150 lines
4.6 KiB
C
150 lines
4.6 KiB
C
/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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* Code for uid-swapping.
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*
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* As far as I am concerned, the code I have written for this software
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* can be used freely for any purpose. Any derived versions of this
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* software must be clearly marked as such, and if the derived work is
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* incompatible with the protocol description in the RFC file, it must be
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* called by a name other than "ssh" or "Secure Shell".
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*/
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#include "includes.h"
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RCSID("$OpenBSD: uidswap.c,v 1.22 2002/05/28 21:24:00 stevesk Exp $");
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#include "log.h"
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#include "uidswap.h"
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/*
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* Note: all these functions must work in all of the following cases:
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* 1. euid=0, ruid=0
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* 2. euid=0, ruid!=0
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* 3. euid!=0, ruid!=0
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* Additionally, they must work regardless of whether the system has
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* POSIX saved uids or not.
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*/
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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
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is not part of the posix specification. */
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#define SAVED_IDS_WORK_WITH_SETEUID
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/* Saved effective uid. */
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static uid_t saved_euid = 0;
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static gid_t saved_egid = 0;
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#endif
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/* Saved effective uid. */
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static int privileged = 0;
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static int temporarily_use_uid_effective = 0;
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static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
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static int saved_egroupslen = -1, user_groupslen = -1;
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/*
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* Temporarily changes to the given uid. If the effective user
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* id is not root, this does nothing. This call cannot be nested.
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*/
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void
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temporarily_use_uid(struct passwd *pw)
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{
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/* Save the current euid, and egroups. */
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#ifdef SAVED_IDS_WORK_WITH_SETEUID
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saved_euid = geteuid();
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saved_egid = getegid();
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debug("temporarily_use_uid: %u/%u (e=%u)",
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(u_int)pw->pw_uid, (u_int)pw->pw_gid, (u_int)saved_euid);
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if (saved_euid != 0) {
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privileged = 0;
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return;
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}
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#else
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if (geteuid() != 0) {
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privileged = 0;
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return;
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}
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#endif /* SAVED_IDS_WORK_WITH_SETEUID */
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privileged = 1;
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temporarily_use_uid_effective = 1;
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saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
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if (saved_egroupslen < 0)
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fatal("getgroups: %.100s", strerror(errno));
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/* set and save the user's groups */
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if (user_groupslen == -1) {
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if (initgroups(pw->pw_name, pw->pw_gid) < 0)
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fatal("initgroups: %s: %.100s", pw->pw_name,
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strerror(errno));
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user_groupslen = getgroups(NGROUPS_MAX, user_groups);
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if (user_groupslen < 0)
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fatal("getgroups: %.100s", strerror(errno));
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}
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/* Set the effective uid to the given (unprivileged) uid. */
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if (setgroups(user_groupslen, user_groups) < 0)
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fatal("setgroups: %.100s", strerror(errno));
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#ifndef SAVED_IDS_WORK_WITH_SETEUID
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/* Propagate the privileged gid to all of our gids. */
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if (setgid(getegid()) < 0)
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debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno));
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/* Propagate the privileged uid to all of our uids. */
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if (setuid(geteuid()) < 0)
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debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
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#endif /* SAVED_IDS_WORK_WITH_SETEUID */
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if (setegid(pw->pw_gid) < 0)
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fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
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strerror(errno));
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if (seteuid(pw->pw_uid) == -1)
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fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
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strerror(errno));
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}
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/*
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* Restores to the original (privileged) uid.
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*/
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void
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restore_uid(void)
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{
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debug("restore_uid");
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/* it's a no-op unless privileged */
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if (!privileged)
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return;
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if (!temporarily_use_uid_effective)
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fatal("restore_uid: temporarily_use_uid not effective");
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#ifdef SAVED_IDS_WORK_WITH_SETEUID
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/* Set the effective uid back to the saved privileged uid. */
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if (seteuid(saved_euid) < 0)
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fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
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if (setegid(saved_egid) < 0)
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fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
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#else /* SAVED_IDS_WORK_WITH_SETEUID */
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/*
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* We are unable to restore the real uid to its unprivileged value.
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* Propagate the real uid (usually more privileged) to effective uid
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* as well.
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*/
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setuid(getuid());
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setgid(getgid());
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#endif /* SAVED_IDS_WORK_WITH_SETEUID */
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if (setgroups(saved_egroupslen, saved_egroups) < 0)
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fatal("setgroups: %.100s", strerror(errno));
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temporarily_use_uid_effective = 0;
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}
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/*
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* Permanently sets all uids to the given uid. This cannot be
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* called while temporarily_use_uid is effective.
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*/
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void
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permanently_set_uid(struct passwd *pw)
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{
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if (temporarily_use_uid_effective)
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fatal("permanently_set_uid: temporarily_use_uid effective");
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if (setgid(pw->pw_gid) < 0)
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fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
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if (setuid(pw->pw_uid) < 0)
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fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
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}
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