Adding upstream version 1:9.2p1.upstream/1%9.2p1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 909 insertions, 0 deletions

diff --git a/auth-options.c b/auth-options.c
new file mode 100644
index 0000000..7cb2a64
--- /dev/null
+++ b/auth-options.c
@@ -0,0 +1,909 @@
+/* $OpenBSD: auth-options.c,v 1.98 2022/02/08 08:59:12 dtucker 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 <stdlib.h>
+#include <netdb.h>
+#include <pwd.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <ctype.h>
+#include <limits.h>
+
+#include "openbsd-compat/sys-queue.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 ((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");
+					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);
+#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;
+
+	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) {
+			sshbuf_free(b);
+			return r;
+		}
+	}
+	if ((r = sshbuf_put_u32(m, n)) != 0 ||
+	    (r = sshbuf_put_stringb(m, b)) != 0) {
+		sshbuf_free(b);
+		return r;
+	}
+	/* success */
+	return 0;
+}
+
+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;
+}