Add crypto_mod_exp() for GnuTLS (libgcrypt)

This allows WPS to be linked with GnuTLS.

diff --git a/src/crypto/crypto_gnutls.c b/src/crypto/crypto_gnutls.c
index 7ab54dfe066a8c73d8ebd9605fbab36d274d5a29..20cbc3518284445f251440c68243e4ba4b6e3b00 100644 (file)
--- a/src/crypto/crypto_gnutls.c
+++ b/src/crypto/crypto_gnutls.c
@@ -163,3 +163,38 @@ void aes_decrypt_deinit(void *ctx)
        gcry_cipher_close(hd);
 }
 #endif /* EAP_TLS_FUNCS */
+
+
+int crypto_mod_exp(const u8 *base, size_t base_len,
+                  const u8 *power, size_t power_len,
+                  const u8 *modulus, size_t modulus_len,
+                  u8 *result, size_t *result_len)
+{
+       gcry_mpi_t bn_base = NULL, bn_exp = NULL, bn_modulus = NULL,
+               bn_result = NULL;
+       int ret = -1;
+
+       if (gcry_mpi_scan(&bn_base, GCRYMPI_FMT_USG, base, base_len, NULL) !=
+           GPG_ERR_NO_ERROR ||
+           gcry_mpi_scan(&bn_exp, GCRYMPI_FMT_USG, power, power_len, NULL) !=
+           GPG_ERR_NO_ERROR ||
+           gcry_mpi_scan(&bn_modulus, GCRYMPI_FMT_USG, modulus, modulus_len,
+                         NULL) != GPG_ERR_NO_ERROR)
+               goto error;
+       bn_result = gcry_mpi_new(modulus_len * 8);
+
+       gcry_mpi_powm(bn_result, bn_base, bn_exp, bn_modulus);
+
+       if (gcry_mpi_print(GCRYMPI_FMT_USG, result, *result_len, result_len,
+                          bn_result) != GPG_ERR_NO_ERROR)
+               goto error;
+
+       ret = 0;
+
+error:
+       gcry_mpi_release(bn_base);
+       gcry_mpi_release(bn_exp);
+       gcry_mpi_release(bn_modulus);
+       gcry_mpi_release(bn_result);
+       return ret;
+}