Mercurial > dropbear
view ecc.c @ 1861:2b3a8026a6ce
Add re-exec for server
This allows ASLR to re-randomize the address
space for every connection, preventing some
vulnerabilities from being exploitable by
repeated probing.
Overhead (memory and time) is yet to be confirmed.
At present this is only enabled on Linux. Other BSD platforms
with fexecve() would probably also work though have not been tested.
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Sun, 30 Jan 2022 10:14:56 +0800 |
parents | 1051e4eea25a |
children |
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#include "includes.h" #include "ecc.h" #include "dbutil.h" #include "bignum.h" #if DROPBEAR_ECC /* .dp members are filled out by dropbear_ecc_fill_dp() at startup */ #if DROPBEAR_ECC_256 struct dropbear_ecc_curve ecc_curve_nistp256 = { 32, /* .ltc_size */ NULL, /* .dp */ &sha256_desc, /* .hash_desc */ "nistp256" /* .name */ }; #endif #if DROPBEAR_ECC_384 struct dropbear_ecc_curve ecc_curve_nistp384 = { 48, /* .ltc_size */ NULL, /* .dp */ &sha384_desc, /* .hash_desc */ "nistp384" /* .name */ }; #endif #if DROPBEAR_ECC_521 struct dropbear_ecc_curve ecc_curve_nistp521 = { 66, /* .ltc_size */ NULL, /* .dp */ &sha512_desc, /* .hash_desc */ "nistp521" /* .name */ }; #endif struct dropbear_ecc_curve *dropbear_ecc_curves[] = { #if DROPBEAR_ECC_256 &ecc_curve_nistp256, #endif #if DROPBEAR_ECC_384 &ecc_curve_nistp384, #endif #if DROPBEAR_ECC_521 &ecc_curve_nistp521, #endif NULL }; void dropbear_ecc_fill_dp() { struct dropbear_ecc_curve **curve; /* libtomcrypt guarantees they're ordered by size */ const ltc_ecc_set_type *dp = ltc_ecc_sets; for (curve = dropbear_ecc_curves; *curve; curve++) { for (;dp->size > 0; dp++) { if (dp->size == (*curve)->ltc_size) { (*curve)->dp = dp; break; } } if (!(*curve)->dp) { dropbear_exit("Missing ECC params %s", (*curve)->name); } } } struct dropbear_ecc_curve* curve_for_dp(const ltc_ecc_set_type *dp) { struct dropbear_ecc_curve **curve = NULL; for (curve = dropbear_ecc_curves; *curve; curve++) { if ((*curve)->dp == dp) { break; } } assert(*curve); return *curve; } ecc_key * new_ecc_key(void) { ecc_key *key = m_malloc(sizeof(*key)); m_mp_alloc_init_multi((mp_int**)&key->pubkey.x, (mp_int**)&key->pubkey.y, (mp_int**)&key->pubkey.z, (mp_int**)&key->k, NULL); return key; } /* Copied from libtomcrypt ecc_import.c (version there is static), modified for different mp_int pointer without LTC_SOURCE */ static int ecc_is_point(const ecc_key *key) { mp_int *prime, *b, *t1, *t2; int err; m_mp_alloc_init_multi(&prime, &b, &t1, &t2, NULL); /* load prime and b */ if ((err = mp_read_radix(prime, key->dp->prime, 16)) != CRYPT_OK) { goto error; } if ((err = mp_read_radix(b, key->dp->B, 16)) != CRYPT_OK) { goto error; } /* compute y^2 */ if ((err = mp_sqr(key->pubkey.y, t1)) != CRYPT_OK) { goto error; } /* compute x^3 */ if ((err = mp_sqr(key->pubkey.x, t2)) != CRYPT_OK) { goto error; } if ((err = mp_mod(t2, prime, t2)) != CRYPT_OK) { goto error; } if ((err = mp_mul(key->pubkey.x, t2, t2)) != CRYPT_OK) { goto error; } /* compute y^2 - x^3 */ if ((err = mp_sub(t1, t2, t1)) != CRYPT_OK) { goto error; } /* compute y^2 - x^3 + 3x */ if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; } if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; } if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK) { goto error; } if ((err = mp_mod(t1, prime, t1)) != CRYPT_OK) { goto error; } while (mp_cmp_d(t1, 0) == LTC_MP_LT) { if ((err = mp_add(t1, prime, t1)) != CRYPT_OK) { goto error; } } while (mp_cmp(t1, prime) != LTC_MP_LT) { if ((err = mp_sub(t1, prime, t1)) != CRYPT_OK) { goto error; } } /* compare to b */ if (mp_cmp(t1, b) != LTC_MP_EQ) { err = CRYPT_INVALID_PACKET; } else { err = CRYPT_OK; } error: mp_clear_multi(prime, b, t1, t2, NULL); m_free(prime); m_free(b); m_free(t1); m_free(t2); return err; } /* For the "ephemeral public key octet string" in ECDH (rfc5656 section 4) */ void buf_put_ecc_raw_pubkey_string(buffer *buf, ecc_key *key) { unsigned long len = key->dp->size*2 + 1; int err; buf_putint(buf, len); err = ecc_ansi_x963_export(key, buf_getwriteptr(buf, len), &len); if (err != CRYPT_OK) { dropbear_exit("ECC error"); } buf_incrwritepos(buf, len); } /* For the "ephemeral public key octet string" in ECDH (rfc5656 section 4) */ ecc_key * buf_get_ecc_raw_pubkey(buffer *buf, const struct dropbear_ecc_curve *curve) { ecc_key *key = NULL; int ret = DROPBEAR_FAILURE; const unsigned int size = curve->dp->size; unsigned char first; TRACE(("enter buf_get_ecc_raw_pubkey")) buf_setpos(buf, 0); first = buf_getbyte(buf); if (first == 2 || first == 3) { dropbear_log(LOG_WARNING, "Dropbear doesn't support ECC point compression"); return NULL; } if (first != 4 || buf->len != 1+2*size) { TRACE(("leave, wrong size")) return NULL; } key = new_ecc_key(); key->dp = curve->dp; if (mp_from_ubin(key->pubkey.x, buf_getptr(buf, size), size) != MP_OKAY) { TRACE(("failed to read x")) goto out; } buf_incrpos(buf, size); if (mp_from_ubin(key->pubkey.y, buf_getptr(buf, size), size) != MP_OKAY) { TRACE(("failed to read y")) goto out; } buf_incrpos(buf, size); mp_set(key->pubkey.z, 1); if (ecc_is_point(key) != CRYPT_OK) { TRACE(("failed, not a point")) goto out; } /* SEC1 3.2.3.1 Check that Q != 0 */ if (mp_cmp_d(key->pubkey.x, 0) == LTC_MP_EQ) { TRACE(("failed, x == 0")) goto out; } if (mp_cmp_d(key->pubkey.y, 0) == LTC_MP_EQ) { TRACE(("failed, y == 0")) goto out; } ret = DROPBEAR_SUCCESS; out: if (ret == DROPBEAR_FAILURE) { if (key) { ecc_free(key); m_free(key); key = NULL; } } return key; } /* a modified version of libtomcrypt's "ecc_shared_secret" to output a mp_int instead. */ mp_int * dropbear_ecc_shared_secret(ecc_key *public_key, const ecc_key *private_key) { ecc_point *result = NULL; mp_int *prime = NULL, *shared_secret = NULL; int err = DROPBEAR_FAILURE; /* type valid? */ if (private_key->type != PK_PRIVATE) { goto out; } if (private_key->dp != public_key->dp) { goto out; } /* make new point */ result = ltc_ecc_new_point(); if (result == NULL) { goto out; } prime = m_malloc(sizeof(*prime)); m_mp_init(prime); if (mp_read_radix(prime, (char *)private_key->dp->prime, 16) != CRYPT_OK) { goto out; } if (ltc_mp.ecc_ptmul(private_key->k, &public_key->pubkey, result, prime, 1) != CRYPT_OK) { goto out; } shared_secret = m_malloc(sizeof(*shared_secret)); m_mp_init(shared_secret); if (mp_copy(result->x, shared_secret) != CRYPT_OK) { goto out; } mp_clear(prime); m_free(prime); ltc_ecc_del_point(result); err = DROPBEAR_SUCCESS; out: if (err == DROPBEAR_FAILURE) { dropbear_exit("ECC error"); } return shared_secret; } #endif