As promised a agent which already does some things. Not very useful

yet but may be of help for using it in ther contexts.

agent/pksign.c

@@ -24,16 +24,149 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
+#include <assert.h>
 #include <unistd.h>
 
 #include "agent.h"
 
 
-/* SIGN whatever information we have accumulated in CTRL and write it back to 
-   OUTFP. */
+static int
+do_encode_md (const unsigned char *digest, size_t digestlen, int algo,
+              unsigned int nbits, GCRY_MPI *r_val)
+{
+  int nframe = (nbits+7) / 8;
+  byte *frame;
+  int i, n;
+  byte asn[100];
+  size_t asnlen;
+
+  asnlen = DIM(asn);
+  if (gcry_md_algo_info (algo, GCRYCTL_GET_ASNOID, asn, &asnlen))
+    {
+      log_error ("No object identifier for algo %d\n", algo);
+      return GNUPG_Internal_Error;
+    }
+
+  if (digestlen + asnlen + 4  > nframe )
+    {
+      log_error ("can't encode a %d bit MD into a %d bits frame\n",
+                 (int)(digestlen*8), (int)nbits);
+      return GNUPG_Internal_Error;
+    }
+  
+  /* We encode the MD in this way:
+   *
+   *	   0  A PAD(n bytes)   0  ASN(asnlen bytes)  MD(len bytes)
+   *
+   * PAD consists of FF bytes.
+   */
+  frame = xtrymalloc (nframe);
+  if (!frame)
+    return GNUPG_Out_Of_Core;
+  n = 0;
+  frame[n++] = 0;
+  frame[n++] = 1; /* block type */
+  i = nframe - digestlen - asnlen -3 ;
+  assert ( i > 1 );
+  memset ( frame+n, 0xff, i ); n += i;
+  frame[n++] = 0;
+  memcpy ( frame+n, asn, asnlen ); n += asnlen;
+  memcpy ( frame+n, digest, digestlen ); n += digestlen;
+  assert ( n == nframe );
+  if (DBG_CRYPTO)
+    {
+      int j;
+      log_debug ("encoded hash:");
+      for (j=0; j < nframe; j++)
+        log_printf (" %02X", frame[j]);
+      log_printf ("\n");
+    }
+      
+  gcry_mpi_scan (r_val, GCRYMPI_FMT_USG, frame, &nframe);
+  xfree (frame);
+  return 0;
+}
+
+
+/* SIGN whatever information we have accumulated in CTRL and write it
+   back to OUTFP. */
 int
 agent_pksign (CTRL ctrl, FILE *outfp) 
 {
+  /* our sample key */
+  const char n[] = "#8732A669BB7C5057AD070EFA54E035C86DF474F7A7EBE2435"
+    "3DADEB86FFE74C32AEEF9E5C6BD7584CB572520167B3E8C89A1FA75C74FF9E938"
+    "2710F3B270B638EB96E7486491D81C53CA8A50B4E840B1C7458A4A1E52EC18D681"
+    "8A2805C9165827F77EF90D55014E4B2AF9386AE8F6462F46A547CB593ABD509311"
+    "4D3D16375F#";
+  const char e[] = "#11#";
+  const char d[] = "#07F3EBABDDDA22D7FB1E8869140D30571586D9B4370DE02213F"
+    "DD0DDAC3C24FC6BEFF0950BB0CAAD755F7AA788DA12BCF90987341AC8781CC7115"
+    "B59A115B05D9D99B3D7AF77854DC2EE6A36154512CC0EAD832601038A88E837112"
+    "AB2A39FD9FBE05E30D6FFA6F43D71C59F423CA43BC91C254A8C89673AB61F326B0"
+    "762FBC9#";
+  const char p[] = "#B2ABAD4328E66303E206C53CFBED17F18F712B1C47C966EE13DD"
+    "AA9AD3616A610ADF513F8376FA48BAE12FED64CECC1E73091A77B45119AF0FC1286A"
+    "85BD9BBD#";
+  const char q[] = "#C1B648B294BB9AEE7FEEB77C4F64E9333E4EA9A7C54D521356FB"
+    "BBB7558A0E7D6331EC7B42E3F0CD7BBBA9B7A013422F615F10DCC1E8462828BF8FC7"
+    "39C5E34B#";
+  const char  u[] = "#A9B5EFF9C80A4A356B9A95EB63E381B262071E5CE9C1F32FF03"
+    "83AD8289BED8BC690555E54411FA2FDB9B49638A21B2046C325F5633B4B1ECABEBFD"
+    "1B3519072#";
 
-  return -1;
+  GCRY_SEXP s_skey, s_hash, s_sig;
+  GCRY_MPI frame;
+  int rc;
+  char *buf;
+  size_t len;
+
+  /* create a secret key as an sexp */
+  log_debug ("Using HARDWIRED secret key\n");
+  asprintf (&buf, "(private-key(oid.1.2.840.113549.1.1.1"
+           "(n %s)(e %s)(d %s)(p %s)(q %s)(u %s)))",
+           n, e, d, p, q, u);
+  /* asprintf does not use our allocation fucntions, so we can't
+     use our free */
+  rc = gcry_sexp_sscan (&s_skey, NULL, buf, strlen(buf));
+  free (buf);
+  if (rc)
+    {
+      log_error ("failed to build S-Exp: %s\n", gcry_strerror (rc));
+      return map_gcry_err (rc);
+    }
+  
+  /* put the hash into a sexp */
+  rc = do_encode_md (ctrl->digest.value,
+                     ctrl->digest.valuelen,
+                     ctrl->digest.algo,
+                     gcry_pk_get_nbits (s_skey),
+                     &frame);
+  if (rc)
+    {
+      /* fixme: clean up some things */
+      return rc;
+    }
+  if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) )
+    BUG ();
+
+
+  /* sign */
+  rc = gcry_pk_sign (&s_sig, s_hash, s_skey);
+  if (rc)
+    {
+      log_error ("signing failed: %s\n", gcry_strerror (rc));
+      return map_gcry_err (rc);
+    }
+
+  len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, NULL, 0);
+  assert (len);
+  buf = xmalloc (len);
+  len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, buf, len);
+  assert (len);
+
+  fwrite (buf, 1, strlen(buf), outfp);
+  return 0;
 }
+
+