gpg: Switch to a hash and CERT record based PKA system.

* common/dns-cert.c (get_dns_cert): Make r_key optional.
* common/pka.c: Rewrite for the new hash based lookup.
* common/t-pka.c: New.
* configure.ac: Remove option --disable-dns-pka.
(USE_DNS_PKA): Remove ac_define.
* g10/getkey.c (parse_auto_key_locate): Always include PKA.

--

Note that although PKA is now always build, it will only work if
support for looking up via DNS has not been disabled.

The new PKA only works with the IPGP DNS certtype and shall be used
only to retrieve the fingerprint and optional the key for the first
time.  Due to the security problems with DNSSEC the former assumption
to validate the key using DNSSEC is not anymore justified.  Instead an
additional layer (e.g. Trust-On-First-Use) needs to be implemented to
track change to the key.  Having a solid way of getting a key matching
a mail address is however a must have.

More work needs to go into a redefinition of the --verify-options
pka-lookups and pka-trust-increase.  The auto-key-locate mechanism
should also be able to continue key fetching with another methods once
the fingerprint has been retrieved with PKA.

Signed-off-by: Werner Koch <[email protected]>

1 files changed, 9 insertions, 6 deletions

diff --git a/common/dns-cert.c b/common/dns-cert.c
index e7be2759b..405ca293e 100644
--- a/common/dns-cert.c
+++ b/common/dns-cert.c
@@ -70,7 +70,7 @@
    returns the first CERT found with a supported type; it is expected
    that only one CERT record is used.  If WANT_CERTTYPE is one of the
    supported certtypes only records wih this certtype are considered
-   and the first found is returned.  */
+   and the first found is returned.  R_KEY is optional. */
 gpg_error_t
 get_dns_cert (const char *name, int want_certtype,
               estream_t *r_key,
@@ -84,7 +84,8 @@ get_dns_cert (const char *name, int want_certtype,
   unsigned int ctype;
   int count;
 
-  *r_key = NULL;
+  if (r_key)
+    *r_key = NULL;
   *r_fpr = NULL;
   *r_fprlen = 0;
   *r_url = NULL;
@@ -129,7 +130,7 @@ get_dns_cert (const char *name, int want_certtype,
 
       if (want_certtype && want_certtype != ctype)
         ; /* Not of the requested certtype.  */
-      else if (ctype == DNS_CERTTYPE_PGP && datalen >= 11)
+      else if (ctype == DNS_CERTTYPE_PGP && datalen >= 11 && r_key)
         {
           /* CERT type is PGP.  Gpg checks for a minimum length of 11,
              thus we do the same.  */
@@ -197,7 +198,8 @@ get_dns_cert (const char *name, int want_certtype,
   int r;
   u16 count;
 
-  *r_key = NULL;
+  if (r_key)
+    *r_key = NULL;
   *r_fpr = NULL;
   *r_fprlen = 0;
   *r_url = NULL;
@@ -292,7 +294,7 @@ get_dns_cert (const char *name, int want_certtype,
           /* 15 bytes takes us to here */
           if (want_certtype && want_certtype != ctype)
             ; /* Not of the requested certtype.  */
-          else if (ctype == DNS_CERTTYPE_PGP && dlen)
+          else if (ctype == DNS_CERTTYPE_PGP && dlen && r_key)
             {
               /* PGP type */
               *r_key = es_fopenmem_init (0, "rwb", pt, dlen);
@@ -355,7 +357,8 @@ get_dns_cert (const char *name, int want_certtype,
 #endif /*!USE_ADNS */
 #else /* !USE_DNS_CERT */
   (void)name;
-  *r_key = NULL;
+  if (r_key)
+    *r_key = NULL;
   *r_fpr = NULL;
   *r_fprlen = 0;
   *r_url = NULL;