X-Git-Url: http://andersk.mit.edu/gitweb/openssh.git/blobdiff_plain/8efc0c151a0f57612e1aa0abb5b7d536db4cf76a..9a6fee8b2b42608a177803d2351d3cfe732910d8:/uidswap.c diff --git a/uidswap.c b/uidswap.c index de9e4625..86c61a4b 100644 --- a/uidswap.c +++ b/uidswap.c @@ -1,95 +1,154 @@ /* - -uidswap.c - -Author: Tatu Ylonen - -Copyright (c) 1995 Tatu Ylonen , Espoo, Finland - All rights reserved - -Created: Sat Sep 9 01:56:14 1995 ylo - -Code for uid-swapping. - -*/ + * Author: Tatu Ylonen + * Copyright (c) 1995 Tatu Ylonen , 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("$Id$"); +RCSID("$OpenBSD: uidswap.c,v 1.23 2002/07/15 17:15:31 stevesk Exp $"); -#include "ssh.h" +#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. */ - -#ifdef _POSIX_SAVED_IDS +/* + * 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 -#endif /* _POSIX_SAVED_IDS */ - /* Saved effective uid. */ -static uid_t saved_euid = 0; +static uid_t saved_euid = 0; +static gid_t saved_egid = 0; +#endif -/* Temporarily changes to the given uid. If the effective user id is not - root, this does nothing. This call cannot be nested. */ +/* 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; -void temporarily_use_uid(uid_t uid) +/* + * 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 - - /* Save the current euid. */ - saved_euid = geteuid(); - - /* Set the effective uid to the given (unprivileged) uid. */ - if (seteuid(uid) == -1) - debug("seteuid %d: %.100s", (int)uid, strerror(errno)); - -#else /* SAVED_IDS_WORK_WITH_SETUID */ - - /* Propagate the privileged uid to all of our uids. */ - if (setuid(geteuid()) < 0) - debug("setuid %d: %.100s", (int)geteuid(), strerror(errno)); - - /* Set the effective uid to the given (unprivileged) uid. */ - if (seteuid(uid) == -1) - debug("seteuid %d: %.100s", (int)uid, strerror(errno)); - + 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); + 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 uid. */ - -void restore_uid() +/* + * Restores to the original (privileged) uid. + */ +void +restore_uid(void) { -#ifdef SAVED_IDS_WORK_WITH_SETEUID - - /* Set the effective uid back to the saved uid. */ - if (seteuid(saved_euid) < 0) - debug("seteuid %d: %.100s", (int)saved_euid, strerror(errno)); + /* 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) < 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()); - + /* + * 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 */ -} -/* Permanently sets all uids to the given uid. This cannot be called while - temporarily_use_uid is effective. */ + if (setgroups(saved_egroupslen, saved_egroups) < 0) + fatal("setgroups: %.100s", strerror(errno)); + temporarily_use_uid_effective = 0; +} -void permanently_set_uid(uid_t uid) +/* + * 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 (setuid(uid) < 0) - debug("setuid %d: %.100s", (int)uid, strerror(errno)); + 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 (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)); }