//#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)
{
}
/*
- * This is called at the beginning of every program that uses libgcrypt. We
- * don't have to initialize any random seed here, but the call to gcry_control
- * is necessary to avoid warnings of the form "missing initialization - please
- * fix the application".
+ * This is called at the beginning of every program that uses libgcrypt. We
+ * 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.
*/
void init_random_seed_or_die(void)
{
- gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
+ const char *ver, *req_ver;
+
+ ver = gcry_check_version(NULL);
+ req_ver = "1.4.0";
+ 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. */
/* rfc 3447, section 7.1.2 */
static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
size_t *out_len)
-{ int ret;
+{
unsigned char *masked_seed = in + 1;
unsigned char *db = in + 1 + HASH_SIZE;
unsigned char seed[HASH_SIZE], seed_mask[HASH_SIZE];
p++;
*out_len = in + in_len - p;
memcpy(out, p, *out_len);
- return ret;
+ return 1;
}
struct asymmetric_key {
key = para_malloc(sizeof(*key));
key->sexp = sexp;
*result = key;
- ret = n_size * 8;
+ ret = n_size;
PARA_INFO_LOG("successfully read %u bit asn public key\n", n_size * 8);
release_e:
free(key);
}
+static int decode_rsa(gcry_sexp_t sexp, int key_size, 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);
+
+ 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;
+}
+
int priv_decrypt(const char *key_file, unsigned char *outbuf,
unsigned char *inbuf, int inlen)
{
gcry_error_t gret;
int ret, key_size;
struct asymmetric_key *priv;
- gcry_mpi_t in_mpi = NULL, out_mpi = NULL;
+ gcry_mpi_t in_mpi = NULL;
gcry_sexp_t in, out, priv_key;
size_t nbytes;
- unsigned char oaep_buf[512];
PARA_INFO_LOG("decrypting %d byte input\n", inlen);
/* key_file -> asymmetric key priv */
ret = -E_MPI_SCAN;
goto key_release;
}
-
/* in_mpi -> in sexp */
- gret = gcry_sexp_build(&in, NULL, "(enc-val(rsa(a %m)))", 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;
}
- out_mpi = gcry_sexp_nth_mpi(out, 0, GCRYMPI_FMT_USG);
- if (!out_mpi) {
- ret = -E_SEXP_FIND;
+ ret = decode_rsa(out, key_size, outbuf, &nbytes);
+ if (ret < 0)
goto out_release;
- }
- 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);
-
- PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
- key_size);
- dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);;
- unpad_oaep(oaep_buf, key_size, outbuf, &nbytes);
- PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
- nbytes);
- dump_buffer("unpadded decrypted buffer", outbuf, nbytes);;
+ PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
ret = nbytes;
- PARA_INFO_LOG("successfully decrypted %u byte message\n", ret);
-out_mpi_release:
- gcry_mpi_release(out_mpi);
out_release:
gcry_sexp_release(out);
in_release:
unsigned len, unsigned char *outbuf)
{
gcry_error_t gret;
- const size_t pad_size = 256;
gcry_sexp_t pub_key, in, out, out_a;
gcry_mpi_t out_mpi = NULL;
size_t nbytes;
int ret;
- unsigned char padded_input[256];
PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
if (!pub_key)
return -E_SEXP_FIND;
-
- /* 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);
+ 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);
+ }
if (gret) {
PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
ret = -E_SEXP_BUILD;
if (!out_a)
goto out_release;
/* convert sexp out_a -> out_mpi */
- out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_STD);
+ out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
if (!out_mpi) {
ret = -E_SEXP_FIND;
goto out_a_release;
projects / paraslash.git / blobdiff