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openssh/sshconnect2.c
djm@openbsd.org 04088725ec upstream: scrub keyboard-interactive authentication prompts coming 
from the server through asmprintf() prior to display; suggested by and ok
dtucker@

OpenBSD-Commit-ID: 31fe93367645c37fbfe4691596bf6cf1e3972a58
2020-11-13 18:32:24 +11:00

2309 lines
63 KiB
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/* $OpenBSD: sshconnect2.c,v 1.336 2020/11/13 07:30:44 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2008 Damien Miller. 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/socket.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <netdb.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H) && !defined(BROKEN_STRNVIS)
#include <vis.h>
#endif
#include "openbsd-compat/sys-queue.h"
#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "sshbuf.h"
#include "packet.h"
#include "compat.h"
#include "cipher.h"
#include "sshkey.h"
#include "kex.h"
#include "myproposal.h"
#include "sshconnect.h"
#include "authfile.h"
#include "dh.h"
#include "authfd.h"
#include "log.h"
#include "misc.h"
#include "readconf.h"
#include "match.h"
#include "dispatch.h"
#include "canohost.h"
#include "msg.h"
#include "pathnames.h"
#include "uidswap.h"
#include "hostfile.h"
#include "ssherr.h"
#include "utf8.h"
#include "ssh-sk.h"
#include "sk-api.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
/* import */
extern char *client_version_string;
extern char *server_version_string;
extern Options options;
/*
* SSH2 key exchange
*/
u_char *session_id2 = NULL;
u_int session_id2_len = 0;
char *xxx_host;
struct sockaddr *xxx_hostaddr;
static int
verify_host_key_callback(struct sshkey *hostkey, struct ssh *ssh)
{
if (verify_host_key(xxx_host, xxx_hostaddr, hostkey) == -1)
fatal("Host key verification failed.");
return 0;
}
/* Returns the first item from a comma-separated algorithm list */
static char *
first_alg(const char *algs)
{
char *ret, *cp;
ret = xstrdup(algs);
if ((cp = strchr(ret, ',')) != NULL)
*cp = '\0';
return ret;
}
static char *
order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
{
char *oavail = NULL, *avail = NULL, *first = NULL, *last = NULL;
char *alg = NULL, *hostname = NULL, *ret = NULL, *best = NULL;
size_t maxlen;
struct hostkeys *hostkeys = NULL;
int ktype;
u_int i;
/* Find all hostkeys for this hostname */
get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
hostkeys = init_hostkeys();
for (i = 0; i < options.num_user_hostfiles; i++)
load_hostkeys(hostkeys, hostname, options.user_hostfiles[i]);
for (i = 0; i < options.num_system_hostfiles; i++)
load_hostkeys(hostkeys, hostname, options.system_hostfiles[i]);
/*
* If a plain public key exists that matches the type of the best
* preference HostkeyAlgorithms, then use the whole list as is.
* Note that we ignore whether the best preference algorithm is a
* certificate type, as sshconnect.c will downgrade certs to
* plain keys if necessary.
*/
best = first_alg(options.hostkeyalgorithms);
if (lookup_key_in_hostkeys_by_type(hostkeys,
sshkey_type_plain(sshkey_type_from_name(best)),
sshkey_ecdsa_nid_from_name(best), NULL)) {
debug3_f("have matching best-preference key type %s, "
"using HostkeyAlgorithms verbatim", best);
ret = xstrdup(options.hostkeyalgorithms);
goto out;
}
/*
* Otherwise, prefer the host key algorithms that match known keys
* while keeping the ordering of HostkeyAlgorithms as much as possible.
*/
oavail = avail = xstrdup(options.hostkeyalgorithms);
maxlen = strlen(avail) + 1;
first = xmalloc(maxlen);
last = xmalloc(maxlen);
*first = *last = '\0';
#define ALG_APPEND(to, from) \
do { \
if (*to != '\0') \
strlcat(to, ",", maxlen); \
strlcat(to, from, maxlen); \
} while (0)
while ((alg = strsep(&avail, ",")) && *alg != '\0') {
if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
fatal_f("unknown alg %s", alg);
/*
* If we have a @cert-authority marker in known_hosts then
* prefer all certificate algorithms.
*/
if (sshkey_type_is_cert(ktype) &&
lookup_marker_in_hostkeys(hostkeys, MRK_CA)) {
ALG_APPEND(first, alg);
continue;
}
/* If the key appears in known_hosts then prefer it */
if (lookup_key_in_hostkeys_by_type(hostkeys,
sshkey_type_plain(ktype),
sshkey_ecdsa_nid_from_name(alg), NULL)) {
ALG_APPEND(first, alg);
continue;
}
/* Otherwise, put it last */
ALG_APPEND(last, alg);
}
#undef ALG_APPEND
xasprintf(&ret, "%s%s%s", first,
(*first == '\0' || *last == '\0') ? "" : ",", last);
if (*first != '\0')
debug3_f("prefer hostkeyalgs: %s", first);
out:
free(best);
free(first);
free(last);
free(hostname);
free(oavail);
free_hostkeys(hostkeys);
return ret;
}
void
ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port)
{
char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
char *s, *all_key;
int r, use_known_hosts_order = 0;
xxx_host = host;
xxx_hostaddr = hostaddr;
/*
* If the user has not specified HostkeyAlgorithms, or has only
* appended or removed algorithms from that list then prefer algorithms
* that are in the list that are supported by known_hosts keys.
*/
if (options.hostkeyalgorithms == NULL ||
options.hostkeyalgorithms[0] == '-' ||
options.hostkeyalgorithms[0] == '+')
use_known_hosts_order = 1;
/* Expand or fill in HostkeyAlgorithms */
all_key = sshkey_alg_list(0, 0, 1, ',');
if ((r = kex_assemble_names(&options.hostkeyalgorithms,
kex_default_pk_alg(), all_key)) != 0)
fatal_fr(r, "kex_assemble_namelist");
free(all_key);
if ((s = kex_names_cat(options.kex_algorithms, "ext-info-c")) == NULL)
fatal_f("kex_names_cat");
myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(s);
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
compat_cipher_proposal(options.ciphers);
myproposal[PROPOSAL_ENC_ALGS_STOC] =
compat_cipher_proposal(options.ciphers);
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
myproposal[PROPOSAL_COMP_ALGS_STOC] =
(char *)compression_alg_list(options.compression);
myproposal[PROPOSAL_MAC_ALGS_CTOS] =
myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
if (use_known_hosts_order) {
/* Query known_hosts and prefer algorithms that appear there */
myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
compat_pkalg_proposal(
order_hostkeyalgs(host, hostaddr, port));
} else {
/* Use specified HostkeyAlgorithms exactly */
myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
compat_pkalg_proposal(options.hostkeyalgorithms);
}
if (options.rekey_limit || options.rekey_interval)
ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
options.rekey_interval);
/* start key exchange */
if ((r = kex_setup(ssh, myproposal)) != 0)
fatal_r(r, "kex_setup");
#ifdef WITH_OPENSSL
ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
# ifdef OPENSSL_HAS_ECC
ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
# endif
#endif
ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_client;
ssh->kex->verify_host_key=&verify_host_key_callback;
ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &ssh->kex->done);
/* remove ext-info from the KEX proposals for rekeying */
myproposal[PROPOSAL_KEX_ALGS] =
compat_kex_proposal(options.kex_algorithms);
if ((r = kex_prop2buf(ssh->kex->my, myproposal)) != 0)
fatal_r(r, "kex_prop2buf");
session_id2 = ssh->kex->session_id;
session_id2_len = ssh->kex->session_id_len;
#ifdef DEBUG_KEXDH
/* send 1st encrypted/maced/compressed message */
if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 ||
(r = sshpkt_put_cstring(ssh, "markus")) != 0 ||
(r = sshpkt_send(ssh)) != 0 ||
(r = ssh_packet_write_wait(ssh)) != 0)
fatal_fr(r, "send packet");
#endif
}
/*
* Authenticate user
*/
typedef struct cauthctxt Authctxt;
typedef struct cauthmethod Authmethod;
typedef struct identity Identity;
typedef struct idlist Idlist;
struct identity {
TAILQ_ENTRY(identity) next;
int agent_fd; /* >=0 if agent supports key */
struct sshkey *key; /* public/private key */
char *filename; /* comment for agent-only keys */
int tried;
int isprivate; /* key points to the private key */
int userprovided;
};
TAILQ_HEAD(idlist, identity);
struct cauthctxt {
const char *server_user;
const char *local_user;
const char *host;
const char *service;
struct cauthmethod *method;
sig_atomic_t success;
char *authlist;
#ifdef GSSAPI
/* gssapi */
gss_OID_set gss_supported_mechs;
u_int mech_tried;
#endif
/* pubkey */
struct idlist keys;
int agent_fd;
/* hostbased */
Sensitive *sensitive;
char *oktypes, *ktypes;
const char *active_ktype;
/* kbd-interactive */
int info_req_seen;
int attempt_kbdint;
/* password */
int attempt_passwd;
/* generic */
void *methoddata;
};
struct cauthmethod {
char *name; /* string to compare against server's list */
int (*userauth)(struct ssh *ssh);
void (*cleanup)(struct ssh *ssh);
int *enabled; /* flag in option struct that enables method */
int *batch_flag; /* flag in option struct that disables method */
};
static int input_userauth_service_accept(int, u_int32_t, struct ssh *);
static int input_userauth_ext_info(int, u_int32_t, struct ssh *);
static int input_userauth_success(int, u_int32_t, struct ssh *);
static int input_userauth_failure(int, u_int32_t, struct ssh *);
static int input_userauth_banner(int, u_int32_t, struct ssh *);
static int input_userauth_error(int, u_int32_t, struct ssh *);
static int input_userauth_info_req(int, u_int32_t, struct ssh *);
static int input_userauth_pk_ok(int, u_int32_t, struct ssh *);
static int input_userauth_passwd_changereq(int, u_int32_t, struct ssh *);
static int userauth_none(struct ssh *);
static int userauth_pubkey(struct ssh *);
static int userauth_passwd(struct ssh *);
static int userauth_kbdint(struct ssh *);
static int userauth_hostbased(struct ssh *);
#ifdef GSSAPI
static int userauth_gssapi(struct ssh *);
static void userauth_gssapi_cleanup(struct ssh *);
static int input_gssapi_response(int type, u_int32_t, struct ssh *);
static int input_gssapi_token(int type, u_int32_t, struct ssh *);
static int input_gssapi_error(int, u_int32_t, struct ssh *);
static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
#endif
void userauth(struct ssh *, char *);
static void pubkey_cleanup(struct ssh *);
static int sign_and_send_pubkey(struct ssh *ssh, Identity *);
static void pubkey_prepare(Authctxt *);
static void pubkey_reset(Authctxt *);
static struct sshkey *load_identity_file(Identity *);
static Authmethod *authmethod_get(char *authlist);
static Authmethod *authmethod_lookup(const char *name);
static char *authmethods_get(void);
Authmethod authmethods[] = {
#ifdef GSSAPI
{"gssapi-with-mic",
userauth_gssapi,
userauth_gssapi_cleanup,
&options.gss_authentication,
NULL},
#endif
{"hostbased",
userauth_hostbased,
NULL,
&options.hostbased_authentication,
NULL},
{"publickey",
userauth_pubkey,
NULL,
&options.pubkey_authentication,
NULL},
{"keyboard-interactive",
userauth_kbdint,
NULL,
&options.kbd_interactive_authentication,
&options.batch_mode},
{"password",
userauth_passwd,
NULL,
&options.password_authentication,
&options.batch_mode},
{"none",
userauth_none,
NULL,
NULL,
NULL},
{NULL, NULL, NULL, NULL, NULL}
};
void
ssh_userauth2(struct ssh *ssh, const char *local_user,
const char *server_user, char *host, Sensitive *sensitive)
{
Authctxt authctxt;
int r;
if (options.challenge_response_authentication)
options.kbd_interactive_authentication = 1;
if (options.preferred_authentications == NULL)
options.preferred_authentications = authmethods_get();
/* setup authentication context */
memset(&authctxt, 0, sizeof(authctxt));
authctxt.server_user = server_user;
authctxt.local_user = local_user;
authctxt.host = host;
authctxt.service = "ssh-connection"; /* service name */
authctxt.success = 0;
authctxt.method = authmethod_lookup("none");
authctxt.authlist = NULL;
authctxt.methoddata = NULL;
authctxt.sensitive = sensitive;
authctxt.active_ktype = authctxt.oktypes = authctxt.ktypes = NULL;
authctxt.info_req_seen = 0;
authctxt.attempt_kbdint = 0;
authctxt.attempt_passwd = 0;
#if GSSAPI
authctxt.gss_supported_mechs = NULL;
authctxt.mech_tried = 0;
#endif
authctxt.agent_fd = -1;
pubkey_prepare(&authctxt);
if (authctxt.method == NULL) {
fatal_f("internal error: cannot send userauth none request");
}
if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, "ssh-userauth")) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
ssh->authctxt = &authctxt;
ssh_dispatch_init(ssh, &input_userauth_error);
ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &input_userauth_ext_info);
ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_ACCEPT, &input_userauth_service_accept);
ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt.success); /* loop until success */
pubkey_cleanup(ssh);
ssh->authctxt = NULL;
ssh_dispatch_range(ssh, SSH2_MSG_USERAUTH_MIN, SSH2_MSG_USERAUTH_MAX, NULL);
if (!authctxt.success)
fatal("Authentication failed.");
debug("Authentication succeeded (%s).", authctxt.method->name);
}
/* ARGSUSED */
static int
input_userauth_service_accept(int type, u_int32_t seq, struct ssh *ssh)
{
int r;
if (ssh_packet_remaining(ssh) > 0) {
char *reply;
if ((r = sshpkt_get_cstring(ssh, &reply, NULL)) != 0)
goto out;
debug2("service_accept: %s", reply);
free(reply);
} else {
debug2("buggy server: service_accept w/o service");
}
if ((r = sshpkt_get_end(ssh)) != 0)
goto out;
debug("SSH2_MSG_SERVICE_ACCEPT received");
/* initial userauth request */
userauth_none(ssh);
ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &input_userauth_error);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
r = 0;
out:
return r;
}
/* ARGSUSED */
static int
input_userauth_ext_info(int type, u_int32_t seqnr, struct ssh *ssh)
{
return kex_input_ext_info(type, seqnr, ssh);
}
void
userauth(struct ssh *ssh, char *authlist)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
authctxt->method->cleanup(ssh);
free(authctxt->methoddata);
authctxt->methoddata = NULL;
if (authlist == NULL) {
authlist = authctxt->authlist;
} else {
free(authctxt->authlist);
authctxt->authlist = authlist;
}
for (;;) {
Authmethod *method = authmethod_get(authlist);
if (method == NULL)
fatal("%s@%s: Permission denied (%s).",
authctxt->server_user, authctxt->host, authlist);
authctxt->method = method;
/* reset the per method handler */
ssh_dispatch_range(ssh, SSH2_MSG_USERAUTH_PER_METHOD_MIN,
SSH2_MSG_USERAUTH_PER_METHOD_MAX, NULL);
/* and try new method */
if (method->userauth(ssh) != 0) {
debug2("we sent a %s packet, wait for reply", method->name);
break;
} else {
debug2("we did not send a packet, disable method");
method->enabled = NULL;
}
}
}
/* ARGSUSED */
static int
input_userauth_error(int type, u_int32_t seq, struct ssh *ssh)
{
fatal_f("bad message during authentication: type %d", type);
return 0;
}
/* ARGSUSED */
static int
input_userauth_banner(int type, u_int32_t seq, struct ssh *ssh)
{
char *msg = NULL;
size_t len;
int r;
debug3_f("entering");
if ((r = sshpkt_get_cstring(ssh, &msg, &len)) != 0 ||
(r = sshpkt_get_cstring(ssh, NULL, NULL)) != 0)
goto out;
if (len > 0 && options.log_level >= SYSLOG_LEVEL_INFO)
fmprintf(stderr, "%s", msg);
r = 0;
out:
free(msg);
return r;
}
/* ARGSUSED */
static int
input_userauth_success(int type, u_int32_t seq, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
if (authctxt == NULL)
fatal_f("no authentication context");
free(authctxt->authlist);
authctxt->authlist = NULL;
if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
authctxt->method->cleanup(ssh);
free(authctxt->methoddata);
authctxt->methoddata = NULL;
authctxt->success = 1; /* break out */
return 0;
}
#if 0
static int
input_userauth_success_unexpected(int type, u_int32_t seq, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
if (authctxt == NULL)
fatal_f("no authentication context");
fatal("Unexpected authentication success during %s.",
authctxt->method->name);
return 0;
}
#endif
/* ARGSUSED */
static int
input_userauth_failure(int type, u_int32_t seq, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
char *authlist = NULL;
u_char partial;
if (authctxt == NULL)
fatal("input_userauth_failure: no authentication context");
if (sshpkt_get_cstring(ssh, &authlist, NULL) != 0 ||
sshpkt_get_u8(ssh, &partial) != 0 ||
sshpkt_get_end(ssh) != 0)
goto out;
if (partial != 0) {
verbose("Authenticated with partial success.");
/* reset state */
pubkey_reset(authctxt);
}
debug("Authentications that can continue: %s", authlist);
userauth(ssh, authlist);
authlist = NULL;
out:
free(authlist);
return 0;
}
/*
* Format an identity for logging including filename, key type, fingerprint
* and location (agent, etc.). Caller must free.
*/
static char *
format_identity(Identity *id)
{
char *fp = NULL, *ret = NULL;
const char *note = "";
if (id->key != NULL) {
fp = sshkey_fingerprint(id->key, options.fingerprint_hash,
SSH_FP_DEFAULT);
}
if (id->key) {
if ((id->key->flags & SSHKEY_FLAG_EXT) != 0)
note = " token";
else if (sshkey_is_sk(id->key))
note = " authenticator";
}
xasprintf(&ret, "%s %s%s%s%s%s%s",
id->filename,
id->key ? sshkey_type(id->key) : "", id->key ? " " : "",
fp ? fp : "",
id->userprovided ? " explicit" : "", note,
id->agent_fd != -1 ? " agent" : "");
free(fp);
return ret;
}
/* ARGSUSED */
static int
input_userauth_pk_ok(int type, u_int32_t seq, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
struct sshkey *key = NULL;
Identity *id = NULL;
int pktype, found = 0, sent = 0;
size_t blen;
char *pkalg = NULL, *fp = NULL, *ident = NULL;
u_char *pkblob = NULL;
int r;
if (authctxt == NULL)
fatal("input_userauth_pk_ok: no authentication context");
if ((r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
(r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto done;
if ((pktype = sshkey_type_from_name(pkalg)) == KEY_UNSPEC) {
debug_f("server sent unknown pkalg %s", pkalg);
goto done;
}
if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
debug_r(r, "no key from blob. pkalg %s", pkalg);
goto done;
}
if (key->type != pktype) {
error("input_userauth_pk_ok: type mismatch "
"for decoded key (received %d, expected %d)",
key->type, pktype);
goto done;
}
/*
* search keys in the reverse order, because last candidate has been
* moved to the end of the queue. this also avoids confusion by
* duplicate keys
*/
TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
if (sshkey_equal(key, id->key)) {
found = 1;
break;
}
}
if (!found || id == NULL) {
fp = sshkey_fingerprint(key, options.fingerprint_hash,
SSH_FP_DEFAULT);
error_f("server replied with unknown key: %s %s",
sshkey_type(key), fp == NULL ? "<ERROR>" : fp);
goto done;
}
ident = format_identity(id);
debug("Server accepts key: %s", ident);
sent = sign_and_send_pubkey(ssh, id);
r = 0;
done:
sshkey_free(key);
free(ident);
free(fp);
free(pkalg);
free(pkblob);
/* try another method if we did not send a packet */
if (r == 0 && sent == 0)
userauth(ssh, NULL);
return r;
}
#ifdef GSSAPI
static int
userauth_gssapi(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
Gssctxt *gssctxt = NULL;
OM_uint32 min;
int r, ok = 0;
gss_OID mech = NULL;
/* Try one GSSAPI method at a time, rather than sending them all at
* once. */
if (authctxt->gss_supported_mechs == NULL)
gss_indicate_mechs(&min, &authctxt->gss_supported_mechs);
/* Check to see whether the mechanism is usable before we offer it */
while (authctxt->mech_tried < authctxt->gss_supported_mechs->count &&
!ok) {
mech = &authctxt->gss_supported_mechs->
elements[authctxt->mech_tried];
/* My DER encoding requires length<128 */
if (mech->length < 128 && ssh_gssapi_check_mechanism(&gssctxt,
mech, authctxt->host)) {
ok = 1; /* Mechanism works */
} else {
authctxt->mech_tried++;
}
}
if (!ok || mech == NULL)
return 0;
authctxt->methoddata=(void *)gssctxt;
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
(r = sshpkt_put_u32(ssh, 1)) != 0 ||
(r = sshpkt_put_u32(ssh, (mech->length) + 2)) != 0 ||
(r = sshpkt_put_u8(ssh, SSH_GSS_OIDTYPE)) != 0 ||
(r = sshpkt_put_u8(ssh, mech->length)) != 0 ||
(r = sshpkt_put(ssh, mech->elements, mech->length)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
authctxt->mech_tried++; /* Move along to next candidate */
return 1;
}
static void
userauth_gssapi_cleanup(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
Gssctxt *gssctxt = (Gssctxt *)authctxt->methoddata;
ssh_gssapi_delete_ctx(&gssctxt);
authctxt->methoddata = NULL;
free(authctxt->gss_supported_mechs);
authctxt->gss_supported_mechs = NULL;
}
static OM_uint32
process_gssapi_token(struct ssh *ssh, gss_buffer_t recv_tok)
{
Authctxt *authctxt = ssh->authctxt;
Gssctxt *gssctxt = authctxt->methoddata;
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
gss_buffer_desc gssbuf;
OM_uint32 status, ms, flags;
int r;
status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
recv_tok, &send_tok, &flags);
if (send_tok.length > 0) {
u_char type = GSS_ERROR(status) ?
SSH2_MSG_USERAUTH_GSSAPI_ERRTOK :
SSH2_MSG_USERAUTH_GSSAPI_TOKEN;
if ((r = sshpkt_start(ssh, type)) != 0 ||
(r = sshpkt_put_string(ssh, send_tok.value,
send_tok.length)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send %u packet", type);
gss_release_buffer(&ms, &send_tok);
}
if (status == GSS_S_COMPLETE) {
/* send either complete or MIC, depending on mechanism */
if (!(flags & GSS_C_INTEG_FLAG)) {
if ((r = sshpkt_start(ssh,
SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send completion");
} else {
struct sshbuf *b;
if ((b = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
ssh_gssapi_buildmic(b, authctxt->server_user,
authctxt->service, "gssapi-with-mic");
if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
fatal_f("sshbuf_mutable_ptr failed");
gssbuf.length = sshbuf_len(b);
status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);
if (!GSS_ERROR(status)) {
if ((r = sshpkt_start(ssh,
SSH2_MSG_USERAUTH_GSSAPI_MIC)) != 0 ||
(r = sshpkt_put_string(ssh, mic.value,
mic.length)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send MIC");
}
sshbuf_free(b);
gss_release_buffer(&ms, &mic);
}
}
return status;
}
/* ARGSUSED */
static int
input_gssapi_response(int type, u_int32_t plen, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
Gssctxt *gssctxt;
size_t oidlen;
u_char *oidv = NULL;
int r;
if (authctxt == NULL)
fatal("input_gssapi_response: no authentication context");
gssctxt = authctxt->methoddata;
/* Setup our OID */
if ((r = sshpkt_get_string(ssh, &oidv, &oidlen)) != 0)
goto done;
if (oidlen <= 2 ||
oidv[0] != SSH_GSS_OIDTYPE ||
oidv[1] != oidlen - 2) {
debug("Badly encoded mechanism OID received");
userauth(ssh, NULL);
goto ok;
}
if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
fatal("Server returned different OID than expected");
if ((r = sshpkt_get_end(ssh)) != 0)
goto done;
if (GSS_ERROR(process_gssapi_token(ssh, GSS_C_NO_BUFFER))) {
/* Start again with next method on list */
debug("Trying to start again");
userauth(ssh, NULL);
goto ok;
}
ok:
r = 0;
done:
free(oidv);
return r;
}
/* ARGSUSED */
static int
input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
gss_buffer_desc recv_tok;
u_char *p = NULL;
size_t len;
OM_uint32 status;
int r;
if (authctxt == NULL)
fatal("input_gssapi_response: no authentication context");
if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
recv_tok.value = p;
recv_tok.length = len;
status = process_gssapi_token(ssh, &recv_tok);
/* Start again with the next method in the list */
if (GSS_ERROR(status)) {
userauth(ssh, NULL);
/* ok */
}
r = 0;
out:
free(p);
return r;
}
/* ARGSUSED */
static int
input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
Gssctxt *gssctxt;
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
gss_buffer_desc recv_tok;
OM_uint32 ms;
u_char *p = NULL;
size_t len;
int r;
if (authctxt == NULL)
fatal("input_gssapi_response: no authentication context");
gssctxt = authctxt->methoddata;
if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0) {
free(p);
return r;
}
/* Stick it into GSSAPI and see what it says */
recv_tok.value = p;
recv_tok.length = len;
(void)ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
&recv_tok, &send_tok, NULL);
free(p);
gss_release_buffer(&ms, &send_tok);
/* Server will be returning a failed packet after this one */
return 0;
}
/* ARGSUSED */
static int
input_gssapi_error(int type, u_int32_t plen, struct ssh *ssh)
{
char *msg = NULL;
char *lang = NULL;
int r;
if ((r = sshpkt_get_u32(ssh, NULL)) != 0 || /* maj */
(r = sshpkt_get_u32(ssh, NULL)) != 0 || /* min */
(r = sshpkt_get_cstring(ssh, &msg, NULL)) != 0 ||
(r = sshpkt_get_cstring(ssh, &lang, NULL)) != 0)
goto out;
r = sshpkt_get_end(ssh);
debug("Server GSSAPI Error:\n%s", msg);
out:
free(msg);
free(lang);
return r;
}
#endif /* GSSAPI */
static int
userauth_none(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
int r;
/* initial userauth request */
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
return 1;
}
static int
userauth_passwd(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
char *password, *prompt = NULL;
const char *host = options.host_key_alias ? options.host_key_alias :
authctxt->host;
int r;
if (authctxt->attempt_passwd++ >= options.number_of_password_prompts)
return 0;
if (authctxt->attempt_passwd != 1)
error("Permission denied, please try again.");
xasprintf(&prompt, "%s@%s's password: ", authctxt->server_user, host);
password = read_passphrase(prompt, 0);
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
(r = sshpkt_put_u8(ssh, 0)) != 0 ||
(r = sshpkt_put_cstring(ssh, password)) != 0 ||
(r = sshpkt_add_padding(ssh, 64)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
free(prompt);
if (password != NULL)
freezero(password, strlen(password));
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
&input_userauth_passwd_changereq);
return 1;
}
/*
* parse PASSWD_CHANGEREQ, prompt user and send SSH2_MSG_USERAUTH_REQUEST
*/
/* ARGSUSED */
static int
input_userauth_passwd_changereq(int type, u_int32_t seqnr, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
char *info = NULL, *lang = NULL, *password = NULL, *retype = NULL;
char prompt[256];
const char *host;
int r;
debug2("input_userauth_passwd_changereq");
if (authctxt == NULL)
fatal("input_userauth_passwd_changereq: "
"no authentication context");
host = options.host_key_alias ? options.host_key_alias : authctxt->host;
if ((r = sshpkt_get_cstring(ssh, &info, NULL)) != 0 ||
(r = sshpkt_get_cstring(ssh, &lang, NULL)) != 0)
goto out;
if (strlen(info) > 0)
logit("%s", info);
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
(r = sshpkt_put_u8(ssh, 1)) != 0) /* additional info */
goto out;
snprintf(prompt, sizeof(prompt),
"Enter %.30s@%.128s's old password: ",
authctxt->server_user, host);
password = read_passphrase(prompt, 0);
if ((r = sshpkt_put_cstring(ssh, password)) != 0)
goto out;
freezero(password, strlen(password));
password = NULL;
while (password == NULL) {
snprintf(prompt, sizeof(prompt),
"Enter %.30s@%.128s's new password: ",
authctxt->server_user, host);
password = read_passphrase(prompt, RP_ALLOW_EOF);
if (password == NULL) {
/* bail out */
r = 0;
goto out;
}
snprintf(prompt, sizeof(prompt),
"Retype %.30s@%.128s's new password: ",
authctxt->server_user, host);
retype = read_passphrase(prompt, 0);
if (strcmp(password, retype) != 0) {
freezero(password, strlen(password));
logit("Mismatch; try again, EOF to quit.");
password = NULL;
}
freezero(retype, strlen(retype));
}
if ((r = sshpkt_put_cstring(ssh, password)) != 0 ||
(r = sshpkt_add_padding(ssh, 64)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
&input_userauth_passwd_changereq);
r = 0;
out:
if (password)
freezero(password, strlen(password));
free(info);
free(lang);
return r;
}
/*
* Select an algorithm for publickey signatures.
* Returns algorithm (caller must free) or NULL if no mutual algorithm found.
*
* Call with ssh==NULL to ignore server-sig-algs extension list and
* only attempt with the key's base signature type.
*/
static char *
key_sig_algorithm(struct ssh *ssh, const struct sshkey *key)
{
char *allowed, *oallowed, *cp, *tmp, *alg = NULL;
/*
* The signature algorithm will only differ from the key algorithm
* for RSA keys/certs and when the server advertises support for
* newer (SHA2) algorithms.
*/
if (ssh == NULL || ssh->kex->server_sig_algs == NULL ||
(key->type != KEY_RSA && key->type != KEY_RSA_CERT) ||
(key->type == KEY_RSA_CERT && (datafellows & SSH_BUG_SIGTYPE))) {
/* Filter base key signature alg against our configuration */
return match_list(sshkey_ssh_name(key),
options.pubkey_key_types, NULL);
}
/*
* For RSA keys/certs, since these might have a different sig type:
* find the first entry in PubkeyAcceptedKeyTypes of the right type
* that also appears in the supported signature algorithms list from
* the server.
*/
oallowed = allowed = xstrdup(options.pubkey_key_types);
while ((cp = strsep(&allowed, ",")) != NULL) {
if (sshkey_type_from_name(cp) != key->type)
continue;
tmp = match_list(sshkey_sigalg_by_name(cp),
ssh->kex->server_sig_algs, NULL);
if (tmp != NULL)
alg = xstrdup(cp);
free(tmp);
if (alg != NULL)
break;
}
free(oallowed);
return alg;
}
static int
identity_sign(struct identity *id, u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen, u_int compat, const char *alg)
{
struct sshkey *sign_key = NULL, *prv = NULL;
int r = SSH_ERR_INTERNAL_ERROR;
struct notifier_ctx *notifier = NULL;
char *fp = NULL, *pin = NULL, *prompt = NULL;
*sigp = NULL;
*lenp = 0;
/* The agent supports this key. */
if (id->key != NULL && id->agent_fd != -1) {
return ssh_agent_sign(id->agent_fd, id->key, sigp, lenp,
data, datalen, alg, compat);
}
/*
* We have already loaded the private key or the private key is
* stored in external hardware.
*/
if (id->key != NULL &&
(id->isprivate || (id->key->flags & SSHKEY_FLAG_EXT))) {
sign_key = id->key;
} else {
/* Load the private key from the file. */
if ((prv = load_identity_file(id)) == NULL)
return SSH_ERR_KEY_NOT_FOUND;
if (id->key != NULL && !sshkey_equal_public(prv, id->key)) {
error_f("private key %s contents do not match public",
id->filename);
r = SSH_ERR_KEY_NOT_FOUND;
goto out;
}
sign_key = prv;
if (sshkey_is_sk(sign_key)) {
if ((sign_key->sk_flags &
SSH_SK_USER_VERIFICATION_REQD)) {
xasprintf(&prompt, "Enter PIN for %s key %s: ",
sshkey_type(sign_key), id->filename);
pin = read_passphrase(prompt, 0);
}
if ((sign_key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) {
/* XXX should batch mode just skip these? */
if ((fp = sshkey_fingerprint(sign_key,
options.fingerprint_hash,
SSH_FP_DEFAULT)) == NULL)
fatal_f("fingerprint failed");
notifier = notify_start(options.batch_mode,
"Confirm user presence for key %s %s",
sshkey_type(sign_key), fp);
free(fp);
}
}
}
if ((r = sshkey_sign(sign_key, sigp, lenp, data, datalen,
alg, options.sk_provider, pin, compat)) != 0) {
debug_fr(r, "sshkey_sign");
goto out;
}
/*
* PKCS#11 tokens may not support all signature algorithms,
* so check what we get back.
*/
if ((r = sshkey_check_sigtype(*sigp, *lenp, alg)) != 0) {
debug_fr(r, "sshkey_check_sigtype");
goto out;
}
/* success */
r = 0;
out:
free(prompt);
if (pin != NULL)
freezero(pin, strlen(pin));
notify_complete(notifier, "User presence confirmed");
sshkey_free(prv);
return r;
}
static int
id_filename_matches(Identity *id, Identity *private_id)
{
const char *suffixes[] = { ".pub", "-cert.pub", NULL };
size_t len = strlen(id->filename), plen = strlen(private_id->filename);
size_t i, slen;
if (strcmp(id->filename, private_id->filename) == 0)
return 1;
for (i = 0; suffixes[i]; i++) {
slen = strlen(suffixes[i]);
if (len > slen && plen == len - slen &&
strcmp(id->filename + (len - slen), suffixes[i]) == 0 &&
memcmp(id->filename, private_id->filename, plen) == 0)
return 1;
}
return 0;
}
static int
sign_and_send_pubkey(struct ssh *ssh, Identity *id)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
struct sshbuf *b = NULL;
Identity *private_id, *sign_id = NULL;
u_char *signature = NULL;
size_t slen = 0, skip = 0;
int r, fallback_sigtype, sent = 0;
char *alg = NULL, *fp = NULL;
const char *loc = "";
if ((fp = sshkey_fingerprint(id->key, options.fingerprint_hash,
SSH_FP_DEFAULT)) == NULL)
return 0;
debug3_f("%s %s", sshkey_type(id->key), fp);
/*
* If the key is an certificate, try to find a matching private key
* and use it to complete the signature.
* If no such private key exists, fall back to trying the certificate
* key itself in case it has a private half already loaded.
* This will try to set sign_id to the private key that will perform
* the signature.
*/
if (sshkey_is_cert(id->key)) {
TAILQ_FOREACH(private_id, &authctxt->keys, next) {
if (sshkey_equal_public(id->key, private_id->key) &&
id->key->type != private_id->key->type) {
sign_id = private_id;
break;
}
}
/*
* Exact key matches are preferred, but also allow
* filename matches for non-PKCS#11/agent keys that
* didn't load public keys. This supports the case
* of keeping just a private key file and public
* certificate on disk.
*/
if (sign_id == NULL &&
!id->isprivate && id->agent_fd == -1 &&
(id->key->flags & SSHKEY_FLAG_EXT) == 0) {
TAILQ_FOREACH(private_id, &authctxt->keys, next) {
if (private_id->key == NULL &&
id_filename_matches(id, private_id)) {
sign_id = private_id;
break;
}
}
}
if (sign_id != NULL) {
debug2_f("using private key \"%s\"%s for "
"certificate", id->filename,
id->agent_fd != -1 ? " from agent" : "");
} else {
debug_f("no separate private key for certificate "
"\"%s\"", id->filename);
}
}
/*
* If the above didn't select another identity to do the signing
* then default to the one we started with.
*/
if (sign_id == NULL)
sign_id = id;
/* assemble and sign data */
for (fallback_sigtype = 0; fallback_sigtype <= 1; fallback_sigtype++) {
free(alg);
slen = 0;
signature = NULL;
if ((alg = key_sig_algorithm(fallback_sigtype ? NULL : ssh,
id->key)) == NULL) {
error_f("no mutual signature supported");
goto out;
}
debug3_f("signing using %s %s", alg, fp);
sshbuf_free(b);
if ((b = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
if (datafellows & SSH_OLD_SESSIONID) {
if ((r = sshbuf_put(b, session_id2,
session_id2_len)) != 0)
fatal_fr(r, "sshbuf_put");
} else {
if ((r = sshbuf_put_string(b, session_id2,
session_id2_len)) != 0)
fatal_fr(r, "sshbuf_put_string");
}
skip = sshbuf_len(b);
if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->server_user)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->method->name)) != 0 ||
(r = sshbuf_put_u8(b, 1)) != 0 ||
(r = sshbuf_put_cstring(b, alg)) != 0 ||
(r = sshkey_puts(id->key, b)) != 0) {
fatal_fr(r, "assemble signed data");
}
/* generate signature */
r = identity_sign(sign_id, &signature, &slen,
sshbuf_ptr(b), sshbuf_len(b), datafellows, alg);
if (r == 0)
break;
else if (r == SSH_ERR_KEY_NOT_FOUND)
goto out; /* soft failure */
else if (r == SSH_ERR_SIGN_ALG_UNSUPPORTED &&
!fallback_sigtype) {
if (sign_id->agent_fd != -1)
loc = "agent ";
else if ((sign_id->key->flags & SSHKEY_FLAG_EXT) != 0)
loc = "token ";
logit("%skey %s %s returned incorrect signature type",
loc, sshkey_type(id->key), fp);
continue;
}
error_fr(r, "signing failed for %s \"%s\"%s",
sshkey_type(sign_id->key), sign_id->filename,
id->agent_fd != -1 ? " from agent" : "");
goto out;
}
if (slen == 0 || signature == NULL) /* shouldn't happen */
fatal_f("no signature");
/* append signature */
if ((r = sshbuf_put_string(b, signature, slen)) != 0)
fatal_fr(r, "append signature");
#ifdef DEBUG_PK
sshbuf_dump(b, stderr);
#endif
/* skip session id and packet type */
if ((r = sshbuf_consume(b, skip + 1)) != 0)
fatal_fr(r, "consume");
/* put remaining data from buffer into packet */
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_putb(ssh, b)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "enqueue request");
/* success */
sent = 1;
out:
free(fp);
free(alg);
sshbuf_free(b);
freezero(signature, slen);
return sent;
}
static int
send_pubkey_test(struct ssh *ssh, Identity *id)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
u_char *blob = NULL;
char *alg = NULL;
size_t bloblen;
u_int have_sig = 0;
int sent = 0, r;
if ((alg = key_sig_algorithm(ssh, id->key)) == NULL) {
debug_f("no mutual signature algorithm");
goto out;
}
if ((r = sshkey_to_blob(id->key, &blob, &bloblen)) != 0) {
/* we cannot handle this key */
debug3_f("cannot handle key");
goto out;
}
/* register callback for USERAUTH_PK_OK message */
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
(r = sshpkt_put_u8(ssh, have_sig)) != 0 ||
(r = sshpkt_put_cstring(ssh, alg)) != 0 ||
(r = sshpkt_put_string(ssh, blob, bloblen)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
sent = 1;
out:
free(alg);
free(blob);
return sent;
}
static struct sshkey *
load_identity_file(Identity *id)
{
struct sshkey *private = NULL;
char prompt[300], *passphrase, *comment;
int r, quit = 0, i;
struct stat st;
if (stat(id->filename, &st) == -1) {
do_log2(id->userprovided ?
SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_DEBUG3,
"no such identity: %s: %s", id->filename, strerror(errno));
return NULL;
}
snprintf(prompt, sizeof prompt,
"Enter passphrase for key '%.100s': ", id->filename);
for (i = 0; i <= options.number_of_password_prompts; i++) {
if (i == 0)
passphrase = "";
else {
passphrase = read_passphrase(prompt, 0);
if (*passphrase == '\0') {
debug2("no passphrase given, try next key");
free(passphrase);
break;
}
}
switch ((r = sshkey_load_private_type(KEY_UNSPEC, id->filename,
passphrase, &private, &comment))) {
case 0:
break;
case SSH_ERR_KEY_WRONG_PASSPHRASE:
if (options.batch_mode) {
quit = 1;
break;
}
if (i != 0)
debug2("bad passphrase given, try again...");
break;
case SSH_ERR_SYSTEM_ERROR:
if (errno == ENOENT) {
debug2_r(r, "Load key \"%s\"", id->filename);
quit = 1;
break;
}
/* FALLTHROUGH */
default:
error_r(r, "Load key \"%s\"", id->filename);
quit = 1;
break;
}
if (private != NULL && sshkey_is_sk(private) &&
options.sk_provider == NULL) {
debug("key \"%s\" is an authenticator-hosted key, "
"but no provider specified", id->filename);
sshkey_free(private);
private = NULL;
quit = 1;
}
if (!quit && private != NULL && id->agent_fd == -1 &&
!(id->key && id->isprivate))
maybe_add_key_to_agent(id->filename, private, comment,
passphrase);
if (i > 0)
freezero(passphrase, strlen(passphrase));
free(comment);
if (private != NULL || quit)
break;
}
return private;
}
static int
key_type_allowed_by_config(struct sshkey *key)
{
if (match_pattern_list(sshkey_ssh_name(key),
options.pubkey_key_types, 0) == 1)
return 1;
/* RSA keys/certs might be allowed by alternate signature types */
switch (key->type) {
case KEY_RSA:
if (match_pattern_list("rsa-sha2-512",
options.pubkey_key_types, 0) == 1)
return 1;
if (match_pattern_list("rsa-sha2-256",
options.pubkey_key_types, 0) == 1)
return 1;
break;
case KEY_RSA_CERT:
if (match_pattern_list("rsa-sha2-512-cert-v01@openssh.com",
options.pubkey_key_types, 0) == 1)
return 1;
if (match_pattern_list("rsa-sha2-256-cert-v01@openssh.com",
options.pubkey_key_types, 0) == 1)
return 1;
break;
}
return 0;
}
/*
* try keys in the following order:
* 1. certificates listed in the config file
* 2. other input certificates
* 3. agent keys that are found in the config file
* 4. other agent keys
* 5. keys that are only listed in the config file
*/
static void
pubkey_prepare(Authctxt *authctxt)
{
struct identity *id, *id2, *tmp;
struct idlist agent, files, *preferred;
struct sshkey *key;
int agent_fd = -1, i, r, found;
size_t j;
struct ssh_identitylist *idlist;
char *ident;
TAILQ_INIT(&agent); /* keys from the agent */
TAILQ_INIT(&files); /* keys from the config file */
preferred = &authctxt->keys;
TAILQ_INIT(preferred); /* preferred order of keys */
/* list of keys stored in the filesystem and PKCS#11 */
for (i = 0; i < options.num_identity_files; i++) {
key = options.identity_keys[i];
if (key && key->cert &&
key->cert->type != SSH2_CERT_TYPE_USER) {
debug_f("ignoring certificate %s: not a user "
"certificate", options.identity_files[i]);
continue;
}
if (key && sshkey_is_sk(key) && options.sk_provider == NULL) {
debug_f("ignoring authenticator-hosted key %s as no "
"SecurityKeyProvider has been specified",
options.identity_files[i]);
continue;
}
options.identity_keys[i] = NULL;
id = xcalloc(1, sizeof(*id));
id->agent_fd = -1;
id->key = key;
id->filename = xstrdup(options.identity_files[i]);
id->userprovided = options.identity_file_userprovided[i];
TAILQ_INSERT_TAIL(&files, id, next);
}
/* list of certificates specified by user */
for (i = 0; i < options.num_certificate_files; i++) {
key = options.certificates[i];
if (!sshkey_is_cert(key) || key->cert == NULL ||
key->cert->type != SSH2_CERT_TYPE_USER) {
debug_f("ignoring certificate %s: not a user "
"certificate", options.identity_files[i]);
continue;
}
if (key && sshkey_is_sk(key) && options.sk_provider == NULL) {
debug_f("ignoring authenticator-hosted key "
"certificate %s as no "
"SecurityKeyProvider has been specified",
options.identity_files[i]);
continue;
}
id = xcalloc(1, sizeof(*id));
id->agent_fd = -1;
id->key = key;
id->filename = xstrdup(options.certificate_files[i]);
id->userprovided = options.certificate_file_userprovided[i];
TAILQ_INSERT_TAIL(preferred, id, next);
}
/* list of keys supported by the agent */
if ((r = ssh_get_authentication_socket(&agent_fd)) != 0) {
if (r != SSH_ERR_AGENT_NOT_PRESENT)
debug_fr(r, "ssh_get_authentication_socket");
} else if ((r = ssh_fetch_identitylist(agent_fd, &idlist)) != 0) {
if (r != SSH_ERR_AGENT_NO_IDENTITIES)
debug_fr(r, "ssh_fetch_identitylist");
close(agent_fd);
} else {
for (j = 0; j < idlist->nkeys; j++) {
found = 0;
TAILQ_FOREACH(id, &files, next) {
/*
* agent keys from the config file are
* preferred
*/
if (sshkey_equal(idlist->keys[j], id->key)) {
TAILQ_REMOVE(&files, id, next);
TAILQ_INSERT_TAIL(preferred, id, next);
id->agent_fd = agent_fd;
found = 1;
break;
}
}
if (!found && !options.identities_only) {
id = xcalloc(1, sizeof(*id));
/* XXX "steals" key/comment from idlist */
id->key = idlist->keys[j];
id->filename = idlist->comments[j];
idlist->keys[j] = NULL;
idlist->comments[j] = NULL;
id->agent_fd = agent_fd;
TAILQ_INSERT_TAIL(&agent, id, next);
}
}
ssh_free_identitylist(idlist);
/* append remaining agent keys */
TAILQ_CONCAT(preferred, &agent, next);
authctxt->agent_fd = agent_fd;
}
/* Prefer PKCS11 keys that are explicitly listed */
TAILQ_FOREACH_SAFE(id, &files, next, tmp) {
if (id->key == NULL || (id->key->flags & SSHKEY_FLAG_EXT) == 0)
continue;
found = 0;
TAILQ_FOREACH(id2, &files, next) {
if (id2->key == NULL ||
(id2->key->flags & SSHKEY_FLAG_EXT) != 0)
continue;
if (sshkey_equal(id->key, id2->key)) {
TAILQ_REMOVE(&files, id, next);
TAILQ_INSERT_TAIL(preferred, id, next);
found = 1;
break;
}
}
/* If IdentitiesOnly set and key not found then don't use it */
if (!found && options.identities_only) {
TAILQ_REMOVE(&files, id, next);
freezero(id, sizeof(*id));
}
}
/* append remaining keys from the config file */
TAILQ_CONCAT(preferred, &files, next);
/* finally, filter by PubkeyAcceptedKeyTypes */
TAILQ_FOREACH_SAFE(id, preferred, next, id2) {
if (id->key != NULL && !key_type_allowed_by_config(id->key)) {
debug("Skipping %s key %s - "
"not in PubkeyAcceptedKeyTypes",
sshkey_ssh_name(id->key), id->filename);
TAILQ_REMOVE(preferred, id, next);
sshkey_free(id->key);
free(id->filename);
memset(id, 0, sizeof(*id));
continue;
}
}
/* List the keys we plan on using */
TAILQ_FOREACH_SAFE(id, preferred, next, id2) {
ident = format_identity(id);
debug("Will attempt key: %s", ident);
free(ident);
}
debug2_f("done");
}
static void
pubkey_cleanup(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
Identity *id;
if (authctxt->agent_fd != -1) {
ssh_close_authentication_socket(authctxt->agent_fd);
authctxt->agent_fd = -1;
}
for (id = TAILQ_FIRST(&authctxt->keys); id;
id = TAILQ_FIRST(&authctxt->keys)) {
TAILQ_REMOVE(&authctxt->keys, id, next);
sshkey_free(id->key);
free(id->filename);
free(id);
}
}
static void
pubkey_reset(Authctxt *authctxt)
{
Identity *id;
TAILQ_FOREACH(id, &authctxt->keys, next)
id->tried = 0;
}
static int
try_identity(Identity *id)
{
if (!id->key)
return (0);
if (sshkey_type_plain(id->key->type) == KEY_RSA &&
(datafellows & SSH_BUG_RSASIGMD5) != 0) {
debug("Skipped %s key %s for RSA/MD5 server",
sshkey_type(id->key), id->filename);
return (0);
}
return 1;
}
static int
userauth_pubkey(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
Identity *id;
int sent = 0;
char *ident;
while ((id = TAILQ_FIRST(&authctxt->keys))) {
if (id->tried++)
return (0);
/* move key to the end of the queue */
TAILQ_REMOVE(&authctxt->keys, id, next);
TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
/*
* send a test message if we have the public key. for
* encrypted keys we cannot do this and have to load the
* private key instead
*/
if (id->key != NULL) {
if (try_identity(id)) {
ident = format_identity(id);
debug("Offering public key: %s", ident);
free(ident);
sent = send_pubkey_test(ssh, id);
}
} else {
debug("Trying private key: %s", id->filename);
id->key = load_identity_file(id);
if (id->key != NULL) {
if (try_identity(id)) {
id->isprivate = 1;
sent = sign_and_send_pubkey(ssh, id);
}
sshkey_free(id->key);
id->key = NULL;
id->isprivate = 0;
}
}
if (sent)
return (sent);
}
return (0);
}
/*
* Send userauth request message specifying keyboard-interactive method.
*/
static int
userauth_kbdint(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
int r;
if (authctxt->attempt_kbdint++ >= options.number_of_password_prompts)
return 0;
/* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
if (authctxt->attempt_kbdint > 1 && !authctxt->info_req_seen) {
debug3("userauth_kbdint: disable: no info_req_seen");
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
return 0;
}
debug2("userauth_kbdint");
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
(r = sshpkt_put_cstring(ssh, "")) != 0 || /* lang */
(r = sshpkt_put_cstring(ssh, options.kbd_interactive_devices ?
options.kbd_interactive_devices : "")) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
return 1;
}
/*
* parse INFO_REQUEST, prompt user and send INFO_RESPONSE
*/
static int
input_userauth_info_req(int type, u_int32_t seq, struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
char *name = NULL, *inst = NULL, *lang = NULL, *prompt = NULL;
char *display_prompt = NULL, *response = NULL;
u_char echo = 0;
u_int num_prompts, i;
int r;
debug2_f("entering");
if (authctxt == NULL)
fatal_f("no authentication context");
authctxt->info_req_seen = 1;
if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0 ||
(r = sshpkt_get_cstring(ssh, &inst, NULL)) != 0 ||
(r = sshpkt_get_cstring(ssh, &lang, NULL)) != 0)
goto out;
if (strlen(name) > 0)
logit("%s", name);
if (strlen(inst) > 0)
logit("%s", inst);
if ((r = sshpkt_get_u32(ssh, &num_prompts)) != 0)
goto out;
/*
* Begin to build info response packet based on prompts requested.
* We commit to providing the correct number of responses, so if
* further on we run into a problem that prevents this, we have to
* be sure and clean this up and send a correct error response.
*/
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE)) != 0 ||
(r = sshpkt_put_u32(ssh, num_prompts)) != 0)
goto out;
debug2_f("num_prompts %d", num_prompts);
for (i = 0; i < num_prompts; i++) {
if ((r = sshpkt_get_cstring(ssh, &prompt, NULL)) != 0 ||
(r = sshpkt_get_u8(ssh, &echo)) != 0)
goto out;
if (asmprintf(&display_prompt, INT_MAX, NULL, "(%s@%s) %s",
authctxt->server_user, options.host_key_alias ?
options.host_key_alias : authctxt->host, prompt) == -1)
fatal_f("asmprintf failed");
response = read_passphrase(display_prompt, echo ? RP_ECHO : 0);
if ((r = sshpkt_put_cstring(ssh, response)) != 0)
goto out;
freezero(response, strlen(response));
free(prompt);
free(display_prompt);
display_prompt = response = prompt = NULL;
}
/* done with parsing incoming message. */
if ((r = sshpkt_get_end(ssh)) != 0 ||
(r = sshpkt_add_padding(ssh, 64)) != 0)
goto out;
r = sshpkt_send(ssh);
out:
if (response)
freezero(response, strlen(response));
free(prompt);
free(display_prompt);
free(name);
free(inst);
free(lang);
return r;
}
static int
ssh_keysign(struct ssh *ssh, struct sshkey *key, u_char **sigp, size_t *lenp,
const u_char *data, size_t datalen)
{
struct sshbuf *b;
struct stat st;
pid_t pid;
int r, to[2], from[2], status;
int sock = ssh_packet_get_connection_in(ssh);
u_char rversion = 0, version = 2;
void (*osigchld)(int);
*sigp = NULL;
*lenp = 0;
if (stat(_PATH_SSH_KEY_SIGN, &st) == -1) {
error_f("not installed: %s", strerror(errno));
return -1;
}
if (fflush(stdout) != 0) {
error_f("fflush: %s", strerror(errno));
return -1;
}
if (pipe(to) == -1) {
error_f("pipe: %s", strerror(errno));
return -1;
}
if (pipe(from) == -1) {
error_f("pipe: %s", strerror(errno));
return -1;
}
if ((pid = fork()) == -1) {
error_f("fork: %s", strerror(errno));
return -1;
}
osigchld = ssh_signal(SIGCHLD, SIG_DFL);
if (pid == 0) {
close(from[0]);
if (dup2(from[1], STDOUT_FILENO) == -1)
fatal_f("dup2: %s", strerror(errno));
close(to[1]);
if (dup2(to[0], STDIN_FILENO) == -1)
fatal_f("dup2: %s", strerror(errno));
close(from[1]);
close(to[0]);
if (dup2(sock, STDERR_FILENO + 1) == -1)
fatal_f("dup2: %s", strerror(errno));
sock = STDERR_FILENO + 1;
fcntl(sock, F_SETFD, 0); /* keep the socket on exec */
closefrom(sock + 1);
debug3_f("[child] pid=%ld, exec %s",
(long)getpid(), _PATH_SSH_KEY_SIGN);
execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *)NULL);
fatal_f("exec(%s): %s", _PATH_SSH_KEY_SIGN,
strerror(errno));
}
close(from[1]);
close(to[0]);
sock = STDERR_FILENO + 1;
if ((b = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
/* send # of sock, data to be signed */
if ((r = sshbuf_put_u32(b, sock)) != 0 ||
(r = sshbuf_put_string(b, data, datalen)) != 0)
fatal_fr(r, "buffer error");
if (ssh_msg_send(to[1], version, b) == -1)
fatal_f("couldn't send request");
sshbuf_reset(b);
r = ssh_msg_recv(from[0], b);
close(from[0]);
close(to[1]);
if (r < 0) {
error_f("no reply");
goto fail;
}
errno = 0;
while (waitpid(pid, &status, 0) == -1) {
if (errno != EINTR) {
error_f("waitpid %ld: %s", (long)pid, strerror(errno));
goto fail;
}
}
if (!WIFEXITED(status)) {
error_f("exited abnormally");
goto fail;
}
if (WEXITSTATUS(status) != 0) {
error_f("exited with status %d", WEXITSTATUS(status));
goto fail;
}
if ((r = sshbuf_get_u8(b, &rversion)) != 0) {
error_fr(r, "buffer error");
goto fail;
}
if (rversion != version) {
error_f("bad version");
goto fail;
}
if ((r = sshbuf_get_string(b, sigp, lenp)) != 0) {
error_fr(r, "buffer error");
fail:
ssh_signal(SIGCHLD, osigchld);
sshbuf_free(b);
return -1;
}
ssh_signal(SIGCHLD, osigchld);
sshbuf_free(b);
return 0;
}
static int
userauth_hostbased(struct ssh *ssh)
{
Authctxt *authctxt = (Authctxt *)ssh->authctxt;
struct sshkey *private = NULL;
struct sshbuf *b = NULL;
u_char *sig = NULL, *keyblob = NULL;
char *fp = NULL, *chost = NULL, *lname = NULL;
size_t siglen = 0, keylen = 0;
int i, r, success = 0;
if (authctxt->ktypes == NULL) {
authctxt->oktypes = xstrdup(options.hostbased_key_types);
authctxt->ktypes = authctxt->oktypes;
}
/*
* Work through each listed type pattern in HostbasedKeyTypes,
* trying each hostkey that matches the type in turn.
*/
for (;;) {
if (authctxt->active_ktype == NULL)
authctxt->active_ktype = strsep(&authctxt->ktypes, ",");
if (authctxt->active_ktype == NULL ||
*authctxt->active_ktype == '\0')
break;
debug3_f("trying key type %s", authctxt->active_ktype);
/* check for a useful key */
private = NULL;
for (i = 0; i < authctxt->sensitive->nkeys; i++) {
if (authctxt->sensitive->keys[i] == NULL ||
authctxt->sensitive->keys[i]->type == KEY_UNSPEC)
continue;
if (match_pattern_list(
sshkey_ssh_name(authctxt->sensitive->keys[i]),
authctxt->active_ktype, 0) != 1)
continue;
/* we take and free the key */
private = authctxt->sensitive->keys[i];
authctxt->sensitive->keys[i] = NULL;
break;
}
/* Found one */
if (private != NULL)
break;
/* No more keys of this type; advance */
authctxt->active_ktype = NULL;
}
if (private == NULL) {
free(authctxt->oktypes);
authctxt->oktypes = authctxt->ktypes = NULL;
authctxt->active_ktype = NULL;
debug("No more client hostkeys for hostbased authentication.");
goto out;
}
if ((fp = sshkey_fingerprint(private, options.fingerprint_hash,
SSH_FP_DEFAULT)) == NULL) {
error_f("sshkey_fingerprint failed");
goto out;
}
debug_f("trying hostkey %s %s", sshkey_ssh_name(private), fp);
/* figure out a name for the client host */
lname = get_local_name(ssh_packet_get_connection_in(ssh));
if (lname == NULL) {
error_f("cannot get local ipaddr/name");
goto out;
}
/* XXX sshbuf_put_stringf? */
xasprintf(&chost, "%s.", lname);
debug2_f("chost %s", chost);
/* construct data */
if ((b = sshbuf_new()) == NULL) {
error_f("sshbuf_new failed");
goto out;
}
if ((r = sshkey_to_blob(private, &keyblob, &keylen)) != 0) {
error_fr(r, "sshkey_to_blob");
goto out;
}
if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
(r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->server_user)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->method->name)) != 0 ||
(r = sshbuf_put_cstring(b, sshkey_ssh_name(private))) != 0 ||
(r = sshbuf_put_string(b, keyblob, keylen)) != 0 ||
(r = sshbuf_put_cstring(b, chost)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->local_user)) != 0) {
error_fr(r, "buffer error");
goto out;
}
#ifdef DEBUG_PK
sshbuf_dump(b, stderr);
#endif
if ((r = ssh_keysign(ssh, private, &sig, &siglen,
sshbuf_ptr(b), sshbuf_len(b))) != 0) {
error("sign using hostkey %s %s failed",
sshkey_ssh_name(private), fp);
goto out;
}
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
(r = sshpkt_put_cstring(ssh, sshkey_ssh_name(private))) != 0 ||
(r = sshpkt_put_string(ssh, keyblob, keylen)) != 0 ||
(r = sshpkt_put_cstring(ssh, chost)) != 0 ||
(r = sshpkt_put_cstring(ssh, authctxt->local_user)) != 0 ||
(r = sshpkt_put_string(ssh, sig, siglen)) != 0 ||
(r = sshpkt_send(ssh)) != 0) {
error_fr(r, "packet error");
goto out;
}
success = 1;
out:
if (sig != NULL)
freezero(sig, siglen);
free(keyblob);
free(lname);
free(fp);
free(chost);
sshkey_free(private);
sshbuf_free(b);
return success;
}
/* find auth method */
/*
* given auth method name, if configurable options permit this method fill
* in auth_ident field and return true, otherwise return false.
*/
static int
authmethod_is_enabled(Authmethod *method)
{
if (method == NULL)
return 0;
/* return false if options indicate this method is disabled */
if (method->enabled == NULL || *method->enabled == 0)
return 0;
/* return false if batch mode is enabled but method needs interactive mode */
if (method->batch_flag != NULL && *method->batch_flag != 0)
return 0;
return 1;
}
static Authmethod *
authmethod_lookup(const char *name)
{
Authmethod *method = NULL;
if (name != NULL)
for (method = authmethods; method->name != NULL; method++)
if (strcmp(name, method->name) == 0)
return method;
debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
return NULL;
}
/* XXX internal state */
static Authmethod *current = NULL;
static char *supported = NULL;
static char *preferred = NULL;
/*
* Given the authentication method list sent by the server, return the
* next method we should try. If the server initially sends a nil list,
* use a built-in default list.
*/
static Authmethod *
authmethod_get(char *authlist)
{
char *name = NULL;
u_int next;
/* Use a suitable default if we're passed a nil list. */
if (authlist == NULL || strlen(authlist) == 0)
authlist = options.preferred_authentications;
if (supported == NULL || strcmp(authlist, supported) != 0) {
debug3("start over, passed a different list %s", authlist);
free(supported);
supported = xstrdup(authlist);
preferred = options.preferred_authentications;
debug3("preferred %s", preferred);
current = NULL;
} else if (current != NULL && authmethod_is_enabled(current))
return current;
for (;;) {
if ((name = match_list(preferred, supported, &next)) == NULL) {
debug("No more authentication methods to try.");
current = NULL;
return NULL;
}
preferred += next;
debug3("authmethod_lookup %s", name);
debug3("remaining preferred: %s", preferred);
if ((current = authmethod_lookup(name)) != NULL &&
authmethod_is_enabled(current)) {
debug3("authmethod_is_enabled %s", name);
debug("Next authentication method: %s", name);
free(name);
return current;
}
free(name);
}
}
static char *
authmethods_get(void)
{
Authmethod *method = NULL;
struct sshbuf *b;
char *list;
int r;
if ((b = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
for (method = authmethods; method->name != NULL; method++) {
if (authmethod_is_enabled(method)) {
if ((r = sshbuf_putf(b, "%s%s",
sshbuf_len(b) ? "," : "", method->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;
}
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