* called by a name other than "ssh" or "Secure Shell".
*
* SSH2 implementation:
+ * Privilege Separation:
*
- * Copyright (c) 2000 Markus Friedl. All rights reserved.
+ * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
+ * Copyright (c) 2002 Niels Provos. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
*/
#include "includes.h"
-RCSID("$OpenBSD: sshd.c,v 1.215 2001/12/06 13:30:06 markus Exp $");
+RCSID("$OpenBSD: sshd.c,v 1.238 2002/03/23 20:57:26 stevesk Exp $");
#include <openssl/dh.h>
#include <openssl/bn.h>
-#include <openssl/hmac.h>
+#include <openssl/md5.h>
+#include <openssl/rand.h>
#include "ssh.h"
#include "ssh1.h"
#include "misc.h"
#include "dispatch.h"
#include "channels.h"
+#include "session.h"
+#include "monitor_mm.h"
+#include "monitor.h"
+#include "monitor_wrap.h"
+#include "monitor_fdpass.h"
#ifdef LIBWRAP
#include <tcpd.h>
int *startup_pipes = NULL;
int startup_pipe; /* in child */
+/* variables used for privilege separation */
+extern struct monitor *monitor;
+extern int use_privsep;
+
/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
+void demote_sensitive_data(void);
static void do_ssh1_kex(void);
static void do_ssh2_kex(void);
fatal_cleanup();
}
debug("Client protocol version %d.%d; client software version %.100s",
- remote_major, remote_minor, remote_version);
+ remote_major, remote_minor, remote_version);
compat_datafellows(remote_version);
key_free(sensitive_data.server_key);
sensitive_data.server_key = NULL;
}
- for(i = 0; i < options.num_host_key_files; i++) {
+ for (i = 0; i < options.num_host_key_files; i++) {
if (sensitive_data.host_keys[i]) {
key_free(sensitive_data.host_keys[i]);
sensitive_data.host_keys[i] = NULL;
memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
}
+/* Demote private to public keys for network child */
+void
+demote_sensitive_data(void)
+{
+ Key *tmp;
+ int i;
+
+ if (sensitive_data.server_key) {
+ tmp = key_demote(sensitive_data.server_key);
+ key_free(sensitive_data.server_key);
+ sensitive_data.server_key = tmp;
+ }
+
+ for (i = 0; i < options.num_host_key_files; i++) {
+ if (sensitive_data.host_keys[i]) {
+ tmp = key_demote(sensitive_data.host_keys[i]);
+ key_free(sensitive_data.host_keys[i]);
+ sensitive_data.host_keys[i] = tmp;
+ if (tmp->type == KEY_RSA1)
+ sensitive_data.ssh1_host_key = tmp;
+ }
+ }
+
+ /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
+}
+
+static void
+privsep_preauth_child(void)
+{
+ u_int32_t rand[256];
+ int i;
+ struct passwd *pw;
+
+ /* Enable challenge-response authentication for privilege separation */
+ privsep_challenge_enable();
+
+ for (i = 0; i < 256; i++)
+ rand[i] = arc4random();
+ RAND_seed(rand, sizeof(rand));
+
+ /* Demote the private keys to public keys. */
+ demote_sensitive_data();
+
+ if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
+ fatal("%s: no user", SSH_PRIVSEP_USER);
+ memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
+ endpwent();
+
+ /* Change our root directory*/
+ if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
+ fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
+ strerror(errno));
+ if (chdir("/") == -1)
+ fatal("chdir(\"/\"): %s", strerror(errno));
+
+ /* Drop our privileges */
+ debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
+ (u_int)pw->pw_gid);
+ do_setusercontext(pw);
+}
+
+static Authctxt*
+privsep_preauth(void)
+{
+ Authctxt *authctxt = NULL;
+ int status;
+ pid_t pid;
+
+ /* Set up unprivileged child process to deal with network data */
+ monitor = monitor_init();
+ /* Store a pointer to the kex for later rekeying */
+ monitor->m_pkex = &xxx_kex;
+
+ pid = fork();
+ if (pid == -1) {
+ fatal("fork of unprivileged child failed");
+ } else if (pid != 0) {
+ debug2("Network child is on pid %d", pid);
+
+ close(monitor->m_recvfd);
+ authctxt = monitor_child_preauth(monitor);
+ close(monitor->m_sendfd);
+
+ /* Sync memory */
+ monitor_sync(monitor);
+
+ /* Wait for the child's exit status */
+ waitpid(pid, &status, 0);
+
+ return (authctxt);
+ } else {
+ /* child */
+
+ close(monitor->m_sendfd);
+
+ /* Demote the child */
+ if (getuid() == 0 || geteuid() == 0)
+ privsep_preauth_child();
+ setproctitle("%s", "[net]");
+ }
+ return (NULL);
+}
+
+static void
+privsep_postauth(Authctxt *authctxt)
+{
+ extern Authctxt *x_authctxt;
+
+ /* XXX - Remote port forwarding */
+ x_authctxt = authctxt;
+
+ if (authctxt->pw->pw_uid == 0 || options.use_login) {
+ /* File descriptor passing is broken or root login */
+ monitor_apply_keystate(monitor);
+ use_privsep = 0;
+ return;
+ }
+
+ /* Authentication complete */
+ alarm(0);
+ if (startup_pipe != -1) {
+ close(startup_pipe);
+ startup_pipe = -1;
+ }
+
+ /* New socket pair */
+ monitor_reinit(monitor);
+
+ monitor->m_pid = fork();
+ if (monitor->m_pid == -1)
+ fatal("fork of unprivileged child failed");
+ else if (monitor->m_pid != 0) {
+ debug2("User child is on pid %d", monitor->m_pid);
+ close(monitor->m_recvfd);
+ monitor_child_postauth(monitor);
+
+ /* NEVERREACHED */
+ exit(0);
+ }
+
+ close(monitor->m_sendfd);
+
+ /* Demote the private keys to public keys. */
+ demote_sensitive_data();
+
+ /* Drop privileges */
+ do_setusercontext(authctxt->pw);
+
+ /* It is safe now to apply the key state */
+ monitor_apply_keystate(monitor);
+}
+
static char *
list_hostkey_types(void)
{
- static char buf[1024];
+ Buffer b;
+ char *p;
int i;
- buf[0] = '\0';
- for(i = 0; i < options.num_host_key_files; i++) {
+
+ buffer_init(&b);
+ for (i = 0; i < options.num_host_key_files; i++) {
Key *key = sensitive_data.host_keys[i];
if (key == NULL)
continue;
switch (key->type) {
case KEY_RSA:
case KEY_DSA:
- strlcat(buf, key_ssh_name(key), sizeof buf);
- strlcat(buf, ",", sizeof buf);
+ if (buffer_len(&b) > 0)
+ buffer_append(&b, ",", 1);
+ p = key_ssh_name(key);
+ buffer_append(&b, p, strlen(p));
break;
}
}
- i = strlen(buf);
- if (i > 0 && buf[i-1] == ',')
- buf[i-1] = '\0';
- debug("list_hostkey_types: %s", buf);
- return buf;
+ buffer_append(&b, "\0", 1);
+ p = xstrdup(buffer_ptr(&b));
+ buffer_free(&b);
+ debug("list_hostkey_types: %s", p);
+ return p;
}
-static Key *
+Key *
get_hostkey_by_type(int type)
{
int i;
- for(i = 0; i < options.num_host_key_files; i++) {
+ for (i = 0; i < options.num_host_key_files; i++) {
Key *key = sensitive_data.host_keys[i];
if (key != NULL && key->type == type)
return key;
return NULL;
}
+Key *
+get_hostkey_by_index(int ind)
+{
+ if (ind < 0 || ind >= options.num_host_key_files)
+ return (NULL);
+ return (sensitive_data.host_keys[ind]);
+}
+
+int
+get_hostkey_index(Key *key)
+{
+ int i;
+ for (i = 0; i < options.num_host_key_files; i++) {
+ if (key == sensitive_data.host_keys[i])
+ return (i);
+ }
+ return (-1);
+}
+
/*
* returns 1 if connection should be dropped, 0 otherwise.
* dropping starts at connection #max_startups_begin with a probability
int listen_sock, maxfd;
int startup_p[2];
int startups = 0;
+ Authctxt *authctxt;
Key *key;
int ret, key_used = 0;
utmp_len = atoi(optarg);
break;
case 'o':
- if (process_server_config_line(&options, optarg,
+ if (process_server_config_line(&options, optarg,
"command-line", 0) != 0)
- exit(1);
+ exit(1);
break;
case '?':
default:
* key (unless started from inetd)
*/
log_init(__progname,
- options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
- options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
+ options.log_level == SYSLOG_LEVEL_NOT_SET ?
+ SYSLOG_LEVEL_INFO : options.log_level,
+ options.log_facility == SYSLOG_FACILITY_NOT_SET ?
+ SYSLOG_FACILITY_AUTH : options.log_facility,
!inetd_flag);
#ifdef _CRAY
/* load private host keys */
sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
- for(i = 0; i < options.num_host_key_files; i++)
+ for (i = 0; i < options.num_host_key_files; i++)
sensitive_data.host_keys[i] = NULL;
sensitive_data.server_key = NULL;
sensitive_data.ssh1_host_key = NULL;
sensitive_data.have_ssh1_key = 0;
sensitive_data.have_ssh2_key = 0;
- for(i = 0; i < options.num_host_key_files; i++) {
+ for (i = 0; i < options.num_host_key_files; i++) {
key = key_load_private(options.host_key_files[i], "", NULL);
sensitive_data.host_keys[i] = key;
if (key == NULL) {
/* Chdir to the root directory so that the current disk can be
unmounted if desired. */
chdir("/");
-
+
/* ignore SIGPIPE */
signal(SIGPIPE, SIG_IGN);
* close.
*/
setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
- (void *) &on, sizeof(on));
+ &on, sizeof(on));
linger.l_onoff = 1;
linger.l_linger = 5;
setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
- (void *) &linger, sizeof(linger));
+ &linger, sizeof(linger));
debug("Bind to port %s on %s.", strport, ntop);
}
if (fcntl(newsock, F_SETFL, 0) < 0) {
error("newsock del O_NONBLOCK: %s", strerror(errno));
+ close(newsock);
continue;
}
if (drop_connection(startups) == 1) {
/* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
linger.l_onoff = 1;
linger.l_linger = 5;
- setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
+ setsockopt(sock_in, SOL_SOCKET, SO_LINGER, &linger, sizeof(linger));
/* Set keepalives if requested. */
if (options.keepalives &&
- setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
+ setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
sizeof(on)) < 0)
error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
* machine, he can connect from any port. So do not use these
* authentication methods from machines that you do not trust.
*/
- if (remote_port >= IPPORT_RESERVED ||
- remote_port < IPPORT_RESERVED / 2) {
+ if (options.rhosts_authentication &&
+ (remote_port >= IPPORT_RESERVED ||
+ remote_port < IPPORT_RESERVED / 2)) {
debug("Rhosts Authentication disabled, "
"originating port %d not trusted.", remote_port);
options.rhosts_authentication = 0;
packet_set_nonblocking();
+ if (use_privsep)
+ if ((authctxt = privsep_preauth()) != NULL)
+ goto authenticated;
+
/* perform the key exchange */
/* authenticate user and start session */
if (compat20) {
do_ssh2_kex();
- do_authentication2();
+ authctxt = do_authentication2();
} else {
do_ssh1_kex();
- do_authentication();
+ authctxt = do_authentication();
}
+ /*
+ * If we use privilege separation, the unprivileged child transfers
+ * the current keystate and exits
+ */
+ if (use_privsep) {
+ mm_send_keystate(monitor);
+ exit(0);
+ }
+
+ authenticated:
+ /*
+ * In privilege separation, we fork another child and prepare
+ * file descriptor passing.
+ */
+ if (use_privsep) {
+ privsep_postauth(authctxt);
+ /* the monitor process [priv] will not return */
+ if (!compat20)
+ destroy_sensitive_data();
+ }
+
+ /* Perform session preparation. */
+ do_authenticated(authctxt);
+
/* The connection has been terminated. */
verbose("Closing connection to %.100s", remote_ip);
#endif /* USE_PAM */
packet_close();
+
+ if (use_privsep)
+ mm_terminate();
+
exit(0);
}
+/*
+ * Decrypt session_key_int using our private server key and private host key
+ * (key with larger modulus first).
+ */
+int
+ssh1_session_key(BIGNUM *session_key_int)
+{
+ int rsafail = 0;
+
+ if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
+ /* Server key has bigger modulus. */
+ if (BN_num_bits(sensitive_data.server_key->rsa->n) <
+ BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
+ fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
+ get_remote_ipaddr(),
+ BN_num_bits(sensitive_data.server_key->rsa->n),
+ BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
+ SSH_KEY_BITS_RESERVED);
+ }
+ if (rsa_private_decrypt(session_key_int, session_key_int,
+ sensitive_data.server_key->rsa) <= 0)
+ rsafail++;
+ if (rsa_private_decrypt(session_key_int, session_key_int,
+ sensitive_data.ssh1_host_key->rsa) <= 0)
+ rsafail++;
+ } else {
+ /* Host key has bigger modulus (or they are equal). */
+ if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
+ BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
+ fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
+ get_remote_ipaddr(),
+ BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
+ BN_num_bits(sensitive_data.server_key->rsa->n),
+ SSH_KEY_BITS_RESERVED);
+ }
+ if (rsa_private_decrypt(session_key_int, session_key_int,
+ sensitive_data.ssh1_host_key->rsa) < 0)
+ rsafail++;
+ if (rsa_private_decrypt(session_key_int, session_key_int,
+ sensitive_data.server_key->rsa) < 0)
+ rsafail++;
+ }
+ return (rsafail);
+}
/*
* SSH1 key exchange
*/
do_ssh1_kex(void)
{
int i, len;
- int plen, slen;
int rsafail = 0;
BIGNUM *session_key_int;
u_char session_key[SSH_SESSION_KEY_LENGTH];
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
/* Read clients reply (cipher type and session key). */
- packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
+ packet_read_expect(SSH_CMSG_SESSION_KEY);
/* Get cipher type and check whether we accept this. */
cipher_type = packet_get_char();
debug("Encryption type: %.200s", cipher_name(cipher_type));
/* Get the encrypted integer. */
- session_key_int = BN_new();
- packet_get_bignum(session_key_int, &slen);
+ if ((session_key_int = BN_new()) == NULL)
+ fatal("do_ssh1_kex: BN_new failed");
+ packet_get_bignum(session_key_int);
protocol_flags = packet_get_int();
packet_set_protocol_flags(protocol_flags);
+ packet_check_eom();
- packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
+ /* Decrypt session_key_int using host/server keys */
+ rsafail = PRIVSEP(ssh1_session_key(session_key_int));
- /*
- * Decrypt it using our private server key and private host key (key
- * with larger modulus first).
- */
- if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
- /* Server key has bigger modulus. */
- if (BN_num_bits(sensitive_data.server_key->rsa->n) <
- BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
- fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
- get_remote_ipaddr(),
- BN_num_bits(sensitive_data.server_key->rsa->n),
- BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
- SSH_KEY_BITS_RESERVED);
- }
- if (rsa_private_decrypt(session_key_int, session_key_int,
- sensitive_data.server_key->rsa) <= 0)
- rsafail++;
- if (rsa_private_decrypt(session_key_int, session_key_int,
- sensitive_data.ssh1_host_key->rsa) <= 0)
- rsafail++;
- } else {
- /* Host key has bigger modulus (or they are equal). */
- if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
- BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
- fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
- get_remote_ipaddr(),
- BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
- BN_num_bits(sensitive_data.server_key->rsa->n),
- SSH_KEY_BITS_RESERVED);
- }
- if (rsa_private_decrypt(session_key_int, session_key_int,
- sensitive_data.ssh1_host_key->rsa) < 0)
- rsafail++;
- if (rsa_private_decrypt(session_key_int, session_key_int,
- sensitive_data.server_key->rsa) < 0)
- rsafail++;
- }
/*
* Extract session key from the decrypted integer. The key is in the
* least significant 256 bits of the integer; the first byte of the
}
if (rsafail) {
int bytes = BN_num_bytes(session_key_int);
- char *buf = xmalloc(bytes);
+ u_char *buf = xmalloc(bytes);
MD5_CTX md;
log("do_connection: generating a fake encryption key");
for (i = 0; i < 16; i++)
session_id[i] = session_key[i] ^ session_key[i + 16];
}
- /* Destroy the private and public keys. They will no longer be needed. */
+ /* Destroy the private and public keys. No longer. */
destroy_sensitive_data();
+ if (use_privsep)
+ mm_ssh1_session_id(session_id);
+
/* Destroy the decrypted integer. It is no longer needed. */
BN_clear_free(session_key_int);
kex->client_version_string=client_version_string;
kex->server_version_string=server_version_string;
kex->load_host_key=&get_hostkey_by_type;
+ kex->host_key_index=&get_hostkey_index;
xxx_kex = kex;
andersk / openssh.git / blobdiff