/src/openssh/auth-options.c

Source
/* $OpenBSD: auth-options.c,v 1.103 2026/09/16 00:33:44 djm Exp $ */
/*
 * Copyright (c) 2018 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 <sys/queue.h>

#include <stdlib.h>
#include <netdb.h>
#include <pwd.h>
#include <string.h>
#include <stdio.h>
#include <stdint.h>
#include <stdarg.h>
#include <ctype.h>
#include <limits.h>

#include "xmalloc.h"
#include "ssherr.h"
#include "log.h"
#include "sshbuf.h"
#include "misc.h"
#include "sshkey.h"
#include "match.h"
#include "ssh2.h"
#include "auth-options.h"

static int
dup_strings(char ***dstp, size_t *ndstp, char **src, size_t nsrc)
{
  char **dst;
  size_t i, j;

  *dstp = NULL;
  *ndstp = 0;

  if (nsrc == 0)
    return 0;
  if (nsrc >= SIZE_MAX / sizeof(*src) ||
      (dst = calloc(nsrc, sizeof(*src))) == NULL)
    return -1;
  for (i = 0; i < nsrc; i++) {
    if ((dst[i] = strdup(src[i])) == NULL) {
      for (j = 0; j < i; j++)
        free(dst[j]);
      free(dst);
      return -1;
    }
  }
  /* success */
  *dstp = dst;
  *ndstp = nsrc;
  return 0;
}

#define OPTIONS_CRITICAL  1
#define OPTIONS_EXTENSIONS  2
static int
cert_option_list(struct sshauthopt *opts, struct sshbuf *oblob,
    u_int which, int crit)
{
  char *command, *allowed;
  char *name = NULL;
  struct sshbuf *c = NULL, *data = NULL;
  int r, ret = -1, found;

  if ((c = sshbuf_fromb(oblob)) == NULL) {
    error_f("sshbuf_fromb failed");
    goto out;
  }

  while (sshbuf_len(c) > 0) {
    sshbuf_free(data);
    data = NULL;
    if ((r = sshbuf_get_cstring(c, &name, NULL)) != 0 ||
        (r = sshbuf_froms(c, &data)) != 0) {
      error_r(r, "Unable to parse certificate options");
      goto out;
    }
    debug3("found certificate option \"%.100s\" len %zu",
        name, sshbuf_len(data));
    found = 0;
    if ((which & OPTIONS_EXTENSIONS) != 0) {
      if (strcmp(name, "no-touch-required") == 0) {
        opts->no_require_user_presence = 1;
        found = 1;
      } else if (strcmp(name, "permit-X11-forwarding") == 0) {
        opts->permit_x11_forwarding_flag = 1;
        found = 1;
      } else if (strcmp(name,
          "permit-agent-forwarding") == 0) {
        opts->permit_agent_forwarding_flag = 1;
        found = 1;
      } else if (strcmp(name,
          "permit-port-forwarding") == 0) {
        opts->permit_port_forwarding_flag = 1;
        found = 1;
      } else if (strcmp(name, "permit-pty") == 0) {
        opts->permit_pty_flag = 1;
        found = 1;
      } else if (strcmp(name, "permit-user-rc") == 0) {
        opts->permit_user_rc = 1;
        found = 1;
      }
    }
    if (!found && (which & OPTIONS_CRITICAL) != 0) {
      if (strcmp(name, "verify-required") == 0) {
        opts->require_verify = 1;
        found = 1;
      } else if (strcmp(name, "force-command") == 0) {
        if ((r = sshbuf_get_cstring(data, &command,
            NULL)) != 0) {
          error_r(r, "Unable to parse \"%s\" "
              "section", name);
          goto out;
        }
        if (opts->force_command != NULL) {
          error("Certificate has multiple "
              "force-command options");
          free(command);
          goto out;
        }
        opts->force_command = command;
        found = 1;
      } else if (strcmp(name, "source-address") == 0) {
        if ((r = sshbuf_get_cstring(data, &allowed,
            NULL)) != 0) {
          error_r(r, "Unable to parse \"%s\" "
              "section", name);
          goto out;
        }
        if (opts->required_from_host_cert != NULL) {
          error("Certificate has multiple "
              "source-address options");
          free(allowed);
          goto out;
        }
        /* Check syntax */
        if (addr_match_cidr_list(NULL, allowed) == -1) {
          error("Certificate source-address "
              "contents invalid");
          free(allowed);
          goto out;
        }
        opts->required_from_host_cert = allowed;
        found = 1;
      }
    }

    if (!found) {
      if (crit) {
        error("Certificate critical option \"%s\" "
            "is not supported", name);
        goto out;
      } else {
        logit("Certificate extension \"%s\" "
            "is not supported", name);
      }
    } else if (sshbuf_len(data) != 0) {
      error("Certificate option \"%s\" corrupt "
          "(extra data)", name);
      goto out;
    }
    free(name);
    name = NULL;
  }
  /* successfully parsed all options */
  ret = 0;

 out:
  free(name);
  sshbuf_free(data);
  sshbuf_free(c);
  return ret;
}

struct sshauthopt *
sshauthopt_new(void)
{
  struct sshauthopt *ret;

  if ((ret = calloc(1, sizeof(*ret))) == NULL)
    return NULL;
  ret->force_tun_device = -1;
  return ret;
}

void
sshauthopt_free(struct sshauthopt *opts)
{
  size_t i;

  if (opts == NULL)
    return;

  free(opts->cert_principals);
  free(opts->force_command);
  free(opts->required_from_host_cert);
  free(opts->required_from_host_keys);

  for (i = 0; i < opts->nenv; i++)
    free(opts->env[i]);
  free(opts->env);

  for (i = 0; i < opts->npermitopen; i++)
    free(opts->permitopen[i]);
  free(opts->permitopen);

  for (i = 0; i < opts->npermitlisten; i++)
    free(opts->permitlisten[i]);
  free(opts->permitlisten);

  freezero(opts, sizeof(*opts));
}

struct sshauthopt *
sshauthopt_new_with_keys_defaults(void)
{
  struct sshauthopt *ret = NULL;

  if ((ret = sshauthopt_new()) == NULL)
    return NULL;

  /* Defaults for authorized_keys flags */
  ret->permit_port_forwarding_flag = 1;
  ret->permit_agent_forwarding_flag = 1;
  ret->permit_x11_forwarding_flag = 1;
  ret->permit_pty_flag = 1;
  ret->permit_user_rc = 1;
  return ret;
}

/*
 * Parse and record a permitopen/permitlisten directive.
 * Return 0 on success. Return -1 on failure and sets *errstrp to error reason.
 */
static int
handle_permit(const char **optsp, int allow_bare_port,
    char ***permitsp, size_t *npermitsp, const char **errstrp)
{
  char *opt, *tmp, *cp, *host, **permits = *permitsp;
  size_t npermits = *npermitsp;
  const char *errstr = "unknown error";

  if (npermits > SSH_AUTHOPT_PERMIT_MAX) {
    *errstrp = "too many permission directives";
    return -1;
  }
  if ((opt = opt_dequote(optsp, &errstr)) == NULL) {
    return -1;
  }
  if (allow_bare_port && strchr(opt, ':') == NULL) {
    /*
     * Allow a bare port number in permitlisten to indicate a
     * listen_host wildcard.
     */
    if (asprintf(&tmp, "*:%s", opt) == -1) {
      free(opt);
      *errstrp = "memory allocation failed";
      return -1;
    }
    free(opt);
    opt = tmp;
  }
  if ((tmp = strdup(opt)) == NULL) {
    free(opt);
    *errstrp = "memory allocation failed";
    return -1;
  }
  cp = tmp;
  /* validate syntax before recording it. */
  host = hpdelim2(&cp, NULL);
  if (host == NULL || strlen(host) >= NI_MAXHOST) {
    free(tmp);
    free(opt);
    *errstrp = "invalid permission hostname";
    return -1;
  }
  /*
   * don't want to use permitopen_port to avoid
   * dependency on channels.[ch] here.
   */
  if (cp == NULL ||
      (strcmp(cp, "*") != 0 && a2port(cp) <= 0)) {
    free(tmp);
    free(opt);
    *errstrp = "invalid permission port";
    return -1;
  }
  /* XXX - add streamlocal support */
  free(tmp);
  /* Record it */
  if ((permits = recallocarray(permits, npermits, npermits + 1,
      sizeof(*permits))) == NULL) {
    free(opt);
    /* NB. don't update *permitsp if alloc fails */
    *errstrp = "memory allocation failed";
    return -1;
  }
  permits[npermits++] = opt;
  *permitsp = permits;
  *npermitsp = npermits;
  return 0;
}

struct sshauthopt *
sshauthopt_parse(const char *opts, const char **errstrp)
{
  char **oarray, *opt, *cp, *tmp;
  int r;
  struct sshauthopt *ret = NULL;
  const char *errstr = "unknown error";
  uint64_t valid_before;
  size_t i, l;

  if (errstrp != NULL)
    *errstrp = NULL;
  if ((ret = sshauthopt_new_with_keys_defaults()) == NULL)
    goto alloc_fail;

  if (opts == NULL)
    return ret;

  while (*opts && *opts != ' ' && *opts != '\t') {
    /* flag options */
    if ((r = opt_flag("restrict", 0, &opts)) != -1) {
      ret->restricted = 1;
      ret->permit_port_forwarding_flag = 0;
      ret->permit_agent_forwarding_flag = 0;
      ret->permit_x11_forwarding_flag = 0;
      ret->permit_pty_flag = 0;
      ret->permit_user_rc = 0;
    } else if ((r = opt_flag("cert-authority", 0, &opts)) != -1) {
      ret->cert_authority = r;
    } else if ((r = opt_flag("port-forwarding", 1, &opts)) != -1) {
      ret->permit_port_forwarding_flag = r == 1;
    } else if ((r = opt_flag("agent-forwarding", 1, &opts)) != -1) {
      ret->permit_agent_forwarding_flag = r == 1;
    } else if ((r = opt_flag("x11-forwarding", 1, &opts)) != -1) {
      ret->permit_x11_forwarding_flag = r == 1;
    } else if ((r = opt_flag("touch-required", 1, &opts)) != -1) {
      ret->no_require_user_presence = r != 1; /* NB. flip */
    } else if ((r = opt_flag("verify-required", 1, &opts)) != -1) {
      ret->require_verify = r == 1;
    } else if ((r = opt_flag("pty", 1, &opts)) != -1) {
      ret->permit_pty_flag = r == 1;
    } else if ((r = opt_flag("user-rc", 1, &opts)) != -1) {
      ret->permit_user_rc = r == 1;
    } else if (opt_match(&opts, "command")) {
      if (ret->force_command != NULL) {
        errstr = "multiple \"command\" clauses";
        goto fail;
      }
      ret->force_command = opt_dequote(&opts, &errstr);
      if (ret->force_command == NULL)
        goto fail;
    } else if (opt_match(&opts, "principals")) {
      if (ret->cert_principals != NULL) {
        errstr = "multiple \"principals\" clauses";
        goto fail;
      }
      ret->cert_principals = opt_dequote(&opts, &errstr);
      if (ret->cert_principals == NULL)
        goto fail;
    } else if (opt_match(&opts, "from")) {
      if (ret->required_from_host_keys != NULL) {
        errstr = "multiple \"from\" clauses";
        goto fail;
      }
      ret->required_from_host_keys = opt_dequote(&opts,
          &errstr);
      if (ret->required_from_host_keys == NULL)
        goto fail;
    } else if (opt_match(&opts, "expiry-time")) {
      if ((opt = opt_dequote(&opts, &errstr)) == NULL)
        goto fail;
      if (parse_absolute_time(opt, &valid_before) != 0 ||
          valid_before == 0) {
        free(opt);
        errstr = "invalid expires time";
        goto fail;
      }
      free(opt);
      if (ret->valid_before == 0 ||
          valid_before < ret->valid_before)
        ret->valid_before = valid_before;
    } else if (opt_match(&opts, "environment")) {
      if (ret->nenv > SSH_AUTHOPT_ENV_MAX) {
        errstr = "too many environment strings";
        goto fail;
      }
      if ((opt = opt_dequote(&opts, &errstr)) == NULL)
        goto fail;
      /* env name must be alphanumeric and followed by '=' */
      if ((tmp = strchr(opt, '=')) == NULL) {
        free(opt);
        errstr = "invalid environment string";
        goto fail;
      }
      if ((cp = strdup(opt)) == NULL) {
        free(opt);
        goto alloc_fail;
      }
      l = (size_t)(tmp - opt);
      cp[l] = '\0'; /* truncate at '=' */
      if (!valid_env_name(cp)) {
        free(cp);
        free(opt);
        errstr = "invalid environment string";
        goto fail;
      }
      /* Check for duplicates; XXX O(n*log(n)) */
      for (i = 0; i < ret->nenv; i++) {
        if (strncmp(ret->env[i], cp, l) == 0 &&
            ret->env[i][l] == '=')
          break;
      }
      free(cp);
      /* First match wins */
      if (i >= ret->nenv) {
        /* Append it. */
        oarray = ret->env;
        if ((ret->env = recallocarray(ret->env,
            ret->nenv, ret->nenv + 1,
            sizeof(*ret->env))) == NULL) {
          free(opt);
          /* put it back for cleanup */
          ret->env = oarray;
          goto alloc_fail;
        }
        ret->env[ret->nenv++] = opt;
        opt = NULL; /* transferred */
      }
      free(opt);
    } else if (opt_match(&opts, "permitopen")) {
      if (handle_permit(&opts, 0, &ret->permitopen,
          &ret->npermitopen, &errstr) != 0)
        goto fail;
    } else if (opt_match(&opts, "permitlisten")) {
      if (handle_permit(&opts, 1, &ret->permitlisten,
          &ret->npermitlisten, &errstr) != 0)
        goto fail;
    } else if (opt_match(&opts, "tunnel")) {
      if ((opt = opt_dequote(&opts, &errstr)) == NULL)
        goto fail;
      ret->force_tun_device = a2tun(opt, NULL);
      free(opt);
      if (ret->force_tun_device == SSH_TUNID_ERR) {
        errstr = "invalid tun device";
        goto fail;
      }
    }
    /*
     * Skip the comma, and move to the next option
     * (or break out if there are no more).
     */
    if (*opts == '\0' || *opts == ' ' || *opts == '\t')
      break;   /* End of options. */
    /* Anything other than a comma is an unknown option */
    if (*opts != ',') {
      errstr = "unknown key option";
      goto fail;
    }
    opts++;
    if (*opts == '\0') {
      errstr = "unexpected end-of-options";
      goto fail;
    }
  }

  /* success */
  if (errstrp != NULL)
    *errstrp = NULL;
  return ret;

alloc_fail:
  errstr = "memory allocation failed";
fail:
  sshauthopt_free(ret);
  if (errstrp != NULL)
    *errstrp = errstr;
  return NULL;
}

struct sshauthopt *
sshauthopt_from_cert(struct sshkey *k)
{
  struct sshauthopt *ret;

  if (k == NULL || !sshkey_type_is_cert(k->type) || k->cert == NULL ||
      k->cert->type != SSH2_CERT_TYPE_USER)
    return NULL;

  if ((ret = sshauthopt_new()) == NULL)
    return NULL;

  /* Handle options and critical extensions separately */
  if (cert_option_list(ret, k->cert->critical,
      OPTIONS_CRITICAL, 1) == -1) {
    sshauthopt_free(ret);
    return NULL;
  }
  if (cert_option_list(ret, k->cert->extensions,
      OPTIONS_EXTENSIONS, 0) == -1) {
    sshauthopt_free(ret);
    return NULL;
  }
  /* success */
  return ret;
}

/*
 * Merges "additional" options to "primary" and returns the result.
 * NB. Some options from primary have primacy.
 */
struct sshauthopt *
sshauthopt_merge(const struct sshauthopt *primary,
    const struct sshauthopt *additional, const char **errstrp)
{
  struct sshauthopt *ret;
  const char *errstr = "internal error";
  const char *tmp;

  if (errstrp != NULL)
    *errstrp = NULL;

  if ((ret = sshauthopt_new()) == NULL)
    goto alloc_fail;

  /* cert_authority and cert_principals are cleared in result */

  /* Prefer access lists from primary. */
  /* XXX err is both set and mismatch? */
  tmp = primary->required_from_host_cert;
  if (tmp == NULL)
    tmp = additional->required_from_host_cert;
  if (tmp != NULL && (ret->required_from_host_cert = strdup(tmp)) == NULL)
    goto alloc_fail;
  tmp = primary->required_from_host_keys;
  if (tmp == NULL)
    tmp = additional->required_from_host_keys;
  if (tmp != NULL && (ret->required_from_host_keys = strdup(tmp)) == NULL)
    goto alloc_fail;

  /*
   * force_tun_device, permitopen/permitlisten and environment all
   * prefer the primary.
   */
  ret->force_tun_device = primary->force_tun_device;
  if (ret->force_tun_device == -1)
    ret->force_tun_device = additional->force_tun_device;
  if (primary->nenv > 0) {
    if (dup_strings(&ret->env, &ret->nenv,
        primary->env, primary->nenv) != 0)
      goto alloc_fail;
  } else if (additional->nenv) {
    if (dup_strings(&ret->env, &ret->nenv,
        additional->env, additional->nenv) != 0)
      goto alloc_fail;
  }
  if (primary->npermitopen > 0) {
    if (dup_strings(&ret->permitopen, &ret->npermitopen,
        primary->permitopen, primary->npermitopen) != 0)
      goto alloc_fail;
  } else if (additional->npermitopen > 0) {
    if (dup_strings(&ret->permitopen, &ret->npermitopen,
        additional->permitopen, additional->npermitopen) != 0)
      goto alloc_fail;
  }

  if (primary->npermitlisten > 0) {
    if (dup_strings(&ret->permitlisten, &ret->npermitlisten,
        primary->permitlisten, primary->npermitlisten) != 0)
      goto alloc_fail;
  } else if (additional->npermitlisten > 0) {
    if (dup_strings(&ret->permitlisten, &ret->npermitlisten,
        additional->permitlisten, additional->npermitlisten) != 0)
      goto alloc_fail;
  }

#define OPTFLAG_AND(x) ret->x = (primary->x == 1) && (additional->x == 1)
#define OPTFLAG_OR(x) ret->x = (primary->x == 1) || (additional->x == 1)
  /* Permissive flags are logical-AND (i.e. must be set in both) */
  OPTFLAG_AND(permit_port_forwarding_flag);
  OPTFLAG_AND(permit_agent_forwarding_flag);
  OPTFLAG_AND(permit_x11_forwarding_flag);
  OPTFLAG_AND(permit_pty_flag);
  OPTFLAG_AND(permit_user_rc);
  OPTFLAG_AND(no_require_user_presence);
  /* Restrictive flags are logical-OR (i.e. must be set in either) */
  OPTFLAG_OR(require_verify);
  OPTFLAG_OR(restricted);
#undef OPTFLAG_AND

  /* Earliest expiry time should win */
  if (primary->valid_before != 0)
    ret->valid_before = primary->valid_before;
  if (additional->valid_before != 0 &&
      additional->valid_before < ret->valid_before)
    ret->valid_before = additional->valid_before;

  /*
   * When both multiple forced-command are specified, only
   * proceed if they are identical, otherwise fail.
   */
  if (primary->force_command != NULL &&
      additional->force_command != NULL) {
    if (strcmp(primary->force_command,
        additional->force_command) == 0) {
      /* ok */
      ret->force_command = strdup(primary->force_command);
      if (ret->force_command == NULL)
        goto alloc_fail;
    } else {
      errstr = "forced command options do not match";
      goto fail;
    }
  } else if (primary->force_command != NULL) {
    if ((ret->force_command = strdup(
        primary->force_command)) == NULL)
      goto alloc_fail;
  } else if (additional->force_command != NULL) {
    if ((ret->force_command = strdup(
        additional->force_command)) == NULL)
      goto alloc_fail;
  }
  /* success */
  if (errstrp != NULL)
    *errstrp = NULL;
  return ret;

 alloc_fail:
  errstr = "memory allocation failed";
 fail:
  if (errstrp != NULL)
    *errstrp = errstr;
  sshauthopt_free(ret);
  return NULL;
}

/*
 * Copy options
 */
struct sshauthopt *
sshauthopt_copy(const struct sshauthopt *orig)
{
  struct sshauthopt *ret;

  if ((ret = sshauthopt_new()) == NULL)
    return NULL;

#define OPTSCALAR(x) ret->x = orig->x
  OPTSCALAR(permit_port_forwarding_flag);
  OPTSCALAR(permit_agent_forwarding_flag);
  OPTSCALAR(permit_x11_forwarding_flag);
  OPTSCALAR(permit_pty_flag);
  OPTSCALAR(permit_user_rc);
  OPTSCALAR(restricted);
  OPTSCALAR(cert_authority);
  OPTSCALAR(force_tun_device);
  OPTSCALAR(valid_before);
  OPTSCALAR(no_require_user_presence);
  OPTSCALAR(require_verify);
#undef OPTSCALAR
#define OPTSTRING(x) \
  do { \
    if (orig->x != NULL && (ret->x = strdup(orig->x)) == NULL) { \
      sshauthopt_free(ret); \
      return NULL; \
    } \
  } while (0)
  OPTSTRING(cert_principals);
  OPTSTRING(force_command);
  OPTSTRING(required_from_host_cert);
  OPTSTRING(required_from_host_keys);
#undef OPTSTRING

  if (dup_strings(&ret->env, &ret->nenv, orig->env, orig->nenv) != 0 ||
      dup_strings(&ret->permitopen, &ret->npermitopen,
      orig->permitopen, orig->npermitopen) != 0 ||
      dup_strings(&ret->permitlisten, &ret->npermitlisten,
      orig->permitlisten, orig->npermitlisten) != 0) {
    sshauthopt_free(ret);
    return NULL;
  }
  return ret;
}

static int
serialise_array(struct sshbuf *m, char **a, size_t n)
{
  struct sshbuf *b;
  size_t i;
  int r = SSH_ERR_INTERNAL_ERROR;

  if (n > INT_MAX)
    return SSH_ERR_INTERNAL_ERROR;

  if ((b = sshbuf_new()) == NULL) {
    return SSH_ERR_ALLOC_FAIL;
  }
  for (i = 0; i < n; i++) {
    if ((r = sshbuf_put_cstring(b, a[i])) != 0)
      goto out;
  }
  if ((r = sshbuf_put_u32(m, n)) != 0 ||
      (r = sshbuf_put_stringb(m, b)) != 0)
    goto out;
  /* success */
  r = 0;
 out:
  sshbuf_free(b);
  return r;
}

static int
deserialise_array(struct sshbuf *m, char ***ap, size_t *np)
{
  char **a = NULL;
  size_t i, n = 0;
  struct sshbuf *b = NULL;
  u_int tmp;
  int r = SSH_ERR_INTERNAL_ERROR;

  if ((r = sshbuf_get_u32(m, &tmp)) != 0 ||
      (r = sshbuf_froms(m, &b)) != 0)
    goto out;
  if (tmp > INT_MAX) {
    r = SSH_ERR_INVALID_FORMAT;
    goto out;
  }
  n = tmp;
  if (n > 0 && (a = calloc(n, sizeof(*a))) == NULL) {
    r = SSH_ERR_ALLOC_FAIL;
    goto out;
  }
  for (i = 0; i < n; i++) {
    if ((r = sshbuf_get_cstring(b, &a[i], NULL)) != 0)
      goto out;
  }
  /* success */
  r = 0;
  *ap = a;
  a = NULL;
  *np = n;
  n = 0;
 out:
  if (a != NULL) {
    for (i = 0; i < n; i++)
      free(a[i]);
    free(a);
  }
  sshbuf_free(b);
  return r;
}

static int
serialise_nullable_string(struct sshbuf *m, const char *s)
{
  int r;

  if ((r = sshbuf_put_u8(m, s == NULL)) != 0 ||
      (r = sshbuf_put_cstring(m, s)) != 0)
    return r;
  return 0;
}

static int
deserialise_nullable_string(struct sshbuf *m, char **sp)
{
  int r;
  u_char flag;

  *sp = NULL;
  if ((r = sshbuf_get_u8(m, &flag)) != 0 ||
      (r = sshbuf_get_cstring(m, flag ? NULL : sp, NULL)) != 0)
    return r;
  return 0;
}

int
sshauthopt_serialise(const struct sshauthopt *opts, struct sshbuf *m,
    int untrusted)
{
  int r = SSH_ERR_INTERNAL_ERROR;

  /* Flag options */
  if ((r = sshbuf_put_u8(m, opts->permit_port_forwarding_flag)) != 0 ||
      (r = sshbuf_put_u8(m, opts->permit_agent_forwarding_flag)) != 0 ||
      (r = sshbuf_put_u8(m, opts->permit_x11_forwarding_flag)) != 0 ||
      (r = sshbuf_put_u8(m, opts->permit_pty_flag)) != 0 ||
      (r = sshbuf_put_u8(m, opts->permit_user_rc)) != 0 ||
      (r = sshbuf_put_u8(m, opts->restricted)) != 0 ||
      (r = sshbuf_put_u8(m, opts->cert_authority)) != 0 ||
      (r = sshbuf_put_u8(m, opts->no_require_user_presence)) != 0 ||
      (r = sshbuf_put_u8(m, opts->require_verify)) != 0)
    return r;

  /* Simple integer options */
  if ((r = sshbuf_put_u64(m, opts->valid_before)) != 0)
    return r;

  /* tunnel number can be negative to indicate "unset" */
  if ((r = sshbuf_put_u8(m, opts->force_tun_device == -1)) != 0 ||
      (r = sshbuf_put_u32(m, (opts->force_tun_device < 0) ?
      0 : (u_int)opts->force_tun_device)) != 0)
    return r;

  /* String options; these may be NULL */
  if ((r = serialise_nullable_string(m,
      untrusted ? "yes" : opts->cert_principals)) != 0 ||
      (r = serialise_nullable_string(m,
      untrusted ? "true" : opts->force_command)) != 0 ||
      (r = serialise_nullable_string(m,
      untrusted ? NULL : opts->required_from_host_cert)) != 0 ||
      (r = serialise_nullable_string(m,
      untrusted ? NULL : opts->required_from_host_keys)) != 0)
    return r;

  /* Array options */
  if ((r = serialise_array(m, opts->env,
      untrusted ? 0 : opts->nenv)) != 0 ||
      (r = serialise_array(m, opts->permitopen,
      untrusted ? 0 : opts->npermitopen)) != 0 ||
      (r = serialise_array(m, opts->permitlisten,
      untrusted ? 0 : opts->npermitlisten)) != 0)
    return r;

  /* success */
  return 0;
}

int
sshauthopt_deserialise(struct sshbuf *m, struct sshauthopt **optsp)
{
  struct sshauthopt *opts = NULL;
  int r = SSH_ERR_INTERNAL_ERROR;
  u_char f;
  u_int tmp;

  if ((opts = calloc(1, sizeof(*opts))) == NULL)
    return SSH_ERR_ALLOC_FAIL;

  /* Flag options */
#define OPT_FLAG(x) \
  do { \
    if ((r = sshbuf_get_u8(m, &f)) != 0) \
      goto out; \
    opts->x = f; \
  } while (0)
  OPT_FLAG(permit_port_forwarding_flag);
  OPT_FLAG(permit_agent_forwarding_flag);
  OPT_FLAG(permit_x11_forwarding_flag);
  OPT_FLAG(permit_pty_flag);
  OPT_FLAG(permit_user_rc);
  OPT_FLAG(restricted);
  OPT_FLAG(cert_authority);
  OPT_FLAG(no_require_user_presence);
  OPT_FLAG(require_verify);
#undef OPT_FLAG

  /* Simple integer options */
  if ((r = sshbuf_get_u64(m, &opts->valid_before)) != 0)
    goto out;

  /* tunnel number can be negative to indicate "unset" */
  if ((r = sshbuf_get_u8(m, &f)) != 0 ||
      (r = sshbuf_get_u32(m, &tmp)) != 0)
    goto out;
  opts->force_tun_device = f ? -1 : (int)tmp;

  /* String options may be NULL */
  if ((r = deserialise_nullable_string(m, &opts->cert_principals)) != 0 ||
      (r = deserialise_nullable_string(m, &opts->force_command)) != 0 ||
      (r = deserialise_nullable_string(m,
      &opts->required_from_host_cert)) != 0 ||
      (r = deserialise_nullable_string(m,
      &opts->required_from_host_keys)) != 0)
    goto out;

  /* Array options */
  if ((r = deserialise_array(m, &opts->env, &opts->nenv)) != 0 ||
      (r = deserialise_array(m,
      &opts->permitopen, &opts->npermitopen)) != 0 ||
      (r = deserialise_array(m,
      &opts->permitlisten, &opts->npermitlisten)) != 0)
    goto out;

  /* success */
  r = 0;
  *optsp = opts;
  opts = NULL;
 out:
  sshauthopt_free(opts);
  return r;
}

Coverage Report

Created: 2026-10-13 06:56