Merge changes I934c73d4,I28cdc9a0,I9e734da9,I3c079d86

* changes:
  UPSTREAM: depend
  UPSTREAM: upstream: avoid possible NULL deref; from Pedro Martelletto
  Revert "upstream: fix compilation with DEBUG_KEXDH; bz#3160 ok dtucker@"
  Merge upstream-master into master

1 files changed, 754 insertions, 431 deletions

diff --git a/auth2-pubkey.c b/auth2-pubkey.c
index d943efa1..815ea0f2 100644
--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.47 2015/02/17 00:14:05 djm Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.99 2020/02/06 22:30:54 naddy Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -27,8 +27,8 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <sys/wait.h>
 
+#include <stdlib.h>
 #include <errno.h>
 #include <fcntl.h>
 #ifdef HAVE_PATHS_H
@@ -47,12 +47,12 @@
 #include "ssh.h"
 #include "ssh2.h"
 #include "packet.h"
-#include "buffer.h"
+#include "sshbuf.h"
 #include "log.h"
 #include "misc.h"
 #include "servconf.h"
 #include "compat.h"
-#include "key.h"
+#include "sshkey.h"
 #include "hostfile.h"
 #include "auth.h"
 #include "pathnames.h"
@@ -65,124 +65,196 @@
 #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? */
+#include "sk-api.h"
 
 /* import */
 extern ServerOptions options;
 extern u_char *session_id2;
 extern u_int session_id2_len;
 
+static char *
+format_key(const struct sshkey *key)
+{
+	char *ret, *fp = sshkey_fingerprint(key,
+	    options.fingerprint_hash, SSH_FP_DEFAULT);
+
+	xasprintf(&ret, "%s %s", sshkey_type(key), fp);
+	free(fp);
+	return ret;
+}
+
 static int
-userauth_pubkey(Authctxt *authctxt)
+userauth_pubkey(struct ssh *ssh)
 {
-	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);
+	Authctxt *authctxt = ssh->authctxt;
+	struct passwd *pw = authctxt->pw;
+	struct sshbuf *b = NULL;
+	struct sshkey *key = NULL;
+	char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
+	u_char *pkblob = NULL, *sig = NULL, have_sig;
+	size_t blen, slen;
+	int r, pktype;
+	int req_presence = 0, authenticated = 0;
+	struct sshauthopt *authopts = NULL;
+	struct sshkey_sig_details *sig_details = NULL;
+
+	if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
+	    (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
+	    (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
+		fatal("%s: parse request failed: %s", __func__, ssh_err(r));
+
+	if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) {
+		char *keystring;
+		struct sshbuf *pkbuf;
+
+		if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL)
+			fatal("%s: sshbuf_from failed", __func__);
+		if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
+			fatal("%s: sshbuf_dtob64 failed", __func__);
+		debug2("%s: %s user %s %s public key %s %s", __func__,
+		    authctxt->valid ? "valid" : "invalid", authctxt->user,
+		    have_sig ? "attempting" : "querying", pkalg, keystring);
+		sshbuf_free(pkbuf);
+		free(keystring);
 	}
-	pktype = key_type_from_name(pkalg);
+
+	pktype = sshkey_type_from_name(pkalg);
 	if (pktype == KEY_UNSPEC) {
 		/* this is perfectly legal */
-		logit("userauth_pubkey: unsupported public key algorithm: %s",
-		    pkalg);
+		verbose("%s: unsupported public key algorithm: %s",
+		    __func__, pkalg);
+		goto done;
+	}
+	if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
+		error("%s: could not parse key: %s", __func__, ssh_err(r));
 		goto done;
 	}
-	key = key_from_blob(pkblob, blen);
 	if (key == NULL) {
-		error("userauth_pubkey: cannot decode key: %s", pkalg);
+		error("%s: cannot decode key: %s", __func__, pkalg);
 		goto done;
 	}
 	if (key->type != pktype) {
-		error("userauth_pubkey: type mismatch for decoded key "
-		    "(received %d, expected %d)", key->type, pktype);
+		error("%s: type mismatch for decoded key "
+		    "(received %d, expected %d)", __func__, key->type, pktype);
 		goto done;
 	}
-	if (key_type_plain(key->type) == KEY_RSA &&
-	    (datafellows & SSH_BUG_RSASIGMD5) != 0) {
+	if (sshkey_type_plain(key->type) == KEY_RSA &&
+	    (ssh->compat & 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));
+	if (auth2_key_already_used(authctxt, key)) {
+		logit("refusing previously-used %s key", sshkey_type(key));
 		goto done;
 	}
-	if (match_pattern_list(sshkey_ssh_name(key), options.pubkey_key_types,
-	    strlen(options.pubkey_key_types), 0) != 1) {
+	if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) {
 		logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
 		    __func__, sshkey_ssh_name(key));
 		goto done;
 	}
+	if ((r = sshkey_check_cert_sigtype(key,
+	    options.ca_sign_algorithms)) != 0) {
+		logit("%s: certificate signature algorithm %s: %s", __func__,
+		    (key->cert == NULL || key->cert->signature_type == NULL) ?
+		    "(null)" : key->cert->signature_type, ssh_err(r));
+		goto done;
+	}
+	key_s = format_key(key);
+	if (sshkey_is_cert(key))
+		ca_s = format_key(key->cert->signature_key);
 
 	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);
+		debug3("%s: have %s signature for %s%s%s",
+		    __func__, pkalg, key_s,
+		    ca_s == NULL ? "" : " CA ",
+		    ca_s == NULL ? "" : ca_s);
+		if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
+		    (r = sshpkt_get_end(ssh)) != 0)
+			fatal("%s: %s", __func__, ssh_err(r));
+		if ((b = sshbuf_new()) == NULL)
+			fatal("%s: sshbuf_new failed", __func__);
+		if (ssh->compat & SSH_OLD_SESSIONID) {
+			if ((r = sshbuf_put(b, session_id2,
+			    session_id2_len)) != 0)
+				fatal("%s: sshbuf_put session id: %s",
+				    __func__, ssh_err(r));
 		} else {
-			buffer_put_string(&b, session_id2, session_id2_len);
+			if ((r = sshbuf_put_string(b, session_id2,
+			    session_id2_len)) != 0)
+				fatal("%s: sshbuf_put_string session id: %s",
+				    __func__, ssh_err(r));
+		}
+		if (!authctxt->valid || authctxt->user == NULL) {
+			debug2("%s: disabled because of invalid user",
+			    __func__);
+			goto done;
 		}
 		/* 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);
+		if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
+		    (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
+		    (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
+		    (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
+		    (r = sshbuf_put_u8(b, have_sig)) != 0 ||
+		    (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
+		    (r = sshbuf_put_string(b, pkblob, blen)) != 0)
+			fatal("%s: build packet failed: %s",
+			    __func__, ssh_err(r));
 #ifdef DEBUG_PK
-		buffer_dump(&b);
+		sshbuf_dump(b, stderr);
 #endif
-		pubkey_auth_info(authctxt, key, NULL);
-
 		/* test for correct signature */
 		authenticated = 0;
-		if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
-		    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
-		    buffer_len(&b))) == 1) {
+		if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
+		    PRIVSEP(sshkey_verify(key, sig, slen,
+		    sshbuf_ptr(b), sshbuf_len(b),
+		    (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
+		    ssh->compat, &sig_details)) == 0) {
 			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);
+		if (authenticated == 1 && sig_details != NULL) {
+			auth2_record_info(authctxt, "signature count = %u",
+			    sig_details->sk_counter);
+			debug("%s: sk_counter = %u, sk_flags = 0x%02x",
+			    __func__, sig_details->sk_counter,
+			    sig_details->sk_flags);
+			req_presence = (options.pubkey_auth_options &
+			    PUBKEYAUTH_TOUCH_REQUIRED) ||
+			    !authopts->no_require_user_presence;
+			if (req_presence && (sig_details->sk_flags &
+			    SSH_SK_USER_PRESENCE_REQD) == 0) {
+				error("public key %s signature for %s%s from "
+				    "%.128s port %d rejected: user presence "
+				    "(authenticator touch) requirement "
+				    "not met ", key_s,
+				    authctxt->valid ? "" : "invalid user ",
+				    authctxt->user, ssh_remote_ipaddr(ssh),
+				    ssh_remote_port(ssh));
+				authenticated = 0;
+				goto done;
+			}
+		}
+		auth2_record_key(authctxt, authenticated, key);
 	} else {
-		debug("test whether pkalg/pkblob are acceptable");
-		packet_check_eom();
+		debug("%s: test pkalg %s pkblob %s%s%s",
+		    __func__, pkalg, key_s,
+		    ca_s == NULL ? "" : " CA ",
+		    ca_s == NULL ? "" : ca_s);
+
+		if ((r = sshpkt_get_end(ssh)) != 0)
+			fatal("%s: %s", __func__, ssh_err(r));
 
+		if (!authctxt->valid || authctxt->user == NULL) {
+			debug2("%s: disabled because of invalid user",
+			    __func__);
+			goto done;
+		}
 		/* XXX fake reply and always send PK_OK ? */
 		/*
 		 * XXX this allows testing whether a user is allowed
@@ -191,63 +263,37 @@ userauth_pubkey(Authctxt *authctxt)
 		 * if a user is not allowed to login. is this an
 		 * issue? -markus
 		 */
-		if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
-			packet_start(SSH2_MSG_USERAUTH_PK_OK);
-			packet_put_string(pkalg, alen);
-			packet_put_string(pkblob, blen);
-			packet_send();
-			packet_write_wait();
+		if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
+			if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
+			    != 0 ||
+			    (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
+			    (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
+			    (r = sshpkt_send(ssh)) != 0 ||
+			    (r = ssh_packet_write_wait(ssh)) != 0)
+				fatal("%s: %s", __func__, ssh_err(r));
 			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);
+	if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
+		debug("%s: key options inconsistent with existing", __func__);
+		authenticated = 0;
+	}
+	debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
+
+	sshbuf_free(b);
+	sshauthopt_free(authopts);
+	sshkey_free(key);
+	free(userstyle);
 	free(pkalg);
 	free(pkblob);
+	free(key_s);
+	free(ca_s);
+	free(sig);
+	sshkey_sig_details_free(sig_details);
 	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);
-}
-
 static int
 match_principals_option(const char *principal_list, struct sshkey_cert *cert)
 {
@@ -268,21 +314,79 @@ match_principals_option(const char *principal_list, struct sshkey_cert *cert)
 	return 0;
 }
 
+/*
+ * Process a single authorized_principals format line. Returns 0 and sets
+ * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
+ * log preamble for file/line information.
+ */
 static int
-match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
+check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
+    const char *loc, struct sshauthopt **authoptsp)
 {
-	FILE *f;
-	char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
-	u_long linenum = 0;
-	u_int i;
+	u_int i, found = 0;
+	char *ep, *line_opts;
+	const char *reason = NULL;
+	struct sshauthopt *opts = NULL;
 
-	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;
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
+
+	/* 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;
+	}
+	if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
+		debug("%s: bad principals options: %s", loc, reason);
+		auth_debug_add("%s: bad principals options: %s", loc, reason);
+		return -1;
+	}
+	/* Check principals in cert against those on line */
+	for (i = 0; i < cert->nprincipals; i++) {
+		if (strcmp(cp, cert->principals[i]) != 0)
+			continue;
+		debug3("%s: matched principal \"%.100s\"",
+		    loc, cert->principals[i]);
+		found = 1;
 	}
-	while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
+	if (found && authoptsp != NULL) {
+		*authoptsp = opts;
+		opts = NULL;
+	}
+	sshauthopt_free(opts);
+	return found ? 0 : -1;
+}
+
+static int
+process_principals(struct ssh *ssh, FILE *f, const char *file,
+    const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
+{
+	char loc[256], *line = NULL, *cp, *ep;
+	size_t linesize = 0;
+	u_long linenum = 0;
+	u_int found_principal = 0;
+
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
+
+	while (getline(&line, &linesize, f) != -1) {
+		linenum++;
+		/* Always consume entire input */
+		if (found_principal)
+			continue;
+
 		/* Skip leading whitespace. */
 		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 			;
@@ -291,39 +395,313 @@ match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
 			*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("matched principal \"%.100s\" "
-				    "from file \"%s\" on line %lu",
-				    cert->principals[i], file, linenum);
-				if (auth_parse_options(pw, line_opts,
-				    file, linenum) != 1)
-					continue;
-				fclose(f);
-				restore_uid();
-				return 1;
-			}
-		}
+
+		snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
+		if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
+			found_principal = 1;
 	}
+	free(line);
+	return found_principal;
+}
+
+/* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
+
+static int
+match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
+    struct sshkey_cert *cert, struct sshauthopt **authoptsp)
+{
+	FILE *f;
+	int success;
+
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
+
+	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(ssh, f, file, cert, authoptsp);
 	fclose(f);
 	restore_uid();
-	return 0;
+	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 ssh *ssh, struct passwd *user_pw,
+    const struct sshkey *key, struct sshauthopt **authoptsp)
+{
+	struct passwd *runas_pw = NULL;
+	const struct sshkey_cert *cert = key->cert;
+	FILE *f = NULL;
+	int r, ok, found_principal = 0;
+	int i, ac = 0, uid_swapped = 0;
+	pid_t pid;
+	char *tmp, *username = NULL, *command = NULL, **av = NULL;
+	char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
+	char serial_s[32], uidstr[32];
+	void (*osigchld)(int);
+
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
+	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 = ssh_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);
+	runas_pw = getpwnam(username);
+	if (runas_pw == NULL) {
+		error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
+		    username, strerror(errno));
+		goto out;
+	}
+
+	/* Turn the command into an argument vector */
+	if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
+		error("AuthorizedPrincipalsCommand \"%s\" contains "
+		    "invalid quotes", options.authorized_principals_command);
+		goto out;
+	}
+	if (ac == 0) {
+		error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
+		    options.authorized_principals_command);
+		goto out;
+	}
+	if ((ca_fp = sshkey_fingerprint(cert->signature_key,
+	    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
+		error("%s: sshkey_fingerprint failed", __func__);
+		goto out;
+	}
+	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(cert->signature_key, &catext)) != 0) {
+		error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
+		goto out;
+	}
+	if ((r = sshkey_to_base64(key, &keytext)) != 0) {
+		error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
+		goto out;
+	}
+	snprintf(serial_s, sizeof(serial_s), "%llu",
+	    (unsigned long long)cert->serial);
+	snprintf(uidstr, sizeof(uidstr), "%llu",
+	    (unsigned long long)user_pw->pw_uid);
+	for (i = 1; i < ac; i++) {
+		tmp = percent_expand(av[i],
+		    "U", uidstr,
+		    "u", user_pw->pw_name,
+		    "h", user_pw->pw_dir,
+		    "t", sshkey_ssh_name(key),
+		    "T", sshkey_ssh_name(cert->signature_key),
+		    "f", key_fp,
+		    "F", ca_fp,
+		    "k", keytext,
+		    "K", catext,
+		    "i", cert->key_id,
+		    "s", serial_s,
+		    (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 = argv_assemble(ac, av);
+
+	if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
+	    ac, av, &f,
+	    SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
+		goto out;
+
+	uid_swapped = 1;
+	temporarily_use_uid(runas_pw);
+
+	ok = process_principals(ssh, f, "(command)", cert, authoptsp);
+
+	fclose(f);
+	f = NULL;
+
+	if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
+		goto out;
+
+	/* Read completed successfully */
+	found_principal = ok;
+ out:
+	if (f != NULL)
+		fclose(f);
+	ssh_signal(SIGCHLD, osigchld);
+	for (i = 0; i < ac; i++)
+		free(av[i]);
+	free(av);
+	if (uid_swapped)
+		restore_uid();
+	free(command);
+	free(username);
+	free(ca_fp);
+	free(key_fp);
+	free(catext);
+	free(keytext);
+	return found_principal;
+}
+
+/*
+ * Check a single line of an authorized_keys-format file. Returns 0 if key
+ * matches, -1 otherwise. Will return key/cert options via *authoptsp
+ * on success. "loc" is used as file/line location in log messages.
+ */
+static int
+check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
+    char *cp, const char *loc, struct sshauthopt **authoptsp)
+{
+	int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
+	struct sshkey *found = NULL;
+	struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
+	char *key_options = NULL, *fp = NULL;
+	const char *reason = NULL;
+	int ret = -1;
+
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
+
+	if ((found = sshkey_new(want_keytype)) == NULL) {
+		debug3("%s: keytype %d failed", __func__, want_keytype);
+		goto out;
+	}
+
+	/* XXX djm: peek at key type in line and skip if unwanted */
+
+	if (sshkey_read(found, &cp) != 0) {
+		/* no key?  check for options */
+		debug2("%s: check options: '%s'", loc, cp);
+		key_options = cp;
+		if (sshkey_advance_past_options(&cp) != 0) {
+			reason = "invalid key option string";
+			goto fail_reason;
+		}
+		skip_space(&cp);
+		if (sshkey_read(found, &cp) != 0) {
+			/* still no key?  advance to next line*/
+			debug2("%s: advance: '%s'", loc, cp);
+			goto out;
+		}
+	}
+	/* Parse key options now; we need to know if this is a CA key */
+	if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
+		debug("%s: bad key options: %s", loc, reason);
+		auth_debug_add("%s: bad key options: %s", loc, reason);
+		goto out;
+	}
+	/* Ignore keys that don't match or incorrectly marked as CAs */
+	if (sshkey_is_cert(key)) {
+		/* Certificate; check signature key against CA */
+		if (!sshkey_equal(found, key->cert->signature_key) ||
+		    !keyopts->cert_authority)
+			goto out;
+	} else {
+		/* Plain key: check it against key found in file */
+		if (!sshkey_equal(found, key) || keyopts->cert_authority)
+			goto out;
+	}
+
+	/* We have a candidate key, perform authorisation checks */
+	if ((fp = sshkey_fingerprint(found,
+	    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
+		fatal("%s: fingerprint failed", __func__);
+
+	debug("%s: matching %s found: %s %s", loc,
+	    sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
+
+	if (auth_authorise_keyopts(ssh, pw, keyopts,
+	    sshkey_is_cert(key), loc) != 0) {
+		reason = "Refused by key options";
+		goto fail_reason;
+	}
+	/* That's all we need for plain keys. */
+	if (!sshkey_is_cert(key)) {
+		verbose("Accepted key %s %s found at %s",
+		    sshkey_type(found), fp, loc);
+		finalopts = keyopts;
+		keyopts = NULL;
+		goto success;
+	}
+
+	/*
+	 * Additional authorisation for certificates.
+	 */
+
+	/* Parse and check options present in certificate */
+	if ((certopts = sshauthopt_from_cert(key)) == NULL) {
+		reason = "Invalid certificate options";
+		goto fail_reason;
+	}
+	if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
+		reason = "Refused by certificate options";
+		goto fail_reason;
+	}
+	if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
+		goto fail_reason;
+
+	/*
+	 * 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 (keyopts->cert_principals != NULL &&
+	    !match_principals_option(keyopts->cert_principals, key->cert)) {
+		reason = "Certificate does not contain an authorized principal";
+		goto fail_reason;
+	}
+	if (sshkey_cert_check_authority(key, 0, 0,
+	   keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
+		goto fail_reason;
+
+	verbose("Accepted certificate ID \"%s\" (serial %llu) "
+	    "signed by CA %s %s found at %s",
+	    key->cert->key_id,
+	    (unsigned long long)key->cert->serial,
+	    sshkey_type(found), fp, loc);
+
+ success:
+	if (finalopts == NULL)
+		fatal("%s: internal error: missing options", __func__);
+	if (authoptsp != NULL) {
+		*authoptsp = finalopts;
+		finalopts = NULL;
+	}
+	/* success */
+	ret = 0;
+	goto out;
+
+ fail_reason:
+	error("%s", reason);
+	auth_debug_add("%s", reason);
+ out:
+	free(fp);
+	sshauthopt_free(keyopts);
+	sshauthopt_free(certopts);
+	sshauthopt_free(finalopts);
+	sshkey_free(found);
+	return ret;
 }
 
 /*
@@ -331,137 +709,62 @@ match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
  * returns 1 if the key is allowed or 0 otherwise.
  */
 static int
-check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
+check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
+    char *file, struct sshkey *key, struct sshauthopt **authoptsp)
 {
-	char line[SSH_MAX_PUBKEY_BYTES];
-	const char *reason;
+	char *cp, *line = NULL, loc[256];
+	size_t linesize = 0;
 	int found_key = 0;
 	u_long linenum = 0;
-	Key *found;
-	char *fp;
 
-	found_key = 0;
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
 
-	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();
+	while (getline(&line, &linesize, f) != -1) {
+		linenum++;
+		/* Always consume entire file */
+		if (found_key)
+			continue;
 
 		/* Skip leading whitespace, empty and comment lines. */
-		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
-			;
+		cp = line;
+		skip_space(&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);
+		snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
+		if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
 			found_key = 1;
-			break;
-		}
 	}
-	if (found != NULL)
-		key_free(found);
-	if (!found_key)
-		debug2("key not found");
+	free(line);
 	return found_key;
 }
 
 /* Authenticate a certificate key against TrustedUserCAKeys */
 static int
-user_cert_trusted_ca(struct passwd *pw, Key *key)
+user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
+    struct sshauthopt **authoptsp)
 {
 	char *ca_fp, *principals_file = NULL;
 	const char *reason;
-	int ret = 0;
+	struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
+	struct sshauthopt *final_opts = NULL;
+	int r, ret = 0, found_principal = 0, use_authorized_principals;
+
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
 
-	if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
+	if (!sshkey_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);
+	if ((r = 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: %s", __func__,
+		    sshkey_type(key->cert->signature_key), ca_fp,
+		    options.trusted_user_ca_keys, ssh_err(r));
 		goto out;
 	}
 	/*
@@ -470,27 +773,69 @@ user_cert_trusted_ca(struct passwd *pw, Key *key)
 	 * against the username.
 	 */
 	if ((principals_file = authorized_principals_file(pw)) != NULL) {
-		if (!match_principals_file(principals_file, pw, key->cert)) {
-			reason = "Certificate does not contain an "
-			    "authorized principal";
+		if (match_principals_file(ssh, pw, principals_file,
+		    key->cert, &principals_opts))
+			found_principal = 1;
+	}
+	/* Try querying command if specified */
+	if (!found_principal && match_principals_command(ssh, pw, key,
+	    &principals_opts))
+		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";
+		goto fail_reason;
+	}
+	if (use_authorized_principals && principals_opts == NULL)
+		fatal("%s: internal error: missing principals_opts", __func__);
+	if (sshkey_cert_check_authority(key, 0, 1,
+	    use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
+		goto fail_reason;
+
+	/* Check authority from options in key and from principals file/cmd */
+	if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
+		reason = "Invalid certificate options";
+		goto fail_reason;
+	}
+	if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
+		reason = "Refused by certificate options";
+		goto fail_reason;
+	}
+	if (principals_opts == NULL) {
+		final_opts = cert_opts;
+		cert_opts = NULL;
+	} else {
+		if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
+		    "principals") != 0) {
+			reason = "Refused by certificate principals options";
+			goto fail_reason;
+		}
+		if ((final_opts = sshauthopt_merge(principals_opts,
+		    cert_opts, &reason)) == NULL) {
  fail_reason:
 			error("%s", reason);
 			auth_debug_add("%s", reason);
 			goto out;
 		}
 	}
-	if (key_cert_check_authority(key, 0, 1,
-	    principals_file == NULL ? pw->pw_name : NULL, &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,
+	/* Success */
+	verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
+	    "%s CA %s via %s", key->cert->key_id,
+	    (unsigned long long)key->cert->serial,
+	    sshkey_type(key->cert->signature_key), ca_fp,
 	    options.trusted_user_ca_keys);
+	if (authoptsp != NULL) {
+		*authoptsp = final_opts;
+		final_opts = NULL;
+	}
 	ret = 1;
-
  out:
+	sshauthopt_free(principals_opts);
+	sshauthopt_free(cert_opts);
+	sshauthopt_free(final_opts);
 	free(principals_file);
 	free(ca_fp);
 	return ret;
@@ -501,17 +846,22 @@ user_cert_trusted_ca(struct passwd *pw, Key *key)
  * returns 1 if the key is allowed or 0 otherwise.
  */
 static int
-user_key_allowed2(struct passwd *pw, Key *key, char *file)
+user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
+    char *file, struct sshauthopt **authoptsp)
 {
 	FILE *f;
 	int found_key = 0;
 
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
+
 	/* 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);
+		found_key = check_authkeys_file(ssh, pw, f, file,
+		    key, authoptsp);
 		fclose(f);
 	}
 
@@ -524,146 +874,130 @@ user_key_allowed2(struct passwd *pw, Key *key, char *file)
  * returns 1 if the key is allowed or 0 otherwise.
  */
 static int
-user_key_command_allowed2(struct passwd *user_pw, Key *key)
+user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
+    struct sshkey *key, struct sshauthopt **authoptsp)
 {
-	FILE *f;
-	int ok, found_key = 0;
-	struct passwd *pw;
-	struct stat st;
-	int status, devnull, p[2], i;
+	struct passwd *runas_pw = NULL;
+	FILE *f = NULL;
+	int r, ok, found_key = 0;
+	int i, uid_swapped = 0, ac = 0;
 	pid_t pid;
-	char *username, errmsg[512];
+	char *username = NULL, *key_fp = NULL, *keytext = NULL;
+	char uidstr[32], *tmp, *command = NULL, **av = NULL;
+	void (*osigchld)(int);
 
-	if (options.authorized_keys_command == NULL ||
-	    options.authorized_keys_command[0] != '/')
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
+	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 = ssh_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) {
+	runas_pw = getpwnam(username);
+	if (runas_pw == NULL) {
 		error("AuthorizedKeysCommandUser \"%s\" not found: %s",
 		    username, strerror(errno));
-		free(username);
-		return 0;
+		goto out;
 	}
-	free(username);
-
-	temporarily_use_uid(pw);
 
-	if (stat(options.authorized_keys_command, &st) < 0) {
-		error("Could not stat AuthorizedKeysCommand \"%s\": %s",
-		    options.authorized_keys_command, strerror(errno));
+	/* Prepare AuthorizedKeysCommand */
+	if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
+	    SSH_FP_DEFAULT)) == NULL) {
+		error("%s: sshkey_fingerprint failed", __func__);
 		goto out;
 	}
-	if (auth_secure_path(options.authorized_keys_command, &st, NULL, 0,
-	    errmsg, sizeof(errmsg)) != 0) {
-		error("Unsafe AuthorizedKeysCommand: %s", errmsg);
+	if ((r = sshkey_to_base64(key, &keytext)) != 0) {
+		error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
 		goto out;
 	}
 
-	if (pipe(p) != 0) {
-		error("%s: pipe: %s", __func__, strerror(errno));
+	/* Turn the command into an argument vector */
+	if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
+		error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
+		    command);
 		goto out;
 	}
-
-	debug3("Running AuthorizedKeysCommand: \"%s %s\" as \"%s\"",
-	    options.authorized_keys_command, user_pw->pw_name, pw->pw_name);
+	if (ac == 0) {
+		error("AuthorizedKeysCommand \"%s\" yielded no arguments",
+		    command);
+		goto out;
+	}
+	snprintf(uidstr, sizeof(uidstr), "%llu",
+	    (unsigned long long)user_pw->pw_uid);
+	for (i = 1; i < ac; i++) {
+		tmp = percent_expand(av[i],
+		    "U", uidstr,
+		    "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 = argv_assemble(ac, av);
 
 	/*
-	 * Don't want to call this in the child, where it can fatal() and
-	 * run cleanup_exit() code.
+	 * If AuthorizedKeysCommand was run without arguments
+	 * then fall back to the old behaviour of passing the
+	 * target username as a single argument.
 	 */
-	restore_uid();
-
-	switch ((pid = fork())) {
-	case -1: /* error */
-		error("%s: fork: %s", __func__, strerror(errno));
-		close(p[0]);
-		close(p[1]);
-		return 0;
-	case 0: /* child */
-		for (i = 0; i < NSIG; i++)
-			signal(i, SIG_DFL);
-
-		if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
-			error("%s: open %s: %s", __func__, _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", __func__, 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("setresgid %u: %s", (u_int)pw->pw_gid,
-			    strerror(errno));
-			_exit(1);
-		}
-		if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
-			error("setresuid %u: %s", (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", __func__, strerror(errno));
-			_exit(1);
-		}
+	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]);
+	}
 
-		execl(options.authorized_keys_command,
-		    options.authorized_keys_command, user_pw->pw_name, NULL);
+	if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
+	    ac, av, &f,
+	    SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
+		goto out;
 
-		error("AuthorizedKeysCommand %s exec failed: %s",
-		    options.authorized_keys_command, strerror(errno));
-		_exit(127);
-	default: /* parent */
-		break;
-	}
+	uid_swapped = 1;
+	temporarily_use_uid(runas_pw);
 
-	temporarily_use_uid(pw);
+	ok = check_authkeys_file(ssh, user_pw, f,
+	    options.authorized_keys_command, key, authoptsp);
 
-	close(p[1]);
-	if ((f = fdopen(p[0], "r")) == NULL) {
-		error("%s: fdopen: %s", __func__, strerror(errno));
-		close(p[0]);
-		/* Don't leave zombie child */
-		kill(pid, SIGTERM);
-		while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
-			;
-		goto out;
-	}
-	ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);
 	fclose(f);
+	f = NULL;
 
-	while (waitpid(pid, &status, 0) == -1) {
-		if (errno != EINTR) {
-			error("%s: waitpid: %s", __func__, strerror(errno));
-			goto out;
-		}
-	}
-	if (WIFSIGNALED(status)) {
-		error("AuthorizedKeysCommand %s exited on signal %d",
-		    options.authorized_keys_command, WTERMSIG(status));
+	if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
 		goto out;
-	} else if (WEXITSTATUS(status) != 0) {
-		error("AuthorizedKeysCommand %s returned status %d",
-		    options.authorized_keys_command, WEXITSTATUS(status));
-		goto out;
-	}
+
+	/* Read completed successfully */
 	found_key = ok;
  out:
-	restore_uid();
+	if (f != NULL)
+		fclose(f);
+	ssh_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;
 }
 
@@ -671,65 +1005,54 @@ user_key_command_allowed2(struct passwd *user_pw, Key *key)
  * Check whether key authenticates and authorises the user.
  */
 int
-user_key_allowed(struct passwd *pw, Key *key)
+user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
+    int auth_attempt, struct sshauthopt **authoptsp)
 {
-	u_int success, i;
+	u_int success = 0, i;
 	char *file;
+	struct sshauthopt *opts = NULL;
+
+	if (authoptsp != NULL)
+		*authoptsp = NULL;
 
 	if (auth_key_is_revoked(key))
 		return 0;
-	if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
+	if (sshkey_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);
+		success = user_key_allowed2(ssh, pw, key, file, &opts);
 		free(file);
+		if (!success) {
+			sshauthopt_free(opts);
+			opts = NULL;
+		}
 	}
+	if (success)
+		goto out;
 
-	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++;
-}
+	if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
+		goto out;
+	sshauthopt_free(opts);
+	opts = NULL;
 
-/* Checks whether a key has already been used successfully for authentication */
-int
-auth2_userkey_already_used(Authctxt *authctxt, struct sshkey *key)
-{
-	u_int i;
+	if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
+		goto out;
+	sshauthopt_free(opts);
+	opts = NULL;
 
-	for (i = 0; i < authctxt->nprev_userkeys; i++) {
-		if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) {
-			return 1;
-		}
+ out:
+	if (success && authoptsp != NULL) {
+		*authoptsp = opts;
+		opts = NULL;
 	}
-	return 0;
+	sshauthopt_free(opts);
+	return success;
 }
 
 Authmethod method_pubkey = {