gcrypt: Introduce read_openssh_bignum().

[paraslash.git] / gcrypt.c

diff --git a/gcrypt.c b/gcrypt.c
index 58fa507b6e1f96303998e0f6ba0ae47f90beb493..5d151a3cc9f7c42e6322f1748902b14281b49f1c 100644 (file)
--- a/gcrypt.c
+++ b/gcrypt.c
@@ -336,6 +336,26 @@ static int find_privkey_bignum_offset(const unsigned char *data, int len)
        return p - data;
 }
 
+static int read_openssh_bignum(unsigned char *start, unsigned char *end,
+               gcry_mpi_t *bn, unsigned *bitsp)
+{
+       gcry_error_t gret;
+       size_t nscanned;
+       unsigned bits;
+
+       gret = gcry_mpi_scan(bn, GCRYMPI_FMT_SSH, start, end - start, &nscanned);
+       if (gret) {
+               PARA_ERROR_LOG("gcry_mpi_scan: %s\n",
+                       gcry_strerror(gcry_err_code(gret)));
+               return -E_MPI_SCAN;
+       }
+       bits = (nscanned - 4 - (start[4] == '\0')) * 8;
+       if (bitsp)
+               *bitsp = bits;
+       PARA_DEBUG_LOG("scanned %u-bit bignum\n", bits);
+       return nscanned;
+}
+
 static int get_private_key(const char *key_file, struct asymmetric_key **result)
 {
        struct rsa_params params;
@@ -400,10 +420,11 @@ int apc_get_pubkey(const char *key_file, struct asymmetric_key **result)
        unsigned char *blob, *p, *end;
        int ret;
        gcry_error_t gret;
-       size_t nr_scanned, erroff, decoded_size;
+       size_t erroff, decoded_size;
        gcry_mpi_t e, n;
        gcry_sexp_t sexp;
        struct asymmetric_key *key;
+       unsigned bits;
 
        ret = decode_ssh_key(key_file, &blob, &decoded_size);
        if (ret < 0)
@@ -411,23 +432,13 @@ int apc_get_pubkey(const char *key_file, struct asymmetric_key **result)
        p = blob + ret;
        end = blob + decoded_size;
        PARA_DEBUG_LOG("scanning modulus and public exponent\n");
-       gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
-       if (gret) {
-               ret = -E_MPI_SCAN;
-               PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
+       ret = read_openssh_bignum(p, end, &e, NULL);
+       if (ret < 0)
                goto free_blob;
-       }
-       PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
-       p += nr_scanned;
-       if (p >= end)
-               goto release_e;
-       gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
-       if (gret) {
-               ret = -E_MPI_SCAN;
-               PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
+       p += ret;
+       ret = read_openssh_bignum(p, end, &n, &bits);
+       if (ret < 0)
                goto release_e;
-       }
-       PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
        gret = gcry_sexp_build(&sexp, &erroff, RSA_PUBKEY_SEXP, n, e);
        if (gret) {
                PARA_ERROR_LOG("offset %zu: %s\n", erroff,
@@ -435,12 +446,12 @@ int apc_get_pubkey(const char *key_file, struct asymmetric_key **result)
                ret = -E_SEXP_BUILD;
                goto release_n;
        }
-       ret = ROUND_DOWN(nr_scanned, 32);
-       PARA_INFO_LOG("successfully read %d bit ssh public key\n", ret * 8);
+       PARA_INFO_LOG("successfully read %u bit ssh public key\n", bits);
        key = para_malloc(sizeof(*key));
        key->num_bytes = ret;
        key->sexp = sexp;
        *result = key;
+       ret = bits;
 release_n:
        gcry_mpi_release(n);
 release_e: