/src/openssh/krl.c

Source
/* $OpenBSD: krl.c,v 1.62 2025/09/15 04:41:20 djm Exp $ */
/*
 * 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.
 */

#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;

  if (rc == NULL)
    return;
  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);
  freezero(rc, sizeof(*rc));
}

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);
  }
  free(krl);
}

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) {
        r = SSH_ERR_INVALID_FORMAT;
        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)
{
  int r = SSH_ERR_INTERNAL_ERROR;
  struct revoked_certs *rc;
  struct revoked_blob *rb;
  struct sshbuf *sect;
  u_char *sblob = NULL;

  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;
  }
  /* success */
  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
cert_extension_subsection(struct sshbuf *subsect, struct ssh_krl *krl)
{
  int r = SSH_ERR_INTERNAL_ERROR;
  u_char critical = 1;
  struct sshbuf *value = NULL;
  char *name = NULL;

  if ((r = sshbuf_get_cstring(subsect, &name, NULL)) != 0 ||
      (r = sshbuf_get_u8(subsect, &critical)) != 0 ||
      (r = sshbuf_froms(subsect, &value)) != 0) {
    debug_fr(r, "parse");
    error("KRL has invalid certificate extension subsection");
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  if (sshbuf_len(subsect) != 0) {
    error("KRL has invalid certificate extension subsection: "
        "trailing data");
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  debug_f("cert extension %s critical %u len %zu",
      name, critical, sshbuf_len(value));
  /* no extensions are currently supported */
  if (critical) {
    error("KRL contains unsupported critical certificate "
        "subsection \"%s\"", name);
    r = SSH_ERR_FEATURE_UNSUPPORTED;
    goto out;
  }
  /* success */
  r = 0;
 out:
  free(name);
  sshbuf_free(value);
  return r;
}

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;
    case KRL_SECTION_CERT_EXTENSION:
      if ((r = cert_extension_subsection(subsect, krl)) != 0)
        goto out;
      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;
}

static int
extension_section(struct sshbuf *sect, struct ssh_krl *krl)
{
  int r = SSH_ERR_INTERNAL_ERROR;
  u_char critical = 1;
  struct sshbuf *value = NULL;
  char *name = NULL;

  if ((r = sshbuf_get_cstring(sect, &name, NULL)) != 0 ||
      (r = sshbuf_get_u8(sect, &critical)) != 0 ||
      (r = sshbuf_froms(sect, &value)) != 0) {
    debug_fr(r, "parse");
    error("KRL has invalid extension section");
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  if (sshbuf_len(sect) != 0) {
    error("KRL has invalid extension section: trailing data");
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  debug_f("extension %s critical %u len %zu",
      name, critical, sshbuf_len(value));
  /* no extensions are currently supported */
  if (critical) {
    error("KRL contains unsupported critical section \"%s\"", name);
    r = SSH_ERR_FEATURE_UNSUPPORTED;
    goto out;
  }
  /* success */
  r = 0;
 out:
  free(name);
  sshbuf_free(value);
  return r;
}

/* Attempt to parse a KRL */
int
ssh_krl_from_blob(struct sshbuf *buf, struct ssh_krl **krlp)
{
  struct sshbuf *copy = NULL, *sect = NULL;
  struct ssh_krl *krl = NULL;
  char timestamp[64];
  int r = SSH_ERR_INTERNAL_ERROR;
  u_char type;
  u_int format_version;

  *krlp = NULL;

  /* KRL must begin with magic string */
  if ((r = sshbuf_cmp(buf, 0, KRL_MAGIC, sizeof(KRL_MAGIC) - 1)) != 0) {
    debug2_f("bad KRL magic header");
    return SSH_ERR_KRL_BAD_MAGIC;
  }

  if ((krl = ssh_krl_init()) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    error_f("alloc failed");
    goto out;
  }
  /* Don't modify buffer */
  if ((copy = sshbuf_fromb(buf)) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }
  if ((r = sshbuf_consume(copy, sizeof(KRL_MAGIC) - 1)) != 0 ||
      (r = sshbuf_get_u32(copy, &format_version)) != 0)
    goto out;
  if (format_version != KRL_FORMAT_VERSION) {
    error_f("unsupported KRL format version %u", 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) {
    error_fr(r, "parse KRL header");
    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);

  /* Parse and load the KRL sections. */
  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(("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_EXTENSION:
      if ((r = extension_section(sect, krl)) != 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;
    }
  }

  /* Success */
  *krlp = krl;
  r = 0;
 out:
  if (r != 0)
    ssh_krl_free(krl);
  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)) != 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: %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;
}

Coverage Report

Created: 2025-11-03 07:12