1 files changed, 86 insertions, 0 deletions
diff --git a/wsutil/wsgcrypt.c b/wsutil/wsgcrypt.c
index 869111a214..a6d527f4bd 100644
--- a/wsutil/wsgcrypt.c
+++ b/wsutil/wsgcrypt.c
@@ -71,6 +71,92 @@ void crypt_des_ecb(guint8 *output, const guint8 *buffer, const guint8 *key56)
 	gcry_cipher_close(handle);
 }
 
+size_t rsa_decrypt_inplace(const guint len, guchar* data, gcry_sexp_t pk, gboolean pkcs1_padding, char **err)
+{
+	gint        rc = 0;
+	size_t      decr_len = 0, i = 0;
+	gcry_sexp_t s_data = NULL, s_plain = NULL;
+	gcry_mpi_t  encr_mpi = NULL, text = NULL;
+
+	*err = NULL;
+
+	/* create mpi representation of encrypted data */
+	rc = gcry_mpi_scan(&encr_mpi, GCRYMPI_FMT_USG, data, len, NULL);
+	if (rc != 0 ) {
+		*err = g_strdup_printf("can't convert data to mpi (size %d):%s", len, gcry_strerror(rc));
+		return 0;
+	}
+
+	/* put the data into a simple list */
+	rc = gcry_sexp_build(&s_data, NULL, "(enc-val(rsa(a%m)))", encr_mpi);
+	if (rc != 0) {
+		*err = g_strdup_printf("can't build encr_sexp:%s", gcry_strerror(rc));
+		decr_len = 0;
+		goto out;
+	}
+
+	/* pass it to libgcrypt */
+	rc = gcry_pk_decrypt(&s_plain, s_data, pk);
+	if (rc != 0)
+	{
+		*err = g_strdup_printf("can't decrypt key:%s", gcry_strerror(rc));
+		decr_len = 0;
+		goto out;
+	}
+
+	/* convert plain text sexp to mpi format */
+	text = gcry_sexp_nth_mpi(s_plain, 0, 0);
+	if (! text) {
+		*err = g_strdup("can't convert sexp to mpi");
+		decr_len = 0;
+		goto out;
+	}
+
+	/* compute size requested for plaintext buffer */
+	rc = gcry_mpi_print(GCRYMPI_FMT_USG, NULL, 0, &decr_len, text);
+	if (rc != 0) {
+		*err = g_strdup_printf("can't compute decr size:%s", gcry_strerror(rc));
+		decr_len = 0;
+		goto out;
+	}
+
+	/* sanity check on out buffer */
+	if (decr_len > len) {
+		*err = g_strdup_printf("decrypted data is too long ?!? (%" G_GSIZE_MODIFIER "u max %d)", decr_len, len);
+		decr_len = 0;
+		goto out;
+	}
+
+	/* write plain text to newly allocated buffer */
+	rc = gcry_mpi_print(GCRYMPI_FMT_USG, data, len, &decr_len, text);
+	if (rc != 0) {
+		*err = g_strdup_printf("can't print decr data to mpi (size %" G_GSIZE_MODIFIER "u):%s", decr_len, gcry_strerror(rc));
+		decr_len = 0;
+		goto out;
+	}
+
+	if (pkcs1_padding) {
+		/* strip the padding*/
+		rc = 0;
+		for (i = 1; i < decr_len; i++) {
+			if (data[i] == 0) {
+				rc = (gint) i+1;
+				break;
+			}
+		}
+
+		decr_len -= rc;
+		memmove(data, data+rc, decr_len);
+	}
+
+out:
+	gcry_sexp_release(s_data);
+	gcry_sexp_release(s_plain);
+	gcry_mpi_release(encr_mpi);
+	gcry_mpi_release(text);
+	return decr_len;
+}
+
 /*
  * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
  *