Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 1 | /* $OpenBSD: uidswap.c,v 1.37 2015/01/16 06:40:12 deraadt Exp $ */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 2 | /* |
| 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. |
| 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". |
| 13 | */ |
| 14 | |
| 15 | #include "includes.h" |
| 16 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 17 | #include <errno.h> |
| 18 | #include <pwd.h> |
| 19 | #include <string.h> |
| 20 | #include <unistd.h> |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 21 | #include <limits.h> |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 22 | #include <stdarg.h> |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 23 | #include <stdlib.h> |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 24 | |
| 25 | #include <grp.h> |
| 26 | |
| 27 | #include "log.h" |
| 28 | #include "uidswap.h" |
| 29 | #include "xmalloc.h" |
| 30 | |
| 31 | #ifdef ANDROID |
| 32 | #include <private/android_filesystem_config.h> |
| 33 | #include <sys/capability.h> |
Greg Hartman | f5c67b4 | 2015-02-27 07:55:00 -0800 | [diff] [blame] | 34 | #include <sys/prctl.h> |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 35 | #endif |
| 36 | |
| 37 | /* |
| 38 | * Note: all these functions must work in all of the following cases: |
| 39 | * 1. euid=0, ruid=0 |
| 40 | * 2. euid=0, ruid!=0 |
| 41 | * 3. euid!=0, ruid!=0 |
| 42 | * Additionally, they must work regardless of whether the system has |
| 43 | * POSIX saved uids or not. |
| 44 | */ |
| 45 | |
| 46 | #if defined(_POSIX_SAVED_IDS) && !defined(BROKEN_SAVED_UIDS) |
| 47 | /* Lets assume that posix saved ids also work with seteuid, even though that |
| 48 | is not part of the posix specification. */ |
| 49 | #define SAVED_IDS_WORK_WITH_SETEUID |
| 50 | /* Saved effective uid. */ |
| 51 | static uid_t saved_euid = 0; |
| 52 | static gid_t saved_egid = 0; |
| 53 | #endif |
| 54 | |
| 55 | /* Saved effective uid. */ |
| 56 | static int privileged = 0; |
| 57 | static int temporarily_use_uid_effective = 0; |
| 58 | static gid_t *saved_egroups = NULL, *user_groups = NULL; |
| 59 | static int saved_egroupslen = -1, user_groupslen = -1; |
| 60 | |
| 61 | /* |
| 62 | * Temporarily changes to the given uid. If the effective user |
| 63 | * id is not root, this does nothing. This call cannot be nested. |
| 64 | */ |
| 65 | void |
| 66 | temporarily_use_uid(struct passwd *pw) |
| 67 | { |
| 68 | /* Save the current euid, and egroups. */ |
| 69 | #ifdef SAVED_IDS_WORK_WITH_SETEUID |
| 70 | saved_euid = geteuid(); |
| 71 | saved_egid = getegid(); |
| 72 | debug("temporarily_use_uid: %u/%u (e=%u/%u)", |
| 73 | (u_int)pw->pw_uid, (u_int)pw->pw_gid, |
| 74 | (u_int)saved_euid, (u_int)saved_egid); |
| 75 | #ifndef HAVE_CYGWIN |
| 76 | if (saved_euid != 0) { |
| 77 | privileged = 0; |
| 78 | return; |
| 79 | } |
| 80 | #endif |
| 81 | #else |
| 82 | if (geteuid() != 0) { |
| 83 | privileged = 0; |
| 84 | return; |
| 85 | } |
| 86 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| 87 | |
| 88 | privileged = 1; |
| 89 | temporarily_use_uid_effective = 1; |
| 90 | |
| 91 | saved_egroupslen = getgroups(0, NULL); |
| 92 | if (saved_egroupslen < 0) |
| 93 | fatal("getgroups: %.100s", strerror(errno)); |
| 94 | if (saved_egroupslen > 0) { |
| 95 | saved_egroups = xrealloc(saved_egroups, |
| 96 | saved_egroupslen, sizeof(gid_t)); |
| 97 | if (getgroups(saved_egroupslen, saved_egroups) < 0) |
| 98 | fatal("getgroups: %.100s", strerror(errno)); |
| 99 | } else { /* saved_egroupslen == 0 */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 100 | free(saved_egroups); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 101 | } |
| 102 | |
| 103 | /* set and save the user's groups */ |
| 104 | if (user_groupslen == -1) { |
| 105 | if (initgroups(pw->pw_name, pw->pw_gid) < 0) |
| 106 | fatal("initgroups: %s: %.100s", pw->pw_name, |
| 107 | strerror(errno)); |
| 108 | |
| 109 | user_groupslen = getgroups(0, NULL); |
| 110 | if (user_groupslen < 0) |
| 111 | fatal("getgroups: %.100s", strerror(errno)); |
| 112 | if (user_groupslen > 0) { |
| 113 | user_groups = xrealloc(user_groups, |
| 114 | user_groupslen, sizeof(gid_t)); |
| 115 | if (getgroups(user_groupslen, user_groups) < 0) |
| 116 | fatal("getgroups: %.100s", strerror(errno)); |
| 117 | } else { /* user_groupslen == 0 */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 118 | free(user_groups); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 119 | } |
| 120 | } |
| 121 | /* Set the effective uid to the given (unprivileged) uid. */ |
| 122 | if (setgroups(user_groupslen, user_groups) < 0) |
| 123 | fatal("setgroups: %.100s", strerror(errno)); |
| 124 | #ifndef SAVED_IDS_WORK_WITH_SETEUID |
| 125 | /* Propagate the privileged gid to all of our gids. */ |
| 126 | if (setgid(getegid()) < 0) |
| 127 | debug("setgid %u: %.100s", (u_int) getegid(), strerror(errno)); |
| 128 | /* Propagate the privileged uid to all of our uids. */ |
| 129 | if (setuid(geteuid()) < 0) |
| 130 | debug("setuid %u: %.100s", (u_int) geteuid(), strerror(errno)); |
| 131 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| 132 | if (setegid(pw->pw_gid) < 0) |
| 133 | fatal("setegid %u: %.100s", (u_int)pw->pw_gid, |
| 134 | strerror(errno)); |
| 135 | if (seteuid(pw->pw_uid) == -1) |
| 136 | fatal("seteuid %u: %.100s", (u_int)pw->pw_uid, |
| 137 | strerror(errno)); |
| 138 | } |
| 139 | |
| 140 | void |
| 141 | permanently_drop_suid(uid_t uid) |
| 142 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 143 | #ifndef HAVE_CYGWIN |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 144 | uid_t old_uid = getuid(); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 145 | #endif |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 146 | |
| 147 | debug("permanently_drop_suid: %u", (u_int)uid); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 148 | if (setresuid(uid, uid, uid) < 0) |
| 149 | fatal("setresuid %u: %.100s", (u_int)uid, strerror(errno)); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 150 | |
| 151 | #ifndef HAVE_CYGWIN |
| 152 | /* Try restoration of UID if changed (test clearing of saved uid) */ |
| 153 | if (old_uid != uid && |
| 154 | (setuid(old_uid) != -1 || seteuid(old_uid) != -1)) |
| 155 | fatal("%s: was able to restore old [e]uid", __func__); |
| 156 | #endif |
| 157 | |
| 158 | /* Verify UID drop was successful */ |
| 159 | if (getuid() != uid || geteuid() != uid) { |
| 160 | fatal("%s: euid incorrect uid:%u euid:%u (should be %u)", |
| 161 | __func__, (u_int)getuid(), (u_int)geteuid(), (u_int)uid); |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | /* |
| 166 | * Restores to the original (privileged) uid. |
| 167 | */ |
| 168 | void |
| 169 | restore_uid(void) |
| 170 | { |
| 171 | /* it's a no-op unless privileged */ |
| 172 | if (!privileged) { |
| 173 | debug("restore_uid: (unprivileged)"); |
| 174 | return; |
| 175 | } |
| 176 | if (!temporarily_use_uid_effective) |
| 177 | fatal("restore_uid: temporarily_use_uid not effective"); |
| 178 | |
| 179 | #ifdef SAVED_IDS_WORK_WITH_SETEUID |
| 180 | debug("restore_uid: %u/%u", (u_int)saved_euid, (u_int)saved_egid); |
| 181 | /* Set the effective uid back to the saved privileged uid. */ |
| 182 | if (seteuid(saved_euid) < 0) |
| 183 | fatal("seteuid %u: %.100s", (u_int)saved_euid, strerror(errno)); |
| 184 | if (setegid(saved_egid) < 0) |
| 185 | fatal("setegid %u: %.100s", (u_int)saved_egid, strerror(errno)); |
| 186 | #else /* SAVED_IDS_WORK_WITH_SETEUID */ |
| 187 | /* |
| 188 | * We are unable to restore the real uid to its unprivileged value. |
| 189 | * Propagate the real uid (usually more privileged) to effective uid |
| 190 | * as well. |
| 191 | */ |
| 192 | setuid(getuid()); |
| 193 | setgid(getgid()); |
| 194 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| 195 | |
| 196 | if (setgroups(saved_egroupslen, saved_egroups) < 0) |
| 197 | fatal("setgroups: %.100s", strerror(errno)); |
| 198 | temporarily_use_uid_effective = 0; |
| 199 | } |
| 200 | |
| 201 | /* |
| 202 | * Permanently sets all uids to the given uid. This cannot be |
| 203 | * called while temporarily_use_uid is effective. |
| 204 | */ |
| 205 | void |
| 206 | permanently_set_uid(struct passwd *pw) |
| 207 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 208 | #ifndef HAVE_CYGWIN |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 209 | uid_t old_uid = getuid(); |
| 210 | gid_t old_gid = getgid(); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 211 | #endif |
| 212 | #if defined(ANDROID) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 213 | struct __user_cap_header_struct header; |
| 214 | struct __user_cap_data_struct cap; |
| 215 | #endif |
| 216 | |
| 217 | if (pw == NULL) |
| 218 | fatal("permanently_set_uid: no user given"); |
| 219 | if (temporarily_use_uid_effective) |
| 220 | fatal("permanently_set_uid: temporarily_use_uid effective"); |
| 221 | debug("permanently_set_uid: %u/%u", (u_int)pw->pw_uid, |
| 222 | (u_int)pw->pw_gid); |
| 223 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 224 | #if defined(ANDROID) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 225 | if (pw->pw_uid == AID_SHELL) { |
| 226 | prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0); |
| 227 | |
| 228 | /* add extra groups needed for shell user: |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 229 | * - AID_LOG to read system logs (adb logcat) |
| 230 | * - AID_INPUT to diagnose input issues (getevent) |
| 231 | * - AID_INET to diagnose network issues (netcfg, ping) |
| 232 | * - AID_GRAPHICS to access the frame buffer |
| 233 | * - AID_NET_BT and AID_NET_BT_ADMIN to diagnose bluetooth (hcidump) |
| 234 | * - AID_SDCARD_RW to allow writing to the SD card |
| 235 | * - AID_MOUNT to allow unmounting the SD card before rebooting |
| 236 | * - AID_NET_BW_STATS to read out qtaguid statistics. */ |
| 237 | gid_t groups[] = {AID_LOG, AID_INPUT, AID_INET, |
| 238 | AID_GRAPHICS, AID_NET_BT, AID_NET_BT_ADMIN, |
| 239 | AID_SDCARD_RW, AID_MOUNT, AID_NET_BW_STATS}; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 240 | setgroups(sizeof(groups)/sizeof(groups[0]), groups); |
| 241 | } |
| 242 | #endif |
| 243 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 244 | if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0) |
| 245 | fatal("setresgid %u: %.100s", (u_int)pw->pw_gid, strerror(errno)); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 246 | |
| 247 | #ifdef __APPLE__ |
| 248 | /* |
| 249 | * OS X requires initgroups after setgid to opt back into |
| 250 | * memberd support for >16 supplemental groups. |
| 251 | */ |
| 252 | if (initgroups(pw->pw_name, pw->pw_gid) < 0) |
| 253 | fatal("initgroups %.100s %u: %.100s", |
| 254 | pw->pw_name, (u_int)pw->pw_gid, strerror(errno)); |
| 255 | #endif |
| 256 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 257 | if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0) |
| 258 | fatal("setresuid %u: %.100s", (u_int)pw->pw_uid, strerror(errno)); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 259 | |
| 260 | #ifndef HAVE_CYGWIN |
| 261 | /* Try restoration of GID if changed (test clearing of saved gid) */ |
| 262 | if (old_gid != pw->pw_gid && pw->pw_uid != 0 && |
| 263 | (setgid(old_gid) != -1 || setegid(old_gid) != -1)) |
| 264 | fatal("%s: was able to restore old [e]gid", __func__); |
| 265 | #endif |
| 266 | |
| 267 | /* Verify GID drop was successful */ |
| 268 | if (getgid() != pw->pw_gid || getegid() != pw->pw_gid) { |
| 269 | fatal("%s: egid incorrect gid:%u egid:%u (should be %u)", |
| 270 | __func__, (u_int)getgid(), (u_int)getegid(), |
| 271 | (u_int)pw->pw_gid); |
| 272 | } |
| 273 | |
| 274 | #ifndef HAVE_CYGWIN |
| 275 | /* Try restoration of UID if changed (test clearing of saved uid) */ |
| 276 | if (old_uid != pw->pw_uid && |
| 277 | (setuid(old_uid) != -1 || seteuid(old_uid) != -1)) |
| 278 | fatal("%s: was able to restore old [e]uid", __func__); |
| 279 | #endif |
| 280 | |
| 281 | /* Verify UID drop was successful */ |
| 282 | if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid) { |
| 283 | fatal("%s: euid incorrect uid:%u euid:%u (should be %u)", |
| 284 | __func__, (u_int)getuid(), (u_int)geteuid(), |
| 285 | (u_int)pw->pw_uid); |
| 286 | } |
| 287 | |
| 288 | #ifdef ANDROID |
| 289 | if (pw->pw_uid == AID_SHELL) { |
| 290 | /* set CAP_SYS_BOOT capability, so "adb reboot" will succeed */ |
| 291 | header.version = _LINUX_CAPABILITY_VERSION; |
| 292 | header.pid = 0; |
| 293 | cap.effective = cap.permitted = (1 << CAP_SYS_BOOT); |
| 294 | cap.inheritable = 0; |
| 295 | capset(&header, &cap); |
| 296 | } |
| 297 | #endif |
| 298 | |
| 299 | } |