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Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.1

1.1     ! deraadt     1: /*
        !             2:
        !             3: uidswap.c
        !             4:
        !             5: Author: Tatu Ylonen <ylo@cs.hut.fi>
        !             6:
        !             7: Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
        !             8:                    All rights reserved
        !             9:
        !            10: Created: Sat Sep  9 01:56:14 1995 ylo
        !            11:
        !            12: Code for uid-swapping.
        !            13:
        !            14: */
        !            15:
        !            16: #include "includes.h"
        !            17: RCSID("$Id: uidswap.c,v 1.2 1999/05/04 11:59:27 bg Exp $");
        !            18:
        !            19: #include "ssh.h"
        !            20: #include "uidswap.h"
        !            21:
        !            22: /* Note: all these functions must work in all of the following cases:
        !            23:
        !            24:    1. euid=0, ruid=0
        !            25:    2. euid=0, ruid!=0
        !            26:    3. euid!=0, ruid!=0
        !            27:
        !            28:    Additionally, they must work regardless of whether the system has
        !            29:    POSIX saved uids or not. */
        !            30:
        !            31: #ifdef HAVE_SETEUID
        !            32:
        !            33: #ifdef _POSIX_SAVED_IDS
        !            34: /* Lets assume that posix saved ids also work with seteuid, even though that
        !            35:    is not part of the posix specification. */
        !            36: #define SAVED_IDS_WORK_WITH_SETEUID
        !            37: #endif /* _POSIX_SAVED_IDS */
        !            38:
        !            39: /* Saved effective uid. */
        !            40: static uid_t saved_euid = 0;
        !            41:
        !            42: /* Temporarily changes to the given uid.  If the effective user id is not
        !            43:    root, this does nothing.  This call cannot be nested. */
        !            44:
        !            45: void temporarily_use_uid(uid_t uid)
        !            46: {
        !            47: #ifdef SAVED_IDS_WORK_WITH_SETEUID
        !            48:
        !            49:   /* Save the current euid. */
        !            50:   saved_euid = geteuid();
        !            51:
        !            52:   /* Set the effective uid to the given (unprivileged) uid. */
        !            53:   if (seteuid(uid) == -1)
        !            54:     debug("seteuid %d: %.100s", (int)uid, strerror(errno));
        !            55:
        !            56: #else /* SAVED_IDS_WORK_WITH_SETUID */
        !            57:
        !            58:   /* Propagate the privileged uid to all of our uids. */
        !            59:   if (setuid(geteuid()) < 0)
        !            60:     debug("setuid %d: %.100s", (int)geteuid(), strerror(errno));
        !            61:
        !            62:   /* Set the effective uid to the given (unprivileged) uid. */
        !            63:   if (seteuid(uid) == -1)
        !            64:     debug("seteuid %d: %.100s", (int)uid, strerror(errno));
        !            65:
        !            66: #endif /* SAVED_IDS_WORK_WITH_SETEUID */
        !            67:
        !            68: }
        !            69:
        !            70: /* Restores to the original uid. */
        !            71:
        !            72: void restore_uid()
        !            73: {
        !            74: #ifdef SAVED_IDS_WORK_WITH_SETEUID
        !            75:
        !            76:   /* Set the effective uid back to the saved uid. */
        !            77:   if (seteuid(saved_euid) < 0)
        !            78:     debug("seteuid %d: %.100s", (int)saved_euid, strerror(errno));
        !            79:
        !            80: #else /* SAVED_IDS_WORK_WITH_SETEUID */
        !            81:
        !            82:   /* We are unable to restore the real uid to its unprivileged value. */
        !            83:   /* Propagate the real uid (usually more privileged) to effective uid
        !            84:      as well. */
        !            85:   setuid(getuid());
        !            86:
        !            87: #endif /* SAVED_IDS_WORK_WITH_SETEUID */
        !            88: }
        !            89:
        !            90: /* Permanently sets all uids to the given uid.  This cannot be called while
        !            91:    temporarily_use_uid is effective. */
        !            92:
        !            93: void permanently_set_uid(uid_t uid)
        !            94: {
        !            95:   if (setuid(uid) < 0)
        !            96:     debug("setuid %d: %.100s", (int)uid, strerror(errno));
        !            97: }
        !            98:
        !            99: #else /* HAVE_SETEUID */
        !           100:
        !           101: YOUR_SYSTEM_DOES_NOT_PERMIT_UID_SWAPPING_READ_AND_EDIT_UIDSWAP_C;
        !           102: /* If we ever come here, if means that your system does not support any of
        !           103:    the uid swapping methods we are aware of.  Tough.  This means that
        !           104:    ssh will have to read certain files as root, which causes some security
        !           105:    problems.  Unless your are very concerned about security, you can
        !           106:    comment out the above line.  The effect is that local users on your
        !           107:    machine might be able to read each other's files.  Also, you may encounter
        !           108:    problems if home directories are on a NFS volume.  You may also
        !           109:    encounter other problems; please don't complain unless you have some idea
        !           110:    how to fix it. */
        !           111:
        !           112: void temporarily_use_uid(uid_t uid)
        !           113: {
        !           114: }
        !           115:
        !           116: void restore_uid()
        !           117: {
        !           118: }
        !           119:
        !           120: void permanently_set_uid(uid_t uid)
        !           121: {
        !           122:   if (setuid(uid) < 0)
        !           123:     debug("setuid %d: %.100s", (int)uid, strerror(errno));
        !           124: }
        !           125:
        !           126: #endif /* HAVE_SETEUID */