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gpg: With --auto-key-retrieve prefer WKD over keyservers.

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* g10/mainproc.c (check_sig_and_print): Print a hint on how to make
use of the preferred keyserver.  Remove keyserver lookup just by the
keyid.  Try a WKD lookup before a keyserver lookup.
--

The use of the the keyid for lookups does not make much sense anymore
since for quite some time we do have the fingerprint as part of the
signature.

GnuPG-bug-id: 4595
Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2019-07-05 09:31:58 +02:00
parent b0e8724b10
commit 96bf8f4778
No known key found for this signature in database
GPG key ID: E3FDFF218E45B72B
3 changed files with 85 additions and 57 deletions
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2
g10/keyserver.c
View file

@ -333,7 +333,7 @@ parse_keyserver_uri (const char *string,int require_scheme)
{
/* Three slashes means network path with a default host name.
This is a hack because it does not crok all possible
combiantions. We should better repalce all code bythe parser
combinations. We should better replace all code by the parser
from http.c. */
keyserver->path = xstrdup (uri+2);
}

116
g10/mainproc.c
View file

@ -1843,7 +1843,6 @@ check_sig_and_print (CTX c, kbnode_t node)
int is_revkey = 0;
char *issuer_fpr = NULL;
PKT_public_key *pk = NULL; /* The public key for the signature or NULL. */
int tried_ks_by_fpr;
const void *extrahash = NULL;
size_t extrahashlen = 0;
@ -2002,12 +2001,17 @@ check_sig_and_print (CTX c, kbnode_t node)
rc = do_check_sig (c, node, extrahash, extrahashlen,
NULL, &is_expkey, &is_revkey, &pk);
/* If the key isn't found, check for a preferred keyserver. */
if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY && sig->flags.pref_ks)
/* If the key isn't found, check for a preferred keyserver. Note
* that this is only done if honor-keyserver-url has been set. We
* test for this in the loop so that we can show info about the
* preferred keyservers. */
if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY
&& sig->flags.pref_ks)
{
const byte *p;
int seq = 0;
size_t n;
int any_pref_ks = 0;
while ((p=enum_sig_subpkt (sig->hashed,SIGSUBPKT_PREF_KS,&n,&seq,NULL)))
{
@ -2018,9 +2022,10 @@ check_sig_and_print (CTX c, kbnode_t node)
log_info(_("Key available at: ") );
print_utf8_buffer (log_get_stream(), p, n);
log_printf ("\n");
any_pref_ks = 1;
if (opt.keyserver_options.options&KEYSERVER_AUTO_KEY_RETRIEVE
&& opt.keyserver_options.options&KEYSERVER_HONOR_KEYSERVER_URL)
if ((opt.keyserver_options.options&KEYSERVER_AUTO_KEY_RETRIEVE)
&& (opt.keyserver_options.options&KEYSERVER_HONOR_KEYSERVER_URL))
{
struct keyserver_spec *spec;
@ -2029,6 +2034,10 @@ check_sig_and_print (CTX c, kbnode_t node)
{
int res;
if (DBG_LOOKUP)
log_debug ("trying auto-key-retrieve method %s\n",
"Pref-KS");
free_public_key (pk);
pk = NULL;
glo_ctrl.in_auto_key_retrieve++;
@ -2037,6 +2046,9 @@ check_sig_and_print (CTX c, kbnode_t node)
if (!res)
rc = do_check_sig (c, node, extrahash, extrahashlen,
NULL, &is_expkey, &is_revkey, &pk);
else if (DBG_LOOKUP)
log_debug ("lookup via %s failed: %s\n", "Pref-KS",
gpg_strerror (res));
free_keyserver_spec (spec);
if (!rc)
@ -2044,10 +2056,44 @@ check_sig_and_print (CTX c, kbnode_t node)
}
}
}
if (any_pref_ks
&& (opt.keyserver_options.options&KEYSERVER_AUTO_KEY_RETRIEVE)
&& !(opt.keyserver_options.options&KEYSERVER_HONOR_KEYSERVER_URL))
log_info (_("Note: Use '%s' to make use of this info\n"),
"--keyserver-option honor-keyserver-url");
}
/* If the above methods didn't work, our next try is to retrieve the
* key from the WKD. This requires that WKD is in the AKL and the
* Signer's UID is in the signature. */
if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY
&& (opt.keyserver_options.options & KEYSERVER_AUTO_KEY_RETRIEVE)
&& !opt.flags.disable_signer_uid
&& akl_has_wkd_method ()
&& sig->signers_uid)
{
int res;
if (DBG_LOOKUP)
log_debug ("trying auto-key-retrieve method %s\n", "WKD");
free_public_key (pk);
pk = NULL;
glo_ctrl.in_auto_key_retrieve++;
res = keyserver_import_wkd (c->ctrl, sig->signers_uid, 1, NULL, NULL);
glo_ctrl.in_auto_key_retrieve--;
/* Fixme: If the fingerprint is embedded in the signature,
* compare it to the fingerprint of the returned key. */
if (!res)
rc = do_check_sig (c, node, extrahash, extrahashlen,
NULL, &is_expkey, &is_revkey, &pk);
else if (DBG_LOOKUP)
log_debug ("lookup via %s failed: %s\n", "WKD", gpg_strerror (res));
}
/* If the avove methods didn't work, our next try is to use the URI
* from a DNS PKA record. */
* from a DNS PKA record. This is a legacy method which will
* eventually be removed. */
if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY
&& (opt.keyserver_options.options & KEYSERVER_AUTO_KEY_RETRIEVE)
&& (opt.keyserver_options.options & KEYSERVER_HONOR_PKA_RECORD))
@ -2064,6 +2110,9 @@ check_sig_and_print (CTX c, kbnode_t node)
spec = parse_keyserver_uri (uri, 1);
if (spec)
{
if (DBG_LOOKUP)
log_debug ("trying auto-key-retrieve method %s\n", "PKA");
free_public_key (pk);
pk = NULL;
glo_ctrl.in_auto_key_retrieve++;
@ -2073,16 +2122,16 @@ check_sig_and_print (CTX c, kbnode_t node)
if (!res)
rc = do_check_sig (c, node, extrahash, extrahashlen,
NULL, &is_expkey, &is_revkey, &pk);
else if (DBG_LOOKUP)
log_debug ("lookup via %s failed: %s\n", "PKA",
gpg_strerror (res));
}
}
}
/* If the above methods didn't work, our next try is to locate
* the key via its fingerprint from a keyserver. This requires
* that the signers fingerprint is encoded in the signature. We
* favor this over the WKD method (to be tried next), because an
* arbitrary keyserver is less subject to web bug like monitoring. */
tried_ks_by_fpr = 0;
* that the signers fingerprint is encoded in the signature. */
if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY
&& (opt.keyserver_options.options&KEYSERVER_AUTO_KEY_RETRIEVE)
&& keyserver_any_configured (c->ctrl))
@ -2094,60 +2143,23 @@ check_sig_and_print (CTX c, kbnode_t node)
p = issuer_fpr_raw (sig, &n);
if (p)
{
if (DBG_LOOKUP)
log_debug ("trying auto-key-retrieve method %s\n", "KS");
/* v4 or v5 packet with a SHA-1/256 fingerprint. */
free_public_key (pk);
pk = NULL;
glo_ctrl.in_auto_key_retrieve++;
res = keyserver_import_fprint (c->ctrl, p, n, opt.keyserver, 1);
tried_ks_by_fpr = 1;
glo_ctrl.in_auto_key_retrieve--;
if (!res)
rc = do_check_sig (c, node, extrahash, extrahashlen,
NULL, &is_expkey, &is_revkey, &pk);
else if (DBG_LOOKUP)
log_debug ("lookup via %s failed: %s\n", "KS", gpg_strerror (res));
}
}
/* If the above methods didn't work, our next try is to retrieve the
* key from the WKD. */
if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY
&& (opt.keyserver_options.options & KEYSERVER_AUTO_KEY_RETRIEVE)
&& !opt.flags.disable_signer_uid
&& akl_has_wkd_method ()
&& sig->signers_uid)
{
int res;
free_public_key (pk);
pk = NULL;
glo_ctrl.in_auto_key_retrieve++;
res = keyserver_import_wkd (c->ctrl, sig->signers_uid, 1, NULL, NULL);
glo_ctrl.in_auto_key_retrieve--;
/* Fixme: If the fingerprint is embedded in the signature,
* compare it to the fingerprint of the returned key. */
if (!res)
rc = do_check_sig (c, node, extrahash, extrahashlen,
NULL, &is_expkey, &is_revkey, &pk);
}
/* If the above methods did't work, our next try is to use a
* keyserver. */
if (gpg_err_code (rc) == GPG_ERR_NO_PUBKEY
&& (opt.keyserver_options.options&KEYSERVER_AUTO_KEY_RETRIEVE)
&& !tried_ks_by_fpr
&& keyserver_any_configured (c->ctrl))
{
int res;
free_public_key (pk);
pk = NULL;
glo_ctrl.in_auto_key_retrieve++;
res = keyserver_import_keyid (c->ctrl, sig->keyid, opt.keyserver, 1);
glo_ctrl.in_auto_key_retrieve--;
if (!res)
rc = do_check_sig (c, node, extrahash, extrahashlen,
NULL, &is_expkey, &is_revkey, &pk);
}
if (!rc || gpg_err_code (rc) == GPG_ERR_BAD_SIGNATURE)
{
kbnode_t un, keyblock;