diff options
Diffstat (limited to 'src/lib/crypt_ops/crypto_dh.c')
| -rw-r--r-- | src/lib/crypt_ops/crypto_dh.c | 484 |
1 files changed, 43 insertions, 441 deletions
diff --git a/src/lib/crypt_ops/crypto_dh.c b/src/lib/crypt_ops/crypto_dh.c index 3e82996935..673ef311f9 100644 --- a/src/lib/crypt_ops/crypto_dh.c +++ b/src/lib/crypt_ops/crypto_dh.c @@ -7,6 +7,8 @@ /** * \file crypto_dh.c * \brief Block of functions related with DH utilities and operations. + * over Z_p. We aren't using this for any new crypto -- EC is more + * efficient. **/ #include "lib/crypt_ops/compat_openssl.h" @@ -17,411 +19,50 @@ #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> - -/** 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 */ -}; - -static int tor_check_dh_key(int severity, const BIGNUM *bn); - -/** Used by tortls.c: Get the DH* from a crypto_dh_t. - */ -DH * -crypto_dh_get_dh_(crypto_dh_t *dh) -{ - return dh->dh; -} - /** Our DH 'g' parameter */ -#define DH_GENERATOR 2 - -/** 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. +const unsigned DH_GENERATOR = 2; +/** This is the 1024-bit safe prime that Apache uses for its DH stuff; see + * modules/ssl/ssl_engine_dh.c; Apache also uses a generator of 2 with this + * prime. */ -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. +const char TLS_DH_PRIME[] = + "D67DE440CBBBDC1936D693D34AFD0AD50C84D239A45F520BB88174CB98" + "BCE951849F912E639C72FB13B4B4D7177E16D55AC179BA420B2A29FE324A" + "467A635E81FF5901377BEDDCFD33168A461AAD3B72DAE8860078045B07A7" + "DBCA7874087D1510EA9FCC9DDD330507DD62DB88AEAA747DE0F4D6E2BD68" + "B0E7393E0F24218EB3"; +/** + * This is from rfc2409, section 6.2. It's a safe prime, and + * supposedly it equals: + * 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }. */ -static void -crypto_set_dh_generator(void) -{ - BIGNUM *generator; - int r; +const char OAKLEY_PRIME_2[] = + "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08" + "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B" + "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9" + "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6" + "49286651ECE65381FFFFFFFFFFFFFFFF"; - 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); - - /* This is the 1024-bit safe prime that Apache uses for its DH stuff; see - * modules/ssl/ssl_engine_dh.c; Apache also uses a generator of 2 with this - * prime. - */ - r = BN_hex2bn(&tls_prime, - "D67DE440CBBBDC1936D693D34AFD0AD50C84D239A45F520BB88174CB98" - "BCE951849F912E639C72FB13B4B4D7177E16D55AC179BA420B2A29FE324A" - "467A635E81FF5901377BEDDCFD33168A461AAD3B72DAE8860078045B07A7" - "DBCA7874087D1510EA9FCC9DDD330507DD62DB88AEAA747DE0F4D6E2BD68" - "B0E7393E0F24218EB3"); - 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); - - /* This is from rfc2409, section 6.2. It's a safe prime, and - supposedly it equals: - 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }. - */ - r = BN_hex2bn(&circuit_dh_prime, - "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E08" - "8A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B" - "302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9" - "A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE6" - "49286651ECE65381FFFFFFFFFFFFFFFF"); - 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_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_init(void) { - 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: +#ifdef ENABLE_OPENSSL + crypto_dh_init_openssl(); #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_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; +#ifdef ENABLE_NSS + crypto_dh_init_nss(); #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) +void +crypto_dh_free_all(void) { - 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; +#ifdef ENABLE_OPENSSL + crypto_dh_free_all_openssl(); +#endif +#ifdef ENABLE_NSS + crypto_dh_free_all_nss(); +#endif } /** Given a DH key exchange object, and our peer's value of g^y (as a @@ -439,31 +80,20 @@ 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; - } + unsigned char *secret_tmp = NULL; + size_t secret_len=0, secret_tmp_len=0; 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."); + + ssize_t result = crypto_dh_handshake(severity, dh, pubkey, pubkey_len, + secret_tmp, secret_tmp_len); + if (result < 0) goto error; - } + secret_len = result; - if (crypto_expand_key_material_TAP((uint8_t*)secret_tmp, secret_len, + if (crypto_expand_key_material_TAP(secret_tmp, secret_len, (uint8_t*)secret_out, secret_bytes_out)<0) goto error; secret_len = secret_bytes_out; @@ -472,9 +102,6 @@ crypto_dh_compute_secret(int severity, crypto_dh_t *dh, error: result = -1; done: - crypto_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); @@ -484,28 +111,3 @@ crypto_dh_compute_secret(int severity, crypto_dh_t *dh, 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; -} |