1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320
|
.\"
.\" Copyright (c) 1994-1996, 1998-2005, 2007-2018
.\" Todd C. Miller <Todd.Miller@sudo.ws>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.\" Sponsored in part by the Defense Advanced Research Projects
.\" Agency (DARPA) and Air Force Research Laboratory, Air Force
.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
.\"
.nr SL @SEMAN@
.nr BA @BAMAN@
.nr LC @LCMAN@
.nr PS @PSMAN@
.Dd November 25, 2018
.Dt SUDO @mansectsu@
.Os Sudo @PACKAGE_VERSION@
.Sh NAME
.Nm sudo ,
.Nm sudoedit
.Nd execute a command as another user
.Sh SYNOPSIS
.Nm sudo
.Fl h | K | k | V
.Nm sudo
.Fl v
.Op Fl AknS
.if \n(BA \{\
.Op Fl a Ar type
.\}
.Op Fl g Ar group
.Op Fl h Ar host
.Op Fl p Ar prompt
.Op Fl u Ar user
.Nm sudo
.Fl l
.Op Fl AknS
.if \n(BA \{\
.Op Fl a Ar type
.\}
.Op Fl g Ar group
.Op Fl h Ar host
.Op Fl p Ar prompt
.Op Fl U Ar user
.Op Fl u Ar user
.Op Ar command
.Nm sudo
.Op Fl AbEHnPS
.if \n(BA \{\
.Op Fl a Ar type
.\}
.Op Fl C Ar num
.if \n(LC \{\
.Op Fl c Ar class
.\}
.Op Fl g Ar group
.Op Fl h Ar host
.Op Fl p Ar prompt
.if \n(SL \{\
.Op Fl r Ar role
.Op Fl t Ar type
.\}
.Op Fl T Ar timeout
.Op Fl u Ar user
.Op Ar VAR Ns = Ns Ar value
.Op Fl i | s
.Op Ar command
.Nm sudoedit
.Op Fl AknS
.if \n(BA \{\
.Op Fl a Ar type
.\}
.Op Fl C Ar num
.if \n(LC \{\
.Op Fl c Ar class
.\}
.Op Fl g Ar group
.Op Fl h Ar host
.Op Fl p Ar prompt
.Op Fl T Ar timeout
.Op Fl u Ar user
.Ar
.Sh DESCRIPTION
.Nm
allows a permitted user to execute a
.Ar command
as the superuser or another user, as specified by the security
policy.
The invoking user's real
.Pq Em not No effective
user ID is used to determine the user name with which
to query the security policy.
.Pp
.Nm
supports a plugin architecture for security policies and input/output
logging.
Third parties can develop and distribute their own policy and I/O
logging plugins to work seamlessly with the
.Nm
front end.
The default security policy is
.Em sudoers ,
which is configured via the file
.Pa @sysconfdir@/sudoers ,
or via LDAP.
See the
.Sx Plugins
section for more information.
.Pp
The security policy determines what privileges, if any, a user has
to run
.Nm .
The policy may require that users authenticate themselves with a
password or another authentication mechanism.
If authentication is required,
.Nm
will exit if the user's password is not entered within a configurable
time limit.
This limit is policy-specific; the default password prompt timeout
for the
.Em sudoers
security policy is
.Li @password_timeout@
minutes.
.Pp
Security policies may support credential caching to allow the user
to run
.Nm
again for a period of time without requiring authentication.
The
.Em sudoers
policy caches credentials for
.Li @timeout@
minutes, unless overridden in
.Xr sudoers @mansectform@ .
By running
.Nm
with the
.Fl v
option, a user can update the cached credentials without running a
.Ar command .
.Pp
When invoked as
.Nm sudoedit ,
the
.Fl e
option (described below), is implied.
.Pp
Security policies may log successful and failed attempts to use
.Nm .
If an I/O plugin is configured, the running command's input and
output may be logged as well.
.Pp
The options are as follows:
.Bl -tag -width Fl
.It Fl A , -askpass
Normally, if
.Nm
requires a password, it will read it from the user's terminal.
If the
.Fl A Pq Em askpass
option is specified, a (possibly graphical) helper program is
executed to read the user's password and output the password to the
standard output.
If the
.Ev SUDO_ASKPASS
environment variable is set, it specifies the path to the helper
program.
Otherwise, if
.Xr sudo.conf @mansectform@
contains a line specifying the askpass program, that value will be
used.
For example:
.Bd -literal -offset 4n
# Path to askpass helper program
Path askpass /usr/X11R6/bin/ssh-askpass
.Ed
.Pp
If no askpass program is available,
.Nm
will exit with an error.
.if \n(BA \{\
.It Fl a Ar type , Fl -auth-type Ns = Ns Ar type
Use the specified
.Bx
authentication
.Ar type
when validating the user, if allowed by
.Pa /etc/login.conf .
The system administrator may specify a list of sudo-specific
authentication methods by adding an
.Dq auth-sudo
entry in
.Pa /etc/login.conf .
This option is only available on systems that support
.Bx
authentication.
.\}
.It Fl b , -background
Run the given command in the background.
Note that it is not possible to use shell job control to manipulate
background processes started by
.Nm .
Most interactive commands will fail to work properly in background
mode.
.It Fl C Ar num , Fl -close-from Ns = Ns Ar num
Close all file descriptors greater than or equal to
.Ar num
before executing a command.
Values less than three are not permitted.
By default,
.Nm
will close all open file descriptors other than standard input,
standard output and standard error when executing a command.
The security policy may restrict the user's ability to use this option.
The
.Em sudoers
policy only permits use of the
.Fl C
option when the administrator has enabled the
.Em closefrom_override
option.
.if \n(LC \{\
.It Fl c Ar class , Fl -login-class Ns = Ns Ar class
Run the command with resource limits and scheduling priority of
the specified login
.Ar class .
The
.Ar class
argument can be either a class name as defined in
.Pa /etc/login.conf ,
or a single
.Ql \-
character.
If
.Ar class
is
.Cm - ,
the default login class of the target user will be used.
Otherwise, the command must be run as the superuser (user ID 0), or
.Nm
must be run from a shell that is already running as the superuser.
If the command is being run as a login shell, additional
.Pa /etc/login.conf
settings, such as the umask and environment variables, will
be applied, if present.
This option is only available on systems with
.Bx
login classes.
.\}
.It Fl E , -preserve-env
Indicates to the security policy that the user wishes to
preserve their existing environment variables.
The security policy may return an error if the user does not have
permission to preserve the environment.
.It Fl -preserve-env=list
Indicates to the security policy that the user wishes to add the
comma-separated list of environment variables to those preserved
from the user's environment.
The security policy may return an error if the user does not have
permission to preserve the environment.
.It Fl e , -edit
Edit one or more files instead of running a command.
In lieu of a path name, the string "sudoedit" is used when consulting
the security policy.
If the user is authorized by the policy, the following steps are
taken:
.Bl -enum -offset 4
.It
Temporary copies are made of the files to be edited with the owner
set to the invoking user.
.It
The editor specified by the policy is run to edit the temporary
files.
The
.Em sudoers
policy uses the
.Ev SUDO_EDITOR ,
.Ev VISUAL
and
.Ev EDITOR
environment variables (in that order).
If none of
.Ev SUDO_EDITOR ,
.Ev VISUAL
or
.Ev EDITOR
are set, the first program listed in the
.Em editor
.Xr sudoers @mansectform@
option is used.
.It
If they have been modified, the temporary files are copied back to
their original location and the temporary versions are removed.
.El
.Pp
To help prevent the editing of unauthorized files, the following
restrictions are enforced unless explicitly allowed by the security policy:
.Bl -bullet -offset 4 -width 1n
.It
Symbolic links may not be edited (version 1.8.15 and higher).
.It
Symbolic links along the path to be edited are not followed when the
parent directory is writable by the invoking user unless that user
is root (version 1.8.16 and higher).
.It
Files located in a directory that is writable by the invoking user may
not be edited unless that user is root (version 1.8.16 and higher).
.El
.Pp
Users are never allowed to edit device special files.
.Pp
If the specified file does not exist, it will be created.
Note that unlike most commands run by
.Em sudo ,
the editor is run with the invoking user's environment unmodified.
If, for some reason,
.Nm
is unable to update a file with its edited version, the user will
receive a warning and the edited copy will remain in a temporary
file.
.It Fl g Ar group , Fl -group Ns = Ns Ar group
Run the command with the primary group set to
.Ar group
instead of the primary group specified by the target
user's password database entry.
The
.Ar group
may be either a group name or a numeric group ID
.Pq GID
prefixed with the
.Ql #
character (e.g.,
.Li #0
for GID 0).
When running a command as a GID, many shells require that the
.Ql #
be escaped with a backslash
.Pq Ql \e .
If no
.Fl u
option is specified, the command will be run as the invoking user.
In either case, the primary group will be set to
.Ar group .
The
.Em sudoers
policy permits any of the target user's groups to be specified via
the
.Fl g
option as long as the
.Fl P
option is not in use.
.It Fl H , -set-home
Request that the security policy set the
.Ev HOME
environment variable to the home directory specified by the target
user's password database entry.
Depending on the policy, this may be the default behavior.
.It Fl h , -help
Display a short help message to the standard output and exit.
.It Fl h Ar host , Fl -host Ns = Ns Ar host
Run the command on the specified
.Ar host
if the security policy plugin supports remote commands.
Note that the
.Em sudoers
plugin does not currently support running remote commands.
This may also be used in conjunction with the
.Fl l
option to list a user's privileges for the remote host.
.It Fl i , -login
Run the shell specified by the target user's password database entry
as a login shell.
This means that login-specific resource files such as
.Pa .profile ,
.Pa .bash_profile
or
.Pa .login
will be read by the shell.
If a command is specified, it is passed to the shell for execution
via the shell's
.Fl c
option.
If no command is specified, an interactive shell is executed.
.Nm
attempts to change to that user's home directory before running the
shell.
The command is run with an environment similar to the one
a user would receive at log in.
Note that most shells behave differently when a command is specified
as compared to an interactive session; consult the shell's manual
for details.
The
.Em Command environment
section in the
.Xr sudoers @mansectform@
manual documents how the
.Fl i
option affects the environment in which a command is run when the
.Em sudoers
policy is in use.
.It Fl K , -remove-timestamp
Similar to the
.Fl k
option, except that it removes the user's cached credentials entirely
and may not be used in conjunction with a command or other option.
This option does not require a password.
Not all security policies support credential caching.
.It Fl k , -reset-timestamp
When used without a command, invalidates the user's cached credentials.
In other words, the next time
.Nm
is run a password will be required.
This option does not require a password and was added to allow a
user to revoke
.Nm
permissions from a
.Pa .logout
file.
.Pp
When used in conjunction with a command or an option that may require
a password, this option will cause
.Nm
to ignore the user's cached credentials.
As a result,
.Nm
will prompt for a password (if one is required by the security
policy) and will not update the user's cached credentials.
.Pp
Not all security policies support credential caching.
.It Fl l , Fl -list
If no
.Ar command
is specified,
list the allowed (and forbidden) commands for the
invoking user (or the user specified by the
.Fl U
option) on the current host.
A longer list format is used if this option is specified multiple times
and the security policy supports a verbose output format.
.Pp
If a
.Ar command
is specified and is permitted by the security policy, the fully-qualified
path to the command is displayed along with any command line
arguments.
If a
.Ar command
is specified but not allowed by the policy,
.Nm
will exit with a status value of 1.
.It Fl n , -non-interactive
Avoid prompting the user for input of any kind.
If a password is required for the command to run,
.Nm
will display an error message and exit.
.It Fl P , -preserve-groups
Preserve the invoking user's group vector unaltered.
By default, the
.Em sudoers
policy will initialize the group vector to the list of groups the
target user is a member of.
The real and effective group IDs, however, are still set to match
the target user.
.It Fl p Ar prompt , Fl -prompt Ns = Ns Ar prompt
Use a custom password prompt with optional escape sequences.
The following percent
.Pq Ql %
escape sequences are supported by the
.Em sudoers
policy:
.Bl -tag -width 2n
.It Li %H
expanded to the host name including the domain name (on if the
machine's host name is fully qualified or the
.Em fqdn
option is set in
.Xr sudoers @mansectform@ )
.It Li %h
expanded to the local host name without the domain name
.It Li %p
expanded to the name of the user whose password is being requested
(respects the
.Em rootpw ,
.Em targetpw ,
and
.Em runaspw
flags in
.Xr sudoers @mansectform@ )
.It Li \&%U
expanded to the login name of the user the command will be run as
(defaults to root unless the
.Fl u
option is also specified)
.It Li %u
expanded to the invoking user's login name
.It Li %%
two consecutive
.Ql %
characters are collapsed into a single
.Ql %
character
.El
.Pp
The custom prompt will override the default prompt specified by either
the security policy or the
.Ev SUDO_PROMPT
environment variable.
On systems that use PAM, the custom prompt will also override the prompt
specified by a PAM module unless the
.Em passprompt_override
flag is disabled in
.Em sudoers .
.if \n(SL \{\
.It Fl r Ar role , Fl -role Ns = Ns Ar role
Run the command with an SELinux security context that includes
the specified
.Ar role .
.\}
.It Fl S , -stdin
Write the prompt to the standard error and read the password from the
standard input instead of using the terminal device.
.It Fl s , -shell
Run the shell specified by the
.Ev SHELL
environment variable if it is set or the shell specified by the
invoking user's password database entry.
If a command is specified, it is passed to the shell for execution
via the shell's
.Fl c
option.
If no command is specified, an interactive shell is executed.
Note that most shells behave differently when a command is specified
as compared to an interactive session; consult the shell's manual
for details.
.if \n(SL \{\
.It Fl t Ar type , Fl -type Ns = Ns Ar type
Run the command with an SELinux security context that includes
the specified
.Ar type .
If no
.Ar type
is specified, the default type is derived from the role.
.\}
.It Fl U Ar user , Fl -other-user Ns = Ns Ar user
Used in conjunction with the
.Fl l
option to list the privileges for
.Ar user
instead of for the invoking user.
The security policy may restrict listing other users' privileges.
The
.Em sudoers
policy only allows root or a user with the
.Li ALL
privilege on the current host to use this option.
.It Fl T Ar timeout , Fl -command-timeout Ns = Ns Ar timeout
Used to set a timeout for the command.
If the timeout expires before the command has exited, the
command will be terminated.
The security policy may restrict the ability to set command timeouts.
The
.Em sudoers
policy requires that user-specified timeouts be explicitly enabled.
.It Fl u Ar user , Fl -user Ns = Ns Ar user
Run the command as a user other than the default target user
(usually
.Em root ) .
The
.Ar user
may be either a user name or a numeric user ID
.Pq UID
prefixed with the
.Ql #
character (e.g.,
.Li #0
for UID 0).
When running commands as a UID, many shells require that the
.Ql #
be escaped with a backslash
.Pq Ql \e .
Some security policies may restrict UIDs
to those listed in the password database.
The
.Em sudoers
policy allows UIDs that are not in the password database as long as the
.Em targetpw
option is not set.
Other security policies may not support this.
.It Fl V , -version
Print the
.Nm
version string as well as the version string of the security
policy plugin and any I/O plugins.
If the invoking user is already root the
.Fl V
option will display the arguments passed to configure when
.Nm
was built and plugins may display more verbose information such as
default options.
.It Fl v , -validate
Update the user's cached credentials, authenticating the user
if necessary.
For the
.Em sudoers
plugin, this extends the
.Nm
timeout for another
.Li @timeout@
minutes by default, but does not run a command.
Not all security policies support cached credentials.
.It Fl -
The
.Fl -
option indicates that
.Nm
should stop processing command line arguments.
.El
.Pp
Environment variables to be set for the command may also be passed
on the command line in the form of
.Ar VAR Ns = Ns Ar value ,
e.g.,
.Ev LD_LIBRARY_PATH Ns = Ns Pa /usr/local/pkg/lib .
Variables passed on the command line are subject to restrictions
imposed by the security policy plugin.
The
.Em sudoers
policy subjects variables passed on the command line to the same
restrictions as normal environment variables with one important
exception.
If the
.Em setenv
option is set in
.Em sudoers ,
the command to be run has the
.Li SETENV
tag set or the command matched is
.Li ALL ,
the user may set variables that would otherwise be forbidden.
See
.Xr sudoers @mansectform@
for more information.
.Sh COMMAND EXECUTION
When
.Nm
executes a command, the security policy specifies the execution
environment for the command.
Typically, the real and effective user and group and IDs are set to
match those of the target user, as specified in the password database,
and the group vector is initialized based on the group database
(unless the
.Fl P
option was specified).
.Pp
The following parameters may be specified by security policy:
.Bl -bullet -width 1n
.It
real and effective user ID
.It
real and effective group ID
.It
supplementary group IDs
.It
the environment list
.It
current working directory
.It
file creation mode mask (umask)
.if \n(SL \{\
.It
SELinux role and type
.\}
.if \n(PS \{\
.It
Solaris project
.It
Solaris privileges
.\}
.if \n(LC \{\
.It
.Bx
login class
.\}
.It
scheduling priority (aka nice value)
.El
.Ss Process model
There are two distinct ways
.Nm
can run a command.
.Pp
If an I/O logging plugin is configured or if the security policy
explicitly requests it, a new pseudo-terminal
.Pq Dq pty
is allocated and
.Xr fork 2
is used to create a second
.Nm
process, referred to as the
.Em monitor .
The
.Em monitor
creates a new terminal session with itself as the leader and the pty as its
controlling terminal, calls
.Xr fork 2 ,
sets up the execution environment as described above, and then uses the
.Xr execve 2
system call to run the command in the child process.
The
.Em monitor
exists to relay job control signals between the user's
existing terminal and the pty the command is being run in.
This makes it possible to suspend and resume the command.
Without the monitor, the command would be in what POSIX terms an
.Dq orphaned process group
and it would not receive any job control signals from the kernel.
When the command exits or is terminated by a signal, the
.Em monitor
passes the command's exit status to the main
.Nm
process and exits.
After receiving the command's exit status, the main
.Nm
passes the command's exit status to the security policy's close function
and exits.
.Pp
If no pty is used,
.Nm
calls
.Xr fork 2 ,
sets up the execution environment as described above, and uses the
.Xr execve 2
system call to run the command in the child process.
The main
.Nm
process waits until the command has completed, then passes the
command's exit status to the security policy's close function and exits.
As a special case, if the policy plugin does not define a close
function,
.Nm
will execute the command directly instead of calling
.Xr fork 2
first.
The
.Em sudoers
policy plugin will only define a close function when I/O logging
is enabled, a pty is required, or the
.Em pam_session
or
.Em pam_setcred
options are enabled.
Note that
.Em pam_session
and
.Em pam_setcred
are enabled by default on systems using PAM.
.Ss Signal handling
When the command is run as a child of the
.Nm
process,
.Nm
will relay signals it receives to the command.
The
.Dv SIGINT
and
.Dv SIGQUIT
signals are only relayed when the command is being run in a new pty
or when the signal was sent by a user process, not the kernel.
This prevents the command from receiving
.Dv SIGINT
twice each time the user enters control-C.
Some signals, such as
.Dv SIGSTOP
and
.Dv SIGKILL ,
cannot be caught and thus will not be relayed to the command.
As a general rule,
.Dv SIGTSTP
should be used instead of
.Dv SIGSTOP
when you wish to suspend a command being run by
.Nm .
.Pp
As a special case,
.Nm
will not relay signals that were sent by the command it is running.
This prevents the command from accidentally killing itself.
On some systems, the
.Xr reboot @mansectsu@
command sends
.Dv SIGTERM
to all non-system processes other than itself before rebooting
the system.
This prevents
.Nm
from relaying the
.Dv SIGTERM
signal it received back to
.Xr reboot @mansectsu@ ,
which might then exit before the system was actually rebooted,
leaving it in a half-dead state similar to single user mode.
Note, however, that this check only applies to the command run by
.Nm
and not any other processes that the command may create.
As a result, running a script that calls
.Xr reboot @mansectsu@
or
.Xr shutdown @mansectsu@
via
.Nm
may cause the system to end up in this undefined state unless the
.Xr reboot @mansectsu@
or
.Xr shutdown @mansectsu@
are run using the
.Fn exec
family of functions instead of
.Fn system
(which interposes a shell between the command and the calling process).
.Pp
If no I/O logging plugins are loaded and the policy plugin has not
defined a
.Fn close
function, set a command timeout or required that the command be
run in a new pty,
.Nm
may execute the command directly instead of running it as a child process.
.Ss Plugins
Plugins may be specified via
.Li Plugin
directives in the
.Xr sudo.conf @mansectform@
file.
They may be loaded as dynamic shared objects (on systems that support them),
or compiled directly into the
.Nm
binary.
If no
.Xr sudo.conf @mansectform@
file is present, or it contains no
.Li Plugin
lines,
.Nm
will use the traditional
.Em sudoers
security policy and I/O logging.
See the
.Xr sudo.conf @mansectform@
manual for details of the
.Pa @sysconfdir@/sudo.conf
file and the
.Xr sudo_plugin @mansectform@
manual for more information about the
.Nm
plugin architecture.
.Sh EXIT VALUE
Upon successful execution of a command, the exit status from
.Nm
will be the exit status of the program that was executed.
If the command terminated due to receipt of a signal,
.Nm
will send itself the same signal that terminated the command.
.Pp
If the
.Fl l
option was specified without a command,
.Nm
will exit with a value of 0 if the user is allowed to run
.Nm
and they authenticated successfully (as required by the security policy).
If a command is specified with the
.Fl l
option, the exit value will only be 0 if the command is permitted by the
security policy, otherwise it will be 1.
.Pp
If there is an authentication failure, a configuration/permission
problem or if the given command cannot be executed,
.Nm
exits with a value of 1.
In the latter case, the error string is printed to the standard error.
If
.Nm
cannot
.Xr stat 2
one or more entries in the user's
.Ev PATH ,
an error is printed to the standard error.
(If the directory does not exist or if it is not really a directory,
the entry is ignored and no error is printed.)
This should not happen under normal circumstances.
The most common reason for
.Xr stat 2
to return
.Dq permission denied
is if you are running an automounter and one of the directories in
your
.Ev PATH
is on a machine that is currently unreachable.
.Sh SECURITY NOTES
.Nm
tries to be safe when executing external commands.
.Pp
To prevent command spoofing,
.Nm
checks "." and "" (both denoting current directory) last when
searching for a command in the user's
.Ev PATH
(if one or both are in the
.Ev PATH ) .
Note, however, that the actual
.Ev PATH
environment variable is
.Em not
modified and is passed unchanged to the program that
.Nm
executes.
.Pp
Users should
.Em never
be granted
.Nm
privileges to execute files that are writable by the user or
that reside in a directory that is writable by the user.
If the user can modify or replace the command there is no way
to limit what additional commands they can run.
.Pp
Please note that
.Nm
will normally only log the command it explicitly runs.
If a user runs a command such as
.Li sudo su
or
.Li sudo sh ,
subsequent commands run from that shell are not subject to
.Nm sudo Ns 's
security policy.
The same is true for commands that offer shell escapes (including
most editors).
If I/O logging is enabled, subsequent commands will have their input and/or
output logged, but there will not be traditional logs for those commands.
Because of this, care must be taken when giving users access to commands via
.Nm
to verify that the command does not inadvertently give the user an
effective root shell.
For more information, please see the
.Em Preventing shell escapes
section in
.Xr sudoers @mansectform@ .
.Pp
To prevent the disclosure of potentially sensitive information,
.Nm
disables core dumps by default while it is executing (they are
re-enabled for the command that is run).
This historical practice dates from a time when most operating
systems allowed setuid processes to dump core by default.
To aid in debugging
.Nm
crashes, you may wish to re-enable core dumps by setting
.Dq disable_coredump
to false in the
.Xr sudo.conf @mansectform@
file as follows:
.Bd -literal -offset indent
Set disable_coredump false
.Ed
.Pp
See the
.Xr sudo.conf @mansectform@
manual for more information.
.Sh ENVIRONMENT
.Nm
utilizes the following environment variables.
The security policy has control over the actual content of the command's
environment.
.Bl -tag -width 15n
.It Ev EDITOR
Default editor to use in
.Fl e
(sudoedit) mode if neither
.Ev SUDO_EDITOR
nor
.Ev VISUAL
is set.
.It Ev MAIL
Set to the mail spool of the target user when the
.Fl i
option is specified or when
.Em env_reset
is enabled in
.Em sudoers
(unless
.Ev MAIL
is present in the
.Em env_keep
list).
.It Ev HOME
Set to the home directory of the target user when the
.Fl i
or
.Fl H
options are specified, when the
.Fl s
option is specified and
.Em set_home
is set in
.Em sudoers ,
when
.Em always_set_home
is enabled in
.Em sudoers ,
or when
.Em env_reset
is enabled in
.Em sudoers
and
.Em HOME
is not present in the
.Em env_keep
list.
.It Ev LOGNAME
Set to the login name of the target user when the
.Fl i
option is specified, when the
.Em set_logname
option is enabled in
.Em sudoers
or when the
.Em env_reset
option is enabled in
.Em sudoers
(unless
.Ev LOGNAME
is present in the
.Em env_keep
list).
.It Ev PATH
May be overridden by the security policy.
.It Ev SHELL
Used to determine shell to run with
.Fl s
option.
.It Ev SUDO_ASKPASS
Specifies the path to a helper program used to read the password
if no terminal is available or if the
.Fl A
option is specified.
.It Ev SUDO_COMMAND
Set to the command run by sudo.
.It Ev SUDO_EDITOR
Default editor to use in
.Fl e
(sudoedit) mode.
.It Ev SUDO_GID
Set to the group ID of the user who invoked sudo.
.It Ev SUDO_PROMPT
Used as the default password prompt unless
the
.Fl p
option was specified.
.It Ev SUDO_PS1
If set,
.Ev PS1
will be set to its value for the program being run.
.It Ev SUDO_UID
Set to the user ID of the user who invoked sudo.
.It Ev SUDO_USER
Set to the login name of the user who invoked sudo.
.It Ev USER
Set to the same value as
.Ev LOGNAME ,
described above.
.It Ev VISUAL
Default editor to use in
.Fl e
(sudoedit) mode if
.Ev SUDO_EDITOR
is not set.
.El
.Sh FILES
.Bl -tag -width 24n
.It Pa @sysconfdir@/sudo.conf
.Nm
front end configuration
.El
.Sh EXAMPLES
Note: the following examples assume a properly configured security
policy.
.Pp
To get a file listing of an unreadable directory:
.Bd -literal -offset indent
$ sudo ls /usr/local/protected
.Ed
.Pp
To list the home directory of user yaz on a machine where the file
system holding ~yaz is not exported as root:
.Bd -literal -offset indent
$ sudo -u yaz ls ~yaz
.Ed
.Pp
To edit the
.Pa index.html
file as user www:
.Bd -literal -offset indent
$ sudoedit -u www ~www/htdocs/index.html
.Ed
.Pp
To view system logs only accessible to root and users in the adm
group:
.Bd -literal -offset indent
$ sudo -g adm more /var/log/syslog
.Ed
.Pp
To run an editor as jim with a different primary group:
.Bd -literal -offset indent
$ sudoedit -u jim -g audio ~jim/sound.txt
.Ed
.Pp
To shut down a machine:
.Bd -literal -offset indent
$ sudo shutdown -r +15 "quick reboot"
.Ed
.Pp
To make a usage listing of the directories in the /home partition.
Note that this runs the commands in a sub-shell to make the
.Li cd
and file redirection work.
.Bd -literal -offset indent
$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
.Ed
.Sh DIAGNOSTICS
Error messages produced by
.Nm
include:
.Bl -tag -width 4n
.It Li editing files in a writable directory is not permitted
By default,
.Nm sudoedit
does not permit editing a file when any of the parent directories are writable
by the invoking user.
This avoids a race condition that could allow the user to overwrite
an arbitrary file.
See the
.Em sudoedit_checkdir
option in
.Xr sudoers @mansectform@
for more information.
.It Li editing symbolic links is not permitted
By default,
.Nm sudoedit
does not follow symbolic links when opening files.
See the
.Em sudoedit_follow
option in
.Xr sudoers @mansectform@
for more information.
.It Li effective uid is not 0, is sudo installed setuid root?
.Nm
was not run with root privileges.
The
.Nm
binary must be owned by the root user and have the Set-user-ID bit set.
Also, it must not be located on a file system mounted with the
.Sq nosuid
option or on an NFS file system that maps uid 0 to an unprivileged uid.
.It Li effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges?
.Nm
was not run with root privileges.
The
.Nm
binary has the proper owner and permissions but it still did not run
with root privileges.
The most common reason for this is that the file system the
.Nm
binary is located on is mounted with the
.Sq nosuid
option or it is an NFS file system that maps uid 0 to an unprivileged uid.
.It Li fatal error, unable to load plugins
An error occurred while loading or initializing the plugins specified in
.Xr sudo.conf @mansectform@ .
.It Li invalid environment variable name
One or more environment variable names specified via the
.Fl E
option contained an equal sign
.Pq Ql = .
The arguments to the
.Fl E
option should be environment variable names without an associated value.
.It Li no password was provided
When
.Nm
tried to read the password, it did not receive any characters.
This may happen if no terminal is available (or the
.Fl S
option is specified) and the standard input has been redirected from
.Pa /dev/null .
.It Li no tty present and no askpass program specified
.Nm
needs to read the password but there is no mechanism available to do so.
A terminal is not present to read the password from,
.Nm
has not been configured to read from the standard input,
and no askpass program has been specified either via the
.Fl A
option or the
.Ev SUDO_ASKPASS
environment variable.
.It Li no writable temporary directory found
.Nm sudoedit
was unable to find a usable temporary directory in which to store its
intermediate files.
.It Li sudo must be owned by uid 0 and have the setuid bit set
.Nm
was not run with root privileges.
The
.Nm
binary does not have the correct owner or permissions.
It must be owned by the root user and have the Set-user-ID bit set.
.It Li sudoedit is not supported on this platform
It is only possible to run
.Nm sudoedit
on systems that support setting the effective user-ID.
.It Li timed out reading password
The user did not enter a password before the password timeout
(5 minutes by default) expired.
.It Li you do not exist in the passwd database
Your user ID does not appear in the system passwd database.
.It Li you may not specify environment variables in edit mode
It is only possible to specify environment variables when running
a command.
When editing a file, the editor is run with the user's environment unmodified.
.El
.Sh SEE ALSO
.Xr su 1 ,
.Xr stat 2 ,
.Xr login_cap 3 ,
.Xr passwd @mansectform@ ,
.Xr sudo.conf @mansectform@ ,
.Xr sudo_plugin @mansectform@ ,
.Xr sudoers @mansectform@ ,
.Xr sudoreplay @mansectsu@ ,
.Xr visudo @mansectsu@
.Sh HISTORY
See the HISTORY file in the
.Nm
distribution (https://www.sudo.ws/history.html) for a brief
history of sudo.
.Sh AUTHORS
Many people have worked on
.Nm
over the years; this version consists of code written primarily by:
.Bd -ragged -offset indent
.An Todd C. Miller
.Ed
.Pp
See the CONTRIBUTORS file in the
.Nm
distribution (https://www.sudo.ws/contributors.html) for an
exhaustive list of people who have contributed to
.Nm .
.Sh CAVEATS
There is no easy way to prevent a user from gaining a root shell
if that user is allowed to run arbitrary commands via
.Nm .
Also, many programs (such as editors) allow the user to run commands
via shell escapes, thus avoiding
.Nm sudo Ns 's
checks.
However, on most systems it is possible to prevent shell escapes with the
.Xr sudoers @mansectform@
plugin's
.Em noexec
functionality.
.Pp
It is not meaningful to run the
.Li cd
command directly via sudo, e.g.,
.Bd -literal -offset indent
$ sudo cd /usr/local/protected
.Ed
.Pp
since when the command exits the parent process (your shell) will
still be the same.
Please see the
.Sx EXAMPLES
section for more information.
.Pp
Running shell scripts via
.Nm
can expose the same kernel bugs that make setuid shell scripts
unsafe on some operating systems (if your OS has a /dev/fd/ directory,
setuid shell scripts are generally safe).
.Sh BUGS
If you feel you have found a bug in
.Nm ,
please submit a bug report at https://bugzilla.sudo.ws/
.Sh SUPPORT
Limited free support is available via the sudo-users mailing list,
see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
search the archives.
.Sh DISCLAIMER
.Nm
is provided
.Dq AS IS
and any express or implied warranties, including, but not limited
to, the implied warranties of merchantability and fitness for a
particular purpose are disclaimed.
See the LICENSE file distributed with
.Nm
or https://www.sudo.ws/license.html for complete details.
|