#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_read_unsigned_bin(key->pubkey.x, buf_getptr(buf, size), size) != MP_OKAY) { TRACE(("failed to read x")) goto out; } buf_incrpos(buf, size); if (mp_read_unsigned_bin(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