1 files changed, 149 insertions, 0 deletions
diff --git a/src/genrandom.c b/src/genrandom.c
new file mode 100644
index 00000000..a4baa0b2
--- /dev/null
+++ b/src/genrandom.c
@@ -0,0 +1,149 @@
+/* genrandom.c - Wrapper around gpg --gen-random
+ * Copyright (C) 2025 g10 Code GmbH
+ *
+ * This file is part of GPGME.
+ *
+ * GPGME is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * GPGME is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <https://gnu.org/licenses/>.
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include <stdlib.h>
+#include <assert.h>
+
+#include "gpgme.h"
+#include "debug.h"
+#include "context.h"
+#include "ops.h"
+
+
+static gpgme_error_t
+do_genrandom (gpgme_ctx_t ctx, gpgme_data_t dataout, size_t length, int zbase)
+{
+  gpgme_error_t err;
+  const char *argv[4];
+  char countbuf[35];
+
+  if (ctx->protocol != GPGME_PROTOCOL_OPENPGP)
+    return gpg_error (GPG_ERR_UNSUPPORTED_PROTOCOL);
+
+  err = _gpgme_op_reset (ctx, 1/*synchronous*/);
+  if (err)
+    return err;
+
+  snprintf (countbuf, sizeof countbuf, "%zu", length);
+  argv[0] = "--gen-random";
+  argv[1] = zbase? "30" : "2";
+  argv[2] = countbuf;
+  argv[3] = NULL;
+
+  err = _gpgme_engine_op_getdirect (ctx->engine, argv, dataout, 0);
+  if (!err)
+    err = _gpgme_wait_one (ctx);
+
+  return err;
+}
+
+
+/* Fill BUFFER of size BUFSIZE with random bytes retrieved from gpg.
+ * If GPGME_RANDOM_MODE_ZBASE32 is used BUFSIZE needs to be at least
+ * 31 and will be filled with a string of 30 ascii characters followed
+ * by a Nul; the remainder of the buffer is not changed.  In all other
+ * modes the entire buffer will be filled with binary data.  The
+ * function has a limit of 1024 bytes to avoid accidental overuse of
+ * the random generator. */
+gpgme_error_t
+gpgme_op_random_bytes (gpgme_ctx_t ctx, gpgme_random_mode_t mode,
+                       char *buffer, size_t bufsize)
+{
+  gpgme_error_t err = 0;
+  gpgme_data_t data = NULL;
+  char *datap = NULL;
+  size_t datalen;
+
+  TRACE_BEG  (DEBUG_CTX, "gpgme_op_random_bytes", ctx, "mode=%d size=%zu",
+              mode, bufsize);
+
+  if (!ctx || !buffer || !bufsize)
+    err = gpg_error (GPG_ERR_INV_VALUE);
+  else if (mode == GPGME_RANDOM_MODE_ZBASE32)
+    {
+      /* The output is expected to be 30 ascii characters followed by
+       * a trailing Nul. */
+      if (bufsize < 31)
+        err = gpg_error (GPG_ERR_BUFFER_TOO_SHORT);
+    }
+  else if (mode)
+    err = gpg_error (GPG_ERR_INV_VALUE);
+  else if (bufsize > 1024) /* More or an less arbitrary limit.  */
+    err = gpg_error (GPG_ERR_TOO_LARGE);
+
+  if (err)
+    goto leave;
+
+  err = gpgme_data_new (&data);
+  if (err)
+    goto leave;
+
+  err = do_genrandom (ctx, data, bufsize, (mode == GPGME_RANDOM_MODE_ZBASE32));
+  if (!err)
+    err = _gpgme_wait_one (ctx);
+  if (err)
+    goto leave;
+
+  datap = gpgme_data_release_and_get_mem (data, &datalen);
+  data = NULL;
+  if (!datap)
+    {
+      err = gpg_error_from_syserror ();
+      goto leave;
+    }
+  if (datalen > bufsize)
+    {
+      err = gpg_error (GPG_ERR_INTERNAL);
+      goto leave;
+    }
+  if (mode == GPGME_RANDOM_MODE_ZBASE32)
+    {
+      /* Strip trailing LF.  */
+      while (datalen
+             && (datap[datalen-1] == '\n' || datap[datalen-1] == '\r'))
+        datalen--;
+
+      if (datalen != 30)
+        {
+          /* 30 is the holy count, not 29, not 31 and never 32. */
+          err = gpg_error (GPG_ERR_INTERNAL);
+          goto leave;
+        }
+      memcpy (buffer, datap, datalen);
+      buffer[datalen] = 0;
+    }
+  else
+    {
+      if (datalen != bufsize)
+        {
+          err = gpg_error (GPG_ERR_INTERNAL);
+          goto leave;
+        }
+      memcpy (buffer, datap, datalen);
+    }
+
+ leave:
+  free (datap);
+  gpgme_data_release (data);
+  return TRACE_ERR (err);
+}