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monitor.c
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monitor.c
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/* $OpenBSD: monitor.c,v 1.245 2024/09/22 12:56:21 jsg Exp $ */
/*
* Copyright 2002 Niels Provos <[email protected]>
* Copyright 2002 Markus Friedl <[email protected]>
* 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 <errno.h>
#include <fcntl.h>
#include <limits.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif
#include <pwd.h>
#include <signal.h>
#ifdef HAVE_STDINT_H
# include <stdint.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <stdio.h>
#include <unistd.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#else
# ifdef HAVE_SYS_POLL_H
# include <sys/poll.h>
# endif
#endif
#ifdef WITH_OPENSSL
#include <openssl/dh.h>
#endif
#include "openbsd-compat/sys-tree.h"
#include "openbsd-compat/sys-queue.h"
#include "openbsd-compat/openssl-compat.h"
#include "atomicio.h"
#include "xmalloc.h"
#include "ssh.h"
#include "sshkey.h"
#include "sshbuf.h"
#include "hostfile.h"
#include "auth.h"
#include "cipher.h"
#include "kex.h"
#include "dh.h"
#include "auth-pam.h"
#include "packet.h"
#include "auth-options.h"
#include "sshpty.h"
#include "channels.h"
#include "session.h"
#include "sshlogin.h"
#include "canohost.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "monitor.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "monitor_fdpass.h"
#include "compat.h"
#include "ssh2.h"
#include "authfd.h"
#include "match.h"
#include "ssherr.h"
#include "sk-api.h"
#include "srclimit.h"
#ifdef GSSAPI
static Gssctxt *gsscontext = NULL;
#endif
/* Imports */
extern ServerOptions options;
extern u_int utmp_len;
extern struct sshbuf *cfg;
extern struct sshbuf *loginmsg;
extern struct include_list includes;
extern struct sshauthopt *auth_opts; /* XXX move to permanent ssh->authctxt? */
/* State exported from the child */
static struct sshbuf *child_state;
/* Functions on the monitor that answer unprivileged requests */
int mm_answer_moduli(struct ssh *, int, struct sshbuf *);
int mm_answer_sign(struct ssh *, int, struct sshbuf *);
int mm_answer_pwnamallow(struct ssh *, int, struct sshbuf *);
int mm_answer_auth2_read_banner(struct ssh *, int, struct sshbuf *);
int mm_answer_authserv(struct ssh *, int, struct sshbuf *);
int mm_answer_authpassword(struct ssh *, int, struct sshbuf *);
int mm_answer_bsdauthquery(struct ssh *, int, struct sshbuf *);
int mm_answer_bsdauthrespond(struct ssh *, int, struct sshbuf *);
int mm_answer_keyallowed(struct ssh *, int, struct sshbuf *);
int mm_answer_keyverify(struct ssh *, int, struct sshbuf *);
int mm_answer_pty(struct ssh *, int, struct sshbuf *);
int mm_answer_pty_cleanup(struct ssh *, int, struct sshbuf *);
int mm_answer_term(struct ssh *, int, struct sshbuf *);
int mm_answer_state(struct ssh *, int, struct sshbuf *);
#ifdef USE_PAM
int mm_answer_pam_start(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_account(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_init_ctx(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_query(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_respond(struct ssh *, int, struct sshbuf *);
int mm_answer_pam_free_ctx(struct ssh *, int, struct sshbuf *);
#endif
#ifdef GSSAPI
int mm_answer_gss_setup_ctx(struct ssh *, int, struct sshbuf *);
int mm_answer_gss_accept_ctx(struct ssh *, int, struct sshbuf *);
int mm_answer_gss_userok(struct ssh *, int, struct sshbuf *);
int mm_answer_gss_checkmic(struct ssh *, int, struct sshbuf *);
#endif
#ifdef SSH_AUDIT_EVENTS
int mm_answer_audit_event(struct ssh *, int, struct sshbuf *);
int mm_answer_audit_command(struct ssh *, int, struct sshbuf *);
#endif
static Authctxt *authctxt;
/* local state for key verify */
static u_char *key_blob = NULL;
static size_t key_bloblen = 0;
static u_int key_blobtype = MM_NOKEY;
static struct sshauthopt *key_opts = NULL;
static char *hostbased_cuser = NULL;
static char *hostbased_chost = NULL;
static char *auth_method = "unknown";
static char *auth_submethod = NULL;
static u_int session_id2_len = 0;
static u_char *session_id2 = NULL;
static pid_t monitor_child_pid;
int auth_attempted = 0;
struct mon_table {
enum monitor_reqtype type;
int flags;
int (*f)(struct ssh *, int, struct sshbuf *);
};
#define MON_ISAUTH 0x0004 /* Required for Authentication */
#define MON_AUTHDECIDE 0x0008 /* Decides Authentication */
#define MON_ONCE 0x0010 /* Disable after calling */
#define MON_ALOG 0x0020 /* Log auth attempt without authenticating */
#define MON_AUTH (MON_ISAUTH|MON_AUTHDECIDE)
#define MON_PERMIT 0x1000 /* Request is permitted */
static int monitor_read(struct ssh *, struct monitor *, struct mon_table *,
struct mon_table **);
static int monitor_read_log(struct monitor *);
struct mon_table mon_dispatch_proto20[] = {
{MONITOR_REQ_STATE, MON_ONCE, mm_answer_state},
#ifdef WITH_OPENSSL
{MONITOR_REQ_MODULI, MON_ONCE, mm_answer_moduli},
#endif
{MONITOR_REQ_SIGN, MON_ONCE, mm_answer_sign},
{MONITOR_REQ_PWNAM, MON_ONCE, mm_answer_pwnamallow},
{MONITOR_REQ_AUTHSERV, MON_ONCE, mm_answer_authserv},
{MONITOR_REQ_AUTH2_READ_BANNER, MON_ONCE, mm_answer_auth2_read_banner},
{MONITOR_REQ_AUTHPASSWORD, MON_AUTH, mm_answer_authpassword},
#ifdef USE_PAM
{MONITOR_REQ_PAM_START, MON_ONCE, mm_answer_pam_start},
{MONITOR_REQ_PAM_ACCOUNT, 0, mm_answer_pam_account},
{MONITOR_REQ_PAM_INIT_CTX, MON_ONCE, mm_answer_pam_init_ctx},
{MONITOR_REQ_PAM_QUERY, 0, mm_answer_pam_query},
{MONITOR_REQ_PAM_RESPOND, MON_ONCE, mm_answer_pam_respond},
{MONITOR_REQ_PAM_FREE_CTX, MON_ONCE|MON_AUTHDECIDE, mm_answer_pam_free_ctx},
#endif
#ifdef SSH_AUDIT_EVENTS
{MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
#endif
#ifdef BSD_AUTH
{MONITOR_REQ_BSDAUTHQUERY, MON_ISAUTH, mm_answer_bsdauthquery},
{MONITOR_REQ_BSDAUTHRESPOND, MON_AUTH, mm_answer_bsdauthrespond},
#endif
{MONITOR_REQ_KEYALLOWED, MON_ISAUTH, mm_answer_keyallowed},
{MONITOR_REQ_KEYVERIFY, MON_AUTH, mm_answer_keyverify},
#ifdef GSSAPI
{MONITOR_REQ_GSSSETUP, MON_ISAUTH, mm_answer_gss_setup_ctx},
{MONITOR_REQ_GSSSTEP, 0, mm_answer_gss_accept_ctx},
{MONITOR_REQ_GSSUSEROK, MON_ONCE|MON_AUTHDECIDE, mm_answer_gss_userok},
{MONITOR_REQ_GSSCHECKMIC, MON_ONCE, mm_answer_gss_checkmic},
#endif
{0, 0, NULL}
};
struct mon_table mon_dispatch_postauth20[] = {
{MONITOR_REQ_STATE, MON_ONCE, mm_answer_state},
#ifdef WITH_OPENSSL
{MONITOR_REQ_MODULI, 0, mm_answer_moduli},
#endif
{MONITOR_REQ_SIGN, 0, mm_answer_sign},
{MONITOR_REQ_PTY, 0, mm_answer_pty},
{MONITOR_REQ_PTYCLEANUP, 0, mm_answer_pty_cleanup},
{MONITOR_REQ_TERM, 0, mm_answer_term},
#ifdef SSH_AUDIT_EVENTS
{MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
{MONITOR_REQ_AUDIT_COMMAND, MON_PERMIT, mm_answer_audit_command},
#endif
{0, 0, NULL}
};
struct mon_table *mon_dispatch;
/* Specifies if a certain message is allowed at the moment */
static void
monitor_permit(struct mon_table *ent, enum monitor_reqtype type, int permit)
{
while (ent->f != NULL) {
if (ent->type == type) {
ent->flags &= ~MON_PERMIT;
ent->flags |= permit ? MON_PERMIT : 0;
return;
}
ent++;
}
}
static void
monitor_permit_authentications(int permit)
{
struct mon_table *ent = mon_dispatch;
while (ent->f != NULL) {
if (ent->flags & MON_AUTH) {
ent->flags &= ~MON_PERMIT;
ent->flags |= permit ? MON_PERMIT : 0;
}
ent++;
}
}
void
monitor_child_preauth(struct ssh *ssh, struct monitor *pmonitor)
{
struct mon_table *ent;
int authenticated = 0, partial = 0;
debug3("preauth child monitor started");
if (pmonitor->m_recvfd >= 0)
close(pmonitor->m_recvfd);
if (pmonitor->m_log_sendfd >= 0)
close(pmonitor->m_log_sendfd);
pmonitor->m_log_sendfd = pmonitor->m_recvfd = -1;
authctxt = (Authctxt *)ssh->authctxt;
memset(authctxt, 0, sizeof(*authctxt));
ssh->authctxt = authctxt;
authctxt->loginmsg = loginmsg;
mon_dispatch = mon_dispatch_proto20;
/* Permit requests for state, moduli and signatures */
monitor_permit(mon_dispatch, MONITOR_REQ_STATE, 1);
monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
/* The first few requests do not require asynchronous access */
while (!authenticated) {
partial = 0;
auth_method = "unknown";
auth_submethod = NULL;
auth2_authctxt_reset_info(authctxt);
authenticated = (monitor_read(ssh, pmonitor,
mon_dispatch, &ent) == 1);
/* Record that auth was attempted to set exit status later */
if ((ent->flags & MON_AUTH) != 0)
auth_attempted = 1;
/* Special handling for multiple required authentications */
if (options.num_auth_methods != 0) {
if (authenticated &&
!auth2_update_methods_lists(authctxt,
auth_method, auth_submethod)) {
debug3_f("method %s: partial", auth_method);
authenticated = 0;
partial = 1;
}
}
if (authenticated) {
if (!(ent->flags & MON_AUTHDECIDE))
fatal_f("unexpected authentication from %d",
ent->type);
if (authctxt->pw->pw_uid == 0 &&
!auth_root_allowed(ssh, auth_method))
authenticated = 0;
#ifdef USE_PAM
/* PAM needs to perform account checks after auth */
if (options.use_pam && authenticated) {
struct sshbuf *m;
if ((m = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed",
__func__);
mm_request_receive_expect(pmonitor->m_sendfd,
MONITOR_REQ_PAM_ACCOUNT, m);
authenticated = mm_answer_pam_account(
ssh, pmonitor->m_sendfd, m);
sshbuf_free(m);
}
#endif
}
if (ent->flags & (MON_AUTHDECIDE|MON_ALOG)) {
auth_log(ssh, authenticated, partial,
auth_method, auth_submethod);
if (!partial && !authenticated)
authctxt->failures++;
if (authenticated || partial) {
auth2_update_session_info(authctxt,
auth_method, auth_submethod);
}
}
if (authctxt->failures > options.max_authtries) {
/* Shouldn't happen */
fatal_f("privsep child made too many authentication "
"attempts");
}
}
if (!authctxt->valid)
fatal_f("authenticated invalid user");
if (strcmp(auth_method, "unknown") == 0)
fatal_f("authentication method name unknown");
debug_f("user %s authenticated by privileged process", authctxt->user);
auth_attempted = 0;
ssh->authctxt = NULL;
ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
mm_get_keystate(ssh, pmonitor);
/* Drain any buffered messages from the child */
while (pmonitor->m_log_recvfd != -1 && monitor_read_log(pmonitor) == 0)
;
if (pmonitor->m_recvfd >= 0)
close(pmonitor->m_recvfd);
if (pmonitor->m_log_sendfd >= 0)
close(pmonitor->m_log_sendfd);
pmonitor->m_sendfd = pmonitor->m_log_recvfd = -1;
}
static void
monitor_set_child_handler(pid_t pid)
{
monitor_child_pid = pid;
}
static void
monitor_child_handler(int sig)
{
kill(monitor_child_pid, sig);
}
void
monitor_child_postauth(struct ssh *ssh, struct monitor *pmonitor)
{
close(pmonitor->m_recvfd);
pmonitor->m_recvfd = -1;
monitor_set_child_handler(pmonitor->m_pid);
ssh_signal(SIGHUP, &monitor_child_handler);
ssh_signal(SIGTERM, &monitor_child_handler);
ssh_signal(SIGINT, &monitor_child_handler);
#ifdef SIGXFSZ
ssh_signal(SIGXFSZ, SIG_IGN);
#endif
mon_dispatch = mon_dispatch_postauth20;
/* Permit requests for moduli and signatures */
monitor_permit(mon_dispatch, MONITOR_REQ_STATE, 1);
monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
monitor_permit(mon_dispatch, MONITOR_REQ_TERM, 1);
if (auth_opts->permit_pty_flag) {
monitor_permit(mon_dispatch, MONITOR_REQ_PTY, 1);
monitor_permit(mon_dispatch, MONITOR_REQ_PTYCLEANUP, 1);
}
for (;;)
monitor_read(ssh, pmonitor, mon_dispatch, NULL);
}
static int
monitor_read_log(struct monitor *pmonitor)
{
struct sshbuf *logmsg;
u_int len, level, forced;
char *msg;
u_char *p;
int r;
if ((logmsg = sshbuf_new()) == NULL)
fatal_f("sshbuf_new");
/* Read length */
if ((r = sshbuf_reserve(logmsg, 4, &p)) != 0)
fatal_fr(r, "reserve len");
if (atomicio(read, pmonitor->m_log_recvfd, p, 4) != 4) {
if (errno == EPIPE) {
sshbuf_free(logmsg);
debug_f("child log fd closed");
close(pmonitor->m_log_recvfd);
pmonitor->m_log_recvfd = -1;
return -1;
}
fatal_f("log fd read: %s", strerror(errno));
}
if ((r = sshbuf_get_u32(logmsg, &len)) != 0)
fatal_fr(r, "parse len");
if (len <= 4 || len > 8192)
fatal_f("invalid log message length %u", len);
/* Read severity, message */
sshbuf_reset(logmsg);
if ((r = sshbuf_reserve(logmsg, len, &p)) != 0)
fatal_fr(r, "reserve msg");
if (atomicio(read, pmonitor->m_log_recvfd, p, len) != len)
fatal_f("log fd read: %s", strerror(errno));
if ((r = sshbuf_get_u32(logmsg, &level)) != 0 ||
(r = sshbuf_get_u32(logmsg, &forced)) != 0 ||
(r = sshbuf_get_cstring(logmsg, &msg, NULL)) != 0)
fatal_fr(r, "parse");
/* Log it */
if (log_level_name(level) == NULL)
fatal_f("invalid log level %u (corrupted message?)", level);
sshlogdirect(level, forced, "%s [%s]", msg,
mon_dispatch == mon_dispatch_postauth20 ? "postauth" : "preauth");
sshbuf_free(logmsg);
free(msg);
return 0;
}
static int
monitor_read(struct ssh *ssh, struct monitor *pmonitor, struct mon_table *ent,
struct mon_table **pent)
{
struct sshbuf *m;
int r, ret;
u_char type;
struct pollfd pfd[2];
for (;;) {
memset(&pfd, 0, sizeof(pfd));
pfd[0].fd = pmonitor->m_sendfd;
pfd[0].events = POLLIN;
pfd[1].fd = pmonitor->m_log_recvfd;
pfd[1].events = pfd[1].fd == -1 ? 0 : POLLIN;
if (poll(pfd, pfd[1].fd == -1 ? 1 : 2, -1) == -1) {
if (errno == EINTR || errno == EAGAIN)
continue;
fatal_f("poll: %s", strerror(errno));
}
if (pfd[1].revents) {
/*
* Drain all log messages before processing next
* monitor request.
*/
monitor_read_log(pmonitor);
continue;
}
if (pfd[0].revents)
break; /* Continues below */
}
if ((m = sshbuf_new()) == NULL)
fatal_f("sshbuf_new");
mm_request_receive(pmonitor->m_sendfd, m);
if ((r = sshbuf_get_u8(m, &type)) != 0)
fatal_fr(r, "parse type");
debug3_f("checking request %d", type);
while (ent->f != NULL) {
if (ent->type == type)
break;
ent++;
}
if (ent->f != NULL) {
if (!(ent->flags & MON_PERMIT))
fatal_f("unpermitted request %d", type);
ret = (*ent->f)(ssh, pmonitor->m_sendfd, m);
sshbuf_free(m);
/* The child may use this request only once, disable it */
if (ent->flags & MON_ONCE) {
debug2_f("%d used once, disabling now", type);
ent->flags &= ~MON_PERMIT;
}
if (pent != NULL)
*pent = ent;
return ret;
}
fatal_f("unsupported request: %d", type);
/* NOTREACHED */
return (-1);
}
/* allowed key state */
static int
monitor_allowed_key(const u_char *blob, u_int bloblen)
{
/* make sure key is allowed */
if (key_blob == NULL || key_bloblen != bloblen ||
timingsafe_bcmp(key_blob, blob, key_bloblen))
return (0);
return (1);
}
static void
monitor_reset_key_state(void)
{
/* reset state */
free(key_blob);
free(hostbased_cuser);
free(hostbased_chost);
sshauthopt_free(key_opts);
key_blob = NULL;
key_bloblen = 0;
key_blobtype = MM_NOKEY;
key_opts = NULL;
hostbased_cuser = NULL;
hostbased_chost = NULL;
}
int
mm_answer_state(struct ssh *ssh, int sock, struct sshbuf *m)
{
struct sshbuf *inc = NULL, *hostkeys = NULL;
struct sshbuf *opts = NULL, *confdata = NULL;
struct include_item *item = NULL;
int postauth;
int r;
sshbuf_reset(m);
debug_f("config len %zu", sshbuf_len(cfg));
if ((m = sshbuf_new()) == NULL ||
(inc = sshbuf_new()) == NULL ||
(opts = sshbuf_new()) == NULL ||
(confdata = sshbuf_new()) == NULL)
fatal_f("sshbuf_new failed");
/* XXX unneccessary? */
/* pack includes into a string */
TAILQ_FOREACH(item, &includes, entry) {
if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 ||
(r = sshbuf_put_cstring(inc, item->filename)) != 0 ||
(r = sshbuf_put_stringb(inc, item->contents)) != 0)
fatal_fr(r, "compose includes");
}
hostkeys = pack_hostkeys();
/*
* Protocol from monitor to unpriv privsep process:
* string configuration
* uint64 timing_secret XXX move delays to monitor and remove
* string host_keys[] {
* string public_key
* string certificate
* }
* string server_banner
* string client_banner
* string included_files[] {
* string selector
* string filename
* string contents
* }
* string configuration_data (postauth)
* string keystate (postauth)
* string authenticated_user (postauth)
* string session_info (postauth)
* string authopts (postauth)
*/
if ((r = sshbuf_put_stringb(m, cfg)) != 0 ||
(r = sshbuf_put_u64(m, options.timing_secret)) != 0 ||
(r = sshbuf_put_stringb(m, hostkeys)) != 0 ||
(r = sshbuf_put_stringb(m, ssh->kex->server_version)) != 0 ||
(r = sshbuf_put_stringb(m, ssh->kex->client_version)) != 0 ||
(r = sshbuf_put_stringb(m, inc)) != 0)
fatal_fr(r, "compose config");
postauth = (authctxt && authctxt->pw && authctxt->authenticated);
if (postauth) {
/* XXX shouldn't be reachable */
fatal_f("internal error: called in postauth");
}
sshbuf_free(inc);
sshbuf_free(opts);
sshbuf_free(confdata);
mm_request_send(sock, MONITOR_ANS_STATE, m);
debug3_f("done");
return (0);
}
#ifdef WITH_OPENSSL
int
mm_answer_moduli(struct ssh *ssh, int sock, struct sshbuf *m)
{
DH *dh;
const BIGNUM *dh_p, *dh_g;
int r;
u_int min, want, max;
if ((r = sshbuf_get_u32(m, &min)) != 0 ||
(r = sshbuf_get_u32(m, &want)) != 0 ||
(r = sshbuf_get_u32(m, &max)) != 0)
fatal_fr(r, "parse");
debug3_f("got parameters: %d %d %d", min, want, max);
/* We need to check here, too, in case the child got corrupted */
if (max < min || want < min || max < want)
fatal_f("bad parameters: %d %d %d", min, want, max);
sshbuf_reset(m);
dh = choose_dh(min, want, max);
if (dh == NULL) {
if ((r = sshbuf_put_u8(m, 0)) != 0)
fatal_fr(r, "assemble empty");
return (0);
} else {
/* Send first bignum */
DH_get0_pqg(dh, &dh_p, NULL, &dh_g);
if ((r = sshbuf_put_u8(m, 1)) != 0 ||
(r = sshbuf_put_bignum2(m, dh_p)) != 0 ||
(r = sshbuf_put_bignum2(m, dh_g)) != 0)
fatal_fr(r, "assemble");
DH_free(dh);
}
mm_request_send(sock, MONITOR_ANS_MODULI, m);
return (0);
}
#endif
int
mm_answer_sign(struct ssh *ssh, int sock, struct sshbuf *m)
{
extern int auth_sock; /* XXX move to state struct? */
struct sshkey *pubkey, *key;
struct sshbuf *sigbuf = NULL;
u_char *p = NULL, *signature = NULL;
char *alg = NULL;
size_t datlen, siglen;
int r, is_proof = 0, keyid;
u_int compat;
const char proof_req[] = "[email protected]";
debug3_f("entering");
if ((r = sshkey_froms(m, &pubkey)) != 0 ||
(r = sshbuf_get_string(m, &p, &datlen)) != 0 ||
(r = sshbuf_get_cstring(m, &alg, NULL)) != 0 ||
(r = sshbuf_get_u32(m, &compat)) != 0)
fatal_fr(r, "parse");
if ((keyid = get_hostkey_index(pubkey, 1, ssh)) == -1)
fatal_f("unknown hostkey");
debug_f("hostkey %s index %d", sshkey_ssh_name(pubkey), keyid);
sshkey_free(pubkey);
/*
* Supported KEX types use SHA1 (20 bytes), SHA256 (32 bytes),
* SHA384 (48 bytes) and SHA512 (64 bytes).
*
* Otherwise, verify the signature request is for a hostkey
* proof.
*
* XXX perform similar check for KEX signature requests too?
* it's not trivial, since what is signed is the hash, rather
* than the full kex structure...
*/
if (datlen != 20 && datlen != 32 && datlen != 48 && datlen != 64) {
/*
* Construct expected hostkey proof and compare it to what
* the client sent us.
*/
if (session_id2_len == 0) /* hostkeys is never first */
fatal_f("bad data length: %zu", datlen);
if ((key = get_hostkey_public_by_index(keyid, ssh)) == NULL)
fatal_f("no hostkey for index %d", keyid);
if ((sigbuf = sshbuf_new()) == NULL)
fatal_f("sshbuf_new");
if ((r = sshbuf_put_cstring(sigbuf, proof_req)) != 0 ||
(r = sshbuf_put_string(sigbuf, session_id2,
session_id2_len)) != 0 ||
(r = sshkey_puts(key, sigbuf)) != 0)
fatal_fr(r, "assemble private key proof");
if (datlen != sshbuf_len(sigbuf) ||
memcmp(p, sshbuf_ptr(sigbuf), sshbuf_len(sigbuf)) != 0)
fatal_f("bad data length: %zu, hostkey proof len %zu",
datlen, sshbuf_len(sigbuf));
sshbuf_free(sigbuf);
is_proof = 1;
}
/* save session id, it will be passed on the first call */
if (session_id2_len == 0) {
session_id2_len = datlen;
session_id2 = xmalloc(session_id2_len);
memcpy(session_id2, p, session_id2_len);
}
if ((key = get_hostkey_by_index(keyid)) != NULL) {
if ((r = sshkey_sign(key, &signature, &siglen, p, datlen, alg,
options.sk_provider, NULL, compat)) != 0)
fatal_fr(r, "sign");
} else if ((key = get_hostkey_public_by_index(keyid, ssh)) != NULL &&
auth_sock > 0) {
if ((r = ssh_agent_sign(auth_sock, key, &signature, &siglen,
p, datlen, alg, compat)) != 0)
fatal_fr(r, "agent sign");
} else
fatal_f("no hostkey from index %d", keyid);
debug3_f("%s %s signature len=%zu", alg,
is_proof ? "hostkey proof" : "KEX", siglen);
sshbuf_reset(m);
if ((r = sshbuf_put_string(m, signature, siglen)) != 0)
fatal_fr(r, "assemble");
free(alg);
free(p);
free(signature);
mm_request_send(sock, MONITOR_ANS_SIGN, m);
/* Turn on permissions for getpwnam */
monitor_permit(mon_dispatch, MONITOR_REQ_PWNAM, 1);
return (0);
}
#define PUTPW(b, id) \
do { \
if ((r = sshbuf_put_string(b, \
&pwent->id, sizeof(pwent->id))) != 0) \
fatal_fr(r, "assemble %s", #id); \
} while (0)
void
mm_encode_server_options(struct sshbuf *m)
{
int r;
u_int i;
/* XXX this leaks raw pointers to the unpriv child processes */
if ((r = sshbuf_put_string(m, &options, sizeof(options))) != 0)
fatal_fr(r, "assemble options");
#define M_CP_STROPT(x) do { \
if (options.x != NULL && \
(r = sshbuf_put_cstring(m, options.x)) != 0) \
fatal_fr(r, "assemble %s", #x); \
} while (0)
#define M_CP_STRARRAYOPT(x, nx) do { \
for (i = 0; i < options.nx; i++) { \
if ((r = sshbuf_put_cstring(m, options.x[i])) != 0) \
fatal_fr(r, "assemble %s", #x); \
} \
} while (0)
/* See comment in servconf.h */
COPY_MATCH_STRING_OPTS();
#undef M_CP_STROPT
#undef M_CP_STRARRAYOPT
}
/* Retrieves the password entry and also checks if the user is permitted */
int
mm_answer_pwnamallow(struct ssh *ssh, int sock, struct sshbuf *m)
{
struct passwd *pwent;
int r, allowed = 0;
debug3_f("entering");
if (authctxt->attempt++ != 0)
fatal_f("multiple attempts for getpwnam");
if ((r = sshbuf_get_cstring(m, &authctxt->user, NULL)) != 0)
fatal_fr(r, "parse");
pwent = getpwnamallow(ssh, authctxt->user);
setproctitle("%s [priv]", pwent ? authctxt->user : "unknown");
sshbuf_reset(m);
if (pwent == NULL) {
if ((r = sshbuf_put_u8(m, 0)) != 0)
fatal_fr(r, "assemble fakepw");
authctxt->pw = fakepw();
goto out;
}
allowed = 1;
authctxt->pw = pwent;
authctxt->valid = 1;
/* XXX send fake class/dir/shell, etc. */
if ((r = sshbuf_put_u8(m, 1)) != 0)
fatal_fr(r, "assemble ok");
PUTPW(m, pw_uid);
PUTPW(m, pw_gid);
#ifdef HAVE_STRUCT_PASSWD_PW_CHANGE
PUTPW(m, pw_change);
#endif
#ifdef HAVE_STRUCT_PASSWD_PW_EXPIRE
PUTPW(m, pw_expire);
#endif
if ((r = sshbuf_put_cstring(m, pwent->pw_name)) != 0 ||
(r = sshbuf_put_cstring(m, "*")) != 0 ||
#ifdef HAVE_STRUCT_PASSWD_PW_GECOS
(r = sshbuf_put_cstring(m, pwent->pw_gecos)) != 0 ||
#endif
#ifdef HAVE_STRUCT_PASSWD_PW_CLASS
(r = sshbuf_put_cstring(m, pwent->pw_class)) != 0 ||
#endif
(r = sshbuf_put_cstring(m, pwent->pw_dir)) != 0 ||
(r = sshbuf_put_cstring(m, pwent->pw_shell)) != 0)
fatal_fr(r, "assemble pw");
out:
ssh_packet_set_log_preamble(ssh, "%suser %s",
authctxt->valid ? "authenticating" : "invalid ", authctxt->user);
if (options.refuse_connection) {
logit("administratively prohibited connection for "
"%s%s from %.128s port %d",
authctxt->valid ? "" : "invalid user ",
authctxt->user, ssh_remote_ipaddr(ssh),
ssh_remote_port(ssh));
cleanup_exit(EXIT_CONFIG_REFUSED);
}
/* Send active options to unpriv */
mm_encode_server_options(m);
/* Create valid auth method lists */
if (auth2_setup_methods_lists(authctxt) != 0) {
/*
* The monitor will continue long enough to let the child
* run to its packet_disconnect(), but it must not allow any
* authentication to succeed.
*/
debug_f("no valid authentication method lists");
}
debug3_f("sending MONITOR_ANS_PWNAM: %d", allowed);
mm_request_send(sock, MONITOR_ANS_PWNAM, m);
/* Allow service/style information on the auth context */
monitor_permit(mon_dispatch, MONITOR_REQ_AUTHSERV, 1);
monitor_permit(mon_dispatch, MONITOR_REQ_AUTH2_READ_BANNER, 1);
#ifdef USE_PAM
if (options.use_pam)
monitor_permit(mon_dispatch, MONITOR_REQ_PAM_START, 1);
#endif
return (0);
}
int mm_answer_auth2_read_banner(struct ssh *ssh, int sock, struct sshbuf *m)
{
char *banner;
int r;
sshbuf_reset(m);
banner = auth2_read_banner();
if ((r = sshbuf_put_cstring(m, banner != NULL ? banner : "")) != 0)
fatal_fr(r, "assemble");
mm_request_send(sock, MONITOR_ANS_AUTH2_READ_BANNER, m);
free(banner);
return (0);
}
int
mm_answer_authserv(struct ssh *ssh, int sock, struct sshbuf *m)
{
int r;
monitor_permit_authentications(1);
if ((r = sshbuf_get_cstring(m, &authctxt->service, NULL)) != 0 ||
(r = sshbuf_get_cstring(m, &authctxt->style, NULL)) != 0)
fatal_fr(r, "parse");
debug3_f("service=%s, style=%s", authctxt->service, authctxt->style);
if (strlen(authctxt->style) == 0) {
free(authctxt->style);
authctxt->style = NULL;
}
return (0);
}
/*
* Check that the key type appears in the supplied pattern list, ignoring
* mismatches in the signature algorithm. (Signature algorithm checks are
* performed in the unprivileged authentication code).
* Returns 1 on success, 0 otherwise.
*/
static int
key_base_type_match(const char *method, const struct sshkey *key,
const char *list)
{
char *s, *l, *ol = xstrdup(list);
int found = 0;
l = ol;
for ((s = strsep(&l, ",")); s && *s != '\0'; (s = strsep(&l, ","))) {
if (sshkey_type_from_name(s) == key->type) {
found = 1;
break;
}
}
if (!found) {
error("%s key type %s is not in permitted list %s", method,
sshkey_ssh_name(key), list);
}
free(ol);
return found;
}
int
mm_answer_authpassword(struct ssh *ssh, int sock, struct sshbuf *m)
{
static int call_count;
char *passwd;
int r, authenticated;
size_t plen;
if (!options.password_authentication)
fatal_f("password authentication not enabled");
if ((r = sshbuf_get_cstring(m, &passwd, &plen)) != 0)
fatal_fr(r, "parse");