//#define GCRYPT_DEBUG 1
-static bool libgcrypt_has_oaep;
-static const char *rsa_decrypt_sexp;
-
#ifdef GCRYPT_DEBUG
static void dump_buffer(const char *msg, unsigned char *buf, int len)
{
* don't have to initialize any random seed here, but we must initialize the
* gcrypt library. This task is performed by gcry_check_version() which can
* also check that the gcrypt library version is at least the minimal required
- * version. This function also tells us whether we have to use our own OAEP
- * padding code.
+ * version.
*/
void init_random_seed_or_die(void)
{
const char *ver, *req_ver;
ver = gcry_check_version(NULL);
- req_ver = "1.4.0";
+ req_ver = "1.5.0";
if (!gcry_check_version(req_ver)) {
PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
req_ver, ver);
exit(EXIT_FAILURE);
}
- req_ver = "1.5.0";
- if (gcry_check_version(req_ver)) {
- libgcrypt_has_oaep = true;
- rsa_decrypt_sexp = "(enc-val(flags oaep)(rsa(a %m)))";
- } else {
- libgcrypt_has_oaep = false;
- rsa_decrypt_sexp = "(enc-val(rsa(a %m)))";
- }
}
/** S-expression for the public part of an RSA key. */
#define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
/** S-expression for a private RSA key. */
#define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
-
-/* rfc 3447, appendix B.2 */
-static void mgf1(unsigned char *seed, size_t seed_len, unsigned result_len,
- unsigned char *result)
-{
- gcry_error_t gret;
- gcry_md_hd_t handle;
- size_t n;
- unsigned char *md;
- unsigned char octet_string[4], *rp = result, *end = rp + result_len;
-
- assert(result_len / HASH_SIZE < 1ULL << 31);
- gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
- assert(gret == 0);
- for (n = 0; rp < end; n++) {
- gcry_md_write(handle, seed, seed_len);
- octet_string[0] = (unsigned char)((n >> 24) & 255);
- octet_string[1] = (unsigned char)((n >> 16) & 255);
- octet_string[2] = (unsigned char)((n >> 8)) & 255;
- octet_string[3] = (unsigned char)(n & 255);
- gcry_md_write(handle, octet_string, 4);
- gcry_md_final(handle);
- md = gcry_md_read(handle, GCRY_MD_SHA1);
- memcpy(rp, md, PARA_MIN(HASH_SIZE, (int)(end - rp)));
- rp += HASH_SIZE;
- gcry_md_reset(handle);
- }
- gcry_md_close(handle);
-}
-
-/** The sha1 hash of an empty file. */
-static const unsigned char empty_hash[HASH_SIZE] =
- "\xda" "\x39" "\xa3" "\xee" "\x5e"
- "\x6b" "\x4b" "\x0d" "\x32" "\x55"
- "\xbf" "\xef" "\x95" "\x60" "\x18"
- "\x90" "\xaf" "\xd8" "\x07" "\x09";
-
-/* rfc3447, section 7.1.1 */
-static void pad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
- size_t out_len)
-{
- size_t ps_len = out_len - in_len - 2 * HASH_SIZE - 2;
- size_t n, mask_len = out_len - HASH_SIZE - 1;
- unsigned char *seed = out + 1, *db = seed + HASH_SIZE,
- *ps = db + HASH_SIZE, *one = ps + ps_len;
- unsigned char *db_mask, seed_mask[HASH_SIZE];
-
- assert(in_len <= out_len - 2 - 2 * HASH_SIZE);
- assert(out_len > 2 * HASH_SIZE + 2);
- PARA_DEBUG_LOG("padding %zu byte input -> %zu byte output\n",
- in_len, out_len);
- dump_buffer("unpadded buffer", in, in_len);
-
- out[0] = '\0';
- get_random_bytes_or_die(seed, HASH_SIZE);
- memcpy(db, empty_hash, HASH_SIZE);
- memset(ps, 0, ps_len);
- *one = 0x01;
- memcpy(one + 1, in, in_len);
- db_mask = para_malloc(mask_len);
- mgf1(seed, HASH_SIZE, mask_len, db_mask);
- for (n = 0; n < mask_len; n++)
- db[n] ^= db_mask[n];
- mgf1(db, mask_len, HASH_SIZE, seed_mask);
- for (n = 0; n < HASH_SIZE; n++)
- seed[n] ^= seed_mask[n];
- free(db_mask);
- dump_buffer("padded buffer", out, out_len);
-}
-
-/* rfc 3447, section 7.1.2 */
-static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
- size_t *out_len)
-{
- unsigned char *masked_seed = in + 1;
- unsigned char *db = in + 1 + HASH_SIZE;
- unsigned char seed[HASH_SIZE], seed_mask[HASH_SIZE];
- unsigned char *db_mask, *p;
- size_t n, mask_len = in_len - HASH_SIZE - 1;
-
- mgf1(db, mask_len, HASH_SIZE, seed_mask);
- for (n = 0; n < HASH_SIZE; n++)
- seed[n] = masked_seed[n] ^ seed_mask[n];
- db_mask = para_malloc(mask_len);
- mgf1(seed, HASH_SIZE, mask_len, db_mask);
- for (n = 0; n < mask_len; n++)
- db[n] ^= db_mask[n];
- free(db_mask);
- if (memcmp(db, empty_hash, HASH_SIZE))
- return -E_OEAP;
- for (p = db + HASH_SIZE; p < in + in_len - 1; p++)
- if (*p != '\0')
- break;
- if (p >= in + in_len - 1)
- return -E_OEAP;
- p++;
- *out_len = in + in_len - p;
- memcpy(out, p, *out_len);
- return 1;
-}
+/** S-expression for decryption. */
+#define RSA_DECRYPT_SEXP "(enc-val(flags oaep)(rsa(a %m)))"
struct asymmetric_key {
gcry_sexp_t sexp;
free(key);
}
-static int decode_rsa(gcry_sexp_t sexp, int key_size, unsigned char *outbuf,
- size_t *nbytes)
+static int decode_rsa(gcry_sexp_t sexp, unsigned char *outbuf, size_t *nbytes)
{
- int ret;
- gcry_error_t gret;
- unsigned char oaep_buf[512];
- gcry_mpi_t out_mpi;
-
- if (libgcrypt_has_oaep) {
- const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
-
- if (!p) {
- PARA_ERROR_LOG("could not get data from list\n");
- return -E_OEAP;
- }
- memcpy(outbuf, p, *nbytes);
- return 1;
- }
- out_mpi = gcry_sexp_nth_mpi(sexp, 0, GCRYMPI_FMT_USG);
- if (!out_mpi)
- return -E_SEXP_FIND;
- gret = gcry_mpi_print(GCRYMPI_FMT_USG, oaep_buf, sizeof(oaep_buf),
- nbytes, out_mpi);
- if (gret) {
- PARA_ERROR_LOG("mpi_print: %s\n", gcrypt_strerror(gret));
- ret = -E_MPI_PRINT;
- goto out_mpi_release;
- }
- /*
- * An oaep-encoded buffer always starts with at least one zero byte.
- * However, leading zeroes in an mpi are omitted in the output of
- * gcry_mpi_print() when using the GCRYMPI_FMT_USG format. The
- * alternative, GCRYMPI_FMT_STD, does not work either because here the
- * leading zero(es) might also be omitted, depending on the value of
- * the second byte.
- *
- * To circumvent this, we shift the oaep buffer to the right. But first
- * we check that the buffer actually started with a zero byte, i.e. that
- * nbytes < key_size. Otherwise a decoding error occurred.
- */
- ret = -E_SEXP_DECRYPT;
- if (*nbytes >= key_size)
- goto out_mpi_release;
- memmove(oaep_buf + key_size - *nbytes, oaep_buf, *nbytes);
- memset(oaep_buf, 0, key_size - *nbytes);
+ const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
- PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
- key_size);
- dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);
- ret = unpad_oaep(oaep_buf, key_size, outbuf, nbytes);
- if (ret < 0)
- goto out_mpi_release;
- PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
- *nbytes);
- dump_buffer("unpadded decrypted buffer", outbuf, *nbytes);
- ret = 1;
-out_mpi_release:
- gcry_mpi_release(out_mpi);
- return ret;
+ if (!p) {
+ PARA_ERROR_LOG("could not get data from list\n");
+ return -E_OEAP;
+ }
+ memcpy(outbuf, p, *nbytes);
+ return 1;
}
int priv_decrypt(const char *key_file, unsigned char *outbuf,
unsigned char *inbuf, int inlen)
{
gcry_error_t gret;
- int ret, key_size;
+ int ret;
struct asymmetric_key *priv;
gcry_mpi_t in_mpi = NULL;
gcry_sexp_t in, out, priv_key;
ret = get_private_key(key_file, &priv);
if (ret < 0)
return ret;
- key_size = ret / 8;
/* asymmetric key priv -> sexp priv_key */
ret = -E_SEXP_FIND;
goto key_release;
}
/* in_mpi -> in sexp */
- gret = gcry_sexp_build(&in, NULL, rsa_decrypt_sexp, in_mpi);
+ gret = gcry_sexp_build(&in, NULL, RSA_DECRYPT_SEXP, in_mpi);
if (gret) {
PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
ret = -E_SEXP_BUILD;
ret = -E_SEXP_DECRYPT;
goto in_release;
}
- ret = decode_rsa(out, key_size, outbuf, &nbytes);
+ ret = decode_rsa(out, outbuf, &nbytes);
if (ret < 0)
goto out_release;
PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
if (!pub_key)
return -E_SEXP_FIND;
- if (libgcrypt_has_oaep) {
- gret = gcry_sexp_build(&in, NULL,
- "(data(flags oaep)(value %b))", len, inbuf);
- } else {
- unsigned char padded_input[256];
- const size_t pad_size = 256;
- /* inbuf -> padded inbuf */
- pad_oaep(inbuf, len, padded_input, pad_size);
- /* padded inbuf -> in sexp */
- gret = gcry_sexp_build(&in, NULL,
- "(data(flags raw)(value %b))", pad_size, padded_input);
- }
+ gret = gcry_sexp_build(&in, NULL, "(data(flags oaep)(value %b))", len, inbuf);
if (gret) {
PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
ret = -E_SEXP_BUILD;
projects / paraslash.git / commitdiff