Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.30
1.30 ! stevesk 1: /* $OpenBSD: uidswap.c,v 1.29 2006/06/08 14:45:49 markus 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:
15: #include "includes.h"
1.30 ! stevesk 16:
! 17: #include <sys/types.h>
! 18:
! 19: #include <pwd.h>
1.1 deraadt 20:
1.13 markus 21: #include "log.h"
1.1 deraadt 22: #include "uidswap.h"
23:
1.4 deraadt 24: /*
25: * Note: all these functions must work in all of the following cases:
26: * 1. euid=0, ruid=0
27: * 2. euid=0, ruid!=0
28: * 3. euid!=0, ruid!=0
29: * Additionally, they must work regardless of whether the system has
30: * POSIX saved uids or not.
31: */
1.1 deraadt 32:
33: /* Lets assume that posix saved ids also work with seteuid, even though that
34: is not part of the posix specification. */
1.14 markus 35:
1.1 deraadt 36: /* Saved effective uid. */
1.14 markus 37: static int privileged = 0;
38: static int temporarily_use_uid_effective = 0;
39: static uid_t saved_euid = 0;
40: static gid_t saved_egid;
41: static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
42: static int saved_egroupslen = -1, user_groupslen = -1;
1.1 deraadt 43:
1.4 deraadt 44: /*
45: * Temporarily changes to the given uid. If the effective user
46: * id is not root, this does nothing. This call cannot be nested.
47: */
1.6 markus 48: void
1.14 markus 49: temporarily_use_uid(struct passwd *pw)
1.1 deraadt 50: {
1.14 markus 51: /* Save the current euid, and egroups. */
1.3 markus 52: saved_euid = geteuid();
1.23 stevesk 53: saved_egid = getegid();
54: debug("temporarily_use_uid: %u/%u (e=%u/%u)",
55: (u_int)pw->pw_uid, (u_int)pw->pw_gid,
56: (u_int)saved_euid, (u_int)saved_egid);
1.14 markus 57: if (saved_euid != 0) {
58: privileged = 0;
59: return;
60: }
61: privileged = 1;
62: temporarily_use_uid_effective = 1;
1.19 deraadt 63: saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
1.14 markus 64: if (saved_egroupslen < 0)
65: fatal("getgroups: %.100s", strerror(errno));
66:
67: /* set and save the user's groups */
68: if (user_groupslen == -1) {
69: if (initgroups(pw->pw_name, pw->pw_gid) < 0)
70: fatal("initgroups: %s: %.100s", pw->pw_name,
71: strerror(errno));
1.19 deraadt 72: user_groupslen = getgroups(NGROUPS_MAX, user_groups);
1.14 markus 73: if (user_groupslen < 0)
74: fatal("getgroups: %.100s", strerror(errno));
75: }
1.3 markus 76: /* Set the effective uid to the given (unprivileged) uid. */
1.15 markus 77: if (setgroups(user_groupslen, user_groups) < 0)
1.14 markus 78: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 79: if (setegid(pw->pw_gid) < 0)
1.21 stevesk 80: fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
1.14 markus 81: strerror(errno));
82: if (seteuid(pw->pw_uid) == -1)
1.21 stevesk 83: fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
1.14 markus 84: strerror(errno));
1.1 deraadt 85: }
86:
1.4 deraadt 87: /*
1.16 markus 88: * Restores to the original (privileged) uid.
1.4 deraadt 89: */
1.6 markus 90: void
1.11 markus 91: restore_uid(void)
1.1 deraadt 92: {
1.14 markus 93: /* it's a no-op unless privileged */
1.23 stevesk 94: if (!privileged) {
95: debug("restore_uid: (unprivileged)");
1.14 markus 96: return;
1.23 stevesk 97: }
1.14 markus 98: if (!temporarily_use_uid_effective)
99: fatal("restore_uid: temporarily_use_uid not effective");
1.23 stevesk 100: debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
1.16 markus 101: /* Set the effective uid back to the saved privileged uid. */
1.3 markus 102: if (seteuid(saved_euid) < 0)
1.21 stevesk 103: fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
1.15 markus 104: if (setgroups(saved_egroupslen, saved_egroups) < 0)
1.14 markus 105: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 106: if (setegid(saved_egid) < 0)
1.21 stevesk 107: fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
1.14 markus 108: temporarily_use_uid_effective = 0;
1.1 deraadt 109: }
110:
1.4 deraadt 111: /*
112: * Permanently sets all uids to the given uid. This cannot be
113: * called while temporarily_use_uid is effective.
114: */
1.6 markus 115: void
1.14 markus 116: permanently_set_uid(struct passwd *pw)
1.1 deraadt 117: {
1.14 markus 118: if (temporarily_use_uid_effective)
1.22 stevesk 119: fatal("permanently_set_uid: temporarily_use_uid effective");
1.23 stevesk 120: debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
121: (u_int)pw->pw_gid);
1.27 djm 122: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0)
123: fatal("setresgid %u: %s", (u_int)pw->pw_gid, strerror(errno));
124: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0)
125: fatal("setresuid %u: %s", (u_int)pw->pw_uid, strerror(errno));
1.29 markus 126: }
127:
128: void
129: permanently_drop_suid(uid_t uid)
130: {
131: debug("permanently_drop_suid: %u", (u_int)uid);
132: if (setresuid(uid, uid, uid) != 0)
133: fatal("setresuid %u: %s", (u_int)uid, strerror(errno));
1.1 deraadt 134: }
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