Annotation of src/usr.bin/ssh/uidswap.c, Revision 1.27
1.27 ! djm 1: /* $OpenBSD: uidswap.c,v 1.26 2006/03/25 13:17:03 djm 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"
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();
1.23 stevesk 49: saved_egid = getegid();
50: debug("temporarily_use_uid: %u/%u (e=%u/%u)",
51: (u_int)pw->pw_uid, (u_int)pw->pw_gid,
52: (u_int)saved_euid, (u_int)saved_egid);
1.14 markus 53: if (saved_euid != 0) {
54: privileged = 0;
55: return;
56: }
57: privileged = 1;
58: temporarily_use_uid_effective = 1;
1.19 deraadt 59: saved_egroupslen = getgroups(NGROUPS_MAX, saved_egroups);
1.14 markus 60: if (saved_egroupslen < 0)
61: fatal("getgroups: %.100s", strerror(errno));
62:
63: /* set and save the user's groups */
64: if (user_groupslen == -1) {
65: if (initgroups(pw->pw_name, pw->pw_gid) < 0)
66: fatal("initgroups: %s: %.100s", pw->pw_name,
67: strerror(errno));
1.19 deraadt 68: user_groupslen = getgroups(NGROUPS_MAX, user_groups);
1.14 markus 69: if (user_groupslen < 0)
70: fatal("getgroups: %.100s", strerror(errno));
71: }
1.3 markus 72: /* Set the effective uid to the given (unprivileged) uid. */
1.15 markus 73: if (setgroups(user_groupslen, user_groups) < 0)
1.14 markus 74: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 75: if (setegid(pw->pw_gid) < 0)
1.21 stevesk 76: fatal("setegid %u: %.100s", (u_int)pw->pw_gid,
1.14 markus 77: strerror(errno));
78: if (seteuid(pw->pw_uid) == -1)
1.21 stevesk 79: fatal("seteuid %u: %.100s", (u_int)pw->pw_uid,
1.14 markus 80: strerror(errno));
1.1 deraadt 81: }
82:
1.4 deraadt 83: /*
1.16 markus 84: * Restores to the original (privileged) uid.
1.4 deraadt 85: */
1.6 markus 86: void
1.11 markus 87: restore_uid(void)
1.1 deraadt 88: {
1.14 markus 89: /* it's a no-op unless privileged */
1.23 stevesk 90: if (!privileged) {
91: debug("restore_uid: (unprivileged)");
1.14 markus 92: return;
1.23 stevesk 93: }
1.14 markus 94: if (!temporarily_use_uid_effective)
95: fatal("restore_uid: temporarily_use_uid not effective");
1.23 stevesk 96: debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid);
1.16 markus 97: /* Set the effective uid back to the saved privileged uid. */
1.3 markus 98: if (seteuid(saved_euid) < 0)
1.21 stevesk 99: fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno));
1.15 markus 100: if (setgroups(saved_egroupslen, saved_egroups) < 0)
1.14 markus 101: fatal("setgroups: %.100s", strerror(errno));
1.15 markus 102: if (setegid(saved_egid) < 0)
1.21 stevesk 103: fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno));
1.14 markus 104: temporarily_use_uid_effective = 0;
1.1 deraadt 105: }
106:
1.4 deraadt 107: /*
108: * Permanently sets all uids to the given uid. This cannot be
109: * called while temporarily_use_uid is effective.
110: */
1.6 markus 111: void
1.14 markus 112: permanently_set_uid(struct passwd *pw)
1.1 deraadt 113: {
1.14 markus 114: if (temporarily_use_uid_effective)
1.22 stevesk 115: fatal("permanently_set_uid: temporarily_use_uid effective");
1.23 stevesk 116: debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid,
117: (u_int)pw->pw_gid);
1.27 ! djm 118: if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0)
! 119: fatal("setresgid %u: %s", (u_int)pw->pw_gid, strerror(errno));
! 120: if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0)
! 121: fatal("setresuid %u: %s", (u_int)pw->pw_uid, strerror(errno));
1.1 deraadt 122: }
![[BACK]](/icons/back.gif){kind=icon}
Return to uidswap.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh