Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.35
1.35 ! deraadt 1: /* $OpenBSD: uidswap.c,v 1.34 2006/07/26 02:35:17 stevesk Exp $ */
1.1 deraadt 2: /*
1.4 deraadt 3: * Author: Tatu Ylonen <ylo@cs.hut.fi>
4: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: * All rights reserved
6: * Code for uid-swapping.
1.9 deraadt 7: *
8: * As far as I am concerned, the code I have written for this software
9: * can be used freely for any purpose. Any derived versions of this
10: * software must be clearly marked as such, and if the derived work is
11: * incompatible with the protocol description in the RFC file, it must be
12: * called by a name other than "ssh" or "Secure Shell".
1.4 deraadt 13: */
1.1 deraadt 14:
1.34 stevesk 15: #include <sys/param.h>
1.31 stevesk 16: #include <errno.h>
1.30 stevesk 17: #include <pwd.h>
1.33 stevesk 18: #include <string.h>
1.32 stevesk 19: #include <unistd.h>
1.35 ! deraadt 20: #include <stdarg.h>
1.1 deraadt 21:
1.13 markus 22: #include "log.h"
1.1 deraadt 23: #include "uidswap.h"
24:
1.4 deraadt 25: /*
26: * Note: all these functions must work in all of the following cases:
27: * 1. euid=0, ruid=0
28: * 2. euid=0, ruid!=0
29: * 3. euid!=0, ruid!=0
30: * Additionally, they must work regardless of whether the system has
31: * POSIX saved uids or not.
32: */
1.1 deraadt 33:
34: /* Lets assume that posix saved ids also work with seteuid, even though that
35: is not part of the posix specification. */
1.14 markus 36:
1.1 deraadt 37: /* Saved effective uid. */
1.14 markus 38: static int privileged = 0;
39: static int temporarily_use_uid_effective = 0;
40: static uid_t saved_euid = 0;
41: static gid_t saved_egid;
42: static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
43: static int saved_egroupslen = -1, user_groupslen = -1;
1.1 deraadt 44:
1.4 deraadt 45: /*
46: * Temporarily changes to the given uid. If the effective user
47: * id is not root, this does nothing. This call cannot be nested.
48: */
1.6 markus 49: void
1.14 markus 50: temporarily_use_uid(struct passwd *pw)
1.1 deraadt 51: {
1.14 markus 52: /* Save the current euid, and egroups. */
1.3 markus 53: saved_euid = geteuid();
1.23 stevesk 54: saved_egid = getegid();
55: debug("temporarily_use_uid: %u/%u (e=%u/%u)",
56: (u_int)pw->pw_uid, (u_int)pw->pw_gid,
57: (u_int)saved_euid, (u_int)saved_egid);
1.14 markus 58: if (saved_euid != 0) {
59: privileged = 0;
60: return;
61: }
62: privileged = 1;
63: temporarily_use_uid_effective = 1;
1.19 deraadt 64: saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
1.14 markus 65: if (saved_egroupslen < 0)
66: fatal("getgroups: %.100s", strerror(errno));
67:
68: /* set and save the user's groups */
69: if (user_groupslen == -1) {
70: if (initgroups(pw->pw_name, pw->pw_gid) < 0)
71: fatal("initgroups: %s: %.100s", pw->pw_name,
72: strerror(errno));
1.19 deraadt 73: user_groupslen = getgroups(NGROUPS_MAX, user_groups);
1.14 markus 74: if (user_groupslen < 0)
75: fatal("getgroups: %.100s", strerror(errno));
76: }
1.3 markus 77: /* Set the effective uid to the given (unprivileged) uid. */
1.15 markus 78: if (setgroups(user_groupslen, user_groups) < 0)
1.14 markus 79: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 80: if (setegid(pw->pw_gid) < 0)
1.21 stevesk 81: fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
1.14 markus 82: strerror(errno));
83: if (seteuid(pw->pw_uid) == -1)
1.21 stevesk 84: fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
1.14 markus 85: strerror(errno));
1.1 deraadt 86: }
87:
1.4 deraadt 88: /*
1.16 markus 89: * Restores to the original (privileged) uid.
1.4 deraadt 90: */
1.6 markus 91: void
1.11 markus 92: restore_uid(void)
1.1 deraadt 93: {
1.14 markus 94: /* it's a no-op unless privileged */
1.23 stevesk 95: if (!privileged) {
96: debug("restore_uid: (unprivileged)");
1.14 markus 97: return;
1.23 stevesk 98: }
1.14 markus 99: if (!temporarily_use_uid_effective)
100: fatal("restore_uid: temporarily_use_uid not effective");
1.23 stevesk 101: debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
1.16 markus 102: /* Set the effective uid back to the saved privileged uid. */
1.3 markus 103: if (seteuid(saved_euid) < 0)
1.21 stevesk 104: fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
1.15 markus 105: if (setgroups(saved_egroupslen, saved_egroups) < 0)
1.14 markus 106: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 107: if (setegid(saved_egid) < 0)
1.21 stevesk 108: fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
1.14 markus 109: temporarily_use_uid_effective = 0;
1.1 deraadt 110: }
111:
1.4 deraadt 112: /*
113: * Permanently sets all uids to the given uid. This cannot be
114: * called while temporarily_use_uid is effective.
115: */
1.6 markus 116: void
1.14 markus 117: permanently_set_uid(struct passwd *pw)
1.1 deraadt 118: {
1.14 markus 119: if (temporarily_use_uid_effective)
1.22 stevesk 120: fatal("permanently_set_uid: temporarily_use_uid effective");
1.23 stevesk 121: debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
122: (u_int)pw->pw_gid);
1.27 djm 123: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0)
124: fatal("setresgid %u: %s", (u_int)pw->pw_gid, strerror(errno));
125: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0)
126: fatal("setresuid %u: %s", (u_int)pw->pw_uid, strerror(errno));
1.29 markus 127: }
128:
129: void
130: permanently_drop_suid(uid_t uid)
131: {
132: debug("permanently_drop_suid: %u", (u_int)uid);
133: if (setresuid(uid, uid, uid) != 0)
134: fatal("setresuid %u: %s", (u_int)uid, strerror(errno));
1.1 deraadt 135: }