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Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.9.2.1

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"
1.9.2.1 ! jason      15: RCSID("$OpenBSD: uidswap.c,v 1.13 2001/01/21 19:06:01 markus Exp $");
1.1       deraadt    16:
1.9.2.1 ! jason      17: #include "log.h"
1.1       deraadt    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: /* Saved effective uid. */
                     34: static uid_t saved_euid = 0;
1.9.2.1 ! jason      35: #endif /* _POSIX_SAVED_IDS */
1.1       deraadt    36:
1.4       deraadt    37: /*
                     38:  * Temporarily changes to the given uid.  If the effective user
                     39:  * id is not root, this does nothing.  This call cannot be nested.
                     40:  */
1.6       markus     41: void
1.3       markus     42: temporarily_use_uid(uid_t uid)
1.1       deraadt    43: {
                     44: #ifdef SAVED_IDS_WORK_WITH_SETEUID
1.3       markus     45:        /* Save the current euid. */
                     46:        saved_euid = geteuid();
1.1       deraadt    47:
1.3       markus     48:        /* Set the effective uid to the given (unprivileged) uid. */
                     49:        if (seteuid(uid) == -1)
1.8       deraadt    50:                debug("seteuid %u: %.100s", (u_int) uid, strerror(errno));
1.9.2.1 ! jason      51: #else /* SAVED_IDS_WORK_WITH_SETEUID */
1.3       markus     52:        /* Propagate the privileged uid to all of our uids. */
                     53:        if (setuid(geteuid()) < 0)
1.8       deraadt    54:                debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno));
1.3       markus     55:
                     56:        /* Set the effective uid to the given (unprivileged) uid. */
                     57:        if (seteuid(uid) == -1)
1.8       deraadt    58:                debug("seteuid %u: %.100s", (u_int) uid, strerror(errno));
1.1       deraadt    59: #endif /* SAVED_IDS_WORK_WITH_SETEUID */
                     60: }
                     61:
1.4       deraadt    62: /*
                     63:  * Restores to the original uid.
                     64:  */
1.6       markus     65: void
1.9.2.1 ! jason      66: restore_uid(void)
1.1       deraadt    67: {
                     68: #ifdef SAVED_IDS_WORK_WITH_SETEUID
1.3       markus     69:        /* Set the effective uid back to the saved uid. */
                     70:        if (seteuid(saved_euid) < 0)
1.8       deraadt    71:                debug("seteuid %u: %.100s", (u_int) saved_euid, strerror(errno));
1.1       deraadt    72: #else /* SAVED_IDS_WORK_WITH_SETEUID */
1.5       markus     73:        /*
                     74:         * We are unable to restore the real uid to its unprivileged value.
                     75:         * Propagate the real uid (usually more privileged) to effective uid
                     76:         * as well.
                     77:         */
1.3       markus     78:        setuid(getuid());
1.1       deraadt    79: #endif /* SAVED_IDS_WORK_WITH_SETEUID */
                     80: }
                     81:
1.4       deraadt    82: /*
                     83:  * Permanently sets all uids to the given uid.  This cannot be
                     84:  * called while temporarily_use_uid is effective.
                     85:  */
1.6       markus     86: void
1.3       markus     87: permanently_set_uid(uid_t uid)
1.1       deraadt    88: {
1.3       markus     89:        if (setuid(uid) < 0)
1.8       deraadt    90:                debug("setuid %u: %.100s", (u_int) uid, strerror(errno));
1.1       deraadt    91: }