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/*
* 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"
RCSID("$OpenBSD: auth2.c,v 1.25 2001/01/08 22:29:05 markus Exp $");
#ifdef HAVE_OSF_SIA
# include <sia.h>
# include <siad.h>
#endif
#include <openssl/dsa.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include "xmalloc.h"
#include "rsa.h"
#include "ssh.h"
#include "pty.h"
#include "packet.h"
#include "buffer.h"
#include "servconf.h"
#include "compat.h"
#include "channels.h"
#include "bufaux.h"
#include "ssh2.h"
#include "auth.h"
#include "session.h"
#include "dispatch.h"
#include "auth.h"
#include "key.h"
#include "kex.h"
#include "uidswap.h"
#include "auth-options.h"
/* import */
extern ServerOptions options;
extern u_char *session_id2;
extern int session_id2_len;
#ifdef WITH_AIXAUTHENTICATE
extern char *aixloginmsg;
#endif
#ifdef HAVE_OSF_SIA
extern int saved_argc;
extern char **saved_argv;
#endif
static Authctxt *x_authctxt = NULL;
static int one = 1;
typedef struct Authmethod Authmethod;
struct Authmethod {
char *name;
int (*userauth)(Authctxt *authctxt);
int *enabled;
};
/* protocol */
void input_service_request(int type, int plen, void *ctxt);
void input_userauth_request(int type, int plen, void *ctxt);
void protocol_error(int type, int plen, void *ctxt);
/* helper */
Authmethod *authmethod_lookup(const char *name);
struct passwd *pwcopy(struct passwd *pw);
int user_key_allowed(struct passwd *pw, Key *key);
char *authmethods_get(void);
/* auth */
void userauth_banner(void);
int userauth_none(Authctxt *authctxt);
int userauth_passwd(Authctxt *authctxt);
int userauth_pubkey(Authctxt *authctxt);
int userauth_kbdint(Authctxt *authctxt);
Authmethod authmethods[] = {
{"none",
userauth_none,
&one},
{"publickey",
userauth_pubkey,
&options.pubkey_authentication},
{"keyboard-interactive",
userauth_kbdint,
&options.kbd_interactive_authentication},
{"password",
userauth_passwd,
&options.password_authentication},
{NULL, NULL, NULL}
};
/*
* loop until authctxt->success == TRUE
*/
void
do_authentication2()
{
Authctxt *authctxt = xmalloc(sizeof(*authctxt));
memset(authctxt, 'a', sizeof(*authctxt));
authctxt->valid = 0;
authctxt->attempt = 0;
authctxt->failures = 0;
authctxt->success = 0;
x_authctxt = authctxt; /*XXX*/
#ifdef KRB4
/* turn off kerberos, not supported by SSH2 */
options.kerberos_authentication = 0;
#endif
dispatch_init(&protocol_error);
dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
do_authenticated2();
}
void
protocol_error(int type, int plen, void *ctxt)
{
log("auth: protocol error: type %d plen %d", type, plen);
packet_start(SSH2_MSG_UNIMPLEMENTED);
packet_put_int(0);
packet_send();
packet_write_wait();
}
void
input_service_request(int type, int plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
u_int len;
int accept = 0;
char *service = packet_get_string(&len);
packet_done();
if (authctxt == NULL)
fatal("input_service_request: no authctxt");
if (strcmp(service, "ssh-userauth") == 0) {
if (!authctxt->success) {
accept = 1;
/* now we can handle user-auth requests */
dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
}
}
/* XXX all other service requests are denied */
if (accept) {
packet_start(SSH2_MSG_SERVICE_ACCEPT);
packet_put_cstring(service);
packet_send();
packet_write_wait();
} else {
debug("bad service request %s", service);
packet_disconnect("bad service request %s", service);
}
xfree(service);
}
void
input_userauth_request(int type, int plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
Authmethod *m = NULL;
char *user, *service, *method;
int authenticated = 0;
if (authctxt == NULL)
fatal("input_userauth_request: no authctxt");
user = packet_get_string(NULL);
service = packet_get_string(NULL);
method = packet_get_string(NULL);
debug("userauth-request for user %s service %s method %s", user, service, method);
debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
if (authctxt->attempt++ == 0) {
/* setup auth context */
struct passwd *pw = NULL;
setproctitle("%s", user);
pw = getpwnam(user);
if (pw && allowed_user(pw) && strcmp(service, "ssh-connection")==0) {
authctxt->pw = pwcopy(pw);
authctxt->valid = 1;
debug2("input_userauth_request: setting up authctxt for %s", user);
#ifdef USE_PAM
start_pam(pw);
#endif
} else {
log("input_userauth_request: illegal user %s", user);
}
authctxt->user = xstrdup(user);
authctxt->service = xstrdup(service);
} else if (authctxt->valid) {
if (strcmp(user, authctxt->user) != 0 ||
strcmp(service, authctxt->service) != 0) {
log("input_userauth_request: missmatch: (%s,%s)!=(%s,%s)",
user, service, authctxt->user, authctxt->service);
authctxt->valid = 0;
}
}
m = authmethod_lookup(method);
if (m != NULL) {
debug2("input_userauth_request: try method %s", method);
authenticated = m->userauth(authctxt);
} else {
debug2("input_userauth_request: unsupported method %s", method);
}
if (!authctxt->valid && authenticated == 1) {
log("input_userauth_request: INTERNAL ERROR: authenticated invalid user %s service %s", user, method);
authenticated = 0;
}
/* Special handling for root */
if (authenticated == 1 &&
authctxt->valid && authctxt->pw->pw_uid == 0 && !options.permit_root_login) {
authenticated = 0;
log("ROOT LOGIN REFUSED FROM %.200s", get_canonical_hostname());
}
#ifdef USE_PAM
if (authenticated && authctxt->user && !do_pam_account(authctxt->user, NULL))
authenticated = 0;
#endif /* USE_PAM */
/* Log before sending the reply */
userauth_log(authctxt, authenticated, method);
userauth_reply(authctxt, authenticated);
xfree(service);
xfree(user);
xfree(method);
}
void
userauth_banner(void)
{
struct stat st;
char *banner = NULL;
off_t len, n;
int fd;
if (options.banner == NULL || (datafellows & SSH_BUG_BANNER))
return;
if ((fd = open(options.banner, O_RDONLY)) < 0) {
error("userauth_banner: open %s failed: %s",
options.banner, strerror(errno));
return;
}
if (fstat(fd, &st) < 0)
goto done;
len = st.st_size;
banner = xmalloc(len + 1);
if ((n = read(fd, banner, len)) < 0)
goto done;
banner[n] = '\0';
packet_start(SSH2_MSG_USERAUTH_BANNER);
packet_put_cstring(banner);
packet_put_cstring(""); /* language, unused */
packet_send();
debug("userauth_banner: sent");
done:
if (banner)
xfree(banner);
close(fd);
return;
}
void
userauth_log(Authctxt *authctxt, int authenticated, char *method)
{
void (*authlog) (const char *fmt,...) = verbose;
char *user = NULL, *authmsg = NULL;
/* Raise logging level */
if (authenticated == 1 ||
!authctxt->valid ||
authctxt->failures >= AUTH_FAIL_LOG ||
strcmp(method, "password") == 0)
authlog = log;
if (authenticated == 1) {
authmsg = "Accepted";
} else if (authenticated == 0) {
authmsg = "Failed";
} else {
authmsg = "Postponed";
}
if (authctxt->valid) {
user = authctxt->pw->pw_uid == 0 ? "ROOT" : authctxt->user;
} else {
user = "NOUSER";
}
authlog("%s %s for %.200s from %.200s port %d ssh2",
authmsg,
method,
user,
get_remote_ipaddr(),
get_remote_port());
}
void
userauth_reply(Authctxt *authctxt, int authenticated)
{
char *methods;
/* XXX todo: check if multiple auth methods are needed */
if (authenticated == 1) {
#ifdef WITH_AIXAUTHENTICATE
/* We don't have a pty yet, so just label the line as "ssh" */
if (loginsuccess(authctxt->user?authctxt->user:"NOUSER",
get_canonical_hostname(), "ssh", &aixloginmsg) < 0)
aixloginmsg = NULL;
#endif /* WITH_AIXAUTHENTICATE */
/* turn off userauth */
dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
packet_start(SSH2_MSG_USERAUTH_SUCCESS);
packet_send();
packet_write_wait();
/* now we can break out */
authctxt->success = 1;
} else if (authenticated == 0) {
if (authctxt->failures++ >= AUTH_FAIL_MAX)
packet_disconnect("too many failed userauth_requests");
methods = authmethods_get();
packet_start(SSH2_MSG_USERAUTH_FAILURE);
packet_put_cstring(methods);
packet_put_char(0); /* XXX partial success, unused */
packet_send();
packet_write_wait();
xfree(methods);
} else {
/* do nothing, we did already send a reply */
}
}
int
userauth_none(Authctxt *authctxt)
{
/* disable method "none", only allowed one time */
Authmethod *m = authmethod_lookup("none");
if (m != NULL)
m->enabled = NULL;
packet_done();
userauth_banner();
if (authctxt->valid == 0)
return(0);
#ifdef HAVE_CYGWIN
if (check_nt_auth(1, authctxt->pw->pw_uid) == 0)
return(0);
#endif
#ifdef USE_PAM
return auth_pam_password(authctxt->pw, "");
#elif defined(HAVE_OSF_SIA)
return (sia_validate_user(NULL, saved_argc, saved_argv,
get_canonical_hostname(), authctxt->user?authctxt->user:"NOUSER",
NULL, 0, NULL, "") == SIASUCCESS);
#else /* !HAVE_OSF_SIA && !USE_PAM */
return auth_password(authctxt->pw, "");
#endif /* USE_PAM */
}
int
userauth_passwd(Authctxt *authctxt)
{
char *password;
int authenticated = 0;
int change;
u_int len;
change = packet_get_char();
if (change)
log("password change not supported");
password = packet_get_string(&len);
packet_done();
if (authctxt->valid &&
#ifdef HAVE_CYGWIN
check_nt_auth(1, authctxt->pw->pw_uid) &&
#endif
#ifdef USE_PAM
auth_pam_password(authctxt->pw, password) == 1)
#elif defined(HAVE_OSF_SIA)
sia_validate_user(NULL, saved_argc, saved_argv,
get_canonical_hostname(), authctxt->user?authctxt->user:"NOUSER",
NULL, 0, NULL, password) == SIASUCCESS)
#else /* !USE_PAM && !HAVE_OSF_SIA */
auth_password(authctxt->pw, password) == 1)
#endif /* USE_PAM */
authenticated = 1;
memset(password, 0, len);
xfree(password);
return authenticated;
}
int
userauth_kbdint(Authctxt *authctxt)
{
int authenticated = 0;
char *lang = NULL;
char *devs = NULL;
lang = packet_get_string(NULL);
devs = packet_get_string(NULL);
packet_done();
debug("keyboard-interactive language %s devs %s", lang, devs);
#ifdef USE_PAM
if (authenticated == 0)
authenticated = auth2_pam(authctxt);
#endif
#ifdef SKEY
/* XXX hardcoded, we should look at devs */
if (authenticated == 0)
if (options.skey_authentication != 0)
authenticated = auth2_skey(authctxt);
#endif
xfree(lang);
xfree(devs);
#ifdef HAVE_CYGWIN
if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
return(0);
#endif
return authenticated;
}
int
userauth_pubkey(Authctxt *authctxt)
{
Buffer b;
Key *key;
char *pkalg, *pkblob, *sig;
u_int alen, blen, slen;
int have_sig, pktype;
int authenticated = 0;
if (!authctxt->valid) {
debug2("userauth_pubkey: disabled because of invalid user");
return 0;
}
have_sig = packet_get_char();
if (datafellows & SSH_BUG_PKAUTH) {
debug2("userauth_pubkey: SSH_BUG_PKAUTH");
/* no explicit pkalg given */
pkblob = packet_get_string(&blen);
buffer_init(&b);
buffer_append(&b, pkblob, blen);
/* so we have to extract the pkalg from the pkblob */
pkalg = buffer_get_string(&b, &alen);
buffer_free(&b);
} else {
pkalg = packet_get_string(&alen);
pkblob = packet_get_string(&blen);
}
pktype = key_type_from_name(pkalg);
if (pktype == KEY_UNSPEC) {
/* this is perfectly legal */
log("userauth_pubkey: unsupported public key algorithm: %s", pkalg);
xfree(pkalg);
xfree(pkblob);
return 0;
}
key = key_from_blob(pkblob, blen);
if (key != NULL) {
if (have_sig) {
sig = packet_get_string(&slen);
packet_done();
buffer_init(&b);
if (datafellows & SSH_OLD_SESSIONID) {
buffer_append(&b, session_id2, session_id2_len);
} else {
buffer_put_string(&b, session_id2, session_id2_len);
}
/* reconstruct packet */
buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
buffer_put_cstring(&b, authctxt->user);
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, key_ssh_name(key));
}
buffer_put_string(&b, pkblob, blen);
#ifdef DEBUG_PK
buffer_dump(&b);
#endif
/* test for correct signature */
if (user_key_allowed(authctxt->pw, key) &&
key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
authenticated = 1;
buffer_clear(&b);
xfree(sig);
} else {
debug("test whether pkalg/pkblob are acceptable");
packet_done();
/* XXX fake reply and always send PK_OK ? */
/*
* XXX this allows testing whether a user is allowed
* to login: if you happen to have a valid pubkey this
* message is sent. the message is NEVER sent at all
* if a user is not allowed to login. is this an
* issue? -markus
*/
if (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();
authenticated = -1;
}
}
if (authenticated != 1)
auth_clear_options();
key_free(key);
}
debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
xfree(pkalg);
xfree(pkblob);
#ifdef HAVE_CYGWIN
if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
return(0);
#endif
return authenticated;
}
/* get current user */
struct passwd*
auth_get_user(void)
{
return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
}
#define DELIM ","
char *
authmethods_get(void)
{
Authmethod *method = NULL;
u_int size = 0;
char *list;
for (method = authmethods; method->name != NULL; method++) {
if (strcmp(method->name, "none") == 0)
continue;
if (method->enabled != NULL && *(method->enabled) != 0) {
if (size != 0)
size += strlen(DELIM);
size += strlen(method->name);
}
}
size++; /* trailing '\0' */
list = xmalloc(size);
list[0] = '\0';
for (method = authmethods; method->name != NULL; method++) {
if (strcmp(method->name, "none") == 0)
continue;
if (method->enabled != NULL && *(method->enabled) != 0) {
if (list[0] != '\0')
strlcat(list, DELIM, size);
strlcat(list, method->name, size);
}
}
return list;
}
Authmethod *
authmethod_lookup(const char *name)
{
Authmethod *method = NULL;
if (name != NULL)
for (method = authmethods; method->name != NULL; method++)
if (method->enabled != NULL &&
*(method->enabled) != 0 &&
strcmp(name, method->name) == 0)
return method;
debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
return NULL;
}
/* return 1 if user allows given key */
int
user_key_allowed(struct passwd *pw, Key *key)
{
char line[8192], file[1024];
int found_key = 0;
FILE *f;
u_long linenum = 0;
struct stat st;
Key *found;
if (pw == NULL)
return 0;
/* Temporarily use the user's uid. */
temporarily_use_uid(pw->pw_uid);
/* The authorized keys. */
snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
SSH_USER_PERMITTED_KEYS2);
/* Fail quietly if file does not exist */
if (stat(file, &st) < 0) {
/* Restore the privileged uid. */
restore_uid();
return 0;
}
/* Open the file containing the authorized keys. */
f = fopen(file, "r");
if (!f) {
/* Restore the privileged uid. */
restore_uid();
return 0;
}
if (options.strict_modes) {
int fail = 0;
char buf[1024];
/* Check open file in order to avoid open/stat races */
if (fstat(fileno(f), &st) < 0 ||
(st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
(st.st_mode & 022) != 0) {
snprintf(buf, sizeof buf,
"%s authentication refused for %.100s: "
"bad ownership or modes for '%s'.",
key_type(key), pw->pw_name, file);
fail = 1;
} else {
/* Check path to SSH_USER_PERMITTED_KEYS */
int i;
static const char *check[] = {
"", SSH_USER_DIR, NULL
};
for (i = 0; check[i]; i++) {
snprintf(line, sizeof line, "%.500s/%.100s",
pw->pw_dir, check[i]);
if (stat(line, &st) < 0 ||
(st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
(st.st_mode & 022) != 0) {
snprintf(buf, sizeof buf,
"%s authentication refused for %.100s: "
"bad ownership or modes for '%s'.",
key_type(key), pw->pw_name, line);
fail = 1;
break;
}
}
}
if (fail) {
fclose(f);
log("%s",buf);
restore_uid();
return 0;
}
}
found_key = 0;
found = key_new(key->type);
while (fgets(line, sizeof(line), f)) {
char *cp, *options = NULL;
linenum++;
/* Skip leading whitespace, empty and comment lines. */
for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
;
if (!*cp || *cp == '\n' || *cp == '#')
continue;
if (key_read(found, &cp) == -1) {
/* no key? check if there are options for this key */
int quoted = 0;
debug2("user_key_allowed: check options: '%s'", cp);
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_equal(found, key) &&
auth_parse_options(pw, options, linenum) == 1) {
found_key = 1;
debug("matching key found: file %s, line %ld",
file, linenum);
break;
}
}
restore_uid();
fclose(f);
key_free(found);
return found_key;
}
struct passwd *
pwcopy(struct passwd *pw)
{
struct passwd *copy = xmalloc(sizeof(*copy));
memset(copy, 0, sizeof(*copy));
copy->pw_name = xstrdup(pw->pw_name);
copy->pw_passwd = xstrdup(pw->pw_passwd);
copy->pw_uid = pw->pw_uid;
copy->pw_gid = pw->pw_gid;
#ifdef HAVE_PW_CLASS_IN_PASSWD
copy->pw_class = xstrdup(pw->pw_class);
#endif
copy->pw_dir = xstrdup(pw->pw_dir);
copy->pw_shell = xstrdup(pw->pw_shell);
return copy;
}
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