gpg: Systematically detect and fix signatures that are out of order.

* g10/keyedit.c (sig_comparison): New function.
(fix_key_signature_order): Merge functionality into...
(check_all_keysigs): ... this function.  Rewrite to eliminate
duplicates and use a systematic approach to detecting and moving
signatures that are out of order instead of a heuristic.
(fix_keyblock): Don't call fix_key_signature_order.  Call
check_all_keysigs instead after collapsing the uids.

--
Signed-off-by: Neal H. Walfield <neal@g10code.com>
GnuPG-bug-id: 2236
This commit is contained in:
Neal H. Walfield 2016-02-19 15:52:08 +01:00
parent 44cdb9d73f
commit 2d1d795481
1 changed files with 570 additions and 131 deletions

View File

@ -322,97 +322,584 @@ print_and_check_one_sig (KBNODE keyblock, KBNODE node,
/*
* Check the keysigs and set the flags to indicate errors.
* Returns true if error found.
*/
/* Order two signatures. The actual ordering isn't important. Our
goal is to ensure that identical signatures occur together. */
static int
check_all_keysigs (KBNODE keyblock, int only_selected, int only_selfsigs)
sig_comparison (const void *av, const void *bv)
{
KBNODE kbctx;
KBNODE node;
int inv_sigs = 0;
int no_key = 0;
int oth_err = 0;
int has_selfsig = 0;
int mis_selfsig = 0;
int selected = !only_selected;
int anyuid = 0;
u32 keyid[2];
const KBNODE an = *(const KBNODE *) av;
const KBNODE bn = *(const KBNODE *) bv;
const PKT_signature *a;
const PKT_signature *b;
int ndataa;
int ndatab;
int i;
for (kbctx = NULL; (node = walk_kbnode (keyblock, &kbctx, 0));)
assert (an->pkt->pkttype == PKT_SIGNATURE);
assert (bn->pkt->pkttype == PKT_SIGNATURE);
a = an->pkt->pkt.signature;
b = bn->pkt->pkt.signature;
if (a->digest_algo < b->digest_algo)
return -1;
if (a->digest_algo > b->digest_algo)
return 1;
ndataa = pubkey_get_nsig (a->pubkey_algo);
ndatab = pubkey_get_nsig (a->pubkey_algo);
assert (ndataa == ndatab);
for (i = 0; i < ndataa; i ++)
{
if (node->pkt->pkttype == PKT_PUBLIC_KEY)
{
if (only_selfsigs)
keyid_from_pk (node->pkt->pkt.public_key, keyid);
}
else if (node->pkt->pkttype == PKT_USER_ID)
{
PKT_user_id *uid = node->pkt->pkt.user_id;
if (only_selected)
selected = (node->flag & NODFLG_SELUID);
if (selected)
{
tty_printf ("uid ");
tty_print_utf8_string (uid->name, uid->len);
tty_printf ("\n");
if (anyuid && !has_selfsig)
mis_selfsig++;
has_selfsig = 0;
anyuid = 1;
}
}
else if (selected && node->pkt->pkttype == PKT_SIGNATURE
&& ((node->pkt->pkt.signature->sig_class & ~3) == 0x10
|| node->pkt->pkt.signature->sig_class == 0x30))
{
int selfsig;
PKT_signature *sig = node->pkt->pkt.signature;
if (only_selfsigs
&& !(keyid[0] == sig->keyid[0] && keyid[1] == sig->keyid[1]))
{
/* Not a selfsig but we want only selfsigs - skip. */
/* Static analyzer note: A claim that KEYID above has
garbage is not correct because KEYID is set from the
public key packet which is always the first packet in
a keyblock and thus parsed before this signature. */
}
else if (print_and_check_one_sig (keyblock, node, &inv_sigs,
&no_key, &oth_err, &selfsig,
0, only_selfsigs))
{
if (selfsig)
has_selfsig = 1;
}
/* Hmmm: should we update the trustdb here? */
}
int c = gcry_mpi_cmp (a->data[i], b->data[i]);
if (c != 0)
return c;
}
if (!has_selfsig)
mis_selfsig++;
if (inv_sigs)
tty_printf (ngettext("%d bad signature\n",
"%d bad signatures\n", inv_sigs), inv_sigs);
/* Okay, they are equal. */
return 0;
}
if (no_key)
tty_printf (ngettext("%d signature not checked due to a missing key\n",
"%d signatures not checked due to missing keys\n",
no_key), no_key);
/* Perform a few sanity checks on a keyblock is okay and possibly
repair some damage. Concretely:
if (oth_err)
tty_printf (ngettext("%d signature not checked due to an error\n",
"%d signatures not checked due to errors\n",
oth_err), oth_err);
- Detect duplicate signatures and remove them.
if (mis_selfsig)
tty_printf (ngettext("%d user ID without valid self-signature detected\n",
"%d user IDs without valid self-signatures detected\n",
mis_selfsig), mis_selfsig);
- Detect out of order signatures and relocate them (e.g., a sig
over user id X located under subkey Y).
return inv_sigs || no_key || oth_err || mis_selfsig;
Note: this function does not remove signatures that don't belong or
components that are not signed! (Although it would be trivial to
do so.)
If ONLY_SELFSIGS is true, then this function only reorders self
signatures (it still checks all signatures for duplicates,
however).
Returns 1 if the keyblock was modified, 0 otherwise. */
static int
check_all_keysigs (KBNODE kb, int only_selected, int only_selfsigs)
{
gpg_error_t err;
PKT_public_key *pk;
KBNODE n, n_next, *n_prevp, n2;
char *pending_desc = NULL;
PKT_public_key *issuer;
KBNODE last_printed_component;
KBNODE current_component = NULL;
int dups = 0;
int missing_issuer = 0;
int reordered = 0;
int bad_signature = 0;
int missing_selfsig = 0;
int modified = 0;
assert (kb->pkt->pkttype == PKT_PUBLIC_KEY);
pk = kb->pkt->pkt.public_key;
/* First we look for duplicates. */
{
int nsigs = 0;
KBNODE *sigs;
int i;
int last_i;
/* Count the sigs. */
for (n = kb; n; n = n->next)
if (is_deleted_kbnode (n))
continue;
else if (n->pkt->pkttype == PKT_SIGNATURE)
nsigs ++;
/* Add them all to the SIGS array. */
sigs = xmalloc_clear (sizeof (*sigs) * nsigs);
i = 0;
for (n = kb; n; n = n->next)
{
if (is_deleted_kbnode (n))
continue;
if (n->pkt->pkttype != PKT_SIGNATURE)
continue;
sigs[i] = n;
i ++;
}
assert (i == nsigs);
qsort (sigs, nsigs, sizeof (sigs[0]), sig_comparison);
last_i = 0;
for (i = 1; i < nsigs; i ++)
{
assert (sigs[last_i]);
assert (sigs[last_i]->pkt->pkttype == PKT_SIGNATURE);
assert (sigs[i]);
assert (sigs[i]->pkt->pkttype == PKT_SIGNATURE);
if (sig_comparison (&sigs[last_i], &sigs[i]) == 0)
/* They are the same. Kill the latter. */
{
if (DBG_PACKET)
{
PKT_signature *sig = sigs[i]->pkt->pkt.signature;
log_debug ("Signature appears multiple times, deleting duplicate:\n");
log_debug (" sig: class 0x%x, issuer: %s, timestamp: %s (%lld), digest: %02x %02x\n",
sig->sig_class, keystr (sig->keyid),
isotimestamp (sig->timestamp),
(long long) sig->timestamp,
sig->digest_start[0], sig->digest_start[1]);
}
/* Remove sigs[i] from the keyblock. */
{
KBNODE z, *prevp;
int to_kill = last_i;
last_i = i;
for (prevp = &kb, z = kb; z; prevp = &z->next, z = z->next)
if (z == sigs[to_kill])
break;
*prevp = sigs[to_kill]->next;
sigs[to_kill]->next = NULL;
release_kbnode (sigs[to_kill]);
sigs[to_kill] = NULL;
dups ++;
modified = 1;
}
}
else
last_i = i;
}
xfree (sigs);
}
/* Make sure the sigs occur after the component (public key, subkey,
user id) that they sign. */
issuer = NULL;
last_printed_component = NULL;
for (n_prevp = &kb, n = kb;
n;
/* If we moved n, then n_prevp is need valid. */
n_prevp = (n->next == n_next ? &n->next : n_prevp), n = n_next)
{
PACKET *p;
int processed_current_component;
PKT_signature *sig;
int rc;
int dump_sig_params = 0;
n_next = n->next;
if (is_deleted_kbnode (n))
continue;
p = n->pkt;
if (issuer && issuer != pk)
{
free_public_key (issuer);
issuer = NULL;
}
xfree (pending_desc);
pending_desc = NULL;
switch (p->pkttype)
{
case PKT_PUBLIC_KEY:
assert (p->pkt.public_key == pk);
if (only_selected && ! (n->flag & NODFLG_SELKEY))
{
current_component = NULL;
break;
}
if (DBG_PACKET)
log_debug ("public key %s: timestamp: %s (%lld)\n",
pk_keyid_str (pk),
isotimestamp (pk->timestamp),
(long long) pk->timestamp);
current_component = n;
break;
case PKT_PUBLIC_SUBKEY:
if (only_selected && ! (n->flag & NODFLG_SELKEY))
{
current_component = NULL;
break;
}
if (DBG_PACKET)
log_debug ("subkey %s: timestamp: %s (%lld)\n",
pk_keyid_str (p->pkt.public_key),
isotimestamp (p->pkt.public_key->timestamp),
(long long) p->pkt.public_key->timestamp);
current_component = n;
break;
case PKT_USER_ID:
if (only_selected && ! (n->flag & NODFLG_SELUID))
{
current_component = NULL;
break;
}
if (DBG_PACKET)
log_debug ("user id: %s\n",
p->pkt.user_id->attrib_data
? "[ photo id ]"
: p->pkt.user_id->name);
current_component = n;
break;
case PKT_SIGNATURE:
if (! current_component)
/* The current component is not selected, don't check the
sigs under it. */
break;
sig = n->pkt->pkt.signature;
pending_desc = xasprintf (" sig: class: 0x%x, issuer: %s, timestamp: %s (%lld), digest: %02x %02x",
sig->sig_class,
keystr (sig->keyid),
isotimestamp (sig->timestamp),
(long long) sig->timestamp,
sig->digest_start[0], sig->digest_start[1]);
if (keyid_cmp (pk_keyid (pk), sig->keyid) == 0)
issuer = pk;
else
/* Issuer is a different key. */
{
if (only_selfsigs)
continue;
issuer = xmalloc (sizeof (*issuer));
err = get_pubkey (issuer, sig->keyid);
if (err)
{
xfree (issuer);
issuer = NULL;
if (DBG_PACKET)
{
if (pending_desc)
log_debug ("%s", pending_desc);
log_debug (" Can't check signature allegedly issued by %s: %s\n",
keystr (sig->keyid), gpg_strerror (err));
}
missing_issuer ++;
break;
}
}
if ((err = openpgp_pk_test_algo (sig->pubkey_algo)))
{
if (DBG_PACKET && pending_desc)
log_debug ("%s", pending_desc);
tty_printf (_("can't check signature with unsupported public-key algorithm (%d): %s.\n"),
sig->pubkey_algo, gpg_strerror (err));
break;
}
if ((err = openpgp_md_test_algo (sig->digest_algo)))
{
if (DBG_PACKET && pending_desc)
log_debug ("%s", pending_desc);
tty_printf (_("can't check signature with unsupported message-digest algorithm %d: %s.\n"),
sig->digest_algo, gpg_strerror (err));
break;
}
/* We iterate over the keyblock. Most likely, the matching
component is the current component so always try that
first. */
processed_current_component = 0;
for (n2 = current_component;
n2;
n2 = (processed_current_component ? n2->next : kb),
processed_current_component = 1)
if (is_deleted_kbnode (n2))
continue;
else if (processed_current_component && n2 == current_component)
/* Don't process it twice. */
continue;
else
{
err = check_signature_over_key_or_uid (issuer, sig, kb, n2->pkt,
NULL, NULL);
if (! err)
break;
}
/* n/sig is a signature and n2 is the component (public key,
subkey or user id) that it signs, if any.
current_component is that component that it appears to
apply to (according to the ordering). */
if (current_component == n2)
{
if (DBG_PACKET)
{
log_debug ("%s", pending_desc);
log_debug (" Good signature over last key or uid!\n");
}
rc = 0;
}
else if (n2)
{
assert (n2->pkt->pkttype == PKT_USER_ID
|| n2->pkt->pkttype == PKT_PUBLIC_KEY
|| n2->pkt->pkttype == PKT_PUBLIC_SUBKEY);
if (DBG_PACKET)
{
log_debug ("%s", pending_desc);
log_debug (" Good signature out of order! (Over %s (%d) '%s')\n",
n2->pkt->pkttype == PKT_USER_ID
? "user id"
: n2->pkt->pkttype == PKT_PUBLIC_SUBKEY
? "subkey"
: "primary key",
n2->pkt->pkttype,
n2->pkt->pkttype == PKT_USER_ID
? n2->pkt->pkt.user_id->name
: pk_keyid_str (n2->pkt->pkt.public_key));
}
/* Reorder the packets: move the signature n to be just
after n2. */
/* Unlink the signature. */
assert (n_prevp);
*n_prevp = n->next;
/* Insert the sig immediately after the component. */
n->next = n2->next;
n2->next = n;
reordered ++;
modified = 1;
rc = 0;
}
else
{
if (DBG_PACKET)
{
log_debug ("%s", pending_desc);
log_debug (" Bad signature.\n");
}
if (DBG_PACKET)
dump_sig_params = 1;
bad_signature ++;
rc = GPG_ERR_BAD_SIGNATURE;
}
/* We don't cache the result here, because we haven't
completely checked that the signature is legitimate. For
instance, if we have a revocation certificate on Alice's
key signed by Bob, the signature may be good, but we
haven't checked that Bob is a designated revoker. */
/* cache_sig_result (sig, rc); */
{
int has_selfsig = 0;
if (! rc && issuer == pk)
{
if (n2->pkt->pkttype == PKT_PUBLIC_KEY
&& (/* Direct key signature. */
sig->sig_class == 0x1f
/* Key revocation signature. */
|| sig->sig_class == 0x20))
has_selfsig = 1;
if (n2->pkt->pkttype == PKT_PUBLIC_SUBKEY
&& (/* Subkey binding sig. */
sig->sig_class == 0x18
/* Subkey revocation sig. */
|| sig->sig_class == 0x28))
has_selfsig = 1;
if (n2->pkt->pkttype == PKT_USER_ID
&& (/* Certification sigs. */
sig->sig_class == 0x10
|| sig->sig_class == 0x11
|| sig->sig_class == 0x12
|| sig->sig_class == 0x13
/* Certification revocation sig. */
|| sig->sig_class == 0x30))
has_selfsig = 1;
}
if ((n2 && n2 != last_printed_component)
|| (! n2 && last_printed_component != current_component))
{
int is_reordered = n2 && n2 != current_component;
if (n2)
last_printed_component = n2;
else
last_printed_component = current_component;
if (last_printed_component->pkt->pkttype == PKT_USER_ID)
{
tty_printf ("uid ");
tty_print_utf8_string (last_printed_component
->pkt->pkt.user_id->name,
last_printed_component
->pkt->pkt.user_id->len);
}
else if (last_printed_component->pkt->pkttype
== PKT_PUBLIC_KEY)
tty_printf ("pub %s",
pk_keyid_str (last_printed_component
->pkt->pkt.public_key));
else
tty_printf ("sub %s",
pk_keyid_str (last_printed_component
->pkt->pkt.public_key));
if (is_reordered)
tty_printf (_(" (reordered signatures follow)"));
tty_printf ("\n");
}
print_one_sig (rc, kb, n, NULL, NULL, NULL, has_selfsig,
0, only_selfsigs);
}
if (dump_sig_params)
{
int i;
for (i = 0; i < pubkey_get_nsig (sig->pubkey_algo); i ++)
{
char buffer[1024];
size_t len;
char *printable;
gcry_mpi_print (GCRYMPI_FMT_USG,
buffer, sizeof (buffer), &len,
sig->data[i]);
printable = bin2hex (buffer, len, NULL);
log_info (" %d: %s\n", i, printable);
xfree (printable);
}
}
break;
default:
if (DBG_PACKET)
log_debug ("unhandled packet: %d\n", p->pkttype);
break;
}
}
xfree (pending_desc);
pending_desc = NULL;
if (issuer != pk)
free_public_key (issuer);
issuer = NULL;
/* Identify keys / uids that don't have a self-sig. */
{
int has_selfsig = 0;
PACKET *p;
PKT_signature *sig;
current_component = NULL;
for (n = kb; n; n = n->next)
{
if (is_deleted_kbnode (n))
continue;
p = n->pkt;
switch (p->pkttype)
{
case PKT_PUBLIC_KEY:
case PKT_PUBLIC_SUBKEY:
case PKT_USER_ID:
if (current_component && ! has_selfsig)
missing_selfsig ++;
current_component = n;
has_selfsig = 0;
break;
case PKT_SIGNATURE:
if (! current_component || has_selfsig)
break;
sig = n->pkt->pkt.signature;
if (! (sig->flags.checked && sig->flags.valid))
break;
if (keyid_cmp (pk_keyid (pk), sig->keyid) != 0)
/* Different issuer, couldn't be a self-sig. */
break;
if (current_component->pkt->pkttype == PKT_PUBLIC_KEY
&& (/* Direct key signature. */
sig->sig_class == 0x1f
/* Key revocation signature. */
|| sig->sig_class == 0x20))
has_selfsig = 1;
if (current_component->pkt->pkttype == PKT_PUBLIC_SUBKEY
&& (/* Subkey binding sig. */
sig->sig_class == 0x18
/* Subkey revocation sig. */
|| sig->sig_class == 0x28))
has_selfsig = 1;
if (current_component->pkt->pkttype == PKT_USER_ID
&& (/* Certification sigs. */
sig->sig_class == 0x10
|| sig->sig_class == 0x11
|| sig->sig_class == 0x12
|| sig->sig_class == 0x13
/* Certification revocation sig. */
|| sig->sig_class == 0x30))
has_selfsig = 1;
break;
default:
if (current_component && ! has_selfsig)
missing_selfsig ++;
current_component = NULL;
}
}
}
if (dups || missing_issuer || bad_signature || reordered)
tty_printf (_("key %s:\n"), pk_keyid_str (pk));
if (dups)
tty_printf (ngettext ("%d duplicate signature removed\n",
"%d duplicate signatures removed\n", dups), dups);
if (missing_issuer)
tty_printf (ngettext ("%d signature not checked due to a missing key\n",
"%d signatures not checked due to missing keys\n",
missing_issuer), missing_issuer);
if (bad_signature)
tty_printf (ngettext ("%d bad signature\n",
"%d bad signatures\n",
bad_signature), bad_signature);
if (reordered)
tty_printf (ngettext ("%d signature reordered\n",
"%d signatures reordered\n",
reordered), reordered);
if (only_selfsigs && (bad_signature || reordered))
tty_printf (_("Warning: errors found and only checked self-signatures, run 'check' to check all signatures.\n"));
return modified;
}
@ -1247,54 +1734,6 @@ change_passphrase (ctrl_t ctrl, kbnode_t keyblock)
/*
* There are some keys out (due to a bug in gnupg), where the sequence
* of the packets is wrong. This function fixes that.
* Returns: true if the keyblock has been fixed.
*
* Note: This function does not work if there is more than one user ID.
*/
static int
fix_key_signature_order (KBNODE keyblock)
{
KBNODE node, last, subkey;
int fixed = 0;
/* Locate key signatures of class 0x10..0x13 behind sub key packets. */
for (subkey = last = NULL, node = keyblock; node;
last = node, node = node->next)
{
switch (node->pkt->pkttype)
{
case PKT_PUBLIC_SUBKEY:
case PKT_SECRET_SUBKEY:
if (!subkey)
subkey = last; /* Actually it is the one before the subkey. */
break;
case PKT_SIGNATURE:
if (subkey)
{
PKT_signature *sig = node->pkt->pkt.signature;
if (sig->sig_class >= 0x10 && sig->sig_class <= 0x13)
{
log_info (_("moving a key signature to the correct place\n"));
last->next = node->next;
node->next = subkey->next;
subkey->next = node;
node = last;
fixed = 1;
}
}
break;
default:
break;
}
}
return fixed;
}
/* Fix various problems in the keyblock. Returns true if the keyblock
was changed. Note that a pointer to the keyblock must be given and
the function may change it (i.e. replacing the first node). */
@ -1303,10 +1742,10 @@ fix_keyblock (kbnode_t *keyblockp)
{
int changed = 0;
if (fix_key_signature_order (*keyblockp))
changed++;
if (collapse_uids (keyblockp))
changed++;
if (check_all_keysigs (*keyblockp, 0, 1))
changed++;
reorder_keyblock (*keyblockp);
/* If we modified the keyblock, make sure the flags are right. */
if (changed)