Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.34
1.34 ! stevesk 1: /* $OpenBSD: uidswap.c,v 1.33 2006/07/22 20:48:23 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:
15: #include "includes.h"
1.30 stevesk 16:
17: #include <sys/types.h>
1.34 ! stevesk 18: #include <sys/param.h>
1.30 stevesk 19:
1.31 stevesk 20: #include <errno.h>
1.30 stevesk 21: #include <pwd.h>
1.33 stevesk 22: #include <string.h>
1.32 stevesk 23: #include <unistd.h>
1.1 deraadt 24:
1.13 markus 25: #include "log.h"
1.1 deraadt 26: #include "uidswap.h"
27:
1.4 deraadt 28: /*
29: * Note: all these functions must work in all of the following cases:
30: * 1. euid=0, ruid=0
31: * 2. euid=0, ruid!=0
32: * 3. euid!=0, ruid!=0
33: * Additionally, they must work regardless of whether the system has
34: * POSIX saved uids or not.
35: */
1.1 deraadt 36:
37: /* Lets assume that posix saved ids also work with seteuid, even though that
38: is not part of the posix specification. */
1.14 markus 39:
1.1 deraadt 40: /* Saved effective uid. */
1.14 markus 41: static int privileged = 0;
42: static int temporarily_use_uid_effective = 0;
43: static uid_t saved_euid = 0;
44: static gid_t saved_egid;
45: static gid_t saved_egroups[NGROUPS_MAX], user_groups[NGROUPS_MAX];
46: static int saved_egroupslen = -1, user_groupslen = -1;
1.1 deraadt 47:
1.4 deraadt 48: /*
49: * Temporarily changes to the given uid. If the effective user
50: * id is not root, this does nothing. This call cannot be nested.
51: */
1.6 markus 52: void
1.14 markus 53: temporarily_use_uid(struct passwd *pw)
1.1 deraadt 54: {
1.14 markus 55: /* Save the current euid, and egroups. */
1.3 markus 56: saved_euid = geteuid();
1.23 stevesk 57: saved_egid = getegid();
58: debug("temporarily_use_uid: %u/%u (e=%u/%u)",
59: (u_int)pw->pw_uid, (u_int)pw->pw_gid,
60: (u_int)saved_euid, (u_int)saved_egid);
1.14 markus 61: if (saved_euid != 0) {
62: privileged = 0;
63: return;
64: }
65: privileged = 1;
66: temporarily_use_uid_effective = 1;
1.19 deraadt 67: saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
1.14 markus 68: if (saved_egroupslen < 0)
69: fatal("getgroups: %.100s", strerror(errno));
70:
71: /* set and save the user's groups */
72: if (user_groupslen == -1) {
73: if (initgroups(pw->pw_name, pw->pw_gid) < 0)
74: fatal("initgroups: %s: %.100s", pw->pw_name,
75: strerror(errno));
1.19 deraadt 76: user_groupslen = getgroups(NGROUPS_MAX, user_groups);
1.14 markus 77: if (user_groupslen < 0)
78: fatal("getgroups: %.100s", strerror(errno));
79: }
1.3 markus 80: /* Set the effective uid to the given (unprivileged) uid. */
1.15 markus 81: if (setgroups(user_groupslen, user_groups) < 0)
1.14 markus 82: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 83: if (setegid(pw->pw_gid) < 0)
1.21 stevesk 84: fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
1.14 markus 85: strerror(errno));
86: if (seteuid(pw->pw_uid) == -1)
1.21 stevesk 87: fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
1.14 markus 88: strerror(errno));
1.1 deraadt 89: }
90:
1.4 deraadt 91: /*
1.16 markus 92: * Restores to the original (privileged) uid.
1.4 deraadt 93: */
1.6 markus 94: void
1.11 markus 95: restore_uid(void)
1.1 deraadt 96: {
1.14 markus 97: /* it's a no-op unless privileged */
1.23 stevesk 98: if (!privileged) {
99: debug("restore_uid: (unprivileged)");
1.14 markus 100: return;
1.23 stevesk 101: }
1.14 markus 102: if (!temporarily_use_uid_effective)
103: fatal("restore_uid: temporarily_use_uid not effective");
1.23 stevesk 104: debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
1.16 markus 105: /* Set the effective uid back to the saved privileged uid. */
1.3 markus 106: if (seteuid(saved_euid) < 0)
1.21 stevesk 107: fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
1.15 markus 108: if (setgroups(saved_egroupslen, saved_egroups) < 0)
1.14 markus 109: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 110: if (setegid(saved_egid) < 0)
1.21 stevesk 111: fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
1.14 markus 112: temporarily_use_uid_effective = 0;
1.1 deraadt 113: }
114:
1.4 deraadt 115: /*
116: * Permanently sets all uids to the given uid. This cannot be
117: * called while temporarily_use_uid is effective.
118: */
1.6 markus 119: void
1.14 markus 120: permanently_set_uid(struct passwd *pw)
1.1 deraadt 121: {
1.14 markus 122: if (temporarily_use_uid_effective)
1.22 stevesk 123: fatal("permanently_set_uid: temporarily_use_uid effective");
1.23 stevesk 124: debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
125: (u_int)pw->pw_gid);
1.27 djm 126: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0)
127: fatal("setresgid %u: %s", (u_int)pw->pw_gid, strerror(errno));
128: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0)
129: fatal("setresuid %u: %s", (u_int)pw->pw_uid, strerror(errno));
1.29 markus 130: }
131:
132: void
133: permanently_drop_suid(uid_t uid)
134: {
135: debug("permanently_drop_suid: %u", (u_int)uid);
136: if (setresuid(uid, uid, uid) != 0)
137: fatal("setresuid %u: %s", (u_int)uid, strerror(errno));
1.1 deraadt 138: }
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