Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.21
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"
1.21 ! stevesk 15: RCSID("$OpenBSD: uidswap.c,v 1.20 2002/04/01 21:50:51 stevesk Exp $");
1.1 deraadt 16:
1.13 markus 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: /* Lets assume that posix saved ids also work with seteuid, even though that
30: is not part of the posix specification. */
1.14 markus 31:
1.1 deraadt 32: /* Saved effective uid. */
1.14 markus 33: static int privileged = 0;
34: static int temporarily_use_uid_effective = 0;
35: static uid_t saved_euid = 0;
36: static gid_t saved_egid;
37: static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
38: static int saved_egroupslen = -1, user_groupslen = -1;
1.1 deraadt 39:
1.4 deraadt 40: /*
41: * Temporarily changes to the given uid. If the effective user
42: * id is not root, this does nothing. This call cannot be nested.
43: */
1.6 markus 44: void
1.14 markus 45: temporarily_use_uid(struct passwd *pw)
1.1 deraadt 46: {
1.14 markus 47: /* Save the current euid, and egroups. */
1.3 markus 48: saved_euid = geteuid();
1.21 ! stevesk 49: debug("temporarily_use_uid: %u/%u (e=%u)",
! 50: (u_int)pw->pw_uid, (u_int)pw->pw_gid, (u_int)saved_euid);
1.14 markus 51: if (saved_euid != 0) {
52: privileged = 0;
53: return;
54: }
55: privileged = 1;
56: temporarily_use_uid_effective = 1;
1.19 deraadt 57: saved_egid = getegid();
58: saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
1.14 markus 59: if (saved_egroupslen < 0)
60: fatal("getgroups: %.100s", strerror(errno));
61:
62: /* set and save the user's groups */
63: if (user_groupslen == -1) {
64: if (initgroups(pw->pw_name, pw->pw_gid) < 0)
65: fatal("initgroups: %s: %.100s", pw->pw_name,
66: strerror(errno));
1.19 deraadt 67: user_groupslen = getgroups(NGROUPS_MAX, user_groups);
1.14 markus 68: if (user_groupslen < 0)
69: fatal("getgroups: %.100s", strerror(errno));
70: }
1.3 markus 71: /* Set the effective uid to the given (unprivileged) uid. */
1.15 markus 72: if (setgroups(user_groupslen, user_groups) < 0)
1.14 markus 73: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 74: if (setegid(pw->pw_gid) < 0)
1.21 ! stevesk 75: fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
1.14 markus 76: strerror(errno));
77: if (seteuid(pw->pw_uid) == -1)
1.21 ! stevesk 78: fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
1.14 markus 79: strerror(errno));
1.1 deraadt 80: }
81:
1.4 deraadt 82: /*
1.16 markus 83: * Restores to the original (privileged) uid.
1.4 deraadt 84: */
1.6 markus 85: void
1.11 markus 86: restore_uid(void)
1.1 deraadt 87: {
1.14 markus 88: debug("restore_uid");
89: /* it's a no-op unless privileged */
90: if (!privileged)
91: return;
92: if (!temporarily_use_uid_effective)
93: fatal("restore_uid: temporarily_use_uid not effective");
1.16 markus 94: /* Set the effective uid back to the saved privileged uid. */
1.3 markus 95: if (seteuid(saved_euid) < 0)
1.21 ! stevesk 96: fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
1.15 markus 97: if (setgroups(saved_egroupslen, saved_egroups) < 0)
1.14 markus 98: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 99: if (setegid(saved_egid) < 0)
1.21 ! stevesk 100: fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
1.14 markus 101: temporarily_use_uid_effective = 0;
1.1 deraadt 102: }
103:
1.4 deraadt 104: /*
105: * Permanently sets all uids to the given uid. This cannot be
106: * called while temporarily_use_uid is effective.
107: */
1.6 markus 108: void
1.14 markus 109: permanently_set_uid(struct passwd *pw)
1.1 deraadt 110: {
1.14 markus 111: if (temporarily_use_uid_effective)
112: fatal("restore_uid: temporarily_use_uid effective");
1.16 markus 113: if (setgid(pw->pw_gid) < 0)
1.21 ! stevesk 114: fatal("setgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno));
1.14 markus 115: if (setuid(pw->pw_uid) < 0)
1.21 ! stevesk 116: fatal("setuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno));
1.1 deraadt 117: }