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openssh/krl.c

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/*
* 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 1.52 2020/10/18 11:32:01 djm Exp $ */
#include "includes.h"
#include <sys/types.h>
#include <openbsd-compat/sys-tree.h>
#include <openbsd-compat/sys-queue.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include "sshbuf.h"
#include "ssherr.h"
#include "sshkey.h"
#include "authfile.h"
#include "misc.h"
#include "log.h"
#include "digest.h"
#include "bitmap.h"
#include "utf8.h"
#include "krl.h"
/* #define DEBUG_KRL */
#ifdef DEBUG_KRL
# define KRL_DBG(x) debug3_f 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;
size_t 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 {
struct sshkey *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_blob_tree revoked_sha256s;
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, MINIMUM(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);
RB_INIT(&krl->revoked_sha256s);
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);
}
sshkey_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);
}
RB_FOREACH_SAFE(rb, revoked_blob_tree, &krl->revoked_sha256s, trb) {
RB_REMOVE(revoked_blob_tree, &krl->revoked_sha256s, 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;
}
int
ssh_krl_set_comment(struct ssh_krl *krl, const char *comment)
{
free(krl->comment);
if ((krl->comment = strdup(comment)) == NULL)
return SSH_ERR_ALLOC_FAIL;
return 0;
}
/*
* 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 struct sshkey *ca_key,
struct revoked_certs **rcp, int allow_create)
{
struct revoked_certs *rc;
int r;
*rcp = NULL;
TAILQ_FOREACH(rc, &krl->revoked_certs, entry) {
if ((ca_key == NULL && rc->ca_key == NULL) ||
sshkey_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 SSH_ERR_ALLOC_FAIL;
if (ca_key == NULL)
rc->ca_key = NULL;
else if ((r = sshkey_from_private(ca_key, &rc->ca_key)) != 0) {
free(rc);
return r;
}
RB_INIT(&rc->revoked_serials);
RB_INIT(&rc->revoked_key_ids);
TAILQ_INSERT_TAIL(&krl->revoked_certs, rc, entry);
KRL_DBG(("new CA %s", ca_key == NULL ? "*" : sshkey_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(("insert %llu:%llu", 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 SSH_ERR_ALLOC_FAIL;
memcpy(irs, &rs, sizeof(*irs));
ers = RB_INSERT(revoked_serial_tree, rt, irs);
if (ers != NULL) {
KRL_DBG(("bad: ers != NULL"));
/* Shouldn't happen */
free(irs);
return SSH_ERR_INTERNAL_ERROR;
}
ers = irs;
} else {
KRL_DBG(("overlap found %llu:%llu", 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(("pred %llu:%llu", 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(("pred extend %llu:%llu", 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(("succ %llu:%llu", 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(("succ extend %llu:%llu", ers->lo, ers->hi));
}
RB_REMOVE(revoked_serial_tree, rt, crs);
free(crs);
}
KRL_DBG(("done, final %llu:%llu", ers->lo, ers->hi));
return 0;
}
int
ssh_krl_revoke_cert_by_serial(struct ssh_krl *krl, const struct sshkey *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 struct sshkey *ca_key, u_int64_t lo, u_int64_t hi)
{
struct revoked_certs *rc;
int r;
if (lo > hi || lo == 0)
return SSH_ERR_INVALID_ARGUMENT;
if ((r = revoked_certs_for_ca_key(krl, ca_key, &rc, 1)) != 0)
return r;
return insert_serial_range(&rc->revoked_serials, lo, hi);
}
int
ssh_krl_revoke_cert_by_key_id(struct ssh_krl *krl, const struct sshkey *ca_key,
const char *key_id)
{
struct revoked_key_id *rki, *erki;
struct revoked_certs *rc;
int r;
if ((r = revoked_certs_for_ca_key(krl, ca_key, &rc, 1)) != 0)
return r;
KRL_DBG(("revoke %s", key_id));
if ((rki = calloc(1, sizeof(*rki))) == NULL ||
(rki->key_id = strdup(key_id)) == NULL) {
free(rki);
return SSH_ERR_ALLOC_FAIL;
}
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 struct sshkey *key, u_char **blob, size_t *blen)
{
struct sshkey *kcopy;
int r;
if ((r = sshkey_from_private(key, &kcopy)) != 0)
return r;
if (sshkey_is_cert(kcopy)) {
if ((r = sshkey_drop_cert(kcopy)) != 0) {
sshkey_free(kcopy);
return r;
}
}
r = sshkey_to_blob(kcopy, blob, blen);
sshkey_free(kcopy);
return r;
}
/* Revoke a key blob. Ownership of blob is transferred to the tree */
static int
revoke_blob(struct revoked_blob_tree *rbt, u_char *blob, size_t len)
{
struct revoked_blob *rb, *erb;
if ((rb = calloc(1, sizeof(*rb))) == NULL)
return SSH_ERR_ALLOC_FAIL;
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 struct sshkey *key)
{
u_char *blob;
size_t len;
int r;
debug3_f("revoke type %s", sshkey_type(key));
if ((r = plain_key_blob(key, &blob, &len)) != 0)
return r;
return revoke_blob(&krl->revoked_keys, blob, len);
}
static int
revoke_by_hash(struct revoked_blob_tree *target, const u_char *p, size_t len)
{
u_char *blob;
int r;
/* need to copy hash, as revoke_blob steals ownership */
if ((blob = malloc(len)) == NULL)
return SSH_ERR_SYSTEM_ERROR;
memcpy(blob, p, len);
if ((r = revoke_blob(target, blob, len)) != 0) {
free(blob);
return r;
}
return 0;
}
int
ssh_krl_revoke_key_sha1(struct ssh_krl *krl, const u_char *p, size_t len)
{
debug3_f("revoke by sha1");
if (len != 20)
return SSH_ERR_INVALID_FORMAT;
return revoke_by_hash(&krl->revoked_sha1s, p, len);
}
int
ssh_krl_revoke_key_sha256(struct ssh_krl *krl, const u_char *p, size_t len)
{
debug3_f("revoke by sha256");
if (len != 32)
return SSH_ERR_INVALID_FORMAT;
return revoke_by_hash(&krl->revoked_sha256s, p, len);
}
int
ssh_krl_revoke_key(struct ssh_krl *krl, const struct sshkey *key)
{
/* XXX replace with SHA256? */
if (!sshkey_is_cert(key))
return ssh_krl_revoke_key_explicit(krl, key);
if (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 the most compact section type to emit next 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 = MINIMUM(contig, 1ULL<<31);
last_gap = MINIMUM(last_gap, 1ULL<<31);
next_gap = MINIMUM(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 : MINIMUM(next_gap, 8+64));
cost_bitmap_restart += contig + (final ? 0 : MINIMUM(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;
}
KRL_DBG(("contig %llu last_gap %llu next_gap %llu final %d, costs:"
"list %llu range %llu bitmap %llu new bitmap %llu, "
"selected 0x%02x%s", (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;
}
static int
put_bitmap(struct sshbuf *buf, struct bitmap *bitmap)
{
size_t len;
u_char *blob;
int r;
len = bitmap_nbytes(bitmap);
if ((blob = malloc(len)) == NULL)
return SSH_ERR_ALLOC_FAIL;
if (bitmap_to_string(bitmap, blob, len) != 0) {
free(blob);
return SSH_ERR_INTERNAL_ERROR;
}
r = sshbuf_put_bignum2_bytes(buf, blob, len);
free(blob);
return r;
}
/* Generate a KRL_SECTION_CERTIFICATES KRL section */
static int
revoked_certs_generate(struct revoked_certs *rc, struct sshbuf *buf)
{
int final, force_new_sect, r = SSH_ERR_INTERNAL_ERROR;
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;
struct sshbuf *sect;
struct bitmap *bitmap = NULL;
if ((sect = sshbuf_new()) == NULL)
return SSH_ERR_ALLOC_FAIL;
/* Store the header: optional CA scope key, reserved */
if (rc->ca_key == NULL) {
if ((r = sshbuf_put_string(buf, NULL, 0)) != 0)
goto out;
} else {
if ((r = sshkey_puts(rc->ca_key, buf)) != 0)
goto out;
}
if ((r = sshbuf_put_string(buf, NULL, 0)) != 0)
goto out;
/* 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)) {
KRL_DBG(("serial %llu:%llu state 0x%02x",
(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)) {
KRL_DBG(("finish state 0x%02x", state));
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
case KRL_SECTION_CERT_SERIAL_RANGE:
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if ((r = put_bitmap(sect, bitmap)) != 0)
goto out;
bitmap_free(bitmap);
bitmap = NULL;
break;
}
if ((r = sshbuf_put_u8(buf, state)) != 0 ||
(r = sshbuf_put_stringb(buf, sect)) != 0)
goto out;
sshbuf_reset(sect);
}
/* If we are starting a new section then prepare it now */
if (next_state != state || force_new_sect) {
KRL_DBG(("start state 0x%02x",
next_state));
state = next_state;
sshbuf_reset(sect);
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
case KRL_SECTION_CERT_SERIAL_RANGE:
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if ((bitmap = bitmap_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
bitmap_start = rs->lo;
if ((r = sshbuf_put_u64(sect,
bitmap_start)) != 0)
goto out;
break;
}
}
/* Perform section-specific processing */
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
for (i = 0; i < contig; i++) {
if ((r = sshbuf_put_u64(sect, rs->lo + i)) != 0)
goto out;
}
break;
case KRL_SECTION_CERT_SERIAL_RANGE:
if ((r = sshbuf_put_u64(sect, rs->lo)) != 0 ||
(r = sshbuf_put_u64(sect, rs->hi)) != 0)
goto out;
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if (rs->lo - bitmap_start > INT_MAX) {
error_f("insane bitmap gap");
goto out;
}
for (i = 0; i < contig; i++) {
if (bitmap_set_bit(bitmap,
rs->lo + i - bitmap_start) != 0) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
}
break;
}
last = rs->hi;
}
/* Flush the remaining section, if any */
if (state != 0) {
KRL_DBG(("serial final flush for state 0x%02x", state));
switch (state) {
case KRL_SECTION_CERT_SERIAL_LIST:
case KRL_SECTION_CERT_SERIAL_RANGE:
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if ((r = put_bitmap(sect, bitmap)) != 0)
goto out;
bitmap_free(bitmap);
bitmap = NULL;
break;
}
if ((r = sshbuf_put_u8(buf, state)) != 0 ||
(r = sshbuf_put_stringb(buf, sect)) != 0)
goto out;
}
KRL_DBG(("serial done "));
/* Now output a section for any revocations by key ID */
sshbuf_reset(sect);
RB_FOREACH(rki, revoked_key_id_tree, &rc->revoked_key_ids) {
KRL_DBG(("key ID %s", rki->key_id));
if ((r = sshbuf_put_cstring(sect, rki->key_id)) != 0)
goto out;
}
if (sshbuf_len(sect) != 0) {
if ((r = sshbuf_put_u8(buf, KRL_SECTION_CERT_KEY_ID)) != 0 ||
(r = sshbuf_put_stringb(buf, sect)) != 0)
goto out;
}
r = 0;
out:
bitmap_free(bitmap);
sshbuf_free(sect);
return r;
}
int
ssh_krl_to_blob(struct ssh_krl *krl, struct sshbuf *buf,
struct sshkey **sign_keys, u_int nsign_keys)
{
int r = SSH_ERR_INTERNAL_ERROR;
struct revoked_certs *rc;
struct revoked_blob *rb;
struct sshbuf *sect;
u_char *sblob = NULL;
size_t slen, i;
if (krl->generated_date == 0)
krl->generated_date = time(NULL);
if ((sect = sshbuf_new()) == NULL)
return SSH_ERR_ALLOC_FAIL;
/* Store the header */
if ((r = sshbuf_put(buf, KRL_MAGIC, sizeof(KRL_MAGIC) - 1)) != 0 ||
(r = sshbuf_put_u32(buf, KRL_FORMAT_VERSION)) != 0 ||
(r = sshbuf_put_u64(buf, krl->krl_version)) != 0 ||
(r = sshbuf_put_u64(buf, krl->generated_date)) != 0 ||
(r = sshbuf_put_u64(buf, krl->flags)) != 0 ||
(r = sshbuf_put_string(buf, NULL, 0)) != 0 ||
(r = sshbuf_put_cstring(buf, krl->comment)) != 0)
goto out;
/* Store sections for revoked certificates */
TAILQ_FOREACH(rc, &krl->revoked_certs, entry) {
sshbuf_reset(sect);
if ((r = revoked_certs_generate(rc, sect)) != 0)
goto out;
if ((r = sshbuf_put_u8(buf, KRL_SECTION_CERTIFICATES)) != 0 ||
(r = sshbuf_put_stringb(buf, sect)) != 0)
goto out;
}
/* Finally, output sections for revocations by public key/hash */
sshbuf_reset(sect);
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_keys) {
KRL_DBG(("key len %zu ", rb->len));
if ((r = sshbuf_put_string(sect, rb->blob, rb->len)) != 0)
goto out;
}
if (sshbuf_len(sect) != 0) {
if ((r = sshbuf_put_u8(buf, KRL_SECTION_EXPLICIT_KEY)) != 0 ||
(r = sshbuf_put_stringb(buf, sect)) != 0)
goto out;
}
sshbuf_reset(sect);
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_sha1s) {
KRL_DBG(("hash len %zu ", rb->len));
if ((r = sshbuf_put_string(sect, rb->blob, rb->len)) != 0)
goto out;
}
if (sshbuf_len(sect) != 0) {
if ((r = sshbuf_put_u8(buf,
KRL_SECTION_FINGERPRINT_SHA1)) != 0 ||
(r = sshbuf_put_stringb(buf, sect)) != 0)
goto out;
}
sshbuf_reset(sect);
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_sha256s) {
KRL_DBG(("hash len %zu ", rb->len));
if ((r = sshbuf_put_string(sect, rb->blob, rb->len)) != 0)
goto out;
}
if (sshbuf_len(sect) != 0) {
if ((r = sshbuf_put_u8(buf,
KRL_SECTION_FINGERPRINT_SHA256)) != 0 ||
(r = sshbuf_put_stringb(buf, sect)) != 0)
goto out;
}
for (i = 0; i < nsign_keys; i++) {
KRL_DBG(("sig key %s", sshkey_ssh_name(sign_keys[i])));
if ((r = sshbuf_put_u8(buf, KRL_SECTION_SIGNATURE)) != 0 ||
(r = sshkey_puts(sign_keys[i], buf)) != 0)
goto out;
/* XXX support sk-* keys */
if ((r = sshkey_sign(sign_keys[i], &sblob, &slen,
sshbuf_ptr(buf), sshbuf_len(buf), NULL, NULL,
NULL, 0)) != 0)
goto out;
KRL_DBG(("signature sig len %zu", slen));
if ((r = sshbuf_put_string(buf, sblob, slen)) != 0)
goto out;
}
r = 0;
out:
free(sblob);
sshbuf_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);
if (tm == NULL)
strlcpy(ts, "<INVALID>", nts);
else {
*ts = '\0';
strftime(ts, nts, "%Y%m%dT%H%M%S", tm);
}
}
static int
parse_revoked_certs(struct sshbuf *buf, struct ssh_krl *krl)
{
int r = SSH_ERR_INTERNAL_ERROR;
u_char type;
const u_char *blob;
size_t blen, nbits;
struct sshbuf *subsect = NULL;
u_int64_t serial, serial_lo, serial_hi;
struct bitmap *bitmap = NULL;
char *key_id = NULL;
struct sshkey *ca_key = NULL;
if ((subsect = sshbuf_new()) == NULL)
return SSH_ERR_ALLOC_FAIL;
/* Header: key, reserved */
if ((r = sshbuf_get_string_direct(buf, &blob, &blen)) != 0 ||
(r = sshbuf_skip_string(buf)) != 0)
goto out;
if (blen != 0 && (r = sshkey_from_blob(blob, blen, &ca_key)) != 0)
goto out;
while (sshbuf_len(buf) > 0) {
sshbuf_free(subsect);
subsect = NULL;
if ((r = sshbuf_get_u8(buf, &type)) != 0 ||
(r = sshbuf_froms(buf, &subsect)) != 0)
goto out;
KRL_DBG(("subsection type 0x%02x", type));
/* sshbuf_dump(subsect, stderr); */
switch (type) {
case KRL_SECTION_CERT_SERIAL_LIST:
while (sshbuf_len(subsect) > 0) {
if ((r = sshbuf_get_u64(subsect, &serial)) != 0)
goto out;
if ((r = ssh_krl_revoke_cert_by_serial(krl,
ca_key, serial)) != 0)
goto out;
}
break;
case KRL_SECTION_CERT_SERIAL_RANGE:
if ((r = sshbuf_get_u64(subsect, &serial_lo)) != 0 ||
(r = sshbuf_get_u64(subsect, &serial_hi)) != 0)
goto out;
if ((r = ssh_krl_revoke_cert_by_serial_range(krl,
ca_key, serial_lo, serial_hi)) != 0)
goto out;
break;
case KRL_SECTION_CERT_SERIAL_BITMAP:
if ((bitmap = bitmap_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = sshbuf_get_u64(subsect, &serial_lo)) != 0 ||
(r = sshbuf_get_bignum2_bytes_direct(subsect,
&blob, &blen)) != 0)
goto out;
if (bitmap_from_string(bitmap, blob, blen) != 0) {
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
nbits = bitmap_nbits(bitmap);
for (serial = 0; serial < (u_int64_t)nbits; serial++) {
if (serial > 0 && serial_lo + serial == 0) {
error_f("bitmap wraps u64");
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (!bitmap_test_bit(bitmap, serial))
continue;
if ((r = ssh_krl_revoke_cert_by_serial(krl,
ca_key, serial_lo + serial)) != 0)
goto out;
}
bitmap_free(bitmap);
bitmap = NULL;
break;
case KRL_SECTION_CERT_KEY_ID:
while (sshbuf_len(subsect) > 0) {
if ((r = sshbuf_get_cstring(subsect,
&key_id, NULL)) != 0)
goto out;
if ((r = ssh_krl_revoke_cert_by_key_id(krl,
ca_key, key_id)) != 0)
goto out;
free(key_id);
key_id = NULL;
}
break;
default:
error("Unsupported KRL certificate section %u", type);
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (sshbuf_len(subsect) > 0) {
error("KRL certificate section contains unparsed data");
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
}
r = 0;
out:
if (bitmap != NULL)
bitmap_free(bitmap);
free(key_id);
sshkey_free(ca_key);
sshbuf_free(subsect);
return r;
}
static int
blob_section(struct sshbuf *sect, struct revoked_blob_tree *target_tree,
size_t expected_len)
{
u_char *rdata = NULL;
size_t rlen = 0;
int r;
while (sshbuf_len(sect) > 0) {
if ((r = sshbuf_get_string(sect, &rdata, &rlen)) != 0)
return r;
if (expected_len != 0 && rlen != expected_len) {
error_f("bad length");
free(rdata);
return SSH_ERR_INVALID_FORMAT;
}
if ((r = revoke_blob(target_tree, rdata, rlen)) != 0) {
free(rdata);
return r;
}
}
return 0;
}
/* Attempt to parse a KRL, checking its signature (if any) with sign_ca_keys. */
int
ssh_krl_from_blob(struct sshbuf *buf, struct ssh_krl **krlp,
const struct sshkey **sign_ca_keys, size_t nsign_ca_keys)
{
struct sshbuf *copy = NULL, *sect = NULL;
struct ssh_krl *krl = NULL;
char timestamp[64];
int r = SSH_ERR_INTERNAL_ERROR, sig_seen;
struct sshkey *key = NULL, **ca_used = NULL, **tmp_ca_used;
u_char type;
const u_char *blob;
size_t i, j, sig_off, sects_off, blen, nca_used;
u_int format_version;
nca_used = 0;
*krlp = NULL;
if (sshbuf_len(buf) < sizeof(KRL_MAGIC) - 1 ||
memcmp(sshbuf_ptr(buf), KRL_MAGIC, sizeof(KRL_MAGIC) - 1) != 0) {
debug3_f("not a KRL");
return SSH_ERR_KRL_BAD_MAGIC;
}
/* Take a copy of the KRL buffer so we can verify its signature later */
if ((copy = sshbuf_fromb(buf)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = sshbuf_consume(copy, sizeof(KRL_MAGIC) - 1)) != 0)
goto out;
if ((krl = ssh_krl_init()) == NULL) {
error_f("alloc failed");
goto out;
}
if ((r = sshbuf_get_u32(copy, &format_version)) != 0)
goto out;
if (format_version != KRL_FORMAT_VERSION) {
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
if ((r = sshbuf_get_u64(copy, &krl->krl_version)) != 0 ||
(r = sshbuf_get_u64(copy, &krl->generated_date)) != 0 ||
(r = sshbuf_get_u64(copy, &krl->flags)) != 0 ||
(r = sshbuf_skip_string(copy)) != 0 ||
(r = sshbuf_get_cstring(copy, &krl->comment, NULL)) != 0)
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;
if (sshbuf_len(buf) < sshbuf_len(copy)) {
/* Shouldn't happen */
r = SSH_ERR_INTERNAL_ERROR;
goto out;
}
sects_off = sshbuf_len(buf) - sshbuf_len(copy);
while (sshbuf_len(copy) > 0) {
if ((r = sshbuf_get_u8(copy, &type)) != 0 ||
(r = sshbuf_get_string_direct(copy, &blob, &blen)) != 0)
goto out;
KRL_DBG(("first pass, section 0x%02x", type));
if (type != KRL_SECTION_SIGNATURE) {
if (sig_seen) {
error("KRL contains non-signature section "
"after signature");
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
/* Not interested for now. */
continue;
}
sig_seen = 1;
/* First string component is the signing key */
if ((r = sshkey_from_blob(blob, blen, &key)) != 0) {
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (sshbuf_len(buf) < sshbuf_len(copy)) {
/* Shouldn't happen */
r = SSH_ERR_INTERNAL_ERROR;
goto out;
}
sig_off = sshbuf_len(buf) - sshbuf_len(copy);
/* Second string component is the signature itself */
if ((r = sshbuf_get_string_direct(copy, &blob, &blen)) != 0) {
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
/* Check signature over entire KRL up to this point */
if ((r = sshkey_verify(key, blob, blen,
sshbuf_ptr(buf), sig_off, NULL, 0, NULL)) != 0)
goto out;
/* Check if this key has already signed this KRL */
for (i = 0; i < nca_used; i++) {
if (sshkey_equal(ca_used[i], key)) {
error("KRL signed more than once with "
"the same key");
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
}
/* Record keys used to sign the KRL */
tmp_ca_used = recallocarray(ca_used, nca_used, nca_used + 1,
sizeof(*ca_used));
if (tmp_ca_used == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
ca_used = tmp_ca_used;
ca_used[nca_used++] = key;
key = NULL;
}
if (sshbuf_len(copy) != 0) {
/* Shouldn't happen */
r = SSH_ERR_INTERNAL_ERROR;
goto out;
}
/*
* 2nd pass: parse and load the KRL, skipping the header to the point
* where the section start.
*/
sshbuf_free(copy);
if ((copy = sshbuf_fromb(buf)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = sshbuf_consume(copy, sects_off)) != 0)
goto out;
while (sshbuf_len(copy) > 0) {
sshbuf_free(sect);
sect = NULL;
if ((r = sshbuf_get_u8(copy, &type)) != 0 ||
(r = sshbuf_froms(copy, &sect)) != 0)
goto out;
KRL_DBG(("second pass, section 0x%02x", type));
switch (type) {
case KRL_SECTION_CERTIFICATES:
if ((r = parse_revoked_certs(sect, krl)) != 0)
goto out;
break;
case KRL_SECTION_EXPLICIT_KEY:
if ((r = blob_section(sect,
&krl->revoked_keys, 0)) != 0)
goto out;
break;
case KRL_SECTION_FINGERPRINT_SHA1:
if ((r = blob_section(sect,
&krl->revoked_sha1s, 20)) != 0)
goto out;
break;
case KRL_SECTION_FINGERPRINT_SHA256:
if ((r = blob_section(sect,
&krl->revoked_sha256s, 32)) != 0)
goto out;
break;
case KRL_SECTION_SIGNATURE:
/* Handled above, but still need to stay in synch */
sshbuf_free(sect);
sect = NULL;
if ((r = sshbuf_skip_string(copy)) != 0)
goto out;
break;
default:
error("Unsupported KRL section %u", type);
r = SSH_ERR_INVALID_FORMAT;
goto out;
}
if (sect != NULL && sshbuf_len(sect) > 0) {
error("KRL section contains unparsed data");
r = SSH_ERR_INVALID_FORMAT;
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 {
sshkey_free(ca_used[i]);
ca_used[i] = NULL;
}
}
if (nca_used && !sig_seen) {
error("All keys used to sign KRL were revoked");
r = SSH_ERR_KEY_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 (sshkey_equal(ca_used[j], sign_ca_keys[i])) {
sig_seen = 1;
break;
}
}
}
if (!sig_seen) {
r = SSH_ERR_SIGNATURE_INVALID;
error("KRL not signed with any trusted key");
goto out;
}
}
*krlp = krl;
r = 0;
out:
if (r != 0)
ssh_krl_free(krl);
for (i = 0; i < nca_used; i++)
sshkey_free(ca_used[i]);
free(ca_used);
sshkey_free(key);
sshbuf_free(copy);
sshbuf_free(sect);
return r;
}
/* Checks certificate serial number and key ID revocation */
static int
is_cert_revoked(const struct sshkey *key, struct revoked_certs *rc)
{
struct revoked_serial rs, *ers;
struct revoked_key_id rki, *erki;
/* 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) {
KRL_DBG(("revoked by key ID"));
return SSH_ERR_KEY_REVOKED;
}
/*
* Zero serials numbers are ignored (it's the default when the
* CA doesn't specify one).
*/
if (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(("revoked serial %llu matched %llu:%llu",
key->cert->serial, ers->lo, ers->hi));
return SSH_ERR_KEY_REVOKED;
}
return 0;
}
/* Checks whether a given key/cert is revoked. Does not check its CA */
static int
is_key_revoked(struct ssh_krl *krl, const struct sshkey *key)
{
struct revoked_blob rb, *erb;
struct revoked_certs *rc;
int r;
/* Check explicitly revoked hashes first */
memset(&rb, 0, sizeof(rb));
if ((r = sshkey_fingerprint_raw(key, SSH_DIGEST_SHA1,
&rb.blob, &rb.len)) != 0)
return r;
erb = RB_FIND(revoked_blob_tree, &krl->revoked_sha1s, &rb);
free(rb.blob);
if (erb != NULL) {
KRL_DBG(("revoked by key SHA1"));
return SSH_ERR_KEY_REVOKED;
}
memset(&rb, 0, sizeof(rb));
if ((r = sshkey_fingerprint_raw(key, SSH_DIGEST_SHA256,
&rb.blob, &rb.len)) != 0)
return r;
erb = RB_FIND(revoked_blob_tree, &krl->revoked_sha256s, &rb);
free(rb.blob);
if (erb != NULL) {
KRL_DBG(("revoked by key SHA256"));
return SSH_ERR_KEY_REVOKED;
}
/* Next, explicit keys */
memset(&rb, 0, sizeof(rb));
if ((r = plain_key_blob(key, &rb.blob, &rb.len)) != 0)
return r;
erb = RB_FIND(revoked_blob_tree, &krl->revoked_keys, &rb);
free(rb.blob);
if (erb != NULL) {
KRL_DBG(("revoked by explicit key"));
return SSH_ERR_KEY_REVOKED;
}
if (!sshkey_is_cert(key))
return 0;
/* Check cert revocation for the specified CA */
if ((r = revoked_certs_for_ca_key(krl, key->cert->signature_key,
&rc, 0)) != 0)
return r;
if (rc != NULL) {
if ((r = is_cert_revoked(key, rc)) != 0)
return r;
}
/* Check cert revocation for the wildcard CA */
if ((r = revoked_certs_for_ca_key(krl, NULL, &rc, 0)) != 0)
return r;
if (rc != NULL) {
if ((r = is_cert_revoked(key, rc)) != 0)
return r;
}
KRL_DBG(("%llu no match", key->cert->serial));
return 0;
}
int
ssh_krl_check_key(struct ssh_krl *krl, const struct sshkey *key)
{
int r;
KRL_DBG(("checking key"));
if ((r = is_key_revoked(krl, key)) != 0)
return r;
if (sshkey_is_cert(key)) {
debug2_f("checking CA key");
if ((r = is_key_revoked(krl, key->cert->signature_key)) != 0)
return r;
}
KRL_DBG(("key okay"));
return 0;
}
int
ssh_krl_file_contains_key(const char *path, const struct sshkey *key)
{
struct sshbuf *krlbuf = NULL;
struct ssh_krl *krl = NULL;
int oerrno = 0, r;
if (path == NULL)
return 0;
if ((r = sshbuf_load_file(path, &krlbuf)) != 0) {
oerrno = errno;
goto out;
}
if ((r = ssh_krl_from_blob(krlbuf, &krl, NULL, 0)) != 0)
goto out;
debug2_f("checking KRL %s", path);
r = ssh_krl_check_key(krl, key);
out:
sshbuf_free(krlbuf);
ssh_krl_free(krl);
if (r != 0)
errno = oerrno;
return r;
}
int
krl_dump(struct ssh_krl *krl, FILE *f)
{
struct sshkey *key = NULL;
struct revoked_blob *rb;
struct revoked_certs *rc;
struct revoked_serial *rs;
struct revoked_key_id *rki;
int r, ret = 0;
char *fp, timestamp[64];
/* Try to print in a KRL spec-compatible format */
format_timestamp(krl->generated_date, timestamp, sizeof(timestamp));
fprintf(f, "# KRL version %llu\n",
(unsigned long long)krl->krl_version);
fprintf(f, "# Generated at %s\n", timestamp);
if (krl->comment != NULL && *krl->comment != '\0') {
r = INT_MAX;
asmprintf(&fp, INT_MAX, &r, "%s", krl->comment);
fprintf(f, "# Comment: %s\n", fp);
free(fp);
}
fputc('\n', f);
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_keys) {
if ((r = sshkey_from_blob(rb->blob, rb->len, &key)) != 0) {
ret = SSH_ERR_INVALID_FORMAT;
error_r(r, "parse KRL key");
continue;
}
if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
SSH_FP_DEFAULT)) == NULL) {
ret = SSH_ERR_INVALID_FORMAT;
error("sshkey_fingerprint failed");
continue;
}
fprintf(f, "hash: SHA256:%s # %s\n", fp, sshkey_ssh_name(key));
free(fp);
free(key);
}
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_sha256s) {
fp = tohex(rb->blob, rb->len);
fprintf(f, "hash: SHA256:%s\n", fp);
free(fp);
}
RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_sha1s) {
/*
* There is not KRL spec keyword for raw SHA1 hashes, so
* print them as comments.
*/
fp = tohex(rb->blob, rb->len);
fprintf(f, "# hash SHA1:%s\n", fp);
free(fp);
}
TAILQ_FOREACH(rc, &krl->revoked_certs, entry) {
fputc('\n', f);
if (rc->ca_key == NULL)
fprintf(f, "# Wildcard CA\n");
else {
if ((fp = sshkey_fingerprint(rc->ca_key,
SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) {
ret = SSH_ERR_INVALID_FORMAT;
error("sshkey_fingerprint failed");
continue;
}
fprintf(f, "# CA key %s %s\n",
sshkey_ssh_name(rc->ca_key), fp);
free(fp);
}
RB_FOREACH(rs, revoked_serial_tree, &rc->revoked_serials) {
if (rs->lo == rs->hi) {
fprintf(f, "serial: %llu\n",
(unsigned long long)rs->lo);
} else {
fprintf(f, "serial: %llu-%llu\n",
(unsigned long long)rs->lo,
(unsigned long long)rs->hi);
}
}
RB_FOREACH(rki, revoked_key_id_tree, &rc->revoked_key_ids) {
/*
* We don't want key IDs with embedded newlines to
* mess up the display.
*/
r = INT_MAX;
asmprintf(&fp, INT_MAX, &r, "%s", rki->key_id);
fprintf(f, "id: %s\n", fp);
free(fp);
}
}
return ret;
}
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