openssh-portable/uidswap.c

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/* $OpenBSD: uidswap.c,v 1.42 2019/06/28 13:35:04 deraadt Exp $ */
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/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Code for uid-swapping.
- (djm) Merge OpenBSD changes: - markus@cvs.openbsd.org 2000/09/05 02:59:57 [session.c] print hostname (not hushlogin) - markus@cvs.openbsd.org 2000/09/05 13:18:48 [authfile.c ssh-add.c] enable ssh-add -d for DSA keys - markus@cvs.openbsd.org 2000/09/05 13:20:49 [sftp-server.c] cleanup - markus@cvs.openbsd.org 2000/09/06 03:46:41 [authfile.h] prototype - deraadt@cvs.openbsd.org 2000/09/07 14:27:56 [ALL] cleanup copyright notices on all files. I have attempted to be accurate with the details. everything is now under Tatu's licence (which I copied from his readme), and/or the core-sdi bsd-ish thing for deattack, or various openbsd developers under a 2-term bsd licence. We're not changing any rules, just being accurate. - markus@cvs.openbsd.org 2000/09/07 14:40:30 [channels.c channels.h clientloop.c serverloop.c ssh.c] cleanup window and packet sizes for ssh2 flow control; ok niels - markus@cvs.openbsd.org 2000/09/07 14:53:00 [scp.c] typo - markus@cvs.openbsd.org 2000/09/07 15:13:37 [auth-options.c auth-options.h auth-rh-rsa.c auth-rsa.c auth.c] [authfile.h canohost.c channels.h compat.c hostfile.h log.c match.h] [pty.c readconf.c] some more Copyright fixes - markus@cvs.openbsd.org 2000/09/08 03:02:51 [README.openssh2] bye bye - deraadt@cvs.openbsd.org 2000/09/11 18:38:33 [LICENCE cipher.c] a few more comments about it being ARC4 not RC4 - markus@cvs.openbsd.org 2000/09/12 14:53:11 [log-client.c log-server.c log.c ssh.1 ssh.c ssh.h sshd.8 sshd.c] multiple debug levels - markus@cvs.openbsd.org 2000/09/14 14:25:15 [clientloop.c] typo - deraadt@cvs.openbsd.org 2000/09/15 01:13:51 [ssh-agent.c] check return value for setenv(3) for failure, and deal appropriately
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*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*/
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#include "includes.h"
#include <errno.h>
#include <pwd.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
- deraadt@cvs.openbsd.org 2006/08/03 03:34:42 [OVERVIEW atomicio.c atomicio.h auth-bsdauth.c auth-chall.c auth-krb5.c] [auth-options.c auth-options.h auth-passwd.c auth-rh-rsa.c auth-rhosts.c] [auth-rsa.c auth-skey.c auth.c auth.h auth1.c auth2-chall.c auth2-gss.c] [auth2-hostbased.c auth2-kbdint.c auth2-none.c auth2-passwd.c ] [auth2-pubkey.c auth2.c authfd.c authfd.h authfile.c bufaux.c bufbn.c] [buffer.c buffer.h canohost.c channels.c channels.h cipher-3des1.c] [cipher-bf1.c cipher-ctr.c cipher.c cleanup.c clientloop.c compat.c] [compress.c deattack.c dh.c dispatch.c dns.c dns.h fatal.c groupaccess.c] [groupaccess.h gss-genr.c gss-serv-krb5.c gss-serv.c hostfile.c kex.c] [kex.h kexdh.c kexdhc.c kexdhs.c kexgex.c kexgexc.c kexgexs.c key.c] [key.h log.c log.h mac.c match.c md-sha256.c misc.c misc.h moduli.c] [monitor.c monitor_fdpass.c monitor_mm.c monitor_mm.h monitor_wrap.c] [monitor_wrap.h msg.c nchan.c packet.c progressmeter.c readconf.c] [readconf.h readpass.c rsa.c scard.c scard.h scp.c servconf.c servconf.h] [serverloop.c session.c session.h sftp-client.c sftp-common.c] [sftp-common.h sftp-glob.c sftp-server.c sftp.c ssh-add.c ssh-agent.c] [ssh-dss.c ssh-gss.h ssh-keygen.c ssh-keyscan.c ssh-keysign.c ssh-rsa.c] [ssh.c ssh.h sshconnect.c sshconnect.h sshconnect1.c sshconnect2.c] [sshd.c sshlogin.c sshlogin.h sshpty.c sshpty.h sshtty.c ttymodes.c] [uidswap.c uidswap.h uuencode.c uuencode.h xmalloc.c xmalloc.h] [loginrec.c loginrec.h openbsd-compat/port-aix.c openbsd-compat/port-tun.h] almost entirely get rid of the culture of ".h files that include .h files" ok djm, sort of ok stevesk makes the pain stop in one easy step NB. portable commit contains everything *except* removing includes.h, as that will take a fair bit more work as we move headers that are required for portability workarounds to defines.h. (also, this step wasn't "easy")
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#include <stdarg.h>
#include <stdlib.h>
#include <grp.h>
Hopefully things did not get mixed around too much. It compiles under Linux and works. So that is at least a good sign. =) 20010122 - (bal) OpenBSD Resync - markus@cvs.openbsd.org 2001/01/19 12:45:26 GMT 2001 by markus [servconf.c ssh.h sshd.c] only auth-chall.c needs #ifdef SKEY - markus@cvs.openbsd.org 2001/01/19 15:55:10 GMT 2001 by markus [auth-krb4.c auth-options.c auth-rh-rsa.c auth-rhosts.c auth-rsa.c auth1.c auth2.c channels.c clientloop.c dh.c dispatch.c nchan.c packet.c pathname.h readconf.c scp.c servconf.c serverloop.c session.c ssh-add.c ssh-keygen.c ssh-keyscan.c ssh.c ssh.h ssh1.h sshconnect1.c sshd.c ttymodes.c] move ssh1 definitions to ssh1.h, pathnames to pathnames.h - markus@cvs.openbsd.org 2001/01/19 16:48:14 [sshd.8] fix typo; from stevesk@ - markus@cvs.openbsd.org 2001/01/19 16:50:58 [ssh-dss.c] clear and free digest, make consistent with other code (use dlen); from stevesk@ - markus@cvs.openbsd.org 2001/01/20 15:55:20 GMT 2001 by markus [auth-options.c auth-options.h auth-rsa.c auth2.c] pass the filename to auth_parse_options() - markus@cvs.openbsd.org 2001/01/20 17:59:40 GMT 2001 [readconf.c] fix SIGSEGV from -o ""; problem noted by jehsom@togetherweb.com - stevesk@cvs.openbsd.org 2001/01/20 18:20:29 [sshconnect2.c] dh_new_group() does not return NULL. ok markus@ - markus@cvs.openbsd.org 2001/01/20 21:33:42 [ssh-add.c] do not loop forever if askpass does not exist; from andrew@pimlott.ne.mediaone.net - djm@cvs.openbsd.org 2001/01/20 23:00:56 [servconf.c] Check for NULL return from strdelim; ok markus - djm@cvs.openbsd.org 2001/01/20 23:02:07 [readconf.c] KNF; ok markus - jakob@cvs.openbsd.org 2001/01/21 9:00:33 [ssh-keygen.1] remove -R flag; ok markus@ - markus@cvs.openbsd.org 2001/01/21 19:05:40 [atomicio.c automicio.h auth-chall.c auth-krb4.c auth-options.c auth-options.h auth-passwd.c auth-rh-rsa.c auth-rhosts.c auth-rsa.c auth.c auth.h auth1.c auth2-chall.c auth2.c authfd.c authfile.c bufaux.c bufaux.h buffer.c canahost.c canahost.h channels.c cipher.c cli.c clientloop.c clientloop.h compat.c compress.c deattack.c dh.c dispatch.c groupaccess.c hmac.c hostfile.c kex.c key.c key.h log-client.c log-server.c log.c log.h login.c login.h match.c misc.c misc.h nchan.c packet.c pty.c radix.h readconf.c readpass.c readpass.h rsa.c scp.c servconf.c serverloop.c serverloop.h session.c sftp-server.c ssh-add.c ssh-agent.c ssh-dss.c ssh-keygen.c ssh-keyscan.c ssh-rsa.c ssh.c ssh.h sshconnect.c sshconnect.h sshconnect1.c sshconnect2.c sshd.c tildexpand.c tildexpand.h ttysmodes.c uidswap.c xmalloc.c] split ssh.h and try to cleanup the #include mess. remove unnecessary #includes. rename util.[ch] -> misc.[ch] - (bal) renamed 'PIDDIR' to '_PATH_SSH_PIDDIR' to match OpenBSD tree - (bal) Moved #ifdef KRB4 in auth-krb4.c above the #include to resolve conflict when compiling for non-kerb install - (bal) removed the #ifdef SKEY in auth1.c to match Markus' changes on 1/19.
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#include "log.h"
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#include "uidswap.h"
#include "xmalloc.h"
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/*
* Note: all these functions must work in all of the following cases:
* 1. euid=0, ruid=0
* 2. euid=0, ruid!=0
* 3. euid!=0, ruid!=0
* Additionally, they must work regardless of whether the system has
* POSIX saved uids or not.
*/
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#if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS)
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/* Lets assume that posix saved ids also work with seteuid, even though that
is not part of the posix specification. */
#define SAVED_IDS_WORK_WITH_SETEUID
/* Saved effective uid. */
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static uid_t saved_euid = 0;
static gid_t saved_egid = 0;
#endif
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/* Saved effective uid. */
static int privileged = 0;
static int temporarily_use_uid_effective = 0;
static uid_t user_groups_uid;
static gid_t *saved_egroups = NULL, *user_groups = NULL;
static int saved_egroupslen = -1, user_groupslen = -1;
/*
* Temporarily changes to the given uid. If the effective user
* id is not root, this does nothing. This call cannot be nested.
*/
void
temporarily_use_uid(struct passwd *pw)
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{
/* Save the current euid, and egroups. */
#ifdef SAVED_IDS_WORK_WITH_SETEUID
saved_euid = geteuid();
saved_egid = getegid();
debug("temporarily_use_uid: %u/%u (e=%u/%u)",
(u_int)pw->pw_uid, (u_int)pw->pw_gid,
(u_int)saved_euid, (u_int)saved_egid);
#ifndef HAVE_CYGWIN
if (saved_euid != 0) {
privileged = 0;
return;
}
#endif
#else
if (geteuid() != 0) {
privileged = 0;
return;
}
#endif /* SAVED_IDS_WORK_WITH_SETEUID */
privileged = 1;
temporarily_use_uid_effective = 1;
saved_egroupslen = getgroups(0, NULL);
if (saved_egroupslen == -1)
fatal("getgroups: %.100s", strerror(errno));
if (saved_egroupslen > 0) {
saved_egroups = xreallocarray(saved_egroups,
saved_egroupslen, sizeof(gid_t));
if (getgroups(saved_egroupslen, saved_egroups) == -1)
fatal("getgroups: %.100s", strerror(errno));
} else { /* saved_egroupslen == 0 */
free(saved_egroups);
saved_egroups = NULL;
}
/* set and save the user's groups */
if (user_groupslen == -1 || user_groups_uid != pw->pw_uid) {
if (initgroups(pw->pw_name, pw->pw_gid) == -1)
fatal("initgroups: %s: %.100s", pw->pw_name,
strerror(errno));
user_groupslen = getgroups(0, NULL);
if (user_groupslen == -1)
fatal("getgroups: %.100s", strerror(errno));
if (user_groupslen > 0) {
user_groups = xreallocarray(user_groups,
user_groupslen, sizeof(gid_t));
if (getgroups(user_groupslen, user_groups) == -1)
fatal("getgroups: %.100s", strerror(errno));
} else { /* user_groupslen == 0 */
free(user_groups);
user_groups = NULL;
}
user_groups_uid = pw->pw_uid;
}
/* Set the effective uid to the given (unprivileged) uid. */
if (setgroups(user_groupslen, user_groups) == -1)
fatal("setgroups: %.100s", strerror(errno));
#ifndef SAVED_IDS_WORK_WITH_SETEUID
/* Propagate the privileged gid to all of our gids. */
if (setgid(getegid()) == -1)
debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
/* Propagate the privileged uid to all of our uids. */
if (setuid(geteuid()) == -1)
debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
#endif /* SAVED_IDS_WORK_WITH_SETEUID */
if (setegid(pw->pw_gid) == -1)
fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
strerror(errno));
if (seteuid(pw->pw_uid) == -1)
fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
strerror(errno));
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}
/*
* Restores to the original (privileged) uid.
*/
void
restore_uid(void)
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{
/* it's a no-op unless privileged */
if (!privileged) {
debug("restore_uid: (unprivileged)");
return;
}
if (!temporarily_use_uid_effective)
fatal("restore_uid: temporarily_use_uid not effective");
#ifdef SAVED_IDS_WORK_WITH_SETEUID
debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
/* Set the effective uid back to the saved privileged uid. */
if (seteuid(saved_euid) == -1)
fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
if (setegid(saved_egid) == -1)
fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
#else /* SAVED_IDS_WORK_WITH_SETEUID */
/*
* We are unable to restore the real uid to its unprivileged value.
* Propagate the real uid (usually more privileged) to effective uid
* as well.
*/
if (setuid(getuid()) == -1)
fatal("%s: setuid failed: %s", __func__, strerror(errno));
if (setgid(getgid()) == -1)
fatal("%s: setgid failed: %s", __func__, strerror(errno));
#endif /* SAVED_IDS_WORK_WITH_SETEUID */
if (setgroups(saved_egroupslen, saved_egroups) == -1)
fatal("setgroups: %.100s", strerror(errno));
temporarily_use_uid_effective = 0;
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}
/*
* Permanently sets all uids to the given uid. This cannot be
* called while temporarily_use_uid is effective.
*/
void
permanently_set_uid(struct passwd *pw)
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{
#ifndef NO_UID_RESTORATION_TEST
uid_t old_uid = getuid();
gid_t old_gid = getgid();
#endif
if (pw == NULL)
fatal("permanently_set_uid: no user given");
if (temporarily_use_uid_effective)
fatal("permanently_set_uid: temporarily_use_uid effective");
debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
(u_int)pw->pw_gid);
if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1)
fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
#ifdef __APPLE__
/*
* OS X requires initgroups after setgid to opt back into
* memberd support for >16 supplemental groups.
*/
if (initgroups(pw->pw_name, pw->pw_gid) == -1)
fatal("initgroups %.100s %u: %.100s",
pw->pw_name, (u_int)pw->pw_gid, strerror(errno));
#endif
if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1)
fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
#ifndef NO_UID_RESTORATION_TEST
/* Try restoration of GID if changed (test clearing of saved gid) */
if (old_gid != pw->pw_gid && pw->pw_uid != 0 &&
(setgid(old_gid) != -1 || setegid(old_gid) != -1))
fatal("%s: was able to restore old [e]gid", __func__);
#endif
/* Verify GID drop was successful */
if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) {
fatal("%s: egid incorrect gid:%u egid:%u (should be %u)",
__func__, (u_int)getgid(), (u_int)getegid(),
(u_int)pw->pw_gid);
}
#ifndef NO_UID_RESTORATION_TEST
/* Try restoration of UID if changed (test clearing of saved uid) */
if (old_uid != pw->pw_uid &&
(setuid(old_uid) != -1 || seteuid(old_uid) != -1))
fatal("%s: was able to restore old [e]uid", __func__);
#endif
/* Verify UID drop was successful */
if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) {
fatal("%s: euid incorrect uid:%u euid:%u (should be %u)",
__func__, (u_int)getuid(), (u_int)geteuid(),
(u_int)pw->pw_uid);
}
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}