Return to auth2-pubkey.c CVS log

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If AuthorizedPrincipalsCommand is specified, however
AuthorizedPrincipalsFile is not (or is set to "none"), authentication will
potentially fail due to key_cert_check_authority() failing to locate a
principal that matches the username, even though an authorized principal
has already been matched in the output of the subprocess. Fix this by using
the same logic to determine if pw->pw_name should be passed, as is used to
determine if a authorized principal must be matched earlier on.

ok djm@

/* $OpenBSD: auth2-pubkey.c,v 1.53 2015/06/15 18:44:22 jsing Exp $ */
/*
 * Copyright (c) 2000 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 <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>

#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <limits.h>

#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "compat.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "pathnames.h"
#include "uidswap.h"
#include "auth-options.h"
#include "canohost.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "authfile.h"
#include "match.h"
#include "ssherr.h"
#include "channels.h" /* XXX for session.h */
#include "session.h" /* XXX for child_set_env(); refactor? */

/* import */
extern ServerOptions options;
extern u_char *session_id2;
extern u_int session_id2_len;

static int
userauth_pubkey(Authctxt *authctxt)
{
	Buffer b;
	Key *key = NULL;
	char *pkalg, *userstyle;
	u_char *pkblob, *sig;
	u_int alen, blen, slen;
	int have_sig, pktype;
	int authenticated = 0;

	if (!authctxt->valid) {
		debug2("userauth_pubkey: disabled because of invalid user");
		return 0;
	}
	have_sig = packet_get_char();
	if (datafellows & SSH_BUG_PKAUTH) {
		debug2("userauth_pubkey: SSH_BUG_PKAUTH");
		/* no explicit pkalg given */
		pkblob = packet_get_string(&blen);
		buffer_init(&b);
		buffer_append(&b, pkblob, blen);
		/* so we have to extract the pkalg from the pkblob */
		pkalg = buffer_get_string(&b, &alen);
		buffer_free(&b);
	} else {
		pkalg = packet_get_string(&alen);
		pkblob = packet_get_string(&blen);
	}
	pktype = key_type_from_name(pkalg);
	if (pktype == KEY_UNSPEC) {
		/* this is perfectly legal */
		logit("userauth_pubkey: unsupported public key algorithm: %s",
		    pkalg);
		goto done;
	}
	key = key_from_blob(pkblob, blen);
	if (key == NULL) {
		error("userauth_pubkey: cannot decode key: %s", pkalg);
		goto done;
	}
	if (key->type != pktype) {
		error("userauth_pubkey: type mismatch for decoded key "
		    "(received %d, expected %d)", key->type, pktype);
		goto done;
	}
	if (key_type_plain(key->type) == KEY_RSA &&
	    (datafellows & SSH_BUG_RSASIGMD5) != 0) {
		logit("Refusing RSA key because client uses unsafe "
		    "signature scheme");
		goto done;
	}
	if (auth2_userkey_already_used(authctxt, key)) {
		logit("refusing previously-used %s key", key_type(key));
		goto done;
	}
	if (match_pattern_list(sshkey_ssh_name(key),
	    options.pubkey_key_types, 0) != 1) {
		logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
		    __func__, sshkey_ssh_name(key));
		goto done;
	}

	if (have_sig) {
		sig = packet_get_string(&slen);
		packet_check_eom();
		buffer_init(&b);
		if (datafellows & SSH_OLD_SESSIONID) {
			buffer_append(&b, session_id2, session_id2_len);
		} else {
			buffer_put_string(&b, session_id2, session_id2_len);
		}
		/* reconstruct packet */
		buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
		xasprintf(&userstyle, "%s%s%s", authctxt->user,
		    authctxt->style ? ":" : "",
		    authctxt->style ? authctxt->style : "");
		buffer_put_cstring(&b, userstyle);
		free(userstyle);
		buffer_put_cstring(&b,
		    datafellows & SSH_BUG_PKSERVICE ?
		    "ssh-userauth" :
		    authctxt->service);
		if (datafellows & SSH_BUG_PKAUTH) {
			buffer_put_char(&b, have_sig);
		} else {
			buffer_put_cstring(&b, "publickey");
			buffer_put_char(&b, have_sig);
			buffer_put_cstring(&b, pkalg);
		}
		buffer_put_string(&b, pkblob, blen);
#ifdef DEBUG_PK
		buffer_dump(&b);
#endif
		pubkey_auth_info(authctxt, key, NULL);

		/* test for correct signature */
		authenticated = 0;
		if (PRIVSEP(user_key_allowed(authctxt->pw, key, 1)) &&
		    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
		    buffer_len(&b))) == 1) {
			authenticated = 1;
			/* Record the successful key to prevent reuse */
			auth2_record_userkey(authctxt, key);
			key = NULL; /* Don't free below */
		}
		buffer_free(&b);
		free(sig);
	} else {
		debug("test whether pkalg/pkblob are acceptable");
		packet_check_eom();

		/* XXX fake reply and always send PK_OK ? */
		/*
		 * XXX this allows testing whether a user is allowed
		 * to login: if you happen to have a valid pubkey this
		 * message is sent. the message is NEVER sent at all
		 * if a user is not allowed to login. is this an
		 * issue? -markus
		 */
		if (PRIVSEP(user_key_allowed(authctxt->pw, key, 0))) {
			packet_start(SSH2_MSG_USERAUTH_PK_OK);
			packet_put_string(pkalg, alen);
			packet_put_string(pkblob, blen);
			packet_send();
			packet_write_wait();
			authctxt->postponed = 1;
		}
	}
	if (authenticated != 1)
		auth_clear_options();
done:
	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	if (key != NULL)
		key_free(key);
	free(pkalg);
	free(pkblob);
	return authenticated;
}

void
pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...)
{
	char *fp, *extra;
	va_list ap;
	int i;

	extra = NULL;
	if (fmt != NULL) {
		va_start(ap, fmt);
		i = vasprintf(&extra, fmt, ap);
		va_end(ap);
		if (i < 0 || extra == NULL)
			fatal("%s: vasprintf failed", __func__);	
	}

	if (key_is_cert(key)) {
		fp = sshkey_fingerprint(key->cert->signature_key,
		    options.fingerprint_hash, SSH_FP_DEFAULT);
		auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s", 
		    key_type(key), key->cert->key_id,
		    (unsigned long long)key->cert->serial,
		    key_type(key->cert->signature_key),
		    fp == NULL ? "(null)" : fp,
		    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
		free(fp);
	} else {
		fp = sshkey_fingerprint(key, options.fingerprint_hash,
		    SSH_FP_DEFAULT);
		auth_info(authctxt, "%s %s%s%s", key_type(key),
		    fp == NULL ? "(null)" : fp,
		    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
		free(fp);
	}
	free(extra);
}

/*
 * Splits 's' into an argument vector. Handles quoted string and basic
 * escape characters (\\, \", \'). Caller must free the argument vector
 * and its members.
 */
static int
split_argv(const char *s, int *argcp, char ***argvp)
{
	int r = SSH_ERR_INTERNAL_ERROR;
	int argc = 0, quote, i, j;
	char *arg, **argv = xcalloc(1, sizeof(*argv));

	*argvp = NULL;
	*argcp = 0;

	for (i = 0; s[i] != '\0'; i++) {
		/* Skip leading whitespace */
		if (s[i] == ' ' || s[i] == '\t')
			continue;

		/* Start of a token */
		quote = 0;
		if (s[i] == '\\' &&
		    (s[i + 1] == '\'' || s[i + 1] == '\"' || s[i + 1] == '\\'))
			i++;
		else if (s[i] == '\'' || s[i] == '"')
			quote = s[i++];

		argv = xreallocarray(argv, (argc + 2), sizeof(*argv));
		arg = argv[argc++] = xcalloc(1, strlen(s + i) + 1);
		argv[argc] = NULL;

		/* Copy the token in, removing escapes */
		for (j = 0; s[i] != '\0'; i++) {
			if (s[i] == '\\') {
				if (s[i + 1] == '\'' ||
				    s[i + 1] == '\"' ||
				    s[i + 1] == '\\') {
					i++; /* Skip '\' */
					arg[j++] = s[i];
				} else {
					/* Unrecognised escape */
					arg[j++] = s[i];
				}
			} else if (quote == 0 && (s[i] == ' ' || s[i] == '\t'))
				break; /* done */
			else if (quote != 0 && s[i] == quote)
				break; /* done */
			else
				arg[j++] = s[i];
		}
		if (s[i] == '\0') {
			if (quote != 0) {
				/* Ran out of string looking for close quote */
				r = SSH_ERR_INVALID_FORMAT;
				goto out;
			}
			break;
		}
	}
	/* Success */
	*argcp = argc;
	*argvp = argv;
	argc = 0;
	argv = NULL;
	r = 0;
 out:
	if (argc != 0 && argv != NULL) {
		for (i = 0; i < argc; i++)
			free(argv[i]);
		free(argv);
	}
	return r;
}

/*
 * Reassemble an argument vector into a string, quoting and escaping as
 * necessary. Caller must free returned string.
 */
static char *
assemble_argv(int argc, char **argv)
{
	int i, j, ws, r;
	char c, *ret;
	struct sshbuf *buf, *arg;

	if ((buf = sshbuf_new()) == NULL || (arg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);

	for (i = 0; i < argc; i++) {
		ws = 0;
		sshbuf_reset(arg);
		for (j = 0; argv[i][j] != '\0'; j++) {
			r = 0;
			c = argv[i][j];
			switch (c) {
			case ' ':
			case '\t':
				ws = 1;
				r = sshbuf_put_u8(arg, c);
				break;
			case '\\':
			case '\'':
			case '"':
				if ((r = sshbuf_put_u8(arg, '\\')) != 0)
					break;
				/* FALLTHROUGH */
			default:
				r = sshbuf_put_u8(arg, c);
				break;
			}
			if (r != 0)
				fatal("%s: sshbuf_put_u8: %s",
				    __func__, ssh_err(r));
		}
		if ((i != 0 && (r = sshbuf_put_u8(buf, ' ')) != 0) ||
		    (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0) ||
		    (r = sshbuf_putb(buf, arg)) != 0 ||
		    (ws != 0 && (r = sshbuf_put_u8(buf, '"')) != 0))
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
	}
	if ((ret = malloc(sshbuf_len(buf) + 1)) == NULL)
		fatal("%s: malloc failed", __func__);
	memcpy(ret, sshbuf_ptr(buf), sshbuf_len(buf));
	ret[sshbuf_len(buf)] = '\0';
	sshbuf_free(buf);
	sshbuf_free(arg);
	return ret;
}

/*
 * Runs command in a subprocess. Returns pid on success and a FILE* to the
 * subprocess' stdout or 0 on failure.
 * NB. "command" is only used for logging.
 */
static pid_t
subprocess(const char *tag, struct passwd *pw, const char *command,
    int ac, char **av, FILE **child)
{
	FILE *f;
	struct stat st;
	int devnull, p[2], i;
	pid_t pid;
	char *cp, errmsg[512];
	u_int envsize;
	char **child_env;

	*child = NULL;

	debug3("%s: %s command \"%s\" running as %s", __func__,
	    tag, command, pw->pw_name);

	/* Verify the path exists and is safe-ish to execute */
	if (*av[0] != '/') {
		error("%s path is not absolute", tag);
		return 0;
	}
	temporarily_use_uid(pw);
	if (stat(av[0], &st) < 0) {
		error("Could not stat %s \"%s\": %s", tag,
		    av[0], strerror(errno));
		restore_uid();
		return 0;
	}
	if (auth_secure_path(av[0], &st, NULL, 0,
	    errmsg, sizeof(errmsg)) != 0) {
		error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
		restore_uid();
		return 0;
	}

	/*
	 * Run the command; stderr is left in place, stdout is the
	 * authorized_keys output.
	 */
	if (pipe(p) != 0) {
		error("%s: pipe: %s", tag, strerror(errno));
		restore_uid();
		return 0;
	}

	/*
	 * Don't want to call this in the child, where it can fatal() and
	 * run cleanup_exit() code.
	 */
	restore_uid();

	switch ((pid = fork())) {
	case -1: /* error */
		error("%s: fork: %s", tag, strerror(errno));
		close(p[0]);
		close(p[1]);
		return 0;
	case 0: /* child */
		/* Prepare a minimal environment for the child. */
		envsize = 5;
		child_env = xcalloc(sizeof(*child_env), envsize);
		child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
		child_set_env(&child_env, &envsize, "USER", pw->pw_name);
		child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
		child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
		if ((cp = getenv("LANG")) != NULL)
			child_set_env(&child_env, &envsize, "LANG", cp);

		for (i = 0; i < NSIG; i++)
			signal(i, SIG_DFL);

		if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
			error("%s: open %s: %s", tag, _PATH_DEVNULL,
			    strerror(errno));
			_exit(1);
		}
		/* Keep stderr around a while longer to catch errors */
		if (dup2(devnull, STDIN_FILENO) == -1 ||
		    dup2(p[1], STDOUT_FILENO) == -1) {
			error("%s: dup2: %s", tag, strerror(errno));
			_exit(1);
		}
		closefrom(STDERR_FILENO + 1);

		/* Don't use permanently_set_uid() here to avoid fatal() */
		if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
			error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
			    strerror(errno));
			_exit(1);
		}
		if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
			error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
			    strerror(errno));
			_exit(1);
		}
		/* stdin is pointed to /dev/null at this point */
		if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
			error("%s: dup2: %s", tag, strerror(errno));
			_exit(1);
		}

		execve(av[0], av, child_env);
		error("%s exec \"%s\": %s", tag, command, strerror(errno));
		_exit(127);
	default: /* parent */
		break;
	}

	close(p[1]);
	if ((f = fdopen(p[0], "r")) == NULL) {
		error("%s: fdopen: %s", tag, strerror(errno));
		close(p[0]);
		/* Don't leave zombie child */
		kill(pid, SIGTERM);
		while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
			;
		return 0;
	}
	/* Success */
	debug3("%s: %s pid %ld", __func__, tag, (long)pid);
	*child = f;
	return pid;
}

/* Returns 0 if pid exited cleanly, non-zero otherwise */
static int
exited_cleanly(pid_t pid, const char *tag, const char *cmd)
{
	int status;

	while (waitpid(pid, &status, 0) == -1) {
		if (errno != EINTR) {
			error("%s: waitpid: %s", tag, strerror(errno));
			return -1;
		}
	}
	if (WIFSIGNALED(status)) {
		error("%s %s exited on signal %d", tag, cmd, WTERMSIG(status));
		return -1;
	} else if (WEXITSTATUS(status) != 0) {
		error("%s %s failed, status %d", tag, cmd, WEXITSTATUS(status));
		return -1;
	}
	return 0;
}

static int
match_principals_option(const char *principal_list, struct sshkey_cert *cert)
{
	char *result;
	u_int i;

	/* XXX percent_expand() sequences for authorized_principals? */

	for (i = 0; i < cert->nprincipals; i++) {
		if ((result = match_list(cert->principals[i],
		    principal_list, NULL)) != NULL) {
			debug3("matched principal from key options \"%.100s\"",
			    result);
			free(result);
			return 1;
		}
	}
	return 0;
}

static int
process_principals(FILE *f, char *file, struct passwd *pw,
    struct sshkey_cert *cert)
{
	char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
	u_long linenum = 0;
	u_int i;

	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
		/* Skip leading whitespace. */
		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
			;
		/* Skip blank and comment lines. */
		if ((ep = strchr(cp, '#')) != NULL)
			*ep = '\0';
		if (!*cp || *cp == '\n')
			continue;
		/* Trim trailing whitespace. */
		ep = cp + strlen(cp) - 1;
		while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
			*ep-- = '\0';
		/*
		 * If the line has internal whitespace then assume it has
		 * key options.
		 */
		line_opts = NULL;
		if ((ep = strrchr(cp, ' ')) != NULL ||
		    (ep = strrchr(cp, '\t')) != NULL) {
			for (; *ep == ' ' || *ep == '\t'; ep++)
				;
			line_opts = cp;
			cp = ep;
		}
		for (i = 0; i < cert->nprincipals; i++) {
			if (strcmp(cp, cert->principals[i]) == 0) {
				debug3("%s:%lu: matched principal \"%.100s\"",
				    file == NULL ? "(command)" : file,
				    linenum, cert->principals[i]);
				if (auth_parse_options(pw, line_opts,
				    file, linenum) != 1)
					continue;
				return 1;
			}
		}
	}
	return 0;
}

static int
match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
{
	FILE *f;
	int success;

	temporarily_use_uid(pw);
	debug("trying authorized principals file %s", file);
	if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
		restore_uid();
		return 0;
	}
	success = process_principals(f, file, pw, cert);
	fclose(f);
	restore_uid();
	return success;
}

/*
 * Checks whether principal is allowed in output of command.
 * returns 1 if the principal is allowed or 0 otherwise.
 */
static int
match_principals_command(struct passwd *user_pw, struct sshkey_cert *cert)
{
	FILE *f = NULL;
	int ok, found_principal = 0;
	struct passwd *pw;
	int i, ac = 0, uid_swapped = 0;
	pid_t pid;
	char *tmp, *username = NULL, *command = NULL, **av = NULL;
	void (*osigchld)(int);

	if (options.authorized_principals_command == NULL)
		return 0;
	if (options.authorized_principals_command_user == NULL) {
		error("No user for AuthorizedPrincipalsCommand specified, "
		    "skipping");
		return 0;
	}

	/*
	 * NB. all returns later this function should go via "out" to
	 * ensure the original SIGCHLD handler is restored properly.
	 */
	osigchld = signal(SIGCHLD, SIG_DFL);

	/* Prepare and verify the user for the command */
	username = percent_expand(options.authorized_principals_command_user,
	    "u", user_pw->pw_name, (char *)NULL);
	pw = getpwnam(username);
	if (pw == NULL) {
		error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
		    username, strerror(errno));
		goto out;
	}

	/* Turn the command into an argument vector */
	if (split_argv(options.authorized_principals_command, &ac, &av) != 0) {
		error("AuthorizedPrincipalsCommand \"%s\" contains "
		    "invalid quotes", command);
		goto out;
	}
	if (ac == 0) {
		error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
		    command);
		goto out;
	}
	for (i = 1; i < ac; i++) {
		tmp = percent_expand(av[i],
		    "u", user_pw->pw_name,
		    "h", user_pw->pw_dir,
		    (char *)NULL);
		if (tmp == NULL)
			fatal("%s: percent_expand failed", __func__);
		free(av[i]);
		av[i] = tmp;
	}
	/* Prepare a printable command for logs, etc. */
	command = assemble_argv(ac, av);

	if ((pid = subprocess("AuthorizedPrincipalsCommand", pw, command,
	    ac, av, &f)) == 0)
		goto out;

	uid_swapped = 1;
	temporarily_use_uid(pw);

	ok = process_principals(f, NULL, pw, cert);

	if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command) != 0)
		goto out;

	/* Read completed successfully */
	found_principal = ok;
 out:
	if (f != NULL)
		fclose(f);
	signal(SIGCHLD, osigchld);
	for (i = 0; i < ac; i++)
		free(av[i]);
	free(av);
	if (uid_swapped)
		restore_uid();
	free(command);
	free(username);
	return found_principal;
}
/*
 * Checks whether key is allowed in authorized_keys-format file,
 * returns 1 if the key is allowed or 0 otherwise.
 */
static int
check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
{
	char line[SSH_MAX_PUBKEY_BYTES];
	const char *reason;
	int found_key = 0;
	u_long linenum = 0;
	Key *found;
	char *fp;

	found_key = 0;

	found = NULL;
	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
		char *cp, *key_options = NULL;
		if (found != NULL)
			key_free(found);
		found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
		auth_clear_options();

		/* Skip leading whitespace, empty and comment lines. */
		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
			;
		if (!*cp || *cp == '\n' || *cp == '#')
			continue;

		if (key_read(found, &cp) != 1) {
			/* no key?  check if there are options for this key */
			int quoted = 0;
			debug2("user_key_allowed: check options: '%s'", cp);
			key_options = cp;
			for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
				if (*cp == '\\' && cp[1] == '"')
					cp++;	/* Skip both */
				else if (*cp == '"')
					quoted = !quoted;
			}
			/* Skip remaining whitespace. */
			for (; *cp == ' ' || *cp == '\t'; cp++)
				;
			if (key_read(found, &cp) != 1) {
				debug2("user_key_allowed: advance: '%s'", cp);
				/* still no key?  advance to next line*/
				continue;
			}
		}
		if (key_is_cert(key)) {
			if (!key_equal(found, key->cert->signature_key))
				continue;
			if (auth_parse_options(pw, key_options, file,
			    linenum) != 1)
				continue;
			if (!key_is_cert_authority)
				continue;
			if ((fp = sshkey_fingerprint(found,
			    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
				continue;
			debug("matching CA found: file %s, line %lu, %s %s",
			    file, linenum, key_type(found), fp);
			/*
			 * If the user has specified a list of principals as
			 * a key option, then prefer that list to matching
			 * their username in the certificate principals list.
			 */
			if (authorized_principals != NULL &&
			    !match_principals_option(authorized_principals,
			    key->cert)) {
				reason = "Certificate does not contain an "
				    "authorized principal";
 fail_reason:
				free(fp);
				error("%s", reason);
				auth_debug_add("%s", reason);
				continue;
			}
			if (key_cert_check_authority(key, 0, 0,
			    authorized_principals == NULL ? pw->pw_name : NULL,
			    &reason) != 0)
				goto fail_reason;
			if (auth_cert_options(key, pw) != 0) {
				free(fp);
				continue;
			}
			verbose("Accepted certificate ID \"%s\" "
			    "signed by %s CA %s via %s", key->cert->key_id,
			    key_type(found), fp, file);
			free(fp);
			found_key = 1;
			break;
		} else if (key_equal(found, key)) {
			if (auth_parse_options(pw, key_options, file,
			    linenum) != 1)
				continue;
			if (key_is_cert_authority)
				continue;
			if ((fp = sshkey_fingerprint(found,
			    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
				continue;
			debug("matching key found: file %s, line %lu %s %s",
			    file, linenum, key_type(found), fp);
			free(fp);
			found_key = 1;
			break;
		}
	}
	if (found != NULL)
		key_free(found);
	if (!found_key)
		debug2("key not found");
	return found_key;
}

/* Authenticate a certificate key against TrustedUserCAKeys */
static int
user_cert_trusted_ca(struct passwd *pw, Key *key)
{
	char *ca_fp, *principals_file = NULL;
	const char *reason;
	int ret = 0, found_principal = 0, use_authorized_principals;

	if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
		return 0;

	if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
	    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
		return 0;

	if (sshkey_in_file(key->cert->signature_key,
	    options.trusted_user_ca_keys, 1, 0) != 0) {
		debug2("%s: CA %s %s is not listed in %s", __func__,
		    key_type(key->cert->signature_key), ca_fp,
		    options.trusted_user_ca_keys);
		goto out;
	}
	/*
	 * If AuthorizedPrincipals is in use, then compare the certificate
	 * principals against the names in that file rather than matching
	 * against the username.
	 */
	if ((principals_file = authorized_principals_file(pw)) != NULL) {
		if (match_principals_file(principals_file, pw, key->cert))
			found_principal = 1;
	}
	/* Try querying command if specified */
	if (!found_principal && match_principals_command(pw, key->cert))
		found_principal = 1;
	/* If principals file or command is specified, then require a match */
	use_authorized_principals = principals_file != NULL ||
            options.authorized_principals_command != NULL;
	if (!found_principal && use_authorized_principals) {
		reason = "Certificate does not contain an authorized principal";
 fail_reason:
		error("%s", reason);
		auth_debug_add("%s", reason);
		goto out;
	}
	if (key_cert_check_authority(key, 0, 1,
	    use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
		goto fail_reason;
	if (auth_cert_options(key, pw) != 0)
		goto out;

	verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
	    key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
	    options.trusted_user_ca_keys);
	ret = 1;

 out:
	free(principals_file);
	free(ca_fp);
	return ret;
}

/*
 * Checks whether key is allowed in file.
 * returns 1 if the key is allowed or 0 otherwise.
 */
static int
user_key_allowed2(struct passwd *pw, Key *key, char *file)
{
	FILE *f;
	int found_key = 0;

	/* Temporarily use the user's uid. */
	temporarily_use_uid(pw);

	debug("trying public key file %s", file);
	if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
		found_key = check_authkeys_file(f, file, key, pw);
		fclose(f);
	}

	restore_uid();
	return found_key;
}

/*
 * Checks whether key is allowed in output of command.
 * returns 1 if the key is allowed or 0 otherwise.
 */
static int
user_key_command_allowed2(struct passwd *user_pw, Key *key)
{
	FILE *f = NULL;
	int r, ok, found_key = 0;
	struct passwd *pw;
	int i, uid_swapped = 0, ac = 0;
	pid_t pid;
	char *username = NULL, *key_fp = NULL, *keytext = NULL;
	char *tmp, *command = NULL, **av = NULL;
	void (*osigchld)(int);

	if (options.authorized_keys_command == NULL)
		return 0;
	if (options.authorized_keys_command_user == NULL) {
		error("No user for AuthorizedKeysCommand specified, skipping");
		return 0;
	}

	/*
	 * NB. all returns later this function should go via "out" to
	 * ensure the original SIGCHLD handler is restored properly.
	 */
	osigchld = signal(SIGCHLD, SIG_DFL);

	/* Prepare and verify the user for the command */
	username = percent_expand(options.authorized_keys_command_user,
	    "u", user_pw->pw_name, (char *)NULL);
	pw = getpwnam(username);
	if (pw == NULL) {
		error("AuthorizedKeysCommandUser \"%s\" not found: %s",
		    username, strerror(errno));
		goto out;
	}

	/* Prepare AuthorizedKeysCommand */
	if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
	    SSH_FP_DEFAULT)) == NULL) {
		error("%s: sshkey_fingerprint failed", __func__);
		goto out;
	}
	if ((r = sshkey_to_base64(key, &keytext)) != 0) {
		error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
		goto out;
	}

	/* Turn the command into an argument vector */
	if (split_argv(options.authorized_keys_command, &ac, &av) != 0) {
		error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
		    command);
		goto out;
	}
	if (ac == 0) {
		error("AuthorizedKeysCommand \"%s\" yielded no arguments",
		    command);
		goto out;
	}
	for (i = 1; i < ac; i++) {
		tmp = percent_expand(av[i],
		    "u", user_pw->pw_name,
		    "h", user_pw->pw_dir,
		    "t", sshkey_ssh_name(key),
		    "f", key_fp,
		    "k", keytext,
		    (char *)NULL);
		if (tmp == NULL)
			fatal("%s: percent_expand failed", __func__);
		free(av[i]);
		av[i] = tmp;
	}
	/* Prepare a printable command for logs, etc. */
	command = assemble_argv(ac, av);

	/*
	 * If AuthorizedKeysCommand was run without arguments
	 * then fall back to the old behaviour of passing the
	 * target username as a single argument.
	 */
	if (ac == 1) {
		av = xreallocarray(av, ac + 2, sizeof(*av));
		av[1] = xstrdup(user_pw->pw_name);
		av[2] = NULL;
		/* Fix up command too, since it is used in log messages */
		free(command);
		xasprintf(&command, "%s %s", av[0], av[1]);
	}

	if ((pid = subprocess("AuthorizedKeysCommand", pw, command,
	    ac, av, &f)) == 0)
		goto out;

	uid_swapped = 1;
	temporarily_use_uid(pw);

	ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);

	if (exited_cleanly(pid, "AuthorizedKeysCommand", command) != 0)
		goto out;

	/* Read completed successfully */
	found_key = ok;
 out:
	if (f != NULL)
		fclose(f);
	signal(SIGCHLD, osigchld);
	for (i = 0; i < ac; i++)
		free(av[i]);
	free(av);
	if (uid_swapped)
		restore_uid();
	free(command);
	free(username);
	free(key_fp);
	free(keytext);
	return found_key;
}

/*
 * Check whether key authenticates and authorises the user.
 */
int
user_key_allowed(struct passwd *pw, Key *key, int auth_attempt)
{
	u_int success, i;
	char *file;

	if (auth_key_is_revoked(key))
		return 0;
	if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
		return 0;

	success = user_cert_trusted_ca(pw, key);
	if (success)
		return success;

	success = user_key_command_allowed2(pw, key);
	if (success > 0)
		return success;

	for (i = 0; !success && i < options.num_authkeys_files; i++) {

		if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
			continue;
		file = expand_authorized_keys(
		    options.authorized_keys_files[i], pw);

		success = user_key_allowed2(pw, key, file);
		free(file);
	}

	return success;
}

/* Records a public key in the list of previously-successful keys */
void
auth2_record_userkey(Authctxt *authctxt, struct sshkey *key)
{
	struct sshkey **tmp;

	if (authctxt->nprev_userkeys >= INT_MAX ||
	    (tmp = reallocarray(authctxt->prev_userkeys,
	    authctxt->nprev_userkeys + 1, sizeof(*tmp))) == NULL)
		fatal("%s: reallocarray failed", __func__);
	authctxt->prev_userkeys = tmp;
	authctxt->prev_userkeys[authctxt->nprev_userkeys] = key;
	authctxt->nprev_userkeys++;
}

/* Checks whether a key has already been used successfully for authentication */
int
auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key)
{
	u_int i;

	for (i = 0; i < authctxt->nprev_userkeys; i++) {
		if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) {
			return 1;
		}
	}
	return 0;
}

Authmethod method_pubkey = {
	"publickey",
	userauth_pubkey,
	&options.pubkey_authentication
};