Move OpenPGP OID helpers to common/.

This is needed so that the agent will be able to export and import
OpenPGP secret keys.  Add test case.

Removed unused function.

common/openpgp-oid.c

@@ -0,0 +1,227 @@
+/* openpgp-oids.c - OID helper for OpenPGP
+ * Copyright (C) 2011 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 <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "util.h"
+
+
+/* Helper for openpgp_oid_from_str.  */
+static size_t
+make_flagged_int (unsigned long value, char *buf, size_t buflen)
+{
+  int more = 0;
+  int shift;
+
+  /* fixme: figure out the number of bits in an ulong and start with
+     that value as shift (after making it a multiple of 7) a more
+     straigtforward implementation is to do it in reverse order using
+     a temporary buffer - saves a lot of compares */
+  for (more=0, shift=28; shift > 0; shift -= 7)
+    {
+      if (more || value >= (1<<shift))
+        {
+          buf[buflen++] = 0x80 | (value >> shift);
+          value -= (value >> shift) << shift;
+          more = 1;
+        }
+    }
+  buf[buflen++] = value;
+  return buflen;
+}
+
+
+/* Convert the OID given in dotted decimal form in STRING to an DER
+ * encoding and store it as an opaque value at R_MPI.  The format of
+ * the DER encoded is not a regular ASN.1 object but the modified
+ * format as used by OpenPGP for the ECC curve description.  On error
+ * the function returns and error code an NULL is stored at R_BUG.
+ * Note that scanning STRING stops at the first white space
+ * character.  */
+gpg_error_t
+openpgp_oid_from_str (const char *string, gcry_mpi_t *r_mpi)
+{
+  unsigned char *buf;
+  size_t buflen;
+  unsigned long val1, val;
+  const char *endp;
+  int arcno;
+
+  *r_mpi = NULL;
+
+  if (!string || !*string)
+    return gpg_error (GPG_ERR_INV_VALUE);
+
+  /* We can safely assume that the encoded OID is shorter than the string. */
+  buf = xtrymalloc (1 + strlen (string) + 2);
+  if (!buf)
+    return gpg_error_from_syserror ();
+  /* Save the first byte for the length.  */
+  buflen = 1;
+
+  val1 = 0; /* Avoid compiler warning.  */
+  arcno = 0;
+  do {
+    arcno++;
+    val = strtoul (string, (char**)&endp, 10);
+    if (!digitp (string) || !(*endp == '.' || !*endp))
+      {
+        xfree (buf);
+        return gpg_error (GPG_ERR_INV_OID_STRING);
+      }
+    if (*endp == '.')
+      string = endp+1;
+
+    if (arcno == 1)
+      {
+        if (val > 2)
+          break; /* Not allowed, error catched below.  */
+        val1 = val;
+      }
+    else if (arcno == 2)
+      { /* Need to combine the first two arcs in one octet.  */
+        if (val1 < 2)
+          {
+            if (val > 39)
+              {
+                xfree (buf);
+                return gpg_error (GPG_ERR_INV_OID_STRING);
+              }
+            buf[buflen++] = val1*40 + val;
+          }
+        else
+          {
+            val += 80;
+            buflen = make_flagged_int (val, buf, buflen);
+          }
+      }
+    else
+      {
+        buflen = make_flagged_int (val, buf, buflen);
+      }
+  } while (*endp == '.');
+
+  if (arcno == 1 || buflen < 2 || buflen > 254 )
+    { /* It is not possible to encode only the first arc.  */
+      xfree (buf);
+      return gpg_error (GPG_ERR_INV_OID_STRING);
+    }
+
+  *buf = buflen - 1;
+  *r_mpi = gcry_mpi_set_opaque (NULL, buf, buflen * 8);
+  if (!*r_mpi)
+    {
+      xfree (buf);
+      return gpg_error_from_syserror ();
+    }
+  return 0;
+}
+
+
+/* Return a malloced string represenation of the OID in the opaque MPI
+   A.  In case of an error NULL is returned and ERRNO is set.  */
+char *
+openpgp_oid_to_str (gcry_mpi_t a)
+{
+  const unsigned char *buf;
+  size_t length;
+  char *string, *p;
+  int n = 0;
+  unsigned long val, valmask;
+
+  valmask = (unsigned long)0xfe << (8 * (sizeof (valmask) - 1));
+
+  if (!a || !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
+    {
+      gpg_err_set_errno (EINVAL);
+      return NULL;
+    }
+
+  buf = gcry_mpi_get_opaque (a, &length);
+  length = (length+7)/8;
+
+  /* The first bytes gives the length; check consistency.  */
+  if (!length || buf[0] != length -1)
+    {
+      gpg_err_set_errno (EINVAL);
+      return NULL;
+    }
+  /* Skip length byte.  */
+  length--;
+  buf++;
+
+  /* To calculate the length of the string we can safely assume an
+     upper limit of 3 decimal characters per byte.  Two extra bytes
+     account for the special first octect */
+  string = p = xtrymalloc (length*(1+3)+2+1);
+  if (!string)
+    return NULL;
+  if (!buf || !length)
+    {
+      *p = 0;
+      return string;
+    }
+
+  if (buf[0] < 40)
+    p += sprintf (p, "0.%d", buf[n]);
+  else if (buf[0] < 80)
+    p += sprintf (p, "1.%d", buf[n]-40);
+  else {
+    val = buf[n] & 0x7f;
+    while ( (buf[n]&0x80) && ++n < length )
+      {
+        if ( (val & valmask) )
+          goto badoid;  /* Overflow.  */
+        val <<= 7;
+        val |= buf[n] & 0x7f;
+      }
+    val -= 80;
+    sprintf (p, "2.%lu", val);
+    p += strlen (p);
+  }
+  for (n++; n < length; n++)
+    {
+      val = buf[n] & 0x7f;
+      while ( (buf[n]&0x80) && ++n < length )
+        {
+          if ( (val & valmask) )
+            goto badoid;  /* Overflow.  */
+          val <<= 7;
+          val |= buf[n] & 0x7f;
+        }
+      sprintf (p, ".%lu", val);
+      p += strlen (p);
+    }
+
+  *p = 0;
+  return string;
+
+ badoid:
+  /* Return a special OID (gnu.gnupg.badoid) to indicate the error
+     case.  The OID is broken and thus we return one which can't do
+     any harm.  Formally this does not need to be a bad OID but an OID
+     with an arc that can't be represented in a 32 bit word is more
+     than likely corrupt.  */
+  xfree (string);
+  return xtrystrdup ("1.3.6.1.4.1.11591.2.12242973");
+}