| /* |
| * 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. |
| * |
| * 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". |
| */ |
| |
| #include "includes.h" |
| RCSID("$OpenBSD: uidswap.c,v 1.16 2001/04/20 16:32:22 markus Exp $"); |
| |
| #include "log.h" |
| #include "uidswap.h" |
| |
| /* |
| * 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. |
| */ |
| |
| #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS) |
| /* 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. */ |
| static uid_t saved_euid = 0; |
| static gid_t saved_egid = 0; |
| #endif |
| |
| /* Saved effective uid. */ |
| static int privileged = 0; |
| static int temporarily_use_uid_effective = 0; |
| static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX]; |
| 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) |
| { |
| /* Save the current euid, and egroups. */ |
| #ifdef SAVED_IDS_WORK_WITH_SETEUID |
| saved_euid = geteuid(); |
| saved_egid = getegid(); |
| debug("temporarily_use_uid: %d/%d (e=%d)", |
| pw->pw_uid, pw->pw_gid, saved_euid); |
| if (saved_euid != 0) { |
| privileged = 0; |
| return; |
| } |
| #else |
| if (geteuid() != 0) { |
| privileged = 0; |
| return; |
| } |
| #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| |
| privileged = 1; |
| temporarily_use_uid_effective = 1; |
| saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups); |
| if (saved_egroupslen < 0) |
| fatal("getgroups: %.100s", strerror(errno)); |
| |
| /* set and save the user's groups */ |
| if (user_groupslen == -1) { |
| if (initgroups(pw->pw_name, pw->pw_gid) < 0) |
| fatal("initgroups: %s: %.100s", pw->pw_name, |
| strerror(errno)); |
| user_groupslen = getgroups(NGROUPS_MAX, user_groups); |
| if (user_groupslen < 0) |
| fatal("getgroups: %.100s", strerror(errno)); |
| } |
| /* Set the effective uid to the given (unprivileged) uid. */ |
| if (setgroups(user_groupslen, user_groups) < 0) |
| fatal("setgroups: %.100s", strerror(errno)); |
| #ifndef SAVED_IDS_WORK_WITH_SETEUID |
| /* Propagate the privileged gid to all of our gids. */ |
| if (setgid(getegid()) < 0) |
| debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno)); |
| /* Propagate the privileged uid to all of our uids. */ |
| if (setuid(geteuid()) < 0) |
| debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno)); |
| #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| if (setegid(pw->pw_gid) < 0) |
| 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)); |
| } |
| |
| /* |
| * Restores to the original (privileged) uid. |
| */ |
| void |
| restore_uid(void) |
| { |
| debug("restore_uid"); |
| /* it's a no-op unless privileged */ |
| if (!privileged) |
| return; |
| if (!temporarily_use_uid_effective) |
| fatal("restore_uid: temporarily_use_uid not effective"); |
| |
| #ifdef SAVED_IDS_WORK_WITH_SETEUID |
| /* Set the effective uid back to the saved privileged uid. */ |
| if (seteuid(saved_euid) < 0) |
| fatal("seteuid %u: %.100s", (u_int) saved_euid, |
| strerror(errno)); |
| if (setegid(saved_egid) < 0) |
| 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. |
| */ |
| setuid(getuid()); |
| setgid(getgid()); |
| #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| |
| if (setgroups(saved_egroupslen, saved_egroups) < 0) |
| fatal("setgroups: %.100s", strerror(errno)); |
| temporarily_use_uid_effective = 0; |
| } |
| |
| /* |
| * 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) |
| { |
| if (temporarily_use_uid_effective) |
| fatal("restore_uid: temporarily_use_uid effective"); |
| if (setgid(pw->pw_gid) < 0) |
| fatal("setgid %u: %.100s", (u_int) pw->pw_gid, strerror(errno)); |
| if (setuid(pw->pw_uid) < 0) |
| fatal("setuid %u: %.100s", (u_int) pw->pw_uid, strerror(errno)); |
| } |