_get0_key(dh->dh, &dh_pub, &dh_priv);
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#else
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dh_pub = dh->dh->pub_key;
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#endif /* defined(OPENSSL_1_1_API) */
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if (!dh_pub) {
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if (crypto_dh_generate_public(dh)<0)
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return -1;
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else {
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#ifdef OPENSSL_1_1_API
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DH_get0_key(dh->dh, &dh_pub, &dh_priv);
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#else
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dh_pub = dh->dh->pub_key;
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#endif
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}
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}
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tor_assert(dh_pub);
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bytes = BN_num_bytes(dh_pub);
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tor_assert(bytes >= 0);
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if (pubkey_len < (size_t)bytes) {
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log_warn(LD_CRYPTO,
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"Weird! pubkey_len (%d) was smaller than DH1024_KEY_LEN (%d)",
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(int) pubkey_len, bytes);
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return -1;
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}
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memset(pubkey, 0, pubkey_len);
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BN_bn2bin(dh_pub, (unsigned char*)(pubkey+(pubkey_len-bytes)));
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return 0;
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}
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/** Check for bad Diffie-Hellman public keys (g^x). Return 0 if the key is
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* okay (in the subgroup [2,p-2]), or -1 if it's bad.
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* See http://www.cl.cam.ac.uk/ftp/users/rja14/psandqs.ps.gz for some tips.
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*/
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static int
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tor_check_dh_key(int severity, const BIGNUM *bn)
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{
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BIGNUM *x;
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char *s;
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tor_assert(bn);
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x = BN_new();
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tor_assert(x);
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if (BUG(!dh_param_p))
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init_dh_param(); //LCOV_EXCL_LINE we already checked whether we did this.
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BN_set_word(x, 1);
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if (BN_cmp(bn,x)<=0) {
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log_fn(severity, LD_CRYPTO, "DH key must be at least 2.");
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goto err;
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}
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BN_copy(x,dh_param_p);
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BN_sub_word(x, 1);
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if (BN_cmp(bn,x)>=0) {
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log_fn(severity, LD_CRYPTO, "DH key must be at most p-2.");
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goto err;
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}
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BN_clear_free(x);
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return 0;
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err:
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BN_clear_free(x);
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s = BN_bn2hex(bn);
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log_fn(severity, LD_CRYPTO, "Rejecting insecure DH key [%s]", s);
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OPENSSL_free(s);
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return -1;
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}
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/** Given a DH key exchange object, and our peer's value of g^y (as a
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* <b>pubkey_len</b>-byte value in <b>pubkey</b>) generate
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* <b>secret_bytes_out</b> bytes of shared key material and write them
|
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* to <b>secret_out</b>. Return the number of bytes generated on success,
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* or -1 on failure.
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*
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* (We generate key material by computing
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* SHA1( g^xy || "\x00" ) || SHA1( g^xy || "\x01" ) || ...
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* where || is concatenation.)
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*/
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ssize_t
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crypto_dh_compute_secret(int severity, crypto_dh_t *dh,
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const char *pubkey, size_t pubkey_len,
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char *secret_out, size_t secret_bytes_out)
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{
|
||||
char *secret_tmp = NULL;
|
||||
BIGNUM *pubkey_bn = NULL;
|
||||
size_t secret_len=0, secret_tmp_len=0;
|
||||
int result=0;
|
||||
tor_assert(dh);
|
||||
tor_assert(secret_bytes_out/DIGEST_LEN <= 255);
|
||||
tor_assert(pubkey_len < INT_MAX);
|
||||
|
||||
if (!(pubkey_bn = BN_bin2bn((const unsigned char*)pubkey,
|
||||
(int)pubkey_len, NULL)))
|
||||
goto error;
|
||||
if (tor_check_dh_key(severity, pubkey_bn)<0) {
|
||||
/* Check for invalid public keys. */
|
||||
log_fn(severity, LD_CRYPTO,"Rejected invalid g^x");
|
||||
goto error;
|
||||
}
|
||||
secret_tmp_len = crypto_dh_get_bytes(dh);
|
||||
secret_tmp = tor_malloc(secret_tmp_len);
|
||||
result = DH_compute_key((unsigned char*)secret_tmp, pubkey_bn, dh->dh);
|
||||
if (result < 0) {
|
||||
log_warn(LD_CRYPTO,"DH_compute_key() failed.");
|
||||
goto error;
|
||||
}
|
||||
secret_len = result;
|
||||
if (crypto_expand_key_material_TAP((uint8_t*)secret_tmp, secret_len,
|
||||
(uint8_t*)secret_out, secret_bytes_out)<0)
|
||||
goto error;
|
||||
secret_len = secret_bytes_out;
|
||||
|
||||
goto done;
|
||||
error:
|
||||
result = -1;
|
||||
done:
|
||||
crypto_openssl_log_errors(LOG_WARN, "completing DH handshake");
|
||||
if (pubkey_bn)
|
||||
BN_clear_free(pubkey_bn);
|
||||
if (secret_tmp) {
|
||||
memwipe(secret_tmp, 0, secret_tmp_len);
|
||||
tor_free(secret_tmp);
|
||||
}
|
||||
if (result < 0)
|
||||
return result;
|
||||
else
|
||||
return secret_len;
|
||||
}
|
||||
|
||||
/** Free a DH key exchange object.
|
||||
*/
|
||||
void
|
||||
crypto_dh_free_(crypto_dh_t *dh)
|
||||
{
|
||||
if (!dh)
|
||||
return;
|
||||
tor_assert(dh->dh);
|
||||
DH_free(dh->dh);
|
||||
tor_free(dh);
|
||||
}
|
||||
|
||||
void
|
||||
crypto_dh_free_all(void)
|
||||
{
|
||||
if (dh_param_p)
|
||||
BN_clear_free(dh_param_p);
|
||||
if (dh_param_p_tls)
|
||||
BN_clear_free(dh_param_p_tls);
|
||||
if (dh_param_g)
|
||||
BN_clear_free(dh_param_g);
|
||||
|
||||
dh_param_p = dh_param_p_tls = dh_param_g = NULL;
|
||||
}
|
||||
const char OAKLEY_PRIME_2[] =
|
||||
"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08"
|
||||
"8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B"
|
||||
"302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9"
|
||||
"A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6"
|
||||
"49286651ECE65381FFFFFFFFFFFFFFFF";
|
||||
|
||||
@ -19,6 +19,10 @@
|
||||
|
||||
typedef struct crypto_dh_t crypto_dh_t;
|
||||
|
||||
extern const unsigned DH_GENERATOR;
|
||||
extern const char TLS_DH_PRIME[];
|
||||
extern const char OAKLEY_PRIME_2[];
|
||||
|
||||
/* Key negotiation */
|
||||
#define DH_TYPE_CIRCUIT 1
|
||||
#define DH_TYPE_REND 2
|
||||
|
||||
490
src/lib/crypt_ops/crypto_dh_openssl.c
Normal file
490
src/lib/crypt_ops/crypto_dh_openssl.c
Normal file
@ -0,0 +1,490 @@
|
||||
/* Copyright (c) 2001, Matej Pfajfar.
|
||||
* Copyright (c) 2001-2004, Roger Dingledine.
|
||||
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
|
||||
* Copyright (c) 2007-2018, The Tor Project, Inc. */
|
||||
/* See LICENSE for licensing information */
|
||||
|
||||
/**
|
||||
* \file crypto_dh_openssl.c
|
||||
* \brief Implement Tor's Z_p diffie-hellman stuff for OpenSSL.
|
||||
**/
|
||||
|
||||
#include "lib/crypt_ops/compat_openssl.h"
|
||||
#include "lib/crypt_ops/crypto_dh.h"
|
||||
#include "lib/crypt_ops/crypto_digest.h"
|
||||
#include "lib/crypt_ops/crypto_hkdf.h"
|
||||
#include "lib/crypt_ops/crypto_util.h"
|
||||
#include "lib/log/log.h"
|
||||
#include "lib/log/util_bug.h"
|
||||
|
||||
DISABLE_GCC_WARNING(redundant-decls)
|
||||
|
||||
#include <openssl/dh.h>
|
||||
|
||||
ENABLE_GCC_WARNING(redundant-decls)
|
||||
|
||||
#include <openssl/bn.h>
|
||||
#include <string.h>
|
||||
|
||||
static int tor_check_dh_key(int severity, const BIGNUM *bn);
|
||||
|
||||
/** A structure to hold the first half (x, g^x) of a Diffie-Hellman handshake
|
||||
* while we're waiting for the second.*/
|
||||
struct crypto_dh_t {
|
||||
DH *dh; /**< The openssl DH object */
|
||||
};
|
||||
|
||||
/** Used by tortls.c: Get the DH* from a crypto_dh_t.
|
||||
*/
|
||||
DH *
|
||||
crypto_dh_get_dh_(crypto_dh_t *dh)
|
||||
{
|
||||
return dh->dh;
|
||||
}
|
||||
|
||||
/** Shared P parameter for our circuit-crypto DH key exchanges. */
|
||||
static BIGNUM *dh_param_p = NULL;
|
||||
/** Shared P parameter for our TLS DH key exchanges. */
|
||||
static BIGNUM *dh_param_p_tls = NULL;
|
||||
/** Shared G parameter for our DH key exchanges. */
|
||||
static BIGNUM *dh_param_g = NULL;
|
||||
|
||||
/** 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.
|
||||
*/
|
||||
static int
|
||||
crypto_validate_dh_params(const BIGNUM *p, const BIGNUM *g)
|
||||
{
|
||||
DH *dh = NULL;
|
||||
int ret = -1;
|
||||
|
||||
/* Copy into a temporary DH object, just so that DH_check() can be called. */
|
||||
if (!(dh = DH_new()))
|
||||
goto out;
|
||||
#ifdef OPENSSL_1_1_API
|
||||
BIGNUM *dh_p, *dh_g;
|
||||
if (!(dh_p = BN_dup(p)))
|
||||
goto out;
|
||||
if (!(dh_g = BN_dup(g)))
|
||||
goto out;
|
||||
if (!DH_set0_pqg(dh, dh_p, NULL, dh_g))
|
||||
goto out;
|
||||
#else /* !(defined(OPENSSL_1_1_API)) */
|
||||
if (!(dh->p = BN_dup(p)))
|
||||
goto out;
|
||||
if (!(dh->g = BN_dup(g)))
|
||||
goto out;
|
||||
#endif /* defined(OPENSSL_1_1_API) */
|
||||
|
||||
/* Perform the validation. */
|
||||
int codes = 0;
|
||||
if (!DH_check(dh, &codes))
|
||||
goto out;
|
||||
if (BN_is_word(g, DH_GENERATOR_2)) {
|
||||
/* Per https://wiki.openssl.org/index.php/Diffie-Hellman_parameters
|
||||
*
|
||||
* OpenSSL checks the prime is congruent to 11 when g = 2; while the
|
||||
* IETF's primes are congruent to 23 when g = 2.
|
||||
*/
|
||||
BN_ULONG residue = BN_mod_word(p, 24);
|
||||
if (residue == 11 || residue == 23)
|
||||
codes &= ~DH_NOT_SUITABLE_GENERATOR;
|
||||
}
|
||||
if (codes != 0) /* Specifics on why the params suck is irrelevant. */
|
||||
goto out;
|
||||
|
||||
/* Things are probably not evil. */
|
||||
ret = 0;
|
||||
|
||||
out:
|
||||
if (dh)
|
||||
DH_free(dh);
|
||||
return ret;
|
||||
}
|
||||
|
||||
/** Set the global Diffie-Hellman generator, used for both TLS and internal
|
||||
* DH stuff.
|
||||
*/
|
||||
static void
|
||||
crypto_set_dh_generator(void)
|
||||
{
|
||||
BIGNUM *generator;
|
||||
int r;
|
||||
|
||||
if (dh_param_g)
|
||||
return;
|
||||
|
||||
generator = BN_new();
|
||||
tor_assert(generator);
|
||||
|
||||
r = BN_set_word(generator, DH_GENERATOR);
|
||||
tor_assert(r);
|
||||
|
||||
dh_param_g = generator;
|
||||
}
|
||||
|
||||
/** Set the global TLS Diffie-Hellman modulus. Use the Apache mod_ssl DH
|
||||
* modulus. */
|
||||
void
|
||||
crypto_set_tls_dh_prime(void)
|
||||
{
|
||||
BIGNUM *tls_prime = NULL;
|
||||
int r;
|
||||
|
||||
/* If the space is occupied, free the previous TLS DH prime */
|
||||
if (BUG(dh_param_p_tls)) {
|
||||
/* LCOV_EXCL_START
|
||||
*
|
||||
* We shouldn't be calling this twice.
|
||||
*/
|
||||
BN_clear_free(dh_param_p_tls);
|
||||
dh_param_p_tls = NULL;
|
||||
/* LCOV_EXCL_STOP */
|
||||
}
|
||||
|
||||
tls_prime = BN_new();
|
||||
tor_assert(tls_prime);
|
||||
|
||||
r = BN_hex2bn(&tls_prime, TLS_DH_PRIME);
|
||||
tor_assert(r);
|
||||
|
||||
tor_assert(tls_prime);
|
||||
|
||||
dh_param_p_tls = tls_prime;
|
||||
crypto_set_dh_generator();
|
||||
tor_assert(0 == crypto_validate_dh_params(dh_param_p_tls, dh_param_g));
|
||||
}
|
||||
|
||||
/** Initialize dh_param_p and dh_param_g if they are not already
|
||||
* set. */
|
||||
static void
|
||||
init_dh_param(void)
|
||||
{
|
||||
BIGNUM *circuit_dh_prime;
|
||||
int r;
|
||||
if (BUG(dh_param_p && dh_param_g))
|
||||
return; // LCOV_EXCL_LINE This function isn't supposed to be called twice.
|
||||
|
||||
circuit_dh_prime = BN_new();
|
||||
tor_assert(circuit_dh_prime);
|
||||
|
||||
r = BN_hex2bn(&circuit_dh_prime, OAKLEY_PRIME_2);
|
||||
tor_assert(r);
|
||||
|
||||
/* Set the new values as the global DH parameters. */
|
||||
dh_param_p = circuit_dh_prime;
|
||||
crypto_set_dh_generator();
|
||||
tor_assert(0 == crypto_validate_dh_params(dh_param_p, dh_param_g));
|
||||
|
||||
if (!dh_param_p_tls) {
|
||||
crypto_set_tls_dh_prime();
|
||||
}
|
||||
}
|
||||
|
||||
/** Number of bits to use when choosing the x or y value in a Diffie-Hellman
|
||||
* handshake. Since we exponentiate by this value, choosing a smaller one
|
||||
* lets our handhake go faster.
|
||||
*/
|
||||
#define DH_PRIVATE_KEY_BITS 320
|
||||
|
||||
/** Allocate and return a new DH object for a key exchange. Returns NULL on
|
||||
* failure.
|
||||
*/
|
||||
crypto_dh_t *
|
||||
crypto_dh_new(int dh_type)
|
||||
{
|
||||
crypto_dh_t *res = tor_malloc_zero(sizeof(crypto_dh_t));
|
||||
|
||||
tor_assert(dh_type == DH_TYPE_CIRCUIT || dh_type == DH_TYPE_TLS ||
|
||||
dh_type == DH_TYPE_REND);
|
||||
|
||||
if (!dh_param_p)
|
||||
init_dh_param();
|
||||
|
||||
if (!(res->dh = DH_new()))
|
||||
goto err;
|
||||
|
||||
#ifdef OPENSSL_1_1_API
|
||||
BIGNUM *dh_p = NULL, *dh_g = NULL;
|
||||
|
||||
if (dh_type == DH_TYPE_TLS) {
|
||||
dh_p = BN_dup(dh_param_p_tls);
|
||||
} else {
|
||||
dh_p = BN_dup(dh_param_p);
|
||||
}
|
||||
if (!dh_p)
|
||||
goto err;
|
||||
|
||||
dh_g = BN_dup(dh_param_g);
|
||||
if (!dh_g) {
|
||||
BN_free(dh_p);
|
||||
goto err;
|
||||
}
|
||||
|
||||
if (!DH_set0_pqg(res->dh, dh_p, NULL, dh_g)) {
|
||||
goto err;
|
||||
}
|
||||
|
||||
if (!DH_set_length(res->dh, DH_PRIVATE_KEY_BITS))
|
||||
goto err;
|
||||
#else /* !(defined(OPENSSL_1_1_API)) */
|
||||
if (dh_type == DH_TYPE_TLS) {
|
||||
if (!(res->dh->p = BN_dup(dh_param_p_tls)))
|
||||
goto err;
|
||||
} else {
|
||||
if (!(res->dh->p = BN_dup(dh_param_p)))
|
||||
goto err;
|
||||
}
|
||||
|
||||
if (!(res->dh->g = BN_dup(dh_param_g)))
|
||||
goto err;
|
||||
|
||||
res->dh->length = DH_PRIVATE_KEY_BITS;
|
||||
#endif /* defined(OPENSSL_1_1_API) */
|
||||
|
||||
return res;
|
||||
|
||||
/* LCOV_EXCL_START
|
||||
* This error condition is only reached when an allocation fails */
|
||||
err:
|
||||
crypto_openssl_log_errors(LOG_WARN, "creating DH object");
|
||||
if (res->dh) DH_free(res->dh); /* frees p and g too */
|
||||
tor_free(res);
|
||||
return NULL;
|
||||
/* LCOV_EXCL_STOP */
|
||||
}
|
||||
|
||||
/** Return a copy of <b>dh</b>, sharing its internal state. */
|
||||
crypto_dh_t *
|
||||
crypto_dh_dup(const crypto_dh_t *dh)
|
||||
{
|
||||
crypto_dh_t *dh_new = tor_malloc_zero(sizeof(crypto_dh_t));
|
||||
tor_assert(dh);
|
||||
tor_assert(dh->dh);
|
||||
dh_new->dh = dh->dh;
|
||||
DH_up_ref(dh->dh);
|
||||
return dh_new;
|
||||
}
|
||||
|
||||
/** Return the length of the DH key in <b>dh</b>, in bytes.
|
||||
*/
|
||||
int
|
||||
crypto_dh_get_bytes(crypto_dh_t *dh)
|
||||
{
|
||||
tor_assert(dh);
|
||||
return DH_size(dh->dh);
|
||||
}
|
||||
|
||||
/** Generate \<x,g^x\> for our part of the key exchange. Return 0 on
|
||||
* success, -1 on failure.
|
||||
*/
|
||||
int
|
||||
crypto_dh_generate_public(crypto_dh_t *dh)
|
||||
{
|
||||
#ifndef OPENSSL_1_1_API
|
||||
again:
|
||||
#endif
|
||||
if (!DH_generate_key(dh->dh)) {
|
||||
/* LCOV_EXCL_START
|
||||
* To test this we would need some way to tell openssl to break DH. */
|
||||
crypto_openssl_log_errors(LOG_WARN, "generating DH key");
|
||||
return -1;
|
||||
/* LCOV_EXCL_STOP */
|
||||
}
|
||||
#ifdef OPENSSL_1_1_API
|
||||
/* OpenSSL 1.1.x doesn't appear to let you regenerate a DH key, without
|
||||
* recreating the DH object. I have no idea what sort of aliasing madness
|
||||
* can occur here, so do the check, and just bail on failure.
|
||||
*/
|
||||
const BIGNUM *pub_key, *priv_key;
|
||||
DH_get0_key(dh->dh, &pub_key, &priv_key);
|
||||
if (tor_check_dh_key(LOG_WARN, pub_key)<0) {
|
||||
log_warn(LD_CRYPTO, "Weird! Our own DH key was invalid. I guess once-in-"
|
||||
"the-universe chances really do happen. Treating as a failure.");
|
||||
return -1;
|
||||
}
|
||||
#else /* !(defined(OPENSSL_1_1_API)) */
|
||||
if (tor_check_dh_key(LOG_WARN, dh->dh->pub_key)<0) {
|
||||
/* LCOV_EXCL_START
|
||||
* If this happens, then openssl's DH implementation is busted. */
|
||||
log_warn(LD_CRYPTO, "Weird! Our own DH key was invalid. I guess once-in-"
|
||||
"the-universe chances really do happen. Trying again.");
|
||||
/* Free and clear the keys, so OpenSSL will actually try again. */
|
||||
BN_clear_free(dh->dh->pub_key);
|
||||
BN_clear_free(dh->dh->priv_key);
|
||||
dh->dh->pub_key = dh->dh->priv_key = NULL;
|
||||
goto again;
|
||||
/* LCOV_EXCL_STOP */
|
||||
}
|
||||
#endif /* defined(OPENSSL_1_1_API) */
|
||||
return 0;
|
||||
}
|
||||
|
||||
/** Generate g^x as necessary, and write the g^x for the key exchange
|
||||
* as a <b>pubkey_len</b>-byte value into <b>pubkey</b>. Return 0 on
|
||||
* success, -1 on failure. <b>pubkey_len</b> must be \>= DH1024_KEY_LEN.
|
||||
*/
|
||||
int
|
||||
crypto_dh_get_public(crypto_dh_t *dh, char *pubkey, size_t pubkey_len)
|
||||
{
|
||||
int bytes;
|
||||
tor_assert(dh);
|
||||
|
||||
const BIGNUM *dh_pub;
|
||||
|
||||
#ifdef OPENSSL_1_1_API
|
||||
const BIGNUM *dh_priv;
|
||||
DH_get0_key(dh->dh, &dh_pub, &dh_priv);
|
||||
#else
|
||||
dh_pub = dh->dh->pub_key;
|
||||
#endif /* defined(OPENSSL_1_1_API) */
|
||||
|
||||
if (!dh_pub) {
|
||||
if (crypto_dh_generate_public(dh)<0)
|
||||
return -1;
|
||||
else {
|
||||
#ifdef OPENSSL_1_1_API
|
||||
DH_get0_key(dh->dh, &dh_pub, &dh_priv);
|
||||
#else
|
||||
dh_pub = dh->dh->pub_key;
|
||||
#endif
|
||||
}
|
||||
}
|
||||
|
||||
tor_assert(dh_pub);
|
||||
bytes = BN_num_bytes(dh_pub);
|
||||
tor_assert(bytes >= 0);
|
||||
if (pubkey_len < (size_t)bytes) {
|
||||
log_warn(LD_CRYPTO,
|
||||
"Weird! pubkey_len (%d) was smaller than DH1024_KEY_LEN (%d)",
|
||||
(int) pubkey_len, bytes);
|
||||
return -1;
|
||||
}
|
||||
|
||||
memset(pubkey, 0, pubkey_len);
|
||||
BN_bn2bin(dh_pub, (unsigned char*)(pubkey+(pubkey_len-bytes)));
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/** Check for bad Diffie-Hellman public keys (g^x). Return 0 if the key is
|
||||
* okay (in the subgroup [2,p-2]), or -1 if it's bad.
|
||||
* See http://www.cl.cam.ac.uk/ftp/users/rja14/psandqs.ps.gz for some tips.
|
||||
*/
|
||||
static int
|
||||
tor_check_dh_key(int severity, const BIGNUM *bn)
|
||||
{
|
||||
BIGNUM *x;
|
||||
char *s;
|
||||
tor_assert(bn);
|
||||
x = BN_new();
|
||||
tor_assert(x);
|
||||
if (BUG(!dh_param_p))
|
||||
init_dh_param(); //LCOV_EXCL_LINE we already checked whether we did this.
|
||||
BN_set_word(x, 1);
|
||||
if (BN_cmp(bn,x)<=0) {
|
||||
log_fn(severity, LD_CRYPTO, "DH key must be at least 2.");
|
||||
goto err;
|
||||
}
|
||||
BN_copy(x,dh_param_p);
|
||||
BN_sub_word(x, 1);
|
||||
if (BN_cmp(bn,x)>=0) {
|
||||
log_fn(severity, LD_CRYPTO, "DH key must be at most p-2.");
|
||||
goto err;
|
||||
}
|
||||
BN_clear_free(x);
|
||||
return 0;
|
||||
err:
|
||||
BN_clear_free(x);
|
||||
s = BN_bn2hex(bn);
|
||||
log_fn(severity, LD_CRYPTO, "Rejecting insecure DH key [%s]", s);
|
||||
OPENSSL_free(s);
|
||||
return -1;
|
||||
}
|
||||
|
||||
/** Given a DH key exchange object, and our peer's value of g^y (as a
|
||||
* <b>pubkey_len</b>-byte value in <b>pubkey</b>) generate
|
||||
* <b>secret_bytes_out</b> bytes of shared key material and write them
|
||||
* to <b>secret_out</b>. Return the number of bytes generated on success,
|
||||
* or -1 on failure.
|
||||
*
|
||||
* (We generate key material by computing
|
||||
* SHA1( g^xy || "\x00" ) || SHA1( g^xy || "\x01" ) || ...
|
||||
* where || is concatenation.)
|
||||
*/
|
||||
ssize_t
|
||||
crypto_dh_compute_secret(int severity, crypto_dh_t *dh,
|
||||
const char *pubkey, size_t pubkey_len,
|
||||
char *secret_out, size_t secret_bytes_out)
|
||||
{
|
||||
char *secret_tmp = NULL;
|
||||
BIGNUM *pubkey_bn = NULL;
|
||||
size_t secret_len=0, secret_tmp_len=0;
|
||||
int result=0;
|
||||
tor_assert(dh);
|
||||
tor_assert(secret_bytes_out/DIGEST_LEN <= 255);
|
||||
tor_assert(pubkey_len < INT_MAX);
|
||||
|
||||
if (!(pubkey_bn = BN_bin2bn((const unsigned char*)pubkey,
|
||||
(int)pubkey_len, NULL)))
|
||||
goto error;
|
||||
if (tor_check_dh_key(severity, pubkey_bn)<0) {
|
||||
/* Check for invalid public keys. */
|
||||
log_fn(severity, LD_CRYPTO,"Rejected invalid g^x");
|
||||
goto error;
|
||||
}
|
||||
secret_tmp_len = crypto_dh_get_bytes(dh);
|
||||
secret_tmp = tor_malloc(secret_tmp_len);
|
||||
result = DH_compute_key((unsigned char*)secret_tmp, pubkey_bn, dh->dh);
|
||||
if (result < 0) {
|
||||
log_warn(LD_CRYPTO,"DH_compute_key() failed.");
|
||||
goto error;
|
||||
}
|
||||
secret_len = result;
|
||||
if (crypto_expand_key_material_TAP((uint8_t*)secret_tmp, secret_len,
|
||||
(uint8_t*)secret_out, secret_bytes_out)<0)
|
||||
goto error;
|
||||
secret_len = secret_bytes_out;
|
||||
|
||||
goto done;
|
||||
error:
|
||||
result = -1;
|
||||
done:
|
||||
crypto_openssl_log_errors(LOG_WARN, "completing DH handshake");
|
||||
if (pubkey_bn)
|
||||
BN_clear_free(pubkey_bn);
|
||||
if (secret_tmp) {
|
||||
memwipe(secret_tmp, 0, secret_tmp_len);
|
||||
tor_free(secret_tmp);
|
||||
}
|
||||
if (result < 0)
|
||||
return result;
|
||||
else
|
||||
return secret_len;
|
||||
}
|
||||
|
||||
/** Free a DH key exchange object.
|
||||
*/
|
||||
void
|
||||
crypto_dh_free_(crypto_dh_t *dh)
|
||||
{
|
||||
if (!dh)
|
||||
return;
|
||||
tor_assert(dh->dh);
|
||||
DH_free(dh->dh);
|
||||
tor_free(dh);
|
||||
}
|
||||
|
||||
void
|
||||
crypto_dh_free_all(void)
|
||||
{
|
||||
if (dh_param_p)
|
||||
BN_clear_free(dh_param_p);
|
||||
if (dh_param_p_tls)
|
||||
BN_clear_free(dh_param_p_tls);
|
||||
if (dh_param_g)
|
||||
BN_clear_free(dh_param_g);
|
||||
|
||||
dh_param_p = dh_param_p_tls = dh_param_g = NULL;
|
||||
}
|
||||
@ -9,6 +9,7 @@ src_lib_libtor_crypt_ops_a_SOURCES = \
|
||||
src/lib/crypt_ops/crypto_cipher.c \
|
||||
src/lib/crypt_ops/crypto_curve25519.c \
|
||||
src/lib/crypt_ops/crypto_dh.c \
|
||||
src/lib/crypt_ops/crypto_dh_openssl.c \
|
||||
src/lib/crypt_ops/crypto_digest.c \
|
||||
src/lib/crypt_ops/crypto_ed25519.c \
|
||||
src/lib/crypt_ops/crypto_format.c \
|
||||
|
||||
Loading…
Reference in New Issue
Block a user