/* $OpenBSD: ssh-pkcs11-client.c,v 1.24 2025/07/30 10:17:13 dtucker Exp $ */

/*

 * Copyright (c) 2010 Markus Friedl.  All rights reserved.

 * Copyright (c) 2014 Pedro Martelletto. All rights reserved.

 *

 * 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 <sys/time.h>

#include <sys/socket.h>

#include <stdarg.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <errno.h>

#include <limits.h>

#include "pathnames.h"

#include "xmalloc.h"

#include "sshbuf.h"

#include "log.h"

#include "misc.h"

#include "sshkey.h"

#include "authfd.h"

#include "atomicio.h"

#include "ssh-pkcs11.h"

#include "ssherr.h"

/* borrows code from sftp-server and ssh-agent */

/*

 * Maintain a list of ssh-pkcs11-helper subprocesses. These may be looked up

 * by provider path or their unique keyblobs.

 */

struct helper {

  char *path;

  pid_t pid;

  int fd;

  size_t nkeyblobs;

  struct sshbuf **keyblobs; /* XXX use a tree or something faster */

};

static struct helper **helpers;

static size_t nhelpers;

static struct helper *

helper_by_provider(const char *path)

{

  size_t i;

  for (i = 0; i < nhelpers; i++) {

    if (helpers[i] == NULL || helpers[i]->path == NULL ||

        helpers[i]->fd == -1)

      continue;

    if (strcmp(helpers[i]->path, path) == 0)

      return helpers[i];

  }

  return NULL;

}

static struct helper *

helper_by_key(const struct sshkey *key)

{

  size_t i, j;

  struct sshbuf *keyblob = NULL;

  int r;

  if ((keyblob = sshbuf_new()) == NULL)

    fatal_f("sshbuf_new failed");

  if ((r = sshkey_putb(key, keyblob)) != 0)

    fatal_fr(r, "serialise key");

  for (i = 0; i < nhelpers; i++) {

    if (helpers[i] == NULL)

      continue;

    for (j = 0; j < helpers[i]->nkeyblobs; j++) {

      if (sshbuf_equals(keyblob,

          helpers[i]->keyblobs[j]) == 0) {

        sshbuf_free(keyblob);

        return helpers[i];

      }

    }

  }

  sshbuf_free(keyblob);

  return NULL;

}

static void

helper_add_key(struct helper *helper, struct sshkey *key)

{

  int r;

  helper->keyblobs = xrecallocarray(helper->keyblobs, helper->nkeyblobs,

      helper->nkeyblobs + 1, sizeof(*helper->keyblobs));

  if ((helper->keyblobs[helper->nkeyblobs] = sshbuf_new()) == NULL)

    fatal_f("sshbuf_new failed");

  if ((r = sshkey_putb(key, helper->keyblobs[helper->nkeyblobs])) != 0)

    fatal_fr(r, "shkey_putb failed");

  helper->nkeyblobs++;

  debug3_f("added %s key for provider %s, now has %zu keys",

      sshkey_type(key), helper->path, helper->nkeyblobs);

}

static void

helper_terminate(struct helper *helper)

{

  size_t i;

  int found = 0;

  if (helper == NULL)

    return;

  if (helper->path == NULL)

    fatal_f("inconsistent helper");

  debug3_f("terminating helper for %s; remaining %zu keys",

      helper->path, helper->nkeyblobs);

  close(helper->fd);

  /* XXX waitpid() */

  helper->fd = -1;

  helper->pid = -1;

  /* repack helpers */

  for (i = 0; i < nhelpers; i++) {

    if (helpers[i] == helper) {

      if (found)

        fatal_f("helper recorded more than once");

      found = 1;

    } else if (found)

      helpers[i - 1] = helpers[i];

  }

  if (found) {

    helpers = xrecallocarray(helpers, nhelpers,

        nhelpers - 1, sizeof(*helpers));

    nhelpers--;

  }

  for (i = 0; i < helper->nkeyblobs; i++)

    sshbuf_free(helper->keyblobs[i]);

  free(helper->path);

  free(helper);

}

static void

send_msg(int fd, struct sshbuf *m)

{

  u_char buf[4];

  size_t mlen = sshbuf_len(m);

  int r;

  if (fd == -1)

    return;

  POKE_U32(buf, mlen);

  if (atomicio(vwrite, fd, buf, 4) != 4 ||

      atomicio(vwrite, fd, sshbuf_mutable_ptr(m),

      sshbuf_len(m)) != sshbuf_len(m))

    error("write to helper failed");

  if ((r = sshbuf_consume(m, mlen)) != 0)

    fatal_fr(r, "consume");

}

static int

recv_msg(int fd, struct sshbuf *m)

{

  u_int l, len;

  u_char c, buf[1024];

  int r;

  sshbuf_reset(m);

  if (fd == -1)

    return 0; /* XXX */

  if ((len = atomicio(read, fd, buf, 4)) != 4) {

    error("read from helper failed: %u", len);

    return (0); /* XXX */

  }

  len = PEEK_U32(buf);

  if (len > 256 * 1024)

    fatal("response too long: %u", len);

  /* read len bytes into m */

  while (len > 0) {

    l = len;

    if (l > sizeof(buf))

      l = sizeof(buf);

    if (atomicio(read, fd, buf, l) != l) {

      error("response from helper failed.");

      return (0); /* XXX */

    }

    if ((r = sshbuf_put(m, buf, l)) != 0)

      fatal_fr(r, "sshbuf_put");

    len -= l;

  }

  if ((r = sshbuf_get_u8(m, &c)) != 0)

    fatal_fr(r, "parse type");

  return c;

}

int

pkcs11_init(int interactive)

{

  return 0;

}

void

pkcs11_terminate(void)

{

  size_t i;

  debug3_f("terminating %zu helpers", nhelpers);

  for (i = 0; i < nhelpers; i++)

    helper_terminate(helpers[i]);

}

int

pkcs11_sign(struct sshkey *key,

    u_char **sigp, size_t *lenp,

    const u_char *data, size_t datalen,

    const char *alg, const char *sk_provider,

    const char *sk_pin, u_int compat)

{

  struct sshbuf *msg = NULL;

  struct helper *helper;

  int status, r;

  u_char *signature = NULL;

  size_t signature_len = 0;

  int ret = SSH_ERR_INTERNAL_ERROR;

  if (sigp != NULL)

    *sigp = NULL;

  if (lenp != NULL)

    *lenp = 0;

  if ((helper = helper_by_key(key)) == NULL || helper->fd == -1)

    fatal_f("no helper for %s key", sshkey_type(key));

  if ((msg = sshbuf_new()) == NULL)

    return SSH_ERR_ALLOC_FAIL;

  if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||

      (r = sshkey_puts_plain(key, msg)) != 0 ||

      (r = sshbuf_put_string(msg, data, datalen)) != 0 ||

      (r = sshbuf_put_cstring(msg, alg == NULL ? "" : alg)) != 0 ||

      (r = sshbuf_put_u32(msg, compat)) != 0)

    fatal_fr(r, "compose");

  send_msg(helper->fd, msg);

  sshbuf_reset(msg);

  if ((status = recv_msg(helper->fd, msg)) != SSH2_AGENT_SIGN_RESPONSE) {

    /* XXX translate status to something useful */

    debug_fr(r, "recv_msg");

    ret = SSH_ERR_AGENT_FAILURE;

    goto fail;

  }

  if ((r = sshbuf_get_string(msg, &signature, &signature_len)) != 0)

    fatal_fr(r, "parse");

  /* success */

  if (sigp != NULL) {

    *sigp = signature;

    signature = NULL;

  }

  if (lenp != NULL)

    *lenp = signature_len;

  ret = 0;

 fail:

  free(signature);

  sshbuf_free(msg);

  return ret;

}

/*

 * Make a private PKCS#11-backed certificate by grafting a previously-loaded

 * PKCS#11 private key and a public certificate key.

 */

int

pkcs11_make_cert(const struct sshkey *priv,

    const struct sshkey *certpub, struct sshkey **certprivp)

{

  struct helper *helper = NULL;

  struct sshkey *ret;

  int r;

  if ((helper = helper_by_key(priv)) == NULL || helper->fd == -1)

    fatal_f("no helper for %s key", sshkey_type(priv));

  debug3_f("private key type %s cert type %s on provider %s",

      sshkey_type(priv), sshkey_type(certpub), helper->path);

  *certprivp = NULL;

  if (!sshkey_is_cert(certpub) || sshkey_is_cert(priv) ||

      !sshkey_equal_public(priv, certpub)) {

    error_f("private key %s doesn't match cert %s",

        sshkey_type(priv), sshkey_type(certpub));

    return SSH_ERR_INVALID_ARGUMENT;

  }

  *certprivp = NULL;

  if ((r = sshkey_from_private(priv, &ret)) != 0)

    fatal_fr(r, "copy key");

  ret->flags |= SSHKEY_FLAG_EXT;

  if ((r = sshkey_to_certified(ret)) != 0 ||

      (r = sshkey_cert_copy(certpub, ret)) != 0)

    fatal_fr(r, "graft certificate");

  helper_add_key(helper, ret);

  debug3_f("provider %s: %zu remaining keys",

      helper->path, helper->nkeyblobs);

  /* success */

  *certprivp = ret;

  return 0;

}

static struct helper *

pkcs11_start_helper(const char *path)

{

  int pair[2];

  char *prog, *verbosity = NULL;

  struct helper *helper;

  pid_t pid;

  if (nhelpers >= INT_MAX)

    fatal_f("too many helpers");

  debug3_f("start helper for %s", path);

  if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {

    error_f("socketpair: %s", strerror(errno));

    return NULL;

  }

  helper = xcalloc(1, sizeof(*helper));

  if ((pid = fork()) == -1) {

    error_f("fork: %s", strerror(errno));

    close(pair[0]);

    close(pair[1]);

    free(helper);

    return NULL;

  } else if (pid == 0) {

    if ((dup2(pair[1], STDIN_FILENO) == -1) ||

        (dup2(pair[1], STDOUT_FILENO) == -1)) {

      fprintf(stderr, "dup2: %s\n", strerror(errno));

      _exit(1);

    }

    close(pair[0]);

    close(pair[1]);

    prog = getenv("SSH_PKCS11_HELPER");

    if (prog == NULL || strlen(prog) == 0)

      prog = _PATH_SSH_PKCS11_HELPER;

    if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)

      verbosity = "-vvv";

    debug_f("starting %s %s", prog,

        verbosity == NULL ? "" : verbosity);

    execlp(prog, prog, verbosity, (char *)NULL);

    fprintf(stderr, "exec: %s: %s\n", prog, strerror(errno));

    _exit(1);

  }

  close(pair[1]);

  helper->fd = pair[0];

  helper->path = xstrdup(path);

  helper->pid = pid;

  debug3_f("helper %zu for \"%s\" on fd %d pid %ld", nhelpers,

      helper->path, helper->fd, (long)helper->pid);

  helpers = xrecallocarray(helpers, nhelpers,

      nhelpers + 1, sizeof(*helpers));

  helpers[nhelpers++] = helper;

  return helper;

}

int

pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,

    char ***labelsp)

{

  struct sshkey *k;

  int r, type;

  char *label;

  u_int ret = -1, nkeys, i;

  struct sshbuf *msg;

  struct helper *helper;

  if ((helper = helper_by_provider(name)) == NULL &&

      (helper = pkcs11_start_helper(name)) == NULL)

    return -1;

  debug3_f("add %s", helper->path);

  if ((msg = sshbuf_new()) == NULL)

    fatal_f("sshbuf_new failed");

  if ((r = sshbuf_put_u8(msg, SSH_AGENTC_ADD_SMARTCARD_KEY)) != 0 ||

      (r = sshbuf_put_cstring(msg, name)) != 0 ||

      (r = sshbuf_put_cstring(msg, pin)) != 0)

    fatal_fr(r, "compose");

  send_msg(helper->fd, msg);

  sshbuf_reset(msg);

  type = recv_msg(helper->fd, msg);

  debug3_f("response %d", type);

  if (type == SSH2_AGENT_IDENTITIES_ANSWER) {

    if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)

      fatal_fr(r, "parse nkeys");

    debug3_f("helper return %u keys", nkeys);

    *keysp = xcalloc(nkeys, sizeof(struct sshkey *));

    if (labelsp)

      *labelsp = xcalloc(nkeys, sizeof(char *));

    for (i = 0; i < nkeys; i++) {

      /* XXX clean up properly instead of fatal() */

      if ((r = sshkey_froms(msg, &k)) != 0 ||

          (r = sshbuf_get_cstring(msg, &label, NULL)) != 0)

        fatal_fr(r, "parse key");

      k->flags |= SSHKEY_FLAG_EXT;

      helper_add_key(helper, k);

      (*keysp)[i] = k;

      if (labelsp)

        (*labelsp)[i] = label;

      else

        free(label);

    }

    /* success */

    ret = 0;

  } else if (type == SSH2_AGENT_FAILURE) {

    if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)

      error_fr(r, "failed to parse failure response");

  }

  if (ret != 0) {

    debug_f("no keys; terminate helper");

    helper_terminate(helper);

  }

  sshbuf_free(msg);

  return ret == 0 ? (int)nkeys : -1;

}

int

pkcs11_del_provider(char *name)

{

  struct helper *helper;

  /*

   * ssh-agent deletes keys before calling this, so the helper entry

   * should be gone before we get here.

   */

  debug3_f("delete %s", name ? name : "(null)");

  if ((helper = helper_by_provider(name)) != NULL)

    helper_terminate(helper);

  return 0;

}

void

pkcs11_key_free(struct sshkey *key)

{

  struct helper *helper;

  struct sshbuf *keyblob = NULL;

  size_t i;

  int r, found = 0;

  debug3_f("free %s key", sshkey_type(key));

  if ((helper = helper_by_key(key)) == NULL || helper->fd == -1)

    fatal_f("no helper for %s key", sshkey_type(key));

  if ((keyblob = sshbuf_new()) == NULL)

    fatal_f("sshbuf_new failed");

  if ((r = sshkey_putb(key, keyblob)) != 0)

    fatal_fr(r, "serialise key");

  /* repack keys */

  for (i = 0; i < helper->nkeyblobs; i++) {

    if (sshbuf_equals(keyblob, helper->keyblobs[i]) == 0) {

      if (found)

        fatal_f("key recorded more than once");

      found = 1;

    } else if (found)

      helper->keyblobs[i - 1] = helper->keyblobs[i];

  }

  if (found) {

    helper->keyblobs = xrecallocarray(helper->keyblobs,

        helper->nkeyblobs, helper->nkeyblobs - 1,

        sizeof(*helper->keyblobs));

    helper->nkeyblobs--;

  }

  if (helper->nkeyblobs == 0)

    helper_terminate(helper);

}