freebsd-dev/crypto/openssh/krl.c
2014-03-25 11:05:34 +00:00

1238 lines
32 KiB
C

/*
* Copyright (c) 2012 Damien Miller <djm@mindrot.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* $OpenBSD: krl.c,v 1.14 2014/01/31 16:39:19 tedu Exp $ */
#include "includes.h"
#include <sys/types.h>
#include <sys/param.h>
#include <openbsd-compat/sys-tree.h>
#include <openbsd-compat/sys-queue.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include "buffer.h"
#include "key.h"
#include "authfile.h"
#include "misc.h"
#include "log.h"
#include "xmalloc.h"
#include "krl.h"
/* #define DEBUG_KRL */
#ifdef DEBUG_KRL
# define KRL_DBG(x) debug3 x
#else
# define KRL_DBG(x)
#endif
/*
* Trees of revoked serial numbers, key IDs and keys. This allows
* quick searching, querying and producing lists in canonical order.
*/
/* Tree of serial numbers. XXX make smarter: really need a real sparse bitmap */
struct revoked_serial {
u_int64_t lo, hi;
RB_ENTRY(revoked_serial) tree_entry;
};
static int serial_cmp(struct revoked_serial *a, struct revoked_serial *b);
RB_HEAD(revoked_serial_tree, revoked_serial);
RB_GENERATE_STATIC(revoked_serial_tree, revoked_serial, tree_entry, serial_cmp);
/* Tree of key IDs */
struct revoked_key_id {
char *key_id;
RB_ENTRY(revoked_key_id) tree_entry;
};
static int key_id_cmp(struct revoked_key_id *a, struct revoked_key_id *b);
RB_HEAD(revoked_key_id_tree, revoked_key_id);
RB_GENERATE_STATIC(revoked_key_id_tree, revoked_key_id, tree_entry, key_id_cmp);
/* Tree of blobs (used for keys and fingerprints) */
struct revoked_blob {
u_char *blob;
u_int len;
RB_ENTRY(revoked_blob) tree_entry;
};
static int blob_cmp(struct revoked_blob *a, struct revoked_blob *b);
RB_HEAD(revoked_blob_tree, revoked_blob);
RB_GENERATE_STATIC(revoked_blob_tree, revoked_blob, tree_entry, blob_cmp);
/* Tracks revoked certs for a single CA */
struct revoked_certs {
Key *ca_key;
struct revoked_serial_tree revoked_serials;
struct revoked_key_id_tree revoked_key_ids;
TAILQ_ENTRY(revoked_certs) entry;
};
TAILQ_HEAD(revoked_certs_list, revoked_certs);
struct ssh_krl {
u_int64_t krl_version;
u_int64_t generated_date;
u_int64_t flags;
char *comment;
struct revoked_blob_tree revoked_keys;
struct revoked_blob_tree revoked_sha1s;
struct revoked_certs_list revoked_certs;
};
/* Return equal if a and b overlap */
static int
serial_cmp(struct revoked_serial *a, struct revoked_serial *b)
{
if (a->hi >= b->lo && a->lo <= b->hi)
return 0;
return a->lo < b->lo ? -1 : 1;
}
static int
key_id_cmp(struct revoked_key_id *a, struct revoked_key_id *b)
{
return strcmp(a->key_id, b->key_id);
}
static int
blob_cmp(struct revoked_blob *a, struct revoked_blob *b)
{
int r;
if (a->len != b->len) {
if ((r = memcmp(a->blob, b->blob, MIN(a->len, b->len))) != 0)
return r;
return a->len > b->len ? 1 : -1;
} else
return memcmp(a->blob, b->blob, a->len);
}
struct ssh_krl *
ssh_krl_init(void)
{
struct ssh_krl *krl;
if ((krl = calloc(1, sizeof(*krl))) == NULL)
return NULL;
RB_INIT(&krl->revoked_keys);
RB_INIT(&krl->revoked_sha1s);
TAILQ_INIT(&krl->revoked_certs);
return krl;
}
static void
revoked_certs_free(struct revoked_certs *rc)
{
struct revoked_serial *rs, *trs;
struct revoked_key_id *rki, *trki;
RB_FOREACH_SAFE(rs, revoked_serial_tree, &rc->revoked_serials, trs) {
RB_REMOVE(revoked_serial_tree, &rc->revoked_serials, rs);
free(rs);
}
RB_FOREACH_SAFE(rki, revoked_key_id_tree, &rc->revoked_key_ids, trki) {
RB_REMOVE(revoked_key_id_tree, &rc->revoked_key_ids, rki);
free(rki->key_id);
free(rki);
}
if (rc->ca_key != NULL)
key_free(rc->ca_key);
}
void
ssh_krl_free(struct ssh_krl *krl)
{
struct revoked_blob *rb, *trb;
struct revoked_certs *rc, *trc;
if (krl == NULL)
return;
free(krl->comment);
RB_FOREACH_SAFE(rb, revoked_blob_tree, &krl->revoked_keys, trb) {
RB_REMOVE(revoked_blob_tree, &krl->revoked_keys, rb);
free(rb->blob);
free(rb);
}
RB_FOREACH_SAFE(rb, revoked_blob_tree, &krl->revoked_sha1s, trb) {
RB_REMOVE(revoked_blob_tree, &krl->revoked_sha1s, rb);
free(rb->blob);
free(rb);
}
TAILQ_FOREACH_SAFE(rc, &krl->revoked_certs, entry, trc) {
TAILQ_REMOVE(&krl->revoked_certs, rc, entry);
revoked_certs_free(rc);
}
}
void
ssh_krl_set_version(struct ssh_krl *krl, u_int64_t version)
{
krl->krl_version = version;
}
void
ssh_krl_set_comment(struct ssh_krl *krl, const char *comment)
{
free(krl->comment);
if ((krl->comment = strdup(comment)) == NULL)
fatal("%s: strdup", __func__);
}
/*
* Find the revoked_certs struct for a CA key. If allow_create is set then
* create a new one in the tree if one did not exist already.
*/
static int
revoked_certs_for_ca_key(struct ssh_krl *krl, const Key *ca_key,
struct revoked_certs **rcp, int allow_create)
{
struct revoked_certs *rc;
*rcp = NULL;
TAILQ_FOREACH(rc, &krl->revoked_certs, entry) {
if (key_equal(rc->ca_key, ca_key)) {
*rcp = rc;
return 0;
}
}
if (!allow_create)
return 0;
/* If this CA doesn't exist in the list then add it now */
if ((rc = calloc(1, sizeof(*rc))) == NULL)
return -1;
if ((rc->ca_key = key_from_private(ca_key)) == NULL) {
free(rc);
return -1;
}
RB_INIT(&rc->revoked_serials);
RB_INIT(&rc->revoked_key_ids);
TAILQ_INSERT_TAIL(&krl->revoked_certs, rc, entry);
debug3("%s: new CA %s", __func__, key_type(ca_key));
*rcp = rc;
return 0;
}
static int
insert_serial_range(struct revoked_serial_tree *rt, u_int64_t lo, u_int64_t hi)
{
struct revoked_serial rs, *ers, *crs, *irs;
KRL_DBG(("%s: insert %llu:%llu", __func__, lo, hi));
memset(&rs, 0, sizeof(rs));
rs.lo = lo;
rs.hi = hi;
ers = RB_NFIND(revoked_serial_tree, rt, &rs);
if (ers == NULL || serial_cmp(ers, &rs) != 0) {
/* No entry matches. Just insert */
if ((irs = malloc(sizeof(rs))) == NULL)
return -1;
memcpy(irs, &rs, sizeof(*irs));
ers = RB_INSERT(revoked_serial_tree, rt, irs);
if (ers != NULL) {
KRL_DBG(("%s: bad: ers != NULL", __func__));
/* Shouldn't happen */
free(irs);
return -1;
}
ers = irs;
} else {
KRL_DBG(("%s: overlap found %llu:%llu", __func__,
ers->lo, ers->hi));
/*
* The inserted entry overlaps an existing one. Grow the
* existing entry.
*/
if (ers->lo > lo)
ers->lo = lo;
if (ers->hi < hi)
ers->hi = hi;
}
/*
* The inserted or revised range might overlap or abut adjacent ones;
* coalesce as necessary.
*/
/* Check predecessors */
while ((crs = RB_PREV(revoked_serial_tree, rt, ers)) != NULL) {
KRL_DBG(("%s: pred %llu:%llu", __func__, crs->lo, crs->hi));
if (ers->lo != 0 && crs->hi < ers->lo - 1)
break;
/* This entry overlaps. */
if (crs->lo < ers->lo) {
ers->lo = crs->lo;
KRL_DBG(("%s: pred extend %llu:%llu", __func__,
ers->lo, ers->hi));
}
RB_REMOVE(revoked_serial_tree, rt, crs);
free(crs);
}
/* Check successors */
while ((crs = RB_NEXT(revoked_serial_tree, rt, ers)) != NULL) {
KRL_DBG(("%s: succ %llu:%llu", __func__, crs->lo, crs->hi));
if (ers->hi != (u_int64_t)-1 && crs->lo > ers->hi + 1)
break;
/* This entry overlaps. */
if (crs->hi > ers->hi) {
ers->hi = crs->hi;
KRL_DBG(("%s: succ extend %llu:%llu", __func__,
ers->lo, ers->hi));
}
RB_REMOVE(revoked_serial_tree, rt, crs);
free(crs);
}
KRL_DBG(("%s: done, final %llu:%llu", __func__, ers->lo, ers->hi));
return 0;
}
int
ssh_krl_revoke_cert_by_serial(struct ssh_krl *krl, const Key *ca_key,
u_int64_t serial)
{
return ssh_krl_revoke_cert_by_serial_range(krl, ca_key, serial, serial);
}
int
ssh_krl_revoke_cert_by_serial_range(struct ssh_krl *krl, const Key *ca_key,
u_int64_t lo, u_int64_t hi)
{
struct revoked_certs *rc;
if (lo > hi || lo == 0)
return -1;
if (revoked_certs_for_ca_key(krl, ca_key, &rc, 1) != 0)
return -1;
return insert_serial_range(&rc->revoked_serials, lo, hi);
}
int
ssh_krl_revoke_cert_by_key_id(struct ssh_krl *krl, const Key *ca_key,
const char *key_id)
{
struct revoked_key_id *rki, *erki;
struct revoked_certs *rc;
if (revoked_certs_for_ca_key(krl, ca_key, &rc, 1) != 0)
return -1;
debug3("%s: revoke %s", __func__, key_id);
if ((rki = calloc(1, sizeof(*rki))) == NULL ||
(rki->key_id = strdup(key_id)) == NULL) {
free(rki);
fatal("%s: strdup", __func__);
}
erki = RB_INSERT(revoked_key_id_tree, &rc->revoked_key_ids, rki);
if (erki != NULL) {
free(rki->key_id);
free(rki);
}
return 0;
}
/* Convert "key" to a public key blob without any certificate information */
static int
plain_key_blob(const Key *key, u_char **blob, u_int *blen)
{
Key *kcopy;
int r;
if ((kcopy = key_from_private(key)) == NULL)
return -1;
if (key_is_cert(kcopy)) {
if (key_drop_cert(kcopy) != 0) {
error("%s: key_drop_cert", __func__);
key_free(kcopy);
return -1;
}
}
r = key_to_blob(kcopy, blob, blen);
free(kcopy);
return r == 0 ? -1 : 0;
}
/* Revoke a key blob. Ownership of blob is transferred to the tree */
static int
revoke_blob(struct revoked_blob_tree *rbt, u_char *blob, u_int len)
{
struct revoked_blob *rb, *erb;
if ((rb = calloc(1, sizeof(*rb))) == NULL)
return -1;
rb->blob = blob;
rb->len = len;
erb = RB_INSERT(revoked_blob_tree, rbt, rb);
if (erb != NULL) {
free(rb->blob);
free(rb);
}
return 0;
}
int
ssh_krl_revoke_key_explicit(struct ssh_krl *krl, const Key *key)
{
u_char *blob;
u_int len;
debug3("%s: revoke type %s", __func__, key_type(key));
if (plain_key_blob(key, &blob, &len) != 0)
return -1;
return revoke_blob(&krl->revoked_keys, blob, len);
}
int
ssh_krl_revoke_key_sha1(struct ssh_krl *krl, const Key *key)
{
u_char *blob;
u_int len;
debug3("%s: revoke type %s by sha1", __func__, key_type(key));
if ((blob = key_fingerprint_raw(key, SSH_FP_SHA1, &len)) == NULL)
return -1;
return revoke_blob(&krl->revoked_sha1s, blob, len);
}
int
ssh_krl_revoke_key(struct ssh_krl *krl, const Key *key)
{
if (!key_is_cert(key))
return ssh_krl_revoke_key_sha1(krl, key);
if (key_cert_is_legacy(key) || key->cert->serial == 0) {
return ssh_krl_revoke_cert_by_key_id(krl,
key->cert->signature_key,
key->cert->key_id);
} else {
return ssh_krl_revoke_cert_by_serial(krl,
key->cert->signature_key,
key->cert->serial);
}
}
/*
* Select a copact next section type to emit in a KRL based on the
* current section type, the run length of contiguous revoked serial
* numbers and the gaps from the last and to the next revoked serial.
* Applies a mostly-accurate bit cost model to select the section type
* that will minimise the size of the resultant KRL.
*/
static int
choose_next_state(int current_state, u_int64_t contig, int final,
u_int64_t last_gap, u_int64_t next_gap, int *force_new_section)
{
int new_state;
u_int64_t cost, cost_list, cost_range, cost_bitmap, cost_bitmap_restart;
/*
* Avoid unsigned overflows.
* The limits are high enough to avoid confusing the calculations.
*/
contig = MIN(contig, 1ULL<<31);
last_gap = MIN(last_gap, 1ULL<<31);
next_gap = MIN(next_gap, 1ULL<<31);
/*
* Calculate the cost to switch from the current state to candidates.
* NB. range sections only ever contain a single range, so their
* switching cost is independent of the current_state.
*/
cost_list = cost_bitmap = cost_bitmap_restart = 0;
cost_range = 8;
switch (current_state) {
case KRL_SECTION_CERT_SERIAL_LIST:
cost_bitmap_restart = cost_bitmap = 8 + 64;
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
cost_list = 8;
cost_bitmap_restart = 8 + 64;
break;
case KRL_SECTION_CERT_SERIAL_RANGE:
case 0:
cost_bitmap_restart = cost_bitmap = 8 + 64;
cost_list = 8;
}
/* Estimate base cost in bits of each section type */
cost_list += 64 * contig + (final ? 0 : 8+64);
cost_range += (2 * 64) + (final ? 0 : 8+64);
cost_bitmap += last_gap + contig + (final ? 0 : MIN(next_gap, 8+64));
cost_bitmap_restart += contig + (final ? 0 : MIN(next_gap, 8+64));
/* Convert to byte costs for actual comparison */
cost_list = (cost_list + 7) / 8;
cost_bitmap = (cost_bitmap + 7) / 8;
cost_bitmap_restart = (cost_bitmap_restart + 7) / 8;
cost_range = (cost_range + 7) / 8;
/* Now pick the best choice */
*force_new_section = 0;
new_state = KRL_SECTION_CERT_SERIAL_BITMAP;
cost = cost_bitmap;
if (cost_range < cost) {
new_state = KRL_SECTION_CERT_SERIAL_RANGE;
cost = cost_range;
}
if (cost_list < cost) {
new_state = KRL_SECTION_CERT_SERIAL_LIST;
cost = cost_list;
}
if (cost_bitmap_restart < cost) {
new_state = KRL_SECTION_CERT_SERIAL_BITMAP;
*force_new_section = 1;
cost = cost_bitmap_restart;
}
debug3("%s: contig %llu last_gap %llu next_gap %llu final %d, costs:"
"list %llu range %llu bitmap %llu new bitmap %llu, "
"selected 0x%02x%s", __func__, (long long unsigned)contig,
(long long unsigned)last_gap, (long long unsigned)next_gap, final,
(long long unsigned)cost_list, (long long unsigned)cost_range,
(long long unsigned)cost_bitmap,
(long long unsigned)cost_bitmap_restart, new_state,
*force_new_section ? " restart" : "");
return new_state;
}
/* Generate a KRL_SECTION_CERTIFICATES KRL section */
static int
revoked_certs_generate(struct revoked_certs *rc, Buffer *buf)
{
int final, force_new_sect, r = -1;
u_int64_t i, contig, gap, last = 0, bitmap_start = 0;
struct revoked_serial *rs, *nrs;
struct revoked_key_id *rki;
int next_state, state = 0;
Buffer sect;
u_char *kblob = NULL;
u_int klen;
BIGNUM *bitmap = NULL;
/* Prepare CA scope key blob if we have one supplied */
if (key_to_blob(rc->ca_key, &kblob, &klen) == 0)
return -1;
buffer_init(&sect);
/* Store the header */
buffer_put_string(buf, kblob, klen);
buffer_put_string(buf, NULL, 0); /* Reserved */
free(kblob);
/* Store the revoked serials. */
for (rs = RB_MIN(revoked_serial_tree, &rc->revoked_serials);
rs != NULL;
rs = RB_NEXT(revoked_serial_tree, &rc->revoked_serials, rs)) {
debug3("%s: serial %llu:%llu state 0x%02x", __func__,
(long long unsigned)rs->lo, (long long unsigned)rs->hi,
state);
/* Check contiguous length and gap to next section (if any) */
nrs = RB_NEXT(revoked_serial_tree, &rc->revoked_serials, rs);
final = nrs == NULL;
gap = nrs == NULL ? 0 : nrs->lo - rs->hi;
contig = 1 + (rs->hi - rs->lo);
/* Choose next state based on these */
next_state = choose_next_state(state, contig, final,
state == 0 ? 0 : rs->lo - last, gap, &force_new_sect);
/*
* If the current section is a range section or has a different
* type to the next section, then finish it off now.
*/
if (state != 0 && (force_new_sect || next_state != state ||
state == KRL_SECTION_CERT_SERIAL_RANGE)) {
debug3("%s: finish state 0x%02x", __func__, state);
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
case KRL_SECTION_CERT_SERIAL_RANGE:
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
buffer_put_bignum2(&sect, bitmap);
BN_free(bitmap);
bitmap = NULL;
break;
}
buffer_put_char(buf, state);
buffer_put_string(buf,
buffer_ptr(&sect), buffer_len(&sect));
}
/* If we are starting a new section then prepare it now */
if (next_state != state || force_new_sect) {
debug3("%s: start state 0x%02x", __func__, next_state);
state = next_state;
buffer_clear(&sect);
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
case KRL_SECTION_CERT_SERIAL_RANGE:
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if ((bitmap = BN_new()) == NULL)
goto out;
bitmap_start = rs->lo;
buffer_put_int64(&sect, bitmap_start);
break;
}
}
/* Perform section-specific processing */
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
for (i = 0; i < contig; i++)
buffer_put_int64(&sect, rs->lo + i);
break;
case KRL_SECTION_CERT_SERIAL_RANGE:
buffer_put_int64(&sect, rs->lo);
buffer_put_int64(&sect, rs->hi);
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if (rs->lo - bitmap_start > INT_MAX) {
error("%s: insane bitmap gap", __func__);
goto out;
}
for (i = 0; i < contig; i++) {
if (BN_set_bit(bitmap,
rs->lo + i - bitmap_start) != 1)
goto out;
}
break;
}
last = rs->hi;
}
/* Flush the remaining section, if any */
if (state != 0) {
debug3("%s: serial final flush for state 0x%02x",
__func__, state);
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
case KRL_SECTION_CERT_SERIAL_RANGE:
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
buffer_put_bignum2(&sect, bitmap);
BN_free(bitmap);
bitmap = NULL;
break;
}
buffer_put_char(buf, state);
buffer_put_string(buf,
buffer_ptr(&sect), buffer_len(&sect));
}
debug3("%s: serial done ", __func__);
/* Now output a section for any revocations by key ID */
buffer_clear(&sect);
RB_FOREACH(rki, revoked_key_id_tree, &rc->revoked_key_ids) {
debug3("%s: key ID %s", __func__, rki->key_id);
buffer_put_cstring(&sect, rki->key_id);
}
if (buffer_len(&sect) != 0) {
buffer_put_char(buf, KRL_SECTION_CERT_KEY_ID);
buffer_put_string(buf, buffer_ptr(&sect),
buffer_len(&sect));
}
r = 0;
out:
if (bitmap != NULL)
BN_free(bitmap);
buffer_free(&sect);
return r;
}
int
ssh_krl_to_blob(struct ssh_krl *krl, Buffer *buf, const Key **sign_keys,
u_int nsign_keys)
{
int r = -1;
struct revoked_certs *rc;
struct revoked_blob *rb;
Buffer sect;
u_char *kblob = NULL, *sblob = NULL;
u_int klen, slen, i;
if (krl->generated_date == 0)
krl->generated_date = time(NULL);
buffer_init(&sect);
/* Store the header */
buffer_append(buf, KRL_MAGIC, sizeof(KRL_MAGIC) - 1);
buffer_put_int(buf, KRL_FORMAT_VERSION);
buffer_put_int64(buf, krl->krl_version);
buffer_put_int64(buf, krl->generated_date);
buffer_put_int64(buf, krl->flags);
buffer_put_string(buf, NULL, 0);
buffer_put_cstring(buf, krl->comment ? krl->comment : "");
/* Store sections for revoked certificates */
TAILQ_FOREACH(rc, &krl->revoked_certs, entry) {
if (revoked_certs_generate(rc, &sect) != 0)
goto out;
buffer_put_char(buf, KRL_SECTION_CERTIFICATES);
buffer_put_string(buf, buffer_ptr(&sect),
buffer_len(&sect));
}
/* Finally, output sections for revocations by public key/hash */
buffer_clear(&sect);
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_keys) {
debug3("%s: key len %u ", __func__, rb->len);
buffer_put_string(&sect, rb->blob, rb->len);
}
if (buffer_len(&sect) != 0) {
buffer_put_char(buf, KRL_SECTION_EXPLICIT_KEY);
buffer_put_string(buf, buffer_ptr(&sect),
buffer_len(&sect));
}
buffer_clear(&sect);
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_sha1s) {
debug3("%s: hash len %u ", __func__, rb->len);
buffer_put_string(&sect, rb->blob, rb->len);
}
if (buffer_len(&sect) != 0) {
buffer_put_char(buf, KRL_SECTION_FINGERPRINT_SHA1);
buffer_put_string(buf, buffer_ptr(&sect),
buffer_len(&sect));
}
for (i = 0; i < nsign_keys; i++) {
if (key_to_blob(sign_keys[i], &kblob, &klen) == 0)
goto out;
debug3("%s: signature key len %u", __func__, klen);
buffer_put_char(buf, KRL_SECTION_SIGNATURE);
buffer_put_string(buf, kblob, klen);
if (key_sign(sign_keys[i], &sblob, &slen,
buffer_ptr(buf), buffer_len(buf)) == -1)
goto out;
debug3("%s: signature sig len %u", __func__, slen);
buffer_put_string(buf, sblob, slen);
}
r = 0;
out:
free(kblob);
free(sblob);
buffer_free(&sect);
return r;
}
static void
format_timestamp(u_int64_t timestamp, char *ts, size_t nts)
{
time_t t;
struct tm *tm;
t = timestamp;
tm = localtime(&t);
*ts = '\0';
strftime(ts, nts, "%Y%m%dT%H%M%S", tm);
}
static int
parse_revoked_certs(Buffer *buf, struct ssh_krl *krl)
{
int ret = -1, nbits;
u_char type, *blob;
u_int blen;
Buffer subsect;
u_int64_t serial, serial_lo, serial_hi;
BIGNUM *bitmap = NULL;
char *key_id = NULL;
Key *ca_key = NULL;
buffer_init(&subsect);
if ((blob = buffer_get_string_ptr_ret(buf, &blen)) == NULL ||
buffer_get_string_ptr_ret(buf, NULL) == NULL) { /* reserved */
error("%s: buffer error", __func__);
goto out;
}
if ((ca_key = key_from_blob(blob, blen)) == NULL)
goto out;
while (buffer_len(buf) > 0) {
if (buffer_get_char_ret(&type, buf) != 0 ||
(blob = buffer_get_string_ptr_ret(buf, &blen)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
buffer_clear(&subsect);
buffer_append(&subsect, blob, blen);
debug3("%s: subsection type 0x%02x", __func__, type);
/* buffer_dump(&subsect); */
switch (type) {
case KRL_SECTION_CERT_SERIAL_LIST:
while (buffer_len(&subsect) > 0) {
if (buffer_get_int64_ret(&serial,
&subsect) != 0) {
error("%s: buffer error", __func__);
goto out;
}
if (ssh_krl_revoke_cert_by_serial(krl, ca_key,
serial) != 0) {
error("%s: update failed", __func__);
goto out;
}
}
break;
case KRL_SECTION_CERT_SERIAL_RANGE:
if (buffer_get_int64_ret(&serial_lo, &subsect) != 0 ||
buffer_get_int64_ret(&serial_hi, &subsect) != 0) {
error("%s: buffer error", __func__);
goto out;
}
if (ssh_krl_revoke_cert_by_serial_range(krl, ca_key,
serial_lo, serial_hi) != 0) {
error("%s: update failed", __func__);
goto out;
}
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if ((bitmap = BN_new()) == NULL) {
error("%s: BN_new", __func__);
goto out;
}
if (buffer_get_int64_ret(&serial_lo, &subsect) != 0 ||
buffer_get_bignum2_ret(&subsect, bitmap) != 0) {
error("%s: buffer error", __func__);
goto out;
}
if ((nbits = BN_num_bits(bitmap)) < 0) {
error("%s: bitmap bits < 0", __func__);
goto out;
}
for (serial = 0; serial < (u_int)nbits; serial++) {
if (serial > 0 && serial_lo + serial == 0) {
error("%s: bitmap wraps u64", __func__);
goto out;
}
if (!BN_is_bit_set(bitmap, serial))
continue;
if (ssh_krl_revoke_cert_by_serial(krl, ca_key,
serial_lo + serial) != 0) {
error("%s: update failed", __func__);
goto out;
}
}
BN_free(bitmap);
bitmap = NULL;
break;
case KRL_SECTION_CERT_KEY_ID:
while (buffer_len(&subsect) > 0) {
if ((key_id = buffer_get_cstring_ret(&subsect,
NULL)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
if (ssh_krl_revoke_cert_by_key_id(krl, ca_key,
key_id) != 0) {
error("%s: update failed", __func__);
goto out;
}
free(key_id);
key_id = NULL;
}
break;
default:
error("Unsupported KRL certificate section %u", type);
goto out;
}
if (buffer_len(&subsect) > 0) {
error("KRL certificate section contains unparsed data");
goto out;
}
}
ret = 0;
out:
if (ca_key != NULL)
key_free(ca_key);
if (bitmap != NULL)
BN_free(bitmap);
free(key_id);
buffer_free(&subsect);
return ret;
}
/* Attempt to parse a KRL, checking its signature (if any) with sign_ca_keys. */
int
ssh_krl_from_blob(Buffer *buf, struct ssh_krl **krlp,
const Key **sign_ca_keys, u_int nsign_ca_keys)
{
Buffer copy, sect;
struct ssh_krl *krl;
char timestamp[64];
int ret = -1, r, sig_seen;
Key *key = NULL, **ca_used = NULL;
u_char type, *blob, *rdata = NULL;
u_int i, j, sig_off, sects_off, rlen, blen, format_version, nca_used;
nca_used = 0;
*krlp = NULL;
if (buffer_len(buf) < sizeof(KRL_MAGIC) - 1 ||
memcmp(buffer_ptr(buf), KRL_MAGIC, sizeof(KRL_MAGIC) - 1) != 0) {
debug3("%s: not a KRL", __func__);
/*
* Return success but a NULL *krlp here to signal that the
* file might be a simple list of keys.
*/
return 0;
}
/* Take a copy of the KRL buffer so we can verify its signature later */
buffer_init(&copy);
buffer_append(&copy, buffer_ptr(buf), buffer_len(buf));
buffer_init(&sect);
buffer_consume(&copy, sizeof(KRL_MAGIC) - 1);
if ((krl = ssh_krl_init()) == NULL) {
error("%s: alloc failed", __func__);
goto out;
}
if (buffer_get_int_ret(&format_version, &copy) != 0) {
error("%s: KRL truncated", __func__);
goto out;
}
if (format_version != KRL_FORMAT_VERSION) {
error("%s: KRL unsupported format version %u",
__func__, format_version);
goto out;
}
if (buffer_get_int64_ret(&krl->krl_version, &copy) != 0 ||
buffer_get_int64_ret(&krl->generated_date, &copy) != 0 ||
buffer_get_int64_ret(&krl->flags, &copy) != 0 ||
buffer_get_string_ptr_ret(&copy, NULL) == NULL || /* reserved */
(krl->comment = buffer_get_cstring_ret(&copy, NULL)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
format_timestamp(krl->generated_date, timestamp, sizeof(timestamp));
debug("KRL version %llu generated at %s%s%s",
(long long unsigned)krl->krl_version, timestamp,
*krl->comment ? ": " : "", krl->comment);
/*
* 1st pass: verify signatures, if any. This is done to avoid
* detailed parsing of data whose provenance is unverified.
*/
sig_seen = 0;
sects_off = buffer_len(buf) - buffer_len(&copy);
while (buffer_len(&copy) > 0) {
if (buffer_get_char_ret(&type, &copy) != 0 ||
(blob = buffer_get_string_ptr_ret(&copy, &blen)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
debug3("%s: first pass, section 0x%02x", __func__, type);
if (type != KRL_SECTION_SIGNATURE) {
if (sig_seen) {
error("KRL contains non-signature section "
"after signature");
goto out;
}
/* Not interested for now. */
continue;
}
sig_seen = 1;
/* First string component is the signing key */
if ((key = key_from_blob(blob, blen)) == NULL) {
error("%s: invalid signature key", __func__);
goto out;
}
sig_off = buffer_len(buf) - buffer_len(&copy);
/* Second string component is the signature itself */
if ((blob = buffer_get_string_ptr_ret(&copy, &blen)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
/* Check signature over entire KRL up to this point */
if (key_verify(key, blob, blen,
buffer_ptr(buf), buffer_len(buf) - sig_off) != 1) {
error("bad signaure on KRL");
goto out;
}
/* Check if this key has already signed this KRL */
for (i = 0; i < nca_used; i++) {
if (key_equal(ca_used[i], key)) {
error("KRL signed more than once with "
"the same key");
goto out;
}
}
/* Record keys used to sign the KRL */
ca_used = xrealloc(ca_used, nca_used + 1, sizeof(*ca_used));
ca_used[nca_used++] = key;
key = NULL;
break;
}
/*
* 2nd pass: parse and load the KRL, skipping the header to the point
* where the section start.
*/
buffer_append(&copy, (u_char*)buffer_ptr(buf) + sects_off,
buffer_len(buf) - sects_off);
while (buffer_len(&copy) > 0) {
if (buffer_get_char_ret(&type, &copy) != 0 ||
(blob = buffer_get_string_ptr_ret(&copy, &blen)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
debug3("%s: second pass, section 0x%02x", __func__, type);
buffer_clear(&sect);
buffer_append(&sect, blob, blen);
switch (type) {
case KRL_SECTION_CERTIFICATES:
if ((r = parse_revoked_certs(&sect, krl)) != 0)
goto out;
break;
case KRL_SECTION_EXPLICIT_KEY:
case KRL_SECTION_FINGERPRINT_SHA1:
while (buffer_len(&sect) > 0) {
if ((rdata = buffer_get_string_ret(&sect,
&rlen)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
if (type == KRL_SECTION_FINGERPRINT_SHA1 &&
rlen != 20) {
error("%s: bad SHA1 length", __func__);
goto out;
}
if (revoke_blob(
type == KRL_SECTION_EXPLICIT_KEY ?
&krl->revoked_keys : &krl->revoked_sha1s,
rdata, rlen) != 0)
goto out;
rdata = NULL; /* revoke_blob frees blob */
}
break;
case KRL_SECTION_SIGNATURE:
/* Handled above, but still need to stay in synch */
buffer_clear(&sect);
if ((blob = buffer_get_string_ptr_ret(&copy,
&blen)) == NULL) {
error("%s: buffer error", __func__);
goto out;
}
break;
default:
error("Unsupported KRL section %u", type);
goto out;
}
if (buffer_len(&sect) > 0) {
error("KRL section contains unparsed data");
goto out;
}
}
/* Check that the key(s) used to sign the KRL weren't revoked */
sig_seen = 0;
for (i = 0; i < nca_used; i++) {
if (ssh_krl_check_key(krl, ca_used[i]) == 0)
sig_seen = 1;
else {
key_free(ca_used[i]);
ca_used[i] = NULL;
}
}
if (nca_used && !sig_seen) {
error("All keys used to sign KRL were revoked");
goto out;
}
/* If we have CA keys, then verify that one was used to sign the KRL */
if (sig_seen && nsign_ca_keys != 0) {
sig_seen = 0;
for (i = 0; !sig_seen && i < nsign_ca_keys; i++) {
for (j = 0; j < nca_used; j++) {
if (ca_used[j] == NULL)
continue;
if (key_equal(ca_used[j], sign_ca_keys[i])) {
sig_seen = 1;
break;
}
}
}
if (!sig_seen) {
error("KRL not signed with any trusted key");
goto out;
}
}
*krlp = krl;
ret = 0;
out:
if (ret != 0)
ssh_krl_free(krl);
for (i = 0; i < nca_used; i++) {
if (ca_used[i] != NULL)
key_free(ca_used[i]);
}
free(ca_used);
free(rdata);
if (key != NULL)
key_free(key);
buffer_free(&copy);
buffer_free(&sect);
return ret;
}
/* Checks whether a given key/cert is revoked. Does not check its CA */
static int
is_key_revoked(struct ssh_krl *krl, const Key *key)
{
struct revoked_blob rb, *erb;
struct revoked_serial rs, *ers;
struct revoked_key_id rki, *erki;
struct revoked_certs *rc;
/* Check explicitly revoked hashes first */
memset(&rb, 0, sizeof(rb));
if ((rb.blob = key_fingerprint_raw(key, SSH_FP_SHA1, &rb.len)) == NULL)
return -1;
erb = RB_FIND(revoked_blob_tree, &krl->revoked_sha1s, &rb);
free(rb.blob);
if (erb != NULL) {
debug("%s: revoked by key SHA1", __func__);
return -1;
}
/* Next, explicit keys */
memset(&rb, 0, sizeof(rb));
if (plain_key_blob(key, &rb.blob, &rb.len) != 0)
return -1;
erb = RB_FIND(revoked_blob_tree, &krl->revoked_keys, &rb);
free(rb.blob);
if (erb != NULL) {
debug("%s: revoked by explicit key", __func__);
return -1;
}
if (!key_is_cert(key))
return 0;
/* Check cert revocation */
if (revoked_certs_for_ca_key(krl, key->cert->signature_key,
&rc, 0) != 0)
return -1;
if (rc == NULL)
return 0; /* No entry for this CA */
/* Check revocation by cert key ID */
memset(&rki, 0, sizeof(rki));
rki.key_id = key->cert->key_id;
erki = RB_FIND(revoked_key_id_tree, &rc->revoked_key_ids, &rki);
if (erki != NULL) {
debug("%s: revoked by key ID", __func__);
return -1;
}
/*
* Legacy cert formats lack serial numbers. Zero serials numbers
* are ignored (it's the default when the CA doesn't specify one).
*/
if (key_cert_is_legacy(key) || key->cert->serial == 0)
return 0;
memset(&rs, 0, sizeof(rs));
rs.lo = rs.hi = key->cert->serial;
ers = RB_FIND(revoked_serial_tree, &rc->revoked_serials, &rs);
if (ers != NULL) {
KRL_DBG(("%s: %llu matched %llu:%llu", __func__,
key->cert->serial, ers->lo, ers->hi));
debug("%s: revoked by serial", __func__);
return -1;
}
KRL_DBG(("%s: %llu no match", __func__, key->cert->serial));
return 0;
}
int
ssh_krl_check_key(struct ssh_krl *krl, const Key *key)
{
int r;
debug2("%s: checking key", __func__);
if ((r = is_key_revoked(krl, key)) != 0)
return r;
if (key_is_cert(key)) {
debug2("%s: checking CA key", __func__);
if ((r = is_key_revoked(krl, key->cert->signature_key)) != 0)
return r;
}
debug3("%s: key okay", __func__);
return 0;
}
/* Returns 0 on success, -1 on error or key revoked, -2 if path is not a KRL */
int
ssh_krl_file_contains_key(const char *path, const Key *key)
{
Buffer krlbuf;
struct ssh_krl *krl;
int revoked, fd;
if (path == NULL)
return 0;
if ((fd = open(path, O_RDONLY)) == -1) {
error("open %s: %s", path, strerror(errno));
error("Revoked keys file not accessible - refusing public key "
"authentication");
return -1;
}
buffer_init(&krlbuf);
if (!key_load_file(fd, path, &krlbuf)) {
close(fd);
buffer_free(&krlbuf);
error("Revoked keys file not readable - refusing public key "
"authentication");
return -1;
}
close(fd);
if (ssh_krl_from_blob(&krlbuf, &krl, NULL, 0) != 0) {
buffer_free(&krlbuf);
error("Invalid KRL, refusing public key "
"authentication");
return -1;
}
buffer_free(&krlbuf);
if (krl == NULL) {
debug3("%s: %s is not a KRL file", __func__, path);
return -2;
}
debug2("%s: checking KRL %s", __func__, path);
revoked = ssh_krl_check_key(krl, key) != 0;
ssh_krl_free(krl);
return revoked ? -1 : 0;
}