1 files changed, 254 insertions, 0 deletions
diff --git a/util/pka.c b/util/pka.c
new file mode 100644
index 0000000..3c9e5c4
--- /dev/null
+++ b/util/pka.c
@@ -0,0 +1,254 @@
+/* pka.c - DNS Public Key Association RR access
+ * Copyright (C) 2005 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 2 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef USE_DNS_PKA
+#include <sys/types.h>
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+#endif
+#endif /* USE_DNS_PKA */
+
+#include "memory.h"
+#include "types.h"
+#include "util.h"
+
+
+#ifdef USE_DNS_PKA
+/* Parse the TXT resource record. Format is:
+
+   v=pka1;fpr=a4d94e92b0986ab5ee9dcd755de249965b0358a2;uri=string
+   
+   For simplicity white spaces are not allowed.  Because we expect to
+   use a new RRTYPE for this in the future we define the TXT really
+   strict for simplicity: No white spaces, case sensitivity of the
+   names, order must be as given above.  Only URI is optional.
+
+   This function modifies BUFFER.  On success 0 is returned, the 20
+   byte fingerprint stored at FPR and BUFFER contains the URI or an
+   empty string.
+*/
+static int
+parse_txt_record (char *buffer, unsigned char *fpr)
+{
+  char *p, *pend;
+  int i;
+
+  p = buffer;
+  pend = strchr (p, ';');
+  if (!pend)
+    return -1;
+  *pend++ = 0;
+  if (strcmp (p, "v=pka1"))
+    return -1; /* Wrong or missing version. */
+  
+  p = pend;
+  pend = strchr (p, ';');
+  if (pend)
+    *pend++ = 0;
+  if (strncmp (p, "fpr=", 4))
+    return -1; /* Missing fingerprint part. */
+  p += 4;
+  for (i=0; i < 20 && hexdigitp (p) && hexdigitp (p+1); i++, p += 2)
+    fpr[i] = xtoi_2 (p);
+  if (i != 20)
+    return -1; /* Fingerprint consists not of exactly 40 hexbytes. */
+    
+  p = pend;
+  if (!p || !*p)
+    {
+      *buffer = 0;  
+      return 0; /* Success (no URI given). */
+    }
+  if (strncmp (p, "uri=", 4))
+    return -1; /* Unknown part. */
+  p += 4;
+  /* There is an URI, copy it to the start of the buffer. */
+  while (*p)
+    *buffer++ = *p++;
+  *buffer = 0;
+  return 0;
+}
+
+
+/* For the given email ADDRESS lookup the PKA information in the DNS.
+
+   On success the 20 byte SHA-1 fingerprint is stored at FPR and the
+   URI will be returned in an allocated buffer.  Note that the URI
+   might be an zero length string as this information is optiobnal.
+   Caller must xfree the returned string.
+
+   On error NULL is returned and the 20 bytes at FPR are not
+   defined. */
+char *
+get_pka_info (const char *address, unsigned char *fpr)
+{
+  unsigned char answer[PACKETSZ];
+  int anslen;
+  int qdcount, ancount, nscount, arcount;
+  int rc;
+  unsigned char *p, *pend;
+  const char *domain;
+  char *name;
+
+
+  domain = strrchr (address, '@');
+  if (!domain || domain == address || !domain[1])
+    return NULL; /* invalid mail address given. */
+
+  name = malloc (strlen (address) + 5 + 1);
+  memcpy (name, address, domain - address);
+  strcpy (stpcpy (name + (domain-address), "._pka."), domain+1);
+
+  anslen = res_query (name, C_IN, T_TXT, answer, PACKETSZ);
+  xfree (name);
+  if (anslen < sizeof(HEADER))
+    return NULL; /* DNS resolver returned a too short answer. */
+  if ( (rc=((HEADER*)answer)->rcode) != NOERROR )
+    return NULL; /* DNS resolver returned an error. */
+
+  /* We assume that PACKETSZ is large enough and don't do dynmically
+     expansion of the buffer. */
+  if (anslen > PACKETSZ)
+    return NULL; /* DNS resolver returned a too long answer */
+
+  qdcount = ntohs (((HEADER*)answer)->qdcount);
+  ancount = ntohs (((HEADER*)answer)->ancount);
+  nscount = ntohs (((HEADER*)answer)->nscount);
+  arcount = ntohs (((HEADER*)answer)->arcount);
+
+  if (!ancount)
+    return NULL; /* Got no answer. */
+
+  p = answer + sizeof (HEADER);
+  pend = answer + anslen; /* Actually points directly behind the buffer. */
+
+  while (qdcount-- && p < pend)
+    {
+      rc = dn_skipname (p, pend);
+      if (rc == -1)
+        return NULL;
+      p += rc + QFIXEDSZ; 
+    }
+
+  if (ancount > 1)
+    return NULL; /* more than one possible gpg trustdns record - none used. */
+
+  while (ancount-- && p <= pend)
+    {
+      unsigned int type, class, txtlen, n;
+      char *buffer, *bufp;
+
+      rc = dn_skipname (p, pend);
+      if (rc == -1)
+        return NULL;
+      p += rc;
+      if (p >= pend - 10)
+        return NULL; /* RR too short. */
+
+      type = *p++ << 8;
+      type |= *p++;
+      class = *p++ << 8;
+      class |= *p++;
+      p += 4;
+      txtlen = *p++ << 8;
+      txtlen |= *p++;
+      if (type != T_TXT || class != C_IN)
+        return NULL; /* Answer does not match the query. */
+
+      buffer = bufp = xmalloc (txtlen + 1);
+      while (txtlen && p < pend)
+        {
+          for (n = *p++, txtlen--; txtlen && n && p < pend; txtlen--, n--)
+            *bufp++ = *p++;
+        }
+      *bufp = 0;
+      if (parse_txt_record (buffer, fpr))
+        {
+          xfree (buffer);
+          return NULL; /* Not a valid gpg trustdns RR. */
+        }
+      return buffer;
+    }
+
+  return NULL;
+}
+#else /* !USE_DNS_PKA */
+
+/* Dummy version of the function if we can't use the resolver
+   functions. */
+char *
+get_pka_info (const char *address, unsigned char *fpr)
+{
+  return NULL;
+}
+#endif /* !USE_DNS_PKA */
+
+
+#ifdef TEST
+int
+main(int argc,char *argv[])
+{
+  unsigned char fpr[20];
+  char *uri;
+  int i;
+
+  if (argc < 2)
+    {
+      fprintf (stderr, "usage: pka mail-addresses\n");
+      return 1;
+    }
+  argc--;
+  argv++;
+
+  for (; argc; argc--, argv++)
+    {
+      uri = get_pka_info ( *argv, fpr );
+      printf ("%s", *argv);
+      if (uri)
+        {
+          putchar (' ');
+          for (i=0; i < 20; i++)
+            printf ("%02X", fpr[i]);
+          if (*uri)
+            printf (" %s", uri);
+          xfree (uri);
+        }
+      putchar ('\n');
+    }
+  return 0;
+}
+#endif /* TEST */
+
+/*
+Local Variables:
+compile-command: "cc -DUSE_DNS_PKA -DTEST -I.. -I../include -Wall -g -o pka pka.c -lresolv libutil.a"
+End:
+*/