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Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.9

1.1       deraadt     1: /*
1.4       deraadt     2:  * Author: Tatu Ylonen <ylo@cs.hut.fi>
                      3:  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
                      4:  *                    All rights reserved
                      5:  * Code for uid-swapping.
1.9     ! deraadt     6:  *
        !             7:  * As far as I am concerned, the code I have written for this software
        !             8:  * can be used freely for any purpose.  Any derived versions of this
        !             9:  * software must be clearly marked as such, and if the derived work is
        !            10:  * incompatible with the protocol description in the RFC file, it must be
        !            11:  * called by a name other than "ssh" or "Secure Shell".
1.4       deraadt    12:  */
1.1       deraadt    13:
                     14: #include "includes.h"
1.9     ! deraadt    15: RCSID("$OpenBSD: uidswap.c,v 1.8 2000/08/28 03:50:54 deraadt Exp $");
1.1       deraadt    16:
                     17: #include "ssh.h"
                     18: #include "uidswap.h"
                     19:
1.4       deraadt    20: /*
                     21:  * Note: all these functions must work in all of the following cases:
                     22:  *    1. euid=0, ruid=0
                     23:  *    2. euid=0, ruid!=0
                     24:  *    3. euid!=0, ruid!=0
                     25:  * Additionally, they must work regardless of whether the system has
                     26:  * POSIX saved uids or not.
                     27:  */
1.1       deraadt    28:
                     29: #ifdef _POSIX_SAVED_IDS
                     30: /* Lets assume that posix saved ids also work with seteuid, even though that
                     31:    is not part of the posix specification. */
                     32: #define SAVED_IDS_WORK_WITH_SETEUID
                     33: #endif /* _POSIX_SAVED_IDS */
                     34:
                     35: /* Saved effective uid. */
                     36: static uid_t saved_euid = 0;
                     37:
1.4       deraadt    38: /*
                     39:  * Temporarily changes to the given uid.  If the effective user
                     40:  * id is not root, this does nothing.  This call cannot be nested.
                     41:  */
1.6       markus     42: void
1.3       markus     43: temporarily_use_uid(uid_t uid)
1.1       deraadt    44: {
                     45: #ifdef SAVED_IDS_WORK_WITH_SETEUID
1.3       markus     46:        /* Save the current euid. */
                     47:        saved_euid = geteuid();
1.1       deraadt    48:
1.3       markus     49:        /* Set the effective uid to the given (unprivileged) uid. */
                     50:        if (seteuid(uid) == -1)
1.8       deraadt    51:                debug("seteuid %u: %.100s", (u_int) uid, strerror(errno));
1.1       deraadt    52: #else /* SAVED_IDS_WORK_WITH_SETUID */
1.3       markus     53:        /* Propagate the privileged uid to all of our uids. */
                     54:        if (setuid(geteuid()) < 0)
1.8       deraadt    55:                debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
1.3       markus     56:
                     57:        /* Set the effective uid to the given (unprivileged) uid. */
                     58:        if (seteuid(uid) == -1)
1.8       deraadt    59:                debug("seteuid %u: %.100s", (u_int) uid, strerror(errno));
1.1       deraadt    60: #endif /* SAVED_IDS_WORK_WITH_SETEUID */
                     61: }
                     62:
1.4       deraadt    63: /*
                     64:  * Restores to the original uid.
                     65:  */
1.6       markus     66: void
1.3       markus     67: restore_uid()
1.1       deraadt    68: {
                     69: #ifdef SAVED_IDS_WORK_WITH_SETEUID
1.3       markus     70:        /* Set the effective uid back to the saved uid. */
                     71:        if (seteuid(saved_euid) < 0)
1.8       deraadt    72:                debug("seteuid %u: %.100s", (u_int) saved_euid, strerror(errno));
1.1       deraadt    73: #else /* SAVED_IDS_WORK_WITH_SETEUID */
1.5       markus     74:        /*
                     75:         * We are unable to restore the real uid to its unprivileged value.
                     76:         * Propagate the real uid (usually more privileged) to effective uid
                     77:         * as well.
                     78:         */
1.3       markus     79:        setuid(getuid());
1.1       deraadt    80: #endif /* SAVED_IDS_WORK_WITH_SETEUID */
                     81: }
                     82:
1.4       deraadt    83: /*
                     84:  * Permanently sets all uids to the given uid.  This cannot be
                     85:  * called while temporarily_use_uid is effective.
                     86:  */
1.6       markus     87: void
1.3       markus     88: permanently_set_uid(uid_t uid)
1.1       deraadt    89: {
1.3       markus     90:        if (setuid(uid) < 0)
1.8       deraadt    91:                debug("setuid %u: %.100s", (u_int) uid, strerror(errno));
1.1       deraadt    92: }