1 files changed, 147 insertions, 0 deletions
diff --git a/agent/pkdecrypt.c b/agent/pkdecrypt.c
new file mode 100644
index 0000000..6aed96b
--- /dev/null
+++ b/agent/pkdecrypt.c
@@ -0,0 +1,147 @@
+/* pkdecrypt.c - public key decryption (well, actually using a secret key)
+ *	Copyright (C) 2001, 2003 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+#include "agent.h"
+
+
+/* DECRYPT the stuff in ciphertext which is expected to be a S-Exp.
+   Try to get the key from CTRL and write the decoded stuff back to
+   OUTFP.   The padding information is stored at R_PADDING with -1
+   for not known.  */
+int
+agent_pkdecrypt (ctrl_t ctrl, const char *desc_text,
+                 const unsigned char *ciphertext, size_t ciphertextlen,
+                 membuf_t *outbuf, int *r_padding)
+{
+  gcry_sexp_t s_skey = NULL, s_cipher = NULL, s_plain = NULL;
+  unsigned char *shadow_info = NULL;
+  int rc;
+  char *buf = NULL;
+  size_t len;
+
+  *r_padding = -1;
+
+  if (!ctrl->have_keygrip)
+    {
+      log_error ("speculative decryption not yet supported\n");
+      rc = gpg_error (GPG_ERR_NO_SECKEY);
+      goto leave;
+    }
+
+  rc = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
+  if (rc)
+    {
+      log_error ("failed to convert ciphertext: %s\n", gpg_strerror (rc));
+      rc = gpg_error (GPG_ERR_INV_DATA);
+      goto leave;
+    }
+
+  if (DBG_CRYPTO)
+    {
+      log_printhex (ctrl->keygrip, 20, "keygrip:");
+      log_printhex (ciphertext, ciphertextlen, "cipher: ");
+    }
+  rc = agent_key_from_file (ctrl, NULL, desc_text,
+                            ctrl->keygrip, &shadow_info,
+                            CACHE_MODE_NORMAL, NULL, &s_skey, NULL);
+  if (rc)
+    {
+      if (gpg_err_code (rc) != GPG_ERR_NO_SECKEY)
+        log_error ("failed to read the secret key\n");
+      goto leave;
+    }
+
+  if (shadow_info)
+    { /* divert operation to the smartcard */
+
+      if (!gcry_sexp_canon_len (ciphertext, ciphertextlen, NULL, NULL))
+        {
+          rc = gpg_error (GPG_ERR_INV_SEXP);
+          goto leave;
+        }
+
+      rc = divert_pkdecrypt (ctrl, desc_text, ciphertext,
+                             ctrl->keygrip, shadow_info,
+                             &buf, &len, r_padding);
+      if (rc)
+        {
+          log_error ("smartcard decryption failed: %s\n", gpg_strerror (rc));
+          goto leave;
+        }
+
+      put_membuf_printf (outbuf, "(5:value%u:", (unsigned int)len);
+      put_membuf (outbuf, buf, len);
+      put_membuf (outbuf, ")", 2);
+    }
+  else
+    { /* No smartcard, but a private key */
+/*       if (DBG_CRYPTO ) */
+/*         { */
+/*           log_debug ("skey: "); */
+/*           gcry_sexp_dump (s_skey); */
+/*         } */
+
+      rc = gcry_pk_decrypt (&s_plain, s_cipher, s_skey);
+      if (rc)
+        {
+          log_error ("decryption failed: %s\n", gpg_strerror (rc));
+          goto leave;
+        }
+
+      if (DBG_CRYPTO)
+        {
+          log_debug ("plain: ");
+          gcry_sexp_dump (s_plain);
+        }
+      len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, NULL, 0);
+      assert (len);
+      buf = xmalloc (len);
+      len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, buf, len);
+      assert (len);
+      if (*buf == '(')
+        put_membuf (outbuf, buf, len);
+      else
+        {
+          /* Old style libgcrypt: This is only an S-expression
+             part. Turn it into a complete S-expression. */
+          put_membuf (outbuf, "(5:value", 8);
+          put_membuf (outbuf, buf, len);
+          put_membuf (outbuf, ")", 2);
+        }
+    }
+
+
+ leave:
+  gcry_sexp_release (s_skey);
+  gcry_sexp_release (s_plain);
+  gcry_sexp_release (s_cipher);
+  xfree (buf);
+  xfree (shadow_info);
+  return rc;
+}