/* $OpenBSD: auth2.c,v 1.169 2024/05/17 00:30:23 djm 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 "includes.h"

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/uio.h>

#include <fcntl.h>

#include <limits.h>

#include <pwd.h>

#include <stdarg.h>

#include <string.h>

#include <unistd.h>

#include <time.h>

#include "stdlib.h"

#include "atomicio.h"

#include "xmalloc.h"

#include "ssh2.h"

#include "packet.h"

#include "log.h"

#include "sshbuf.h"

#include "misc.h"

#include "servconf.h"

#include "sshkey.h"

#include "hostfile.h"

#include "auth.h"

#include "dispatch.h"

#include "pathnames.h"

#include "ssherr.h"

#ifdef GSSAPI

#include "ssh-gss.h"

#endif

#include "monitor_wrap.h"

#include "digest.h"

#include "kex.h"

/* import */

extern ServerOptions options;

extern struct sshbuf *loginmsg;

/* methods */

extern Authmethod method_none;

extern Authmethod method_pubkey;

extern Authmethod method_passwd;

extern Authmethod method_kbdint;

extern Authmethod method_hostbased;

#ifdef GSSAPI

extern Authmethod method_gssapi;

#endif

Authmethod *authmethods[] = {

&method_none,

&method_pubkey,

#ifdef GSSAPI

&method_gssapi,

#endif

&method_passwd,

&method_kbdint,

&method_hostbased,

NULL

};

/* protocol */

static int input_service_request(int, u_int32_t, struct ssh *);

static int input_userauth_request(int, u_int32_t, struct ssh *);

/* helper */

static Authmethod *authmethod_byname(const char *);

static Authmethod *authmethod_lookup(Authctxt *, const char *);

static char *authmethods_get(Authctxt *authctxt);

#define MATCH_NONE 0 /* method or submethod mismatch */

#define MATCH_METHOD 1 /* method matches (no submethod specified) */

#define MATCH_BOTH 2 /* method and submethod match */

#define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */

static int list_starts_with(const char *, const char *, const char *);

char *

auth2_read_banner(void)

{

struct stat st;

char *banner = NULL;

size_t len, n;

int fd;

if ((fd = open(options.banner, O_RDONLY)) == -1)

return (NULL);

if (fstat(fd, &st) == -1) {

close(fd);

return (NULL);

}

if (st.st_size <= 0 || st.st_size > 1*1024*1024) {

close(fd);

return (NULL);

}

len = (size_t)st.st_size; /* truncate */

banner = xmalloc(len + 1);

n = atomicio(read, fd, banner, len);

close(fd);

if (n != len) {

free(banner);

return (NULL);

}

banner[n] = '\0';

return (banner);

}

static void

userauth_send_banner(struct ssh *ssh, const char *msg)

{

int r;

if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 ||

(r = sshpkt_put_cstring(ssh, msg)) != 0 ||

(r = sshpkt_put_cstring(ssh, "")) != 0 || /* language, unused */

(r = sshpkt_send(ssh)) != 0)

fatal_fr(r, "send packet");

debug("%s: sent", __func__);

}

static void

userauth_banner(struct ssh *ssh)

{

char *banner = NULL;

if (options.banner == NULL)

return;

if ((banner = mm_auth2_read_banner()) == NULL)

goto done;

userauth_send_banner(ssh, banner);

done:

free(banner);

}

/*

* loop until authctxt->success == TRUE

*/

void

do_authentication2(struct ssh *ssh)

{

Authctxt *authctxt = ssh->authctxt;

ssh_dispatch_init(ssh, &dispatch_protocol_error);

if (ssh->kex->ext_info_c)

ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_input_ext_info);

ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);

ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);

ssh->authctxt = NULL;

}

static int

input_service_request(int type, u_int32_t seq, struct ssh *ssh)

{

Authctxt *authctxt = ssh->authctxt;

char *service = NULL;

int r, acceptit = 0;

if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||

(r = sshpkt_get_end(ssh)) != 0)

goto out;

if (authctxt == NULL)

fatal("input_service_request: no authctxt");

if (strcmp(service, "ssh-userauth") == 0) {

if (!authctxt->success) {

acceptit = 1;

/* now we can handle user-auth requests */

ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,

&input_userauth_request);

}

}

/* XXX all other service requests are denied */

if (acceptit) {

if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 ||

(r = sshpkt_put_cstring(ssh, service)) != 0 ||

(r = sshpkt_send(ssh)) != 0 ||

(r = ssh_packet_write_wait(ssh)) != 0)

goto out;

} else {

debug("bad service request %s", service);

ssh_packet_disconnect(ssh, "bad service request %s", service);

}

ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &dispatch_protocol_error);

r = 0;

out:

free(service);

return r;

}

#define MIN_FAIL_DELAY_SECONDS 0.005

#define MAX_FAIL_DELAY_SECONDS 5.0

static double

user_specific_delay(const char *user)

{

char b[512];

size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);

u_char *hash = xmalloc(len);

double delay;

(void)snprintf(b, sizeof b, "%llu%s",

(unsigned long long)options.timing_secret, user);

if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)

fatal_f("ssh_digest_memory");

/* 0-4.2 ms of delay */

delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;

freezero(hash, len);

debug3_f("user specific delay %0.3lfms", delay/1000);

return MIN_FAIL_DELAY_SECONDS + delay;

}

static void

ensure_minimum_time_since(double start, double seconds)

{

struct timespec ts;

double elapsed = monotime_double() - start, req = seconds, remain;

if (elapsed > MAX_FAIL_DELAY_SECONDS) {

debug3_f("elapsed %0.3lfms exceeded the max delay "

"requested %0.3lfms)", elapsed*1000, req*1000);

return;

}

/* if we've already passed the requested time, scale up */

while ((remain = seconds - elapsed) < 0.0)

seconds *= 2;

ts.tv_sec = remain;

ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;

debug3_f("elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",

elapsed*1000, remain*1000, req*1000);

nanosleep(&ts, NULL);

}

static int

input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)

{

Authctxt *authctxt = ssh->authctxt;

Authmethod *m = NULL;

char *user = NULL, *service = NULL, *method = NULL, *style = NULL;

int r, authenticated = 0;

double tstart = monotime_double();

if (authctxt == NULL)

fatal("input_userauth_request: no authctxt");

if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 ||

(r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||

(r = sshpkt_get_cstring(ssh, &method, NULL)) != 0)

goto out;

debug("userauth-request for user %s service %s method %s", user, service, method);

debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);

if ((style = strchr(user, ':')) != NULL)

*style++ = 0;

if (authctxt->attempt >= 1024)

auth_maxtries_exceeded(ssh);

if (authctxt->attempt++ == 0) {

/* setup auth context */

authctxt->pw = mm_getpwnamallow(ssh, user);

authctxt->user = xstrdup(user);

if (authctxt->pw && strcmp(service, "ssh-connection")==0) {

authctxt->valid = 1;

debug2_f("setting up authctxt for %s", user);

} else {

authctxt->valid = 0;

/* Invalid user, fake password information */

authctxt->pw = fakepw();

#ifdef SSH_AUDIT_EVENTS

mm_audit_event(ssh, SSH_INVALID_USER);

#endif

}

#ifdef USE_PAM

if (options.use_pam)

mm_start_pam(ssh);

#endif

ssh_packet_set_log_preamble(ssh, "%suser %s",

authctxt->valid ? "authenticating " : "invalid ", user);

setproctitle("%s [net]", authctxt->valid ? user : "unknown");

authctxt->service = xstrdup(service);

authctxt->style = style ? xstrdup(style) : NULL;

mm_inform_authserv(service, style);

userauth_banner(ssh);

if ((r = kex_server_update_ext_info(ssh)) != 0)

fatal_fr(r, "kex_server_update_ext_info failed");

if (auth2_setup_methods_lists(authctxt) != 0)

ssh_packet_disconnect(ssh,

"no authentication methods enabled");

} else if (strcmp(user, authctxt->user) != 0 ||

strcmp(service, authctxt->service) != 0) {

ssh_packet_disconnect(ssh, "Change of username or service "

"not allowed: (%s,%s) -> (%s,%s)",

authctxt->user, authctxt->service, user, service);

}

/* reset state */

auth2_challenge_stop(ssh);

#ifdef GSSAPI

/* XXX move to auth2_gssapi_stop() */

ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);

ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);

#endif

auth2_authctxt_reset_info(authctxt);

authctxt->postponed = 0;

authctxt->server_caused_failure = 0;

/* try to authenticate user */

m = authmethod_lookup(authctxt, method);

if (m != NULL && authctxt->failures < options.max_authtries) {

debug2("input_userauth_request: try method %s", method);

authenticated = m->userauth(ssh, method);

}

if (!authctxt->authenticated && strcmp(method, "none") != 0)

ensure_minimum_time_since(tstart,

user_specific_delay(authctxt->user));

userauth_finish(ssh, authenticated, method, NULL);

r = 0;

out:

free(service);

free(user);

free(method);

return r;

}

void

userauth_finish(struct ssh *ssh, int authenticated, const char *packet_method,

const char *submethod)

{

Authctxt *authctxt = ssh->authctxt;

Authmethod *m = NULL;

const char *method = packet_method;

char *methods;

int r, partial = 0;

if (authenticated) {

if (!authctxt->valid) {

fatal("INTERNAL ERROR: authenticated invalid user %s",

authctxt->user);

}

if (authctxt->postponed)

fatal("INTERNAL ERROR: authenticated and postponed");

/* prefer primary authmethod name to possible synonym */

if ((m = authmethod_byname(method)) == NULL)

fatal("INTERNAL ERROR: bad method %s", method);

method = m->cfg->name;

}

/* Special handling for root */

if (authenticated && authctxt->pw->pw_uid == 0 &&

!auth_root_allowed(ssh, method)) {

authenticated = 0;

#ifdef SSH_AUDIT_EVENTS

mm_audit_event(ssh, SSH_LOGIN_ROOT_DENIED);

#endif

}

if (authenticated && options.num_auth_methods != 0) {

if (!auth2_update_methods_lists(authctxt, method, submethod)) {

authenticated = 0;

partial = 1;

}

}

/* Log before sending the reply */

auth_log(ssh, authenticated, partial, method, submethod);

/* Update information exposed to session */

if (authenticated || partial)

auth2_update_session_info(authctxt, method, submethod);

if (authctxt->postponed)

return;

#ifdef USE_PAM

if (options.use_pam && authenticated) {

int r, success = mm_do_pam_account();

/* If PAM returned a message, send it to the user. */

if (sshbuf_len(loginmsg) > 0) {

if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)

fatal("%s: buffer error: %s",

__func__, ssh_err(r));

userauth_send_banner(ssh, sshbuf_ptr(loginmsg));

if ((r = ssh_packet_write_wait(ssh)) != 0) {

sshpkt_fatal(ssh, r,

"%s: send PAM banner", __func__);

}

}

if (!success) {

fatal("Access denied for user %s by PAM account "

"configuration", authctxt->user);

}

}

#endif

if (authenticated == 1) {

/* turn off userauth */

ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,

&dispatch_protocol_ignore);

if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 ||

(r = sshpkt_send(ssh)) != 0 ||

(r = ssh_packet_write_wait(ssh)) != 0)

fatal_fr(r, "send success packet");

/* now we can break out */

authctxt->success = 1;

ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);

} else {

/* Allow initial try of "none" auth without failure penalty */

if (!partial && !authctxt->server_caused_failure &&

(authctxt->attempt > 1 || strcmp(method, "none") != 0))

authctxt->failures++;

if (authctxt->failures >= options.max_authtries) {

#ifdef SSH_AUDIT_EVENTS

mm_audit_event(ssh, SSH_LOGIN_EXCEED_MAXTRIES);

#endif

auth_maxtries_exceeded(ssh);

}

methods = authmethods_get(authctxt);

debug3_f("failure partial=%d next methods=\"%s\"",

partial, methods);

if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 ||

(r = sshpkt_put_cstring(ssh, methods)) != 0 ||

(r = sshpkt_put_u8(ssh, partial)) != 0 ||

(r = sshpkt_send(ssh)) != 0 ||

(r = ssh_packet_write_wait(ssh)) != 0)

fatal_fr(r, "send failure packet");

free(methods);

}

}

/*

* Checks whether method is allowed by at least one AuthenticationMethods

* methods list. Returns 1 if allowed, or no methods lists configured.

* 0 otherwise.

*/

int

auth2_method_allowed(Authctxt *authctxt, const char *method,

const char *submethod)

{

u_int i;

/*

* NB. authctxt->num_auth_methods might be zero as a result of

* auth2_setup_methods_lists(), so check the configuration.

*/

if (options.num_auth_methods == 0)

return 1;

for (i = 0; i < authctxt->num_auth_methods; i++) {

if (list_starts_with(authctxt->auth_methods[i], method,

submethod) != MATCH_NONE)

return 1;

}

return 0;

}

static char *

authmethods_get(Authctxt *authctxt)

{

struct sshbuf *b;

char *list;

int i, r;

if ((b = sshbuf_new()) == NULL)

fatal_f("sshbuf_new failed");

for (i = 0; authmethods[i] != NULL; i++) {

if (strcmp(authmethods[i]->cfg->name, "none") == 0)

continue;

if (authmethods[i]->cfg->enabled == NULL ||

*(authmethods[i]->cfg->enabled) == 0)

continue;

if (!auth2_method_allowed(authctxt, authmethods[i]->cfg->name,

NULL))

continue;

if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",

authmethods[i]->cfg->name)) != 0)

fatal_fr(r, "buffer error");

}

if ((list = sshbuf_dup_string(b)) == NULL)

fatal_f("sshbuf_dup_string failed");

sshbuf_free(b);

return list;

}

static Authmethod *

authmethod_byname(const char *name)

{

int i;

if (name == NULL)

fatal_f("NULL authentication method name");

for (i = 0; authmethods[i] != NULL; i++) {

if (strcmp(name, authmethods[i]->cfg->name) == 0 ||

(authmethods[i]->cfg->synonym != NULL &&

strcmp(name, authmethods[i]->cfg->synonym) == 0))

return authmethods[i];

}

debug_f("unrecognized authentication method name: %s", name);

return NULL;

}

static Authmethod *

authmethod_lookup(Authctxt *authctxt, const char *name)

{

Authmethod *method;

if ((method = authmethod_byname(name)) == NULL)

return NULL;

if (method->cfg->enabled == NULL || *(method->cfg->enabled) == 0) {

debug3_f("method %s not enabled", name);

return NULL;

}

if (!auth2_method_allowed(authctxt, method->cfg->name, NULL)) {

debug3_f("method %s not allowed "

"by AuthenticationMethods", name);

return NULL;

}

return method;

}

/*

* Prune the AuthenticationMethods supplied in the configuration, removing

* any methods lists that include disabled methods. Note that this might

* leave authctxt->num_auth_methods == 0, even when multiple required auth

* has been requested. For this reason, all tests for whether multiple is

* enabled should consult options.num_auth_methods directly.

*/

int

auth2_setup_methods_lists(Authctxt *authctxt)

{

u_int i;

/* First, normalise away the "any" pseudo-method */

if (options.num_auth_methods == 1 &&

strcmp(options.auth_methods[0], "any") == 0) {

free(options.auth_methods[0]);

options.auth_methods[0] = NULL;

options.num_auth_methods = 0;

}

if (options.num_auth_methods == 0)

return 0;

debug3_f("checking methods");

authctxt->auth_methods = xcalloc(options.num_auth_methods,

sizeof(*authctxt->auth_methods));

authctxt->num_auth_methods = 0;

for (i = 0; i < options.num_auth_methods; i++) {

if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {

logit("Authentication methods list \"%s\" contains "

"disabled method, skipping",

options.auth_methods[i]);

continue;

}

debug("authentication methods list %d: %s",

authctxt->num_auth_methods, options.auth_methods[i]);

authctxt->auth_methods[authctxt->num_auth_methods++] =

xstrdup(options.auth_methods[i]);

}

if (authctxt->num_auth_methods == 0) {

error("No AuthenticationMethods left after eliminating "

"disabled methods");

return -1;

}

return 0;

}

static int

list_starts_with(const char *methods, const char *method,

const char *submethod)

{

size_t l = strlen(method);

int match;

const char *p;

if (strncmp(methods, method, l) != 0)

return MATCH_NONE;

p = methods + l;

match = MATCH_METHOD;

if (*p == ':') {

if (!submethod)

return MATCH_PARTIAL;

l = strlen(submethod);

p += 1;

if (strncmp(submethod, p, l))

return MATCH_NONE;

p += l;

match = MATCH_BOTH;

}

if (*p != ',' && *p != '\0')

return MATCH_NONE;

return match;

}

/*

* Remove method from the start of a comma-separated list of methods.

* Returns 0 if the list of methods did not start with that method or 1

* if it did.

*/

static int

remove_method(char **methods, const char *method, const char *submethod)

{

char *omethods = *methods, *p;

size_t l = strlen(method);

int match;

match = list_starts_with(omethods, method, submethod);

if (match != MATCH_METHOD && match != MATCH_BOTH)

return 0;

p = omethods + l;

if (submethod && match == MATCH_BOTH)

p += 1 + strlen(submethod); /* include colon */

if (*p == ',')

p++;

*methods = xstrdup(p);

free(omethods);

return 1;

}

/*

* Called after successful authentication. Will remove the successful method

* from the start of each list in which it occurs. If it was the last method

* in any list, then authentication is deemed successful.

* Returns 1 if the method completed any authentication list or 0 otherwise.

*/

int

auth2_update_methods_lists(Authctxt *authctxt, const char *method,

const char *submethod)

{

u_int i, found = 0;

debug3_f("updating methods list after \"%s\"", method);

for (i = 0; i < authctxt->num_auth_methods; i++) {

if (!remove_method(&(authctxt->auth_methods[i]), method,

submethod))

continue;

found = 1;

if (*authctxt->auth_methods[i] == '\0') {

debug2("authentication methods list %d complete", i);

return 1;

}

debug3("authentication methods list %d remaining: \"%s\"",

i, authctxt->auth_methods[i]);

}

/* This should not happen, but would be bad if it did */

if (!found)

fatal_f("method not in AuthenticationMethods");

return 0;

}

/* Reset method-specific information */

void auth2_authctxt_reset_info(Authctxt *authctxt)

{

sshkey_free(authctxt->auth_method_key);

free(authctxt->auth_method_info);

authctxt->auth_method_key = NULL;

authctxt->auth_method_info = NULL;

}

/* Record auth method-specific information for logs */

void

auth2_record_info(Authctxt *authctxt, const char *fmt, ...)

{

va_list ap;

int i;

free(authctxt->auth_method_info);

authctxt->auth_method_info = NULL;

va_start(ap, fmt);

i = vasprintf(&authctxt->auth_method_info, fmt, ap);

va_end(ap);

if (i == -1)

fatal_f("vasprintf failed");

}

/*

* Records a public key used in authentication. This is used for logging

* and to ensure that the same key is not subsequently accepted again for

* multiple authentication.

*/

void

auth2_record_key(Authctxt *authctxt, int authenticated,

const struct sshkey *key)

{

struct sshkey **tmp, *dup;

int r;

if ((r = sshkey_from_private(key, &dup)) != 0)

fatal_fr(r, "copy key");

sshkey_free(authctxt->auth_method_key);

authctxt->auth_method_key = dup;

if (!authenticated)

return;

/* If authenticated, make sure we don't accept this key again */

if ((r = sshkey_from_private(key, &dup)) != 0)

fatal_fr(r, "copy key");

if (authctxt->nprev_keys >= INT_MAX ||

(tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,

authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)

fatal_f("reallocarray failed");

authctxt->prev_keys = tmp;

authctxt->prev_keys[authctxt->nprev_keys] = dup;

authctxt->nprev_keys++;

}

/* Checks whether a key has already been previously used for authentication */

int

auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)

{

u_int i;

char *fp;

for (i = 0; i < authctxt->nprev_keys; i++) {

if (sshkey_equal_public(key, authctxt->prev_keys[i])) {

fp = sshkey_fingerprint(authctxt->prev_keys[i],

options.fingerprint_hash, SSH_FP_DEFAULT);

debug3_f("key already used: %s %s",

sshkey_type(authctxt->prev_keys[i]),

fp == NULL ? "UNKNOWN" : fp);

free(fp);

return 1;

}

}

return 0;

}

/*

* Updates authctxt->session_info with details of authentication. Should be

* whenever an authentication method succeeds.

*/

void

auth2_update_session_info(Authctxt *authctxt, const char *method,

const char *submethod)

{

int r;

if (authctxt->session_info == NULL) {

if ((authctxt->session_info = sshbuf_new()) == NULL)

fatal_f("sshbuf_new");

}

/* Append method[/submethod] */

if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",

method, submethod == NULL ? "" : "/",

submethod == NULL ? "" : submethod)) != 0)

fatal_fr(r, "append method");

/* Append key if present */

if (authctxt->auth_method_key != NULL) {

if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||

(r = sshkey_format_text(authctxt->auth_method_key,

authctxt->session_info)) != 0)

fatal_fr(r, "append key");

}

if (authctxt->auth_method_info != NULL) {

/* Ensure no ambiguity here */

if (strchr(authctxt->auth_method_info, '\n') != NULL)

fatal_f("auth_method_info contains \\n");

if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||

(r = sshbuf_putf(authctxt->session_info, "%s",

authctxt->auth_method_info)) != 0) {

fatal_fr(r, "append method info");

}

}

if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)

fatal_fr(r, "append");

}