diff options
Diffstat (limited to 'rsa.c')
| -rw-r--r-- | rsa.c | 105 |
1 files changed, 72 insertions, 33 deletions
@@ -43,6 +43,7 @@ #include <stdio.h> #include <stdint.h> #include <stdlib.h> +#include <stddef.h> #include <string.h> #include <assert.h> @@ -99,7 +100,7 @@ void hal_rsa_set_blinding(const int onoff) * RSA key implementation. This structure type is private to this * module, anything else that needs to touch one of these just gets a * typed opaque pointer. We do, however, export the size, so that we - * can make memory allocation the caller's problem (well, maybe). + * can make memory allocation the caller's problem. */ struct rsa_key { @@ -117,14 +118,7 @@ struct rsa_key { const size_t hal_rsa_key_t_size = sizeof(struct rsa_key); /* - * In the long run we want a full RSA implementation, or enough of one - * to cover what we need in PKCS #11. For the moment, though, the - * most urgent thing is to see whether this approach to performing the - * CRT calculation works (and is any faster), followed by whether we - * can use this approach for key generation. - * - * So don't worry about whether the following functions are what we - * want in the long run, they'll probably evolve as we go. + * Error handling. */ #define lose(_code_) \ @@ -166,7 +160,7 @@ static hal_error_t unpack_fp(fp_int *bn, uint8_t *buffer, const size_t length) #if HAL_RSA_USE_MODEXP /* - * Unwrap bignums into byte arrays, feeds them into hal_modexp(), and + * Unwrap bignums into byte arrays, feed them into hal_modexp(), and * wrap result back up as a bignum. */ @@ -204,7 +198,7 @@ static hal_error_t modexp(fp_int *msg, fp_int *exp, fp_int *mod, fp_int *res) /* * Wrapper to let us export our modexp function as a replacement for - * TFM's, to avoid dragging all of the TFM montgomery code in when we + * TFM's, to avoid dragging in all of the TFM montgomery code when we * use TFM's Miller-Rabin test code. * * This code is here rather than in a separate module because of the @@ -335,6 +329,9 @@ static hal_error_t rsa_crt(struct rsa_key *key, fp_int *msg, fp_int *sig) /* * Public API for raw RSA encryption and decryption. + * + * NB: This does not handle PKCS #1.5 padding, at the moment that's up + * to the caller. */ hal_error_t hal_rsa_encrypt(hal_rsa_key_t key_, @@ -456,6 +453,51 @@ hal_error_t hal_rsa_key_load(const hal_rsa_key_type_t type, return HAL_ERROR_BAD_ARGUMENTS; } +/* + * Extract public key components. + */ + +static hal_error_t extract_component(hal_rsa_key_t key_, const size_t offset, + uint8_t *res, size_t *res_len, const size_t res_max) +{ + if (key_.key == NULL) + return HAL_ERROR_BAD_ARGUMENTS; + + fp_int *bn = (fp_int *) (((uint8_t *) key_.key) + offset); + + const size_t len = fp_unsigned_bin_size(bn); + + if (res_len != NULL) + *res_len = len; + + if (len > res_max) + return HAL_ERROR_RESULT_TOO_LONG; + + memset(res, 0, res_max); + fp_to_unsigned_bin(bn, res); + return HAL_OK; +} + +hal_error_t hal_rsa_key_get_modulus(hal_rsa_key_t key_, + uint8_t *res, size_t *res_len, const size_t res_max) +{ + return extract_component(key_, offsetof(struct rsa_key, n), res, res_len, res_max); +} + +hal_error_t hal_rsa_key_get_public_exponent(hal_rsa_key_t key_, + uint8_t *res, size_t *res_len, const size_t res_max) +{ + return extract_component(key_, offsetof(struct rsa_key, e), res, res_len, res_max); +} + +/* + * Generate a prime factor for an RSA keypair. + * + * Get random bytes, munge a few bits, and stuff into a bignum. Keep + * doing this until we find a result that's (probably) prime and for + * which result - 1 is relatively prime with respect to e. + */ + static hal_error_t find_prime(unsigned prime_length, fp_int *e, fp_int *result) { uint8_t buffer[prime_length]; @@ -464,12 +506,6 @@ static hal_error_t find_prime(unsigned prime_length, fp_int *e, fp_int *result) fp_init(&t); - /* - * Get random bytes, munge a few bits, and stuff into a bignum. - * Keep doing this until we find a result that's (probably) prime - * and for which result - 1 is relatively prime with respect to e. - */ - do { if ((err = hal_get_random(buffer, sizeof(buffer))) != HAL_OK) return err; @@ -484,6 +520,10 @@ static hal_error_t find_prime(unsigned prime_length, fp_int *e, fp_int *result) return HAL_OK; } +/* + * Generate a new RSA keypair. + */ + hal_error_t hal_rsa_key_gen(hal_rsa_key_t *key_, void *keybuf, const size_t keybuf_len, const unsigned key_length, @@ -553,6 +593,21 @@ hal_error_t hal_rsa_key_gen(hal_rsa_key_t *key_, #define ASN1_INTEGER 0x02 #define ASN1_SEQUENCE 0x30 +/* + * RSAPrivateKey fields in the required order. + */ + +#define RSAPrivateKey_fields \ + _(&version); \ + _(&key->n); \ + _(&key->e); \ + _(&key->d); \ + _(&key->p); \ + _(&key->q); \ + _(&key->dP); \ + _(&key->dQ); \ + _(&key->u); + static size_t count_length(size_t length) { size_t result = 1; @@ -682,22 +737,6 @@ static hal_error_t decode_integer(fp_int *bn, return HAL_OK; } -/* - * RSAPrivateKey fields in the required order. - */ - -#define RSAPrivateKey_fields \ - _(&version); \ - _(&key->n); \ - _(&key->e); \ - _(&key->d); \ - _(&key->p); \ - _(&key->q); \ - _(&key->dP); \ - _(&key->dQ); \ - _(&key->u); - - hal_error_t hal_rsa_key_to_der(hal_rsa_key_t key_, uint8_t *der, size_t *der_len, const size_t der_max) { |