openssh-portable/auth2.c

496 lines
13 KiB
C

/*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Markus Friedl.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* 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 1.8 2000/05/08 17:42:24 markus Exp $");
#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 "cipher.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 "dsa.h"
#include "uidswap.h"
/* import */
extern ServerOptions options;
extern unsigned char *session_id2;
extern int session_id2_len;
/* protocol */
void input_service_request(int type, int plen);
void input_userauth_request(int type, int plen);
void protocol_error(int type, int plen);
/* auth */
int ssh2_auth_none(struct passwd *pw);
int ssh2_auth_password(struct passwd *pw);
int ssh2_auth_pubkey(struct passwd *pw, unsigned char *raw, unsigned int rlen);
/* helper */
struct passwd* auth_set_user(char *u, char *s);
int user_dsa_key_allowed(struct passwd *pw, Key *key);
typedef struct Authctxt Authctxt;
struct Authctxt {
char *user;
char *service;
struct passwd pw;
int valid;
};
static Authctxt *authctxt = NULL;
static int userauth_success = 0;
/*
* loop until userauth_success == TRUE
*/
void
do_authentication2()
{
/* turn off skey/kerberos, not supported by SSH2 */
#ifdef SKEY
options.skey_authentication = 0;
#endif
#ifdef KRB4
options.kerberos_authentication = 0;
#endif
dispatch_init(&protocol_error);
dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
dispatch_run(DISPATCH_BLOCK, &userauth_success);
do_authenticated2();
}
void
protocol_error(int type, int plen)
{
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)
{
unsigned int len;
int accept = 0;
char *service = packet_get_string(&len);
packet_done();
if (strcmp(service, "ssh-userauth") == 0) {
if (!userauth_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)
{
static void (*authlog) (const char *fmt,...) = verbose;
static int attempt = 0;
unsigned int len, rlen;
int authenticated = 0;
char *raw, *user, *service, *method, *authmsg = NULL;
struct passwd *pw;
#ifdef WITH_AIXAUTHENTICATE
extern char *aixloginmsg;
#endif /* WITH_AIXAUTHENTICATE */
raw = packet_get_raw(&rlen);
if (plen != rlen)
fatal("plen != rlen");
user = packet_get_string(&len);
service = packet_get_string(&len);
method = packet_get_string(&len);
if (++attempt == AUTH_FAIL_MAX) {
#ifdef WITH_AIXAUTHENTICATE
loginfailed(user,get_canonical_hostname(),"ssh");
#endif /* WITH_AIXAUTHENTICATE */
packet_disconnect("too many failed userauth_requests");
}
debug("userauth-request for user %s service %s method %s", user, service, method);
/* XXX we only allow the ssh-connection service */
pw = auth_set_user(user, service);
if (pw && strcmp(service, "ssh-connection")==0) {
if (strcmp(method, "none") == 0) {
authenticated = ssh2_auth_none(pw);
} else if (strcmp(method, "password") == 0) {
authenticated = ssh2_auth_password(pw);
} else if (strcmp(method, "publickey") == 0) {
authenticated = ssh2_auth_pubkey(pw, raw, rlen);
}
}
if (authenticated && pw && pw->pw_uid == 0 && !options.permit_root_login) {
authenticated = 0;
log("ROOT LOGIN REFUSED FROM %.200s",
get_canonical_hostname());
}
#ifdef USE_PAM
if (authenticated && !do_pam_account(pw->pw_name, NULL))
authenticated = 0;
#endif /* USE_PAM */
/* Raise logging level */
if (authenticated == 1 ||
attempt == AUTH_FAIL_LOG ||
strcmp(method, "password") == 0)
authlog = log;
/* Log before sending the reply */
if (authenticated == 1) {
authmsg = "Accepted";
} else if (authenticated == 0) {
authmsg = "Failed";
} else {
authmsg = "Postponed";
}
authlog("%s %s for %.200s from %.200s port %d ssh2",
authmsg,
method,
pw && pw->pw_uid == 0 ? "ROOT" : user,
get_remote_ipaddr(),
get_remote_port());
/* 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(user,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 */
userauth_success = 1;
} else if (authenticated == 0) {
packet_start(SSH2_MSG_USERAUTH_FAILURE);
packet_put_cstring("publickey,password"); /* XXX dynamic */
packet_put_char(0); /* XXX partial success, unused */
packet_send();
packet_write_wait();
}
xfree(service);
xfree(user);
xfree(method);
}
int
ssh2_auth_none(struct passwd *pw)
{
packet_done();
#ifdef USE_PAM
return auth_pam_password(pw, "");
#else /* USE_PAM */
return auth_password(pw, "");
#endif /* USE_PAM */
}
int
ssh2_auth_password(struct passwd *pw)
{
char *password;
int authenticated = 0;
int change;
unsigned int len;
change = packet_get_char();
if (change)
log("password change not supported");
password = packet_get_string(&len);
packet_done();
if (options.password_authentication &&
#ifdef USE_PAM
auth_pam_password(pw, password) == 1)
#else /* USE_PAM */
auth_password(pw, password) == 1)
#endif /* USE_PAM */
authenticated = 1;
memset(password, 0, len);
xfree(password);
return authenticated;
}
int
ssh2_auth_pubkey(struct passwd *pw, unsigned char *raw, unsigned int rlen)
{
Buffer b;
Key *key;
char *pkalg, *pkblob, *sig;
unsigned int alen, blen, slen;
int have_sig;
int authenticated = 0;
if (options.dsa_authentication == 0) {
debug("pubkey auth disabled");
return 0;
}
if (datafellows & SSH_BUG_PUBKEYAUTH) {
log("bug compatibility with ssh-2.0.13 pubkey not implemented");
return 0;
}
have_sig = packet_get_char();
pkalg = packet_get_string(&alen);
if (strcmp(pkalg, KEX_DSS) != 0) {
xfree(pkalg);
log("bad pkalg %s", pkalg); /*XXX*/
return 0;
}
pkblob = packet_get_string(&blen);
key = dsa_key_from_blob(pkblob, blen);
if (key != NULL) {
if (have_sig) {
sig = packet_get_string(&slen);
packet_done();
buffer_init(&b);
buffer_append(&b, session_id2, session_id2_len);
buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
if (slen + 4 > rlen)
fatal("bad rlen/slen");
buffer_append(&b, raw, rlen - slen - 4);
#ifdef DEBUG_DSS
buffer_dump(&b);
#endif
/* test for correct signature */
if (user_dsa_key_allowed(pw, key) &&
dsa_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
authenticated = 1;
buffer_clear(&b);
xfree(sig);
} else {
packet_done();
debug("test key...");
/* test whether pkalg/pkblob are acceptable */
/* 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_dsa_key_allowed(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;
}
}
key_free(key);
}
xfree(pkalg);
xfree(pkblob);
return authenticated;
}
/* set and get current user */
struct passwd*
auth_get_user(void)
{
return (authctxt != NULL && authctxt->valid) ? &authctxt->pw : NULL;
}
struct passwd*
auth_set_user(char *u, char *s)
{
struct passwd *pw, *copy;
if (authctxt == NULL) {
authctxt = xmalloc(sizeof(*authctxt));
authctxt->valid = 0;
authctxt->user = xstrdup(u);
authctxt->service = xstrdup(s);
setproctitle("%s", u);
pw = getpwnam(u);
if (!pw || !allowed_user(pw)) {
log("auth_set_user: illegal user %s", u);
return NULL;
}
#ifdef USE_PAM
start_pam(pw);
#endif
copy = &authctxt->pw;
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;
copy->pw_dir = xstrdup(pw->pw_dir);
copy->pw_shell = xstrdup(pw->pw_shell);
authctxt->valid = 1;
} else {
if (strcmp(u, authctxt->user) != 0 ||
strcmp(s, authctxt->service) != 0) {
log("auth_set_user: missmatch: (%s,%s)!=(%s,%s)",
u, s, authctxt->user, authctxt->service);
return NULL;
}
}
return auth_get_user();
}
/* return 1 if user allows given key */
int
user_dsa_key_allowed(struct passwd *pw, Key *key)
{
char line[8192], file[1024];
int found_key = 0;
unsigned int bits = -1;
FILE *f;
unsigned long linenum = 0;
struct stat st;
Key *found;
/* 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, "DSA authentication refused for %.100s: "
"bad ownership or modes for '%s'.", 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,
"DSA authentication refused for %.100s: "
"bad ownership or modes for '%s'.",
pw->pw_name, line);
fail = 1;
break;
}
}
}
if (fail) {
log(buf);
fclose(f);
restore_uid();
return 0;
}
}
found_key = 0;
found = key_new(KEY_DSA);
while (fgets(line, sizeof(line), f)) {
char *cp;
linenum++;
/* Skip leading whitespace, empty and comment lines. */
for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
;
if (!*cp || *cp == '\n' || *cp == '#')
continue;
bits = key_read(found, &cp);
if (bits == 0)
continue;
if (key_equal(found, key)) {
found_key = 1;
debug("matching key found: file %s, line %ld",
file, linenum);
break;
}
}
restore_uid();
fclose(f);
key_free(found);
return found_key;
}