/src/hpn-ssh/sshkey-xmss.c

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/* $OpenBSD: sshkey-xmss.c,v 1.12 2022/10/28 00:39:29 djm Exp $ */
/*
 * Copyright (c) 2017 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
#ifdef WITH_XMSS

#include <sys/types.h>
#include <sys/uio.h>

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#ifdef HAVE_SYS_FILE_H
# include <sys/file.h>
#endif

#include "ssh2.h"
#include "ssherr.h"
#include "sshbuf.h"
#include "cipher.h"
#include "sshkey.h"
#include "sshkey-xmss.h"
#include "atomicio.h"
#include "log.h"

#include "xmss_fast.h"

/* opaque internal XMSS state */
#define XMSS_MAGIC    "xmss-state-v1"
#define XMSS_CIPHERNAME   "aes256-gcm@openssh.com"
struct ssh_xmss_state {
  xmss_params params;
  u_int32_t n, w, h, k;

  bds_state bds;
  u_char    *stack;
  u_int32_t stackoffset;
  u_char    *stacklevels;
  u_char    *auth;
  u_char    *keep;
  u_char    *th_nodes;
  u_char    *retain;
  treehash_inst *treehash;

  u_int32_t idx;    /* state read from file */
  u_int32_t maxidx;   /* restricted # of signatures */
  int   have_state; /* .state file exists */
  int   lockfd;   /* locked in sshkey_xmss_get_state() */
  u_char    allow_update; /* allow sshkey_xmss_update_state() */
  char    *enc_ciphername;/* encrypt state with cipher */
  u_char    *enc_keyiv; /* encrypt state with key */
  u_int32_t enc_keyiv_len;  /* length of enc_keyiv */
};

int  sshkey_xmss_init_bds_state(struct sshkey *);
int  sshkey_xmss_init_enc_key(struct sshkey *, const char *);
void   sshkey_xmss_free_bds(struct sshkey *);
int  sshkey_xmss_get_state_from_file(struct sshkey *, const char *,
      int *, int);
int  sshkey_xmss_encrypt_state(const struct sshkey *, struct sshbuf *,
      struct sshbuf **);
int  sshkey_xmss_decrypt_state(const struct sshkey *, struct sshbuf *,
      struct sshbuf **);
int  sshkey_xmss_serialize_enc_key(const struct sshkey *, struct sshbuf *);
int  sshkey_xmss_deserialize_enc_key(struct sshkey *, struct sshbuf *);

#define PRINT(...) do { if (printerror) sshlog(__FILE__, __func__, __LINE__, \
    0, SYSLOG_LEVEL_ERROR, NULL, __VA_ARGS__); } while (0)

int
sshkey_xmss_init(struct sshkey *key, const char *name)
{
  struct ssh_xmss_state *state;

  if (key->xmss_state != NULL)
    return SSH_ERR_INVALID_FORMAT;
  if (name == NULL)
    return SSH_ERR_INVALID_FORMAT;
  state = calloc(sizeof(struct ssh_xmss_state), 1);
  if (state == NULL)
    return SSH_ERR_ALLOC_FAIL;
  if (strcmp(name, XMSS_SHA2_256_W16_H10_NAME) == 0) {
    state->n = 32;
    state->w = 16;
    state->h = 10;
  } else if (strcmp(name, XMSS_SHA2_256_W16_H16_NAME) == 0) {
    state->n = 32;
    state->w = 16;
    state->h = 16;
  } else if (strcmp(name, XMSS_SHA2_256_W16_H20_NAME) == 0) {
    state->n = 32;
    state->w = 16;
    state->h = 20;
  } else {
    free(state);
    return SSH_ERR_KEY_TYPE_UNKNOWN;
  }
  if ((key->xmss_name = strdup(name)) == NULL) {
    free(state);
    return SSH_ERR_ALLOC_FAIL;
  }
  state->k = 2; /* XXX hardcoded */
  state->lockfd = -1;
  if (xmss_set_params(&state->params, state->n, state->h, state->w,
      state->k) != 0) {
    free(state);
    return SSH_ERR_INVALID_FORMAT;
  }
  key->xmss_state = state;
  return 0;
}

void
sshkey_xmss_free_state(struct sshkey *key)
{
  struct ssh_xmss_state *state = key->xmss_state;

  sshkey_xmss_free_bds(key);
  if (state) {
    if (state->enc_keyiv) {
      explicit_bzero(state->enc_keyiv, state->enc_keyiv_len);
      free(state->enc_keyiv);
    }
    free(state->enc_ciphername);
    free(state);
  }
  key->xmss_state = NULL;
}

#define SSH_XMSS_K2_MAGIC "k=2"
#define num_stack(x)    ((x->h+1)*(x->n))
#define num_stacklevels(x)  (x->h+1)
#define num_auth(x)   ((x->h)*(x->n))
#define num_keep(x)   ((x->h >> 1)*(x->n))
#define num_th_nodes(x)   ((x->h - x->k)*(x->n))
#define num_retain(x)   (((1ULL << x->k) - x->k - 1) * (x->n))
#define num_treehash(x)   ((x->h) - (x->k))

int
sshkey_xmss_init_bds_state(struct sshkey *key)
{
  struct ssh_xmss_state *state = key->xmss_state;
  u_int32_t i;

  state->stackoffset = 0;
  if ((state->stack = calloc(num_stack(state), 1)) == NULL ||
      (state->stacklevels = calloc(num_stacklevels(state), 1))== NULL ||
      (state->auth = calloc(num_auth(state), 1)) == NULL ||
      (state->keep = calloc(num_keep(state), 1)) == NULL ||
      (state->th_nodes = calloc(num_th_nodes(state), 1)) == NULL ||
      (state->retain = calloc(num_retain(state), 1)) == NULL ||
      (state->treehash = calloc(num_treehash(state),
      sizeof(treehash_inst))) == NULL) {
    sshkey_xmss_free_bds(key);
    return SSH_ERR_ALLOC_FAIL;
  }
  for (i = 0; i < state->h - state->k; i++)
    state->treehash[i].node = &state->th_nodes[state->n*i];
  xmss_set_bds_state(&state->bds, state->stack, state->stackoffset,
      state->stacklevels, state->auth, state->keep, state->treehash,
      state->retain, 0);
  return 0;
}

void
sshkey_xmss_free_bds(struct sshkey *key)
{
  struct ssh_xmss_state *state = key->xmss_state;

  if (state == NULL)
    return;
  free(state->stack);
  free(state->stacklevels);
  free(state->auth);
  free(state->keep);
  free(state->th_nodes);
  free(state->retain);
  free(state->treehash);
  state->stack = NULL;
  state->stacklevels = NULL;
  state->auth = NULL;
  state->keep = NULL;
  state->th_nodes = NULL;
  state->retain = NULL;
  state->treehash = NULL;
}

void *
sshkey_xmss_params(const struct sshkey *key)
{
  struct ssh_xmss_state *state = key->xmss_state;

  if (state == NULL)
    return NULL;
  return &state->params;
}

void *
sshkey_xmss_bds_state(const struct sshkey *key)
{
  struct ssh_xmss_state *state = key->xmss_state;

  if (state == NULL)
    return NULL;
  return &state->bds;
}

int
sshkey_xmss_siglen(const struct sshkey *key, size_t *lenp)
{
  struct ssh_xmss_state *state = key->xmss_state;

  if (lenp == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if (state == NULL)
    return SSH_ERR_INVALID_FORMAT;
  *lenp = 4 + state->n +
      state->params.wots_par.keysize +
      state->h * state->n;
  return 0;
}

size_t
sshkey_xmss_pklen(const struct sshkey *key)
{
  struct ssh_xmss_state *state = key->xmss_state;

  if (state == NULL)
    return 0;
  return state->n * 2;
}

size_t
sshkey_xmss_sklen(const struct sshkey *key)
{
  struct ssh_xmss_state *state = key->xmss_state;

  if (state == NULL)
    return 0;
  return state->n * 4 + 4;
}

int
sshkey_xmss_init_enc_key(struct sshkey *k, const char *ciphername)
{
  struct ssh_xmss_state *state = k->xmss_state;
  const struct sshcipher *cipher;
  size_t keylen = 0, ivlen = 0;

  if (state == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if ((cipher = cipher_by_name(ciphername)) == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  if ((state->enc_ciphername = strdup(ciphername)) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  keylen = cipher_keylen(cipher);
  ivlen = cipher_ivlen(cipher);
  state->enc_keyiv_len = keylen + ivlen;
  if ((state->enc_keyiv = calloc(state->enc_keyiv_len, 1)) == NULL) {
    free(state->enc_ciphername);
    state->enc_ciphername = NULL;
    return SSH_ERR_ALLOC_FAIL;
  }
  arc4random_buf(state->enc_keyiv, state->enc_keyiv_len);
  return 0;
}

int
sshkey_xmss_serialize_enc_key(const struct sshkey *k, struct sshbuf *b)
{
  struct ssh_xmss_state *state = k->xmss_state;
  int r;

  if (state == NULL || state->enc_keyiv == NULL ||
      state->enc_ciphername == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if ((r = sshbuf_put_cstring(b, state->enc_ciphername)) != 0 ||
      (r = sshbuf_put_string(b, state->enc_keyiv,
      state->enc_keyiv_len)) != 0)
    return r;
  return 0;
}

int
sshkey_xmss_deserialize_enc_key(struct sshkey *k, struct sshbuf *b)
{
  struct ssh_xmss_state *state = k->xmss_state;
  size_t len;
  int r;

  if (state == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if ((r = sshbuf_get_cstring(b, &state->enc_ciphername, NULL)) != 0 ||
      (r = sshbuf_get_string(b, &state->enc_keyiv, &len)) != 0)
    return r;
  state->enc_keyiv_len = len;
  return 0;
}

int
sshkey_xmss_serialize_pk_info(const struct sshkey *k, struct sshbuf *b,
    enum sshkey_serialize_rep opts)
{
  struct ssh_xmss_state *state = k->xmss_state;
  u_char have_info = 1;
  u_int32_t idx;
  int r;

  if (state == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if (opts != SSHKEY_SERIALIZE_INFO)
    return 0;
  idx = k->xmss_sk ? PEEK_U32(k->xmss_sk) : state->idx;
  if ((r = sshbuf_put_u8(b, have_info)) != 0 ||
      (r = sshbuf_put_u32(b, idx)) != 0 ||
      (r = sshbuf_put_u32(b, state->maxidx)) != 0)
    return r;
  return 0;
}

int
sshkey_xmss_deserialize_pk_info(struct sshkey *k, struct sshbuf *b)
{
  struct ssh_xmss_state *state = k->xmss_state;
  u_char have_info;
  int r;

  if (state == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  /* optional */
  if (sshbuf_len(b) == 0)
    return 0;
  if ((r = sshbuf_get_u8(b, &have_info)) != 0)
    return r;
  if (have_info != 1)
    return SSH_ERR_INVALID_ARGUMENT;
  if ((r = sshbuf_get_u32(b, &state->idx)) != 0 ||
      (r = sshbuf_get_u32(b, &state->maxidx)) != 0)
    return r;
  return 0;
}

int
sshkey_xmss_generate_private_key(struct sshkey *k, int bits)
{
  int r;
  const char *name;

  if (bits == 10) {
    name = XMSS_SHA2_256_W16_H10_NAME;
  } else if (bits == 16) {
    name = XMSS_SHA2_256_W16_H16_NAME;
  } else if (bits == 20) {
    name = XMSS_SHA2_256_W16_H20_NAME;
  } else {
    name = XMSS_DEFAULT_NAME;
  }
  if ((r = sshkey_xmss_init(k, name)) != 0 ||
      (r = sshkey_xmss_init_bds_state(k)) != 0 ||
      (r = sshkey_xmss_init_enc_key(k, XMSS_CIPHERNAME)) != 0)
    return r;
  if ((k->xmss_pk = malloc(sshkey_xmss_pklen(k))) == NULL ||
      (k->xmss_sk = malloc(sshkey_xmss_sklen(k))) == NULL) {
    return SSH_ERR_ALLOC_FAIL;
  }
  xmss_keypair(k->xmss_pk, k->xmss_sk, sshkey_xmss_bds_state(k),
      sshkey_xmss_params(k));
  return 0;
}

int
sshkey_xmss_get_state_from_file(struct sshkey *k, const char *filename,
    int *have_file, int printerror)
{
  struct sshbuf *b = NULL, *enc = NULL;
  int ret = SSH_ERR_SYSTEM_ERROR, r, fd = -1;
  u_int32_t len;
  unsigned char buf[4], *data = NULL;

  *have_file = 0;
  if ((fd = open(filename, O_RDONLY)) >= 0) {
    *have_file = 1;
    if (atomicio(read, fd, buf, sizeof(buf)) != sizeof(buf)) {
      PRINT("corrupt state file: %s", filename);
      goto done;
    }
    len = PEEK_U32(buf);
    if ((data = calloc(len, 1)) == NULL) {
      ret = SSH_ERR_ALLOC_FAIL;
      goto done;
    }
    if (atomicio(read, fd, data, len) != len) {
      PRINT("cannot read blob: %s", filename);
      goto done;
    }
    if ((enc = sshbuf_from(data, len)) == NULL) {
      ret = SSH_ERR_ALLOC_FAIL;
      goto done;
    }
    sshkey_xmss_free_bds(k);
    if ((r = sshkey_xmss_decrypt_state(k, enc, &b)) != 0) {
      ret = r;
      goto done;
    }
    if ((r = sshkey_xmss_deserialize_state(k, b)) != 0) {
      ret = r;
      goto done;
    }
    ret = 0;
  }
done:
  if (fd != -1)
    close(fd);
  free(data);
  sshbuf_free(enc);
  sshbuf_free(b);
  return ret;
}

int
sshkey_xmss_get_state(const struct sshkey *k, int printerror)
{
  struct ssh_xmss_state *state = k->xmss_state;
  u_int32_t idx = 0;
  char *filename = NULL;
  char *statefile = NULL, *ostatefile = NULL, *lockfile = NULL;
  int lockfd = -1, have_state = 0, have_ostate, tries = 0;
  int ret = SSH_ERR_INVALID_ARGUMENT, r;

  if (state == NULL)
    goto done;
  /*
   * If maxidx is set, then we are allowed a limited number
   * of signatures, but don't need to access the disk.
   * Otherwise we need to deal with the on-disk state.
   */
  if (state->maxidx) {
    /* xmss_sk always contains the current state */
    idx = PEEK_U32(k->xmss_sk);
    if (idx < state->maxidx) {
      state->allow_update = 1;
      return 0;
    }
    return SSH_ERR_INVALID_ARGUMENT;
  }
  if ((filename = k->xmss_filename) == NULL)
    goto done;
  if (asprintf(&lockfile, "%s.lock", filename) == -1 ||
      asprintf(&statefile, "%s.state", filename) == -1 ||
      asprintf(&ostatefile, "%s.ostate", filename) == -1) {
    ret = SSH_ERR_ALLOC_FAIL;
    goto done;
  }
  if ((lockfd = open(lockfile, O_CREAT|O_RDONLY, 0600)) == -1) {
    ret = SSH_ERR_SYSTEM_ERROR;
    PRINT("cannot open/create: %s", lockfile);
    goto done;
  }
  while (flock(lockfd, LOCK_EX|LOCK_NB) == -1) {
    if (errno != EWOULDBLOCK) {
      ret = SSH_ERR_SYSTEM_ERROR;
      PRINT("cannot lock: %s", lockfile);
      goto done;
    }
    if (++tries > 10) {
      ret = SSH_ERR_SYSTEM_ERROR;
      PRINT("giving up on: %s", lockfile);
      goto done;
    }
    usleep(1000*100*tries);
  }
  /* XXX no longer const */
  if ((r = sshkey_xmss_get_state_from_file((struct sshkey *)k,
      statefile, &have_state, printerror)) != 0) {
    if ((r = sshkey_xmss_get_state_from_file((struct sshkey *)k,
        ostatefile, &have_ostate, printerror)) == 0) {
      state->allow_update = 1;
      r = sshkey_xmss_forward_state(k, 1);
      state->idx = PEEK_U32(k->xmss_sk);
      state->allow_update = 0;
    }
  }
  if (!have_state && !have_ostate) {
    /* check that bds state is initialized */
    if (state->bds.auth == NULL)
      goto done;
    PRINT("start from scratch idx 0: %u", state->idx);
  } else if (r != 0) {
    ret = r;
    goto done;
  }
  if (state->idx + 1 < state->idx) {
    PRINT("state wrap: %u", state->idx);
    goto done;
  }
  state->have_state = have_state;
  state->lockfd = lockfd;
  state->allow_update = 1;
  lockfd = -1;
  ret = 0;
done:
  if (lockfd != -1)
    close(lockfd);
  free(lockfile);
  free(statefile);
  free(ostatefile);
  return ret;
}

int
sshkey_xmss_forward_state(const struct sshkey *k, u_int32_t reserve)
{
  struct ssh_xmss_state *state = k->xmss_state;
  u_char *sig = NULL;
  size_t required_siglen;
  unsigned long long smlen;
  u_char data;
  int ret, r;

  if (state == NULL || !state->allow_update)
    return SSH_ERR_INVALID_ARGUMENT;
  if (reserve == 0)
    return SSH_ERR_INVALID_ARGUMENT;
  if (state->idx + reserve <= state->idx)
    return SSH_ERR_INVALID_ARGUMENT;
  if ((r = sshkey_xmss_siglen(k, &required_siglen)) != 0)
    return r;
  if ((sig = malloc(required_siglen)) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  while (reserve-- > 0) {
    state->idx = PEEK_U32(k->xmss_sk);
    smlen = required_siglen;
    if ((ret = xmss_sign(k->xmss_sk, sshkey_xmss_bds_state(k),
        sig, &smlen, &data, 0, sshkey_xmss_params(k))) != 0) {
      r = SSH_ERR_INVALID_ARGUMENT;
      break;
    }
  }
  free(sig);
  return r;
}

int
sshkey_xmss_update_state(const struct sshkey *k, int printerror)
{
  struct ssh_xmss_state *state = k->xmss_state;
  struct sshbuf *b = NULL, *enc = NULL;
  u_int32_t idx = 0;
  unsigned char buf[4];
  char *filename = NULL;
  char *statefile = NULL, *ostatefile = NULL, *nstatefile = NULL;
  int fd = -1;
  int ret = SSH_ERR_INVALID_ARGUMENT;

  if (state == NULL || !state->allow_update)
    return ret;
  if (state->maxidx) {
    /* no update since the number of signatures is limited */
    ret = 0;
    goto done;
  }
  idx = PEEK_U32(k->xmss_sk);
  if (idx == state->idx) {
    /* no signature happened, no need to update */
    ret = 0;
    goto done;
  } else if (idx != state->idx + 1) {
    PRINT("more than one signature happened: idx %u state %u",
        idx, state->idx);
    goto done;
  }
  state->idx = idx;
  if ((filename = k->xmss_filename) == NULL)
    goto done;
  if (asprintf(&statefile, "%s.state", filename) == -1 ||
      asprintf(&ostatefile, "%s.ostate", filename) == -1 ||
      asprintf(&nstatefile, "%s.nstate", filename) == -1) {
    ret = SSH_ERR_ALLOC_FAIL;
    goto done;
  }
  unlink(nstatefile);
  if ((b = sshbuf_new()) == NULL) {
    ret = SSH_ERR_ALLOC_FAIL;
    goto done;
  }
  if ((ret = sshkey_xmss_serialize_state(k, b)) != 0) {
    PRINT("SERLIALIZE FAILED: %d", ret);
    goto done;
  }
  if ((ret = sshkey_xmss_encrypt_state(k, b, &enc)) != 0) {
    PRINT("ENCRYPT FAILED: %d", ret);
    goto done;
  }
  if ((fd = open(nstatefile, O_CREAT|O_WRONLY|O_EXCL, 0600)) == -1) {
    ret = SSH_ERR_SYSTEM_ERROR;
    PRINT("open new state file: %s", nstatefile);
    goto done;
  }
  POKE_U32(buf, sshbuf_len(enc));
  if (atomicio(vwrite, fd, buf, sizeof(buf)) != sizeof(buf)) {
    ret = SSH_ERR_SYSTEM_ERROR;
    PRINT("write new state file hdr: %s", nstatefile);
    close(fd);
    goto done;
  }
  if (atomicio(vwrite, fd, sshbuf_mutable_ptr(enc), sshbuf_len(enc)) !=
      sshbuf_len(enc)) {
    ret = SSH_ERR_SYSTEM_ERROR;
    PRINT("write new state file data: %s", nstatefile);
    close(fd);
    goto done;
  }
  if (fsync(fd) == -1) {
    ret = SSH_ERR_SYSTEM_ERROR;
    PRINT("sync new state file: %s", nstatefile);
    close(fd);
    goto done;
  }
  if (close(fd) == -1) {
    ret = SSH_ERR_SYSTEM_ERROR;
    PRINT("close new state file: %s", nstatefile);
    goto done;
  }
  if (state->have_state) {
    unlink(ostatefile);
    if (link(statefile, ostatefile)) {
      ret = SSH_ERR_SYSTEM_ERROR;
      PRINT("backup state %s to %s", statefile, ostatefile);
      goto done;
    }
  }
  if (rename(nstatefile, statefile) == -1) {
    ret = SSH_ERR_SYSTEM_ERROR;
    PRINT("rename %s to %s", nstatefile, statefile);
    goto done;
  }
  ret = 0;
done:
  if (state->lockfd != -1) {
    close(state->lockfd);
    state->lockfd = -1;
  }
  if (nstatefile)
    unlink(nstatefile);
  free(statefile);
  free(ostatefile);
  free(nstatefile);
  sshbuf_free(b);
  sshbuf_free(enc);
  return ret;
}

int
sshkey_xmss_serialize_state(const struct sshkey *k, struct sshbuf *b)
{
  struct ssh_xmss_state *state = k->xmss_state;
  treehash_inst *th;
  u_int32_t i, node;
  int r;

  if (state == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if (state->stack == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  state->stackoffset = state->bds.stackoffset;  /* copy back */
  if ((r = sshbuf_put_cstring(b, SSH_XMSS_K2_MAGIC)) != 0 ||
      (r = sshbuf_put_u32(b, state->idx)) != 0 ||
      (r = sshbuf_put_string(b, state->stack, num_stack(state))) != 0 ||
      (r = sshbuf_put_u32(b, state->stackoffset)) != 0 ||
      (r = sshbuf_put_string(b, state->stacklevels, num_stacklevels(state))) != 0 ||
      (r = sshbuf_put_string(b, state->auth, num_auth(state))) != 0 ||
      (r = sshbuf_put_string(b, state->keep, num_keep(state))) != 0 ||
      (r = sshbuf_put_string(b, state->th_nodes, num_th_nodes(state))) != 0 ||
      (r = sshbuf_put_string(b, state->retain, num_retain(state))) != 0 ||
      (r = sshbuf_put_u32(b, num_treehash(state))) != 0)
    return r;
  for (i = 0; i < num_treehash(state); i++) {
    th = &state->treehash[i];
    node = th->node - state->th_nodes;
    if ((r = sshbuf_put_u32(b, th->h)) != 0 ||
        (r = sshbuf_put_u32(b, th->next_idx)) != 0 ||
        (r = sshbuf_put_u32(b, th->stackusage)) != 0 ||
        (r = sshbuf_put_u8(b, th->completed)) != 0 ||
        (r = sshbuf_put_u32(b, node)) != 0)
      return r;
  }
  return 0;
}

int
sshkey_xmss_serialize_state_opt(const struct sshkey *k, struct sshbuf *b,
    enum sshkey_serialize_rep opts)
{
  struct ssh_xmss_state *state = k->xmss_state;
  int r = SSH_ERR_INVALID_ARGUMENT;
  u_char have_stack, have_filename, have_enc;

  if (state == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if ((r = sshbuf_put_u8(b, opts)) != 0)
    return r;
  switch (opts) {
  case SSHKEY_SERIALIZE_STATE:
    r = sshkey_xmss_serialize_state(k, b);
    break;
  case SSHKEY_SERIALIZE_FULL:
    if ((r = sshkey_xmss_serialize_enc_key(k, b)) != 0)
      return r;
    r = sshkey_xmss_serialize_state(k, b);
    break;
  case SSHKEY_SERIALIZE_SHIELD:
    /* all of stack/filename/enc are optional */
    have_stack = state->stack != NULL;
    if ((r = sshbuf_put_u8(b, have_stack)) != 0)
      return r;
    if (have_stack) {
      state->idx = PEEK_U32(k->xmss_sk); /* update */
      if ((r = sshkey_xmss_serialize_state(k, b)) != 0)
        return r;
    }
    have_filename = k->xmss_filename != NULL;
    if ((r = sshbuf_put_u8(b, have_filename)) != 0)
      return r;
    if (have_filename &&
        (r = sshbuf_put_cstring(b, k->xmss_filename)) != 0)
      return r;
    have_enc = state->enc_keyiv != NULL;
    if ((r = sshbuf_put_u8(b, have_enc)) != 0)
      return r;
    if (have_enc &&
        (r = sshkey_xmss_serialize_enc_key(k, b)) != 0)
      return r;
    if ((r = sshbuf_put_u32(b, state->maxidx)) != 0 ||
        (r = sshbuf_put_u8(b, state->allow_update)) != 0)
      return r;
    break;
  case SSHKEY_SERIALIZE_DEFAULT:
    r = 0;
    break;
  default:
    r = SSH_ERR_INVALID_ARGUMENT;
    break;
  }
  return r;
}

int
sshkey_xmss_deserialize_state(struct sshkey *k, struct sshbuf *b)
{
  struct ssh_xmss_state *state = k->xmss_state;
  treehash_inst *th;
  u_int32_t i, lh, node;
  size_t ls, lsl, la, lk, ln, lr;
  char *magic;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (state == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if (k->xmss_sk == NULL)
    return SSH_ERR_INVALID_ARGUMENT;
  if ((state->treehash = calloc(num_treehash(state),
      sizeof(treehash_inst))) == NULL)
    return SSH_ERR_ALLOC_FAIL;
  if ((r = sshbuf_get_cstring(b, &magic, NULL)) != 0 ||
      (r = sshbuf_get_u32(b, &state->idx)) != 0 ||
      (r = sshbuf_get_string(b, &state->stack, &ls)) != 0 ||
      (r = sshbuf_get_u32(b, &state->stackoffset)) != 0 ||
      (r = sshbuf_get_string(b, &state->stacklevels, &lsl)) != 0 ||
      (r = sshbuf_get_string(b, &state->auth, &la)) != 0 ||
      (r = sshbuf_get_string(b, &state->keep, &lk)) != 0 ||
      (r = sshbuf_get_string(b, &state->th_nodes, &ln)) != 0 ||
      (r = sshbuf_get_string(b, &state->retain, &lr)) != 0 ||
      (r = sshbuf_get_u32(b, &lh)) != 0)
    goto out;
  if (strcmp(magic, SSH_XMSS_K2_MAGIC) != 0) {
    r = SSH_ERR_INVALID_ARGUMENT;
    goto out;
  }
  /* XXX check stackoffset */
  if (ls != num_stack(state) ||
      lsl != num_stacklevels(state) ||
      la != num_auth(state) ||
      lk != num_keep(state) ||
      ln != num_th_nodes(state) ||
      lr != num_retain(state) ||
      lh != num_treehash(state)) {
    r = SSH_ERR_INVALID_ARGUMENT;
    goto out;
  }
  for (i = 0; i < num_treehash(state); i++) {
    th = &state->treehash[i];
    if ((r = sshbuf_get_u32(b, &th->h)) != 0 ||
        (r = sshbuf_get_u32(b, &th->next_idx)) != 0 ||
        (r = sshbuf_get_u32(b, &th->stackusage)) != 0 ||
        (r = sshbuf_get_u8(b, &th->completed)) != 0 ||
        (r = sshbuf_get_u32(b, &node)) != 0)
      goto out;
    if (node < num_th_nodes(state))
      th->node = &state->th_nodes[node];
  }
  POKE_U32(k->xmss_sk, state->idx);
  xmss_set_bds_state(&state->bds, state->stack, state->stackoffset,
      state->stacklevels, state->auth, state->keep, state->treehash,
      state->retain, 0);
  /* success */
  r = 0;
 out:
  free(magic);
  return r;
}

int
sshkey_xmss_deserialize_state_opt(struct sshkey *k, struct sshbuf *b)
{
  struct ssh_xmss_state *state = k->xmss_state;
  enum sshkey_serialize_rep opts;
  u_char have_state, have_stack, have_filename, have_enc;
  int r;

  if ((r = sshbuf_get_u8(b, &have_state)) != 0)
    return r;

  opts = have_state;
  switch (opts) {
  case SSHKEY_SERIALIZE_DEFAULT:
    r = 0;
    break;
  case SSHKEY_SERIALIZE_SHIELD:
    if ((r = sshbuf_get_u8(b, &have_stack)) != 0)
      return r;
    if (have_stack &&
        (r = sshkey_xmss_deserialize_state(k, b)) != 0)
      return r;
    if ((r = sshbuf_get_u8(b, &have_filename)) != 0)
      return r;
    if (have_filename &&
        (r = sshbuf_get_cstring(b, &k->xmss_filename, NULL)) != 0)
      return r;
    if ((r = sshbuf_get_u8(b, &have_enc)) != 0)
      return r;
    if (have_enc &&
        (r = sshkey_xmss_deserialize_enc_key(k, b)) != 0)
      return r;
    if ((r = sshbuf_get_u32(b, &state->maxidx)) != 0 ||
        (r = sshbuf_get_u8(b, &state->allow_update)) != 0)
      return r;
    break;
  case SSHKEY_SERIALIZE_STATE:
    if ((r = sshkey_xmss_deserialize_state(k, b)) != 0)
      return r;
    break;
  case SSHKEY_SERIALIZE_FULL:
    if ((r = sshkey_xmss_deserialize_enc_key(k, b)) != 0 ||
        (r = sshkey_xmss_deserialize_state(k, b)) != 0)
      return r;
    break;
  default:
    r = SSH_ERR_INVALID_FORMAT;
    break;
  }
  return r;
}

int
sshkey_xmss_encrypt_state(const struct sshkey *k, struct sshbuf *b,
   struct sshbuf **retp)
{
  struct ssh_xmss_state *state = k->xmss_state;
  struct sshbuf *encrypted = NULL, *encoded = NULL, *padded = NULL;
  struct sshcipher_ctx *ciphercontext = NULL;
  const struct sshcipher *cipher;
  u_char *cp, *key, *iv = NULL;
  size_t i, keylen, ivlen, blocksize, authlen, encrypted_len, aadlen;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (retp != NULL)
    *retp = NULL;
  if (state == NULL ||
      state->enc_keyiv == NULL ||
      state->enc_ciphername == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  /*
   * chacha20-poly1305-mt@hpnssh.org and chacha20-poly1305@openssh.com
   * represent different implementations of the same cipher. For key
   * encryption purposes, they're equivalent, and the multithreaded
   * implementation is excessive. It can be assumed that references to the
   * multithreaded implementation in this context are unintentional, so
   * these checks should look for the serial implementation instead.
   *
   * Additionally, the following code is safe regardless of whether the
   * multithreaded implementation is enabled, so no #ifdefs are necessary.
   */
  if (strcmp(state->enc_ciphername, "chacha20-poly1305-mt@hpnssh.org")
      == 0) {
    if ((cipher = cipher_by_name("chacha20-poly1305@openssh.com"))
        == NULL) {
      r = SSH_ERR_INTERNAL_ERROR;
      goto out;
    }
  } else {
    if ((cipher = cipher_by_name(state->enc_ciphername)) == NULL) {
      r = SSH_ERR_INTERNAL_ERROR;
      goto out;
    }
  }
  blocksize = cipher_blocksize(cipher);
  keylen = cipher_keylen(cipher);
  ivlen = cipher_ivlen(cipher);
  authlen = cipher_authlen(cipher);
  if (state->enc_keyiv_len != keylen + ivlen) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  key = state->enc_keyiv;
  if ((encrypted = sshbuf_new()) == NULL ||
      (encoded = sshbuf_new()) == NULL ||
      (padded = sshbuf_new()) == NULL ||
      (iv = malloc(ivlen)) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }

  /* replace first 4 bytes of IV with index to ensure uniqueness */
  memcpy(iv, key + keylen, ivlen);
  POKE_U32(iv, state->idx);

  if ((r = sshbuf_put(encoded, XMSS_MAGIC, sizeof(XMSS_MAGIC))) != 0 ||
      (r = sshbuf_put_u32(encoded, state->idx)) != 0)
    goto out;

  /* padded state will be encrypted */
  if ((r = sshbuf_putb(padded, b)) != 0)
    goto out;
  i = 0;
  while (sshbuf_len(padded) % blocksize) {
    if ((r = sshbuf_put_u8(padded, ++i & 0xff)) != 0)
      goto out;
  }
  encrypted_len = sshbuf_len(padded);

  /* header including the length of state is used as AAD */
  if ((r = sshbuf_put_u32(encoded, encrypted_len)) != 0)
    goto out;
  aadlen = sshbuf_len(encoded);

  /* concat header and state */
  if ((r = sshbuf_putb(encoded, padded)) != 0)
    goto out;

  /* reserve space for encryption of encoded data plus auth tag */
  /* encrypt at offset addlen */
  if ((r = sshbuf_reserve(encrypted,
      encrypted_len + aadlen + authlen, &cp)) != 0 ||
      (r = cipher_init(&ciphercontext, cipher, key, keylen, iv, ivlen, 0,
          CIPHER_ENCRYPT, CIPHER_SERIAL)) != 0 ||
      (r = cipher_crypt(ciphercontext, 0, cp, sshbuf_ptr(encoded),
      encrypted_len, aadlen, authlen)) != 0)
    goto out;

  /* success */
  r = 0;
 out:
  if (retp != NULL) {
    *retp = encrypted;
    encrypted = NULL;
  }
  sshbuf_free(padded);
  sshbuf_free(encoded);
  sshbuf_free(encrypted);
  cipher_free(ciphercontext);
  free(iv);
  return r;
}

int
sshkey_xmss_decrypt_state(const struct sshkey *k, struct sshbuf *encoded,
   struct sshbuf **retp)
{
  struct ssh_xmss_state *state = k->xmss_state;
  struct sshbuf *copy = NULL, *decrypted = NULL;
  struct sshcipher_ctx *ciphercontext = NULL;
  const struct sshcipher *cipher = NULL;
  u_char *key, *iv = NULL, *dp;
  size_t keylen, ivlen, authlen, aadlen;
  u_int blocksize, encrypted_len, index;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (retp != NULL)
    *retp = NULL;
  if (state == NULL ||
      state->enc_keyiv == NULL ||
      state->enc_ciphername == NULL)
    return SSH_ERR_INTERNAL_ERROR;
  /*
   * chacha20-poly1305-mt@hpnssh.org and chacha20-poly1305@openssh.com
   * represent different implementations of the same cipher. For key
   * encryption purposes, they're equivalent, and the multithreaded
   * implementation is excessive. It can be assumed that references to the
   * multithreaded implementation in this context are unintentional, so
   * these checks should look for the serial implementation instead.
   *
   * Additionally, the following code is safe regardless of whether the
   * multithreaded implementation is enabled, so no #ifdefs are necessary.
   */
  if (strcmp(state->enc_ciphername, "chacha20-poly1305-mt@hpnssh.org")
      == 0) {
    if ((cipher = cipher_by_name("chacha20-poly1305@openssh.com"))
        == NULL) {
      r = SSH_ERR_INVALID_FORMAT;
      goto out;
    }
  } else {
    if ((cipher = cipher_by_name(state->enc_ciphername)) == NULL) {
      r = SSH_ERR_INVALID_FORMAT;
      goto out;
    }
  }
  blocksize = cipher_blocksize(cipher);
  keylen = cipher_keylen(cipher);
  ivlen = cipher_ivlen(cipher);
  authlen = cipher_authlen(cipher);
  if (state->enc_keyiv_len != keylen + ivlen) {
    r = SSH_ERR_INTERNAL_ERROR;
    goto out;
  }
  key = state->enc_keyiv;

  if ((copy = sshbuf_fromb(encoded)) == NULL ||
      (decrypted = sshbuf_new()) == NULL ||
      (iv = malloc(ivlen)) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }

  /* check magic */
  if (sshbuf_len(encoded) < sizeof(XMSS_MAGIC) ||
      memcmp(sshbuf_ptr(encoded), XMSS_MAGIC, sizeof(XMSS_MAGIC))) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  /* parse public portion */
  if ((r = sshbuf_consume(encoded, sizeof(XMSS_MAGIC))) != 0 ||
      (r = sshbuf_get_u32(encoded, &index)) != 0 ||
      (r = sshbuf_get_u32(encoded, &encrypted_len)) != 0)
    goto out;

  /* check size of encrypted key blob */
  if (encrypted_len < blocksize || (encrypted_len % blocksize) != 0) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  /* check that an appropriate amount of auth data is present */
  if (sshbuf_len(encoded) < authlen ||
      sshbuf_len(encoded) - authlen < encrypted_len) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }

  aadlen = sshbuf_len(copy) - sshbuf_len(encoded);

  /* replace first 4 bytes of IV with index to ensure uniqueness */
  memcpy(iv, key + keylen, ivlen);
  POKE_U32(iv, index);

  /* decrypt private state of key */
  if ((r = sshbuf_reserve(decrypted, aadlen + encrypted_len, &dp)) != 0 ||
      (r = cipher_init(&ciphercontext, cipher, key, keylen, iv, ivlen, 0,
          CIPHER_DECRYPT, CIPHER_SERIAL)) != 0 ||
      (r = cipher_crypt(ciphercontext, 0, dp, sshbuf_ptr(copy),
      encrypted_len, aadlen, authlen)) != 0)
    goto out;

  /* there should be no trailing data */
  if ((r = sshbuf_consume(encoded, encrypted_len + authlen)) != 0)
    goto out;
  if (sshbuf_len(encoded) != 0) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }

  /* remove AAD */
  if ((r = sshbuf_consume(decrypted, aadlen)) != 0)
    goto out;
  /* XXX encrypted includes unchecked padding */

  /* success */
  r = 0;
  if (retp != NULL) {
    *retp = decrypted;
    decrypted = NULL;
  }
 out:
  cipher_free(ciphercontext);
  sshbuf_free(copy);
  sshbuf_free(decrypted);
  free(iv);
  return r;
}

u_int32_t
sshkey_xmss_signatures_left(const struct sshkey *k)
{
  struct ssh_xmss_state *state = k->xmss_state;
  u_int32_t idx;

  if (sshkey_type_plain(k->type) == KEY_XMSS && state &&
      state->maxidx) {
    idx = k->xmss_sk ? PEEK_U32(k->xmss_sk) : state->idx;
    if (idx < state->maxidx)
      return state->maxidx - idx;
  }
  return 0;
}

int
sshkey_xmss_enable_maxsign(struct sshkey *k, u_int32_t maxsign)
{
  struct ssh_xmss_state *state = k->xmss_state;

  if (sshkey_type_plain(k->type) != KEY_XMSS)
    return SSH_ERR_INVALID_ARGUMENT;
  if (maxsign == 0)
    return 0;
  if (state->idx + maxsign < state->idx)
    return SSH_ERR_INVALID_ARGUMENT;
  state->maxidx = state->idx + maxsign;
  return 0;
}
#endif /* WITH_XMSS */

Coverage Report

Created: 2024-06-18 06:23