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Drop subkey support from the internal OpenPGP parser
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The world of OpenPGP subkeys is scarily complicated and we're failing at
it in too many ways to count. People who need the complexity of a full
implementation can use the Sequoia backend, meanwhile this tames the
internal parser back to something we may be able to support.

Fixes: rpm-software-management#2278
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@pmatilai
pmatilai committed Nov 18, 2022
1 parent d69b94c commit 3fb23b6
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Showing 2 changed files with 21 additions and 227 deletions.
192 changes: 8 additions & 184 deletions rpmio/rpmpgp_internal.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -570,7 +570,7 @@ static int pgpCurveByOid(const uint8_t *p, int l)

static int isKey(pgpDigParams keyp)
{
return keyp->tag == PGPTAG_PUBLIC_KEY || keyp->tag == PGPTAG_PUBLIC_SUBKEY;
return keyp->tag == PGPTAG_PUBLIC_KEY;
}

static int pgpPrtPubkeyParams(uint8_t pubkey_algo,
Expand Down Expand Up @@ -889,77 +889,6 @@ static pgpDigParams pgpDigParamsNew(uint8_t tag)
return digp;
}

static int hashKey(DIGEST_CTX hash, const struct pgpPkt *pkt, int exptag)
{
int rc = -1;
if (pkt->tag == exptag) {
uint8_t head[] = {
0x99,
(pkt->blen >> 8),
(pkt->blen ),
};

rpmDigestUpdate(hash, head, 3);
rpmDigestUpdate(hash, pkt->body, pkt->blen);
rc = 0;
}
return rc;
}

static int pgpVerifySelf(pgpDigParams key, pgpDigParams selfsig,
const struct pgpPkt *all, int i)
{
int rc = -1;
DIGEST_CTX hash = NULL;

switch (selfsig->sigtype) {
case PGPSIGTYPE_SUBKEY_BINDING:
hash = rpmDigestInit(selfsig->hash_algo, 0);
if (hash) {
rc = hashKey(hash, &all[0], PGPTAG_PUBLIC_KEY);
if (!rc)
rc = hashKey(hash, &all[i-1], PGPTAG_PUBLIC_SUBKEY);
}
break;
default:
/* ignore types we can't handle */
rc = 0;
break;
}

if (hash && rc == 0)
rc = pgpVerifySignature(key, selfsig, hash);

rpmDigestFinal(hash, NULL, NULL, 0);

return rc;
}

static int parseSubkeySig(const struct pgpPkt *pkt, uint8_t tag,
pgpDigParams *params_p) {
pgpDigParams params = *params_p = NULL; /* assume failure */

if (pkt->tag != PGPTAG_SIGNATURE)
goto fail;

params = pgpDigParamsNew(tag);

if (pgpPrtSig(tag, pkt->body, pkt->blen, params))
goto fail;

if (params->sigtype != PGPSIGTYPE_SUBKEY_BINDING &&
params->sigtype != PGPSIGTYPE_SUBKEY_REVOKE)
{
goto fail;
}

*params_p = params;
return 0;
fail:
pgpDigParamsFree(params);
return -1;
}

static const size_t RPM_MAX_OPENPGP_BYTES = 65535; /* max number of bytes in a key */

int pgpPrtParams(const uint8_t * pkts, size_t pktlen, unsigned int pkttype,
Expand All @@ -968,19 +897,13 @@ int pgpPrtParams(const uint8_t * pkts, size_t pktlen, unsigned int pkttype,
const uint8_t *p = pkts;
const uint8_t *pend = pkts + pktlen;
pgpDigParams digp = NULL;
pgpDigParams selfsig = NULL;
int i = 0;
int alloced = 16; /* plenty for normal cases */
struct pgpPkt _pkt, *pkt = &_pkt;
int rc = -1; /* assume failure */
int expect = 0;
int prevtag = 0;

if (pktlen > RPM_MAX_OPENPGP_BYTES)
return rc; /* reject absurdly large data */

struct pgpPkt *all = xmalloc(alloced * sizeof(*all));
while (p < pend) {
struct pgpPkt *pkt = &all[i];
if (decodePkt(p, (pend - p), pkt))
break;

Expand All @@ -993,48 +916,16 @@ int pgpPrtParams(const uint8_t * pkts, size_t pktlen, unsigned int pkttype,
} else if (pkt->tag == PGPTAG_PUBLIC_KEY)
break;

if (expect) {
if (pkt->tag != expect)
break;
selfsig = pgpDigParamsNew(pkt->tag);
}

if (pgpPrtPkt(pkt, selfsig ? selfsig : digp))
if (pgpPrtPkt(pkt, digp))
break;

if (selfsig) {
/* subkeys must be followed by binding signature */
int xx = 1; /* assume failure */

if (!(prevtag == PGPTAG_PUBLIC_SUBKEY &&
selfsig->sigtype != PGPSIGTYPE_SUBKEY_BINDING))
xx = pgpVerifySelf(digp, selfsig, all, i);

selfsig = pgpDigParamsFree(selfsig);
if (xx)
break;
expect = 0;
}

if (pkt->tag == PGPTAG_PUBLIC_SUBKEY)
expect = PGPTAG_SIGNATURE;
prevtag = pkt->tag;

i++;
p += (pkt->body - pkt->head) + pkt->blen;
if (pkttype == PGPTAG_SIGNATURE)
break;

if (alloced <= i) {
alloced *= 2;
all = xrealloc(all, alloced * sizeof(*all));
}
}

rc = (digp && (p == pend) && expect == 0) ? 0 : -1;
rc = (digp && (p == pend)) ? 0 : -1;

free(all);
selfsig = pgpDigParamsFree(selfsig);
if (ret && rc == 0) {
*ret = digp;
} else {
Expand All @@ -1047,77 +938,10 @@ int pgpPrtParamsSubkeys(const uint8_t *pkts, size_t pktlen,
pgpDigParams mainkey, pgpDigParams **subkeys,
int *subkeysCount)
{
const uint8_t *p = pkts;
const uint8_t *pend = pkts + pktlen;
pgpDigParams *digps = NULL;
int count = 0;
int alloced = 10;
struct pgpPkt pkt;
int rc, i;

digps = xmalloc(alloced * sizeof(*digps));

while (p < pend) {
if (decodePkt(p, (pend - p), &pkt))
break;

p += (pkt.body - pkt.head) + pkt.blen;

if (pkt.tag == PGPTAG_PUBLIC_SUBKEY) {
if (count == alloced) {
alloced <<= 1;
digps = xrealloc(digps, alloced * sizeof(*digps));
}

digps[count] = pgpDigParamsNew(PGPTAG_PUBLIC_SUBKEY);
/* Copy UID from main key to subkey */
digps[count]->userid = xstrdup(mainkey->userid);

if (getKeyID(pkt.body, pkt.blen, digps[count]->signid)) {
pgpDigParamsFree(digps[count]);
continue;
}

if (pgpPrtKey(pkt.tag, pkt.body, pkt.blen, digps[count])) {
pgpDigParamsFree(digps[count]);
continue;
}

pgpDigParams subkey_sig = NULL;
if (decodePkt(p, pend - p, &pkt) ||
parseSubkeySig(&pkt, 0, &subkey_sig))
{
pgpDigParamsFree(digps[count]);
break;
}

/* Is the subkey revoked or incapable of signing? */
int ignore = subkey_sig->sigtype != PGPSIGTYPE_SUBKEY_BINDING ||
!((subkey_sig->saved & PGPDIG_SIG_HAS_KEY_FLAGS) &&
(subkey_sig->key_flags & 0x02));
if (ignore) {
pgpDigParamsFree(digps[count]);
} else {
digps[count]->key_flags = subkey_sig->key_flags;
digps[count]->saved |= PGPDIG_SIG_HAS_KEY_FLAGS;
count++;
}
p += (pkt.body - pkt.head) + pkt.blen;
pgpDigParamsFree(subkey_sig);
}
}
rc = (p == pend) ? 0 : -1;

if (rc == 0) {
*subkeys = xrealloc(digps, count * sizeof(*digps));
*subkeysCount = count;
} else {
for (i = 0; i < count; i++)
pgpDigParamsFree(digps[i]);
free(digps);
}

return rc;
/* We don't support subkeys due their complexities */
*subkeys = NULL;
*subkeysCount = 0;
return 0;
}

rpmRC pgpVerifySignature(pgpDigParams key, pgpDigParams sig, DIGEST_CTX hashctx)
Expand Down
56 changes: 13 additions & 43 deletions tests/rpmsigdig.at
View file
Original file line number Diff line number Diff line change
Expand Up @@ -510,61 +510,35 @@ Checking package after importing key, no signature:
[])
AT_CLEANUP

AT_SETUP([rpmkeys --import invalid keys])
AT_KEYWORDS([rpmkeys import])
RPMDB_INIT

# The following certificates include subkeys with errors. In general,
# all subkeys should be returned whether they are valid or not. Keys
# should only be rejected when verifying a signature. This is because
# a key's validity depends on the current time. Thus, the time to
# check for validity is when the key is used, not when it is imported.
# The internal OpenPGP implementation checks for validity when the key
# is imported; other implementations should not do this.
AT_SETUP([rpmkeys --import invalid keys])
AT_KEYWORDS([rpmkeys import])
RPMDB_INIT

AT_CHECK_UNQUOTED([
runroot rpmkeys --quiet --import /data/keys/CVE-2021-3521-badbind.asc
echo exit code: $? >&2
],
[ignore],
[0],
[],
[`if test x$PGP = xinternal;
then
echo 'error: /data/keys/CVE-2021-3521-badbind.asc: key 1 import failed.'
echo exit code: 1
else
echo exit code: 0
fi`]
)
[])

AT_CHECK_UNQUOTED([
runroot rpmkeys --quiet --import /data/keys/CVE-2021-3521-nosubsig.asc
echo exit code: $? >&2
],
[ignore],
[0],
[],
[`if test x$PGP = xinternal;
then
echo 'error: /data/keys/CVE-2021-3521-nosubsig.asc: key 1 import failed.'
echo exit code: 1
else
echo exit code: 0
fi`]
)
[])

AT_CHECK_UNQUOTED([
runroot rpmkeys --quiet --import /data/keys/CVE-2021-3521-nosubsig-last.asc
echo exit code: $? >&2
],
[ignore],
[0],
[],
[`if test x$PGP = xinternal;
then
echo 'error: /data/keys/CVE-2021-3521-nosubsig-last.asc: key 1 import failed.'
echo exit code: 1
else
echo exit code: 0
fi`]
)
[])
AT_CLEANUP

# -----------------------------------------
Expand Down Expand Up @@ -627,20 +601,16 @@ gpg(a72b7d4f62837bea) = 4:a72b7d4f62837bea-62553e62
[])
AT_CLEANUP

# The internal OpenPGP parser rejects the key. The Sequoia parser
# just ignores the invalid components and imports the rest. This test
# checks the behavior of the internal parser.
# The key has invalid components but those should be just ignored.
AT_SETUP([rpmkeys type confusion])
AT_SKIP_IF([test x$PGP != xinternal])
AT_CHECK([
RPMDB_INIT

runroot rpmkeys --import /data/keys/type-confusion.asc
],
[1],
[0],
[],
[error: /data/keys/type-confusion.asc: key 1 import failed.]
)
[])
AT_CLEANUP

# ------------------------------
Expand Down

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