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diff --git a/doc/sudo.man.in b/doc/sudo.man.in new file mode 100644 index 0000000..ffcd468 --- /dev/null +++ b/doc/sudo.man.in @@ -0,0 +1,1431 @@ +.\" Automatically generated from an mdoc input file. Do not edit. +.\" +.\" 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@ +.TH "SUDO" "@mansectsu@" "November 25, 2018" "Sudo @PACKAGE_VERSION@" "System Manager's Manual" +.nh +.if n .ad l +.SH "NAME" +\fBsudo\fR, +\fBsudoedit\fR +\- execute a command as another user +.SH "SYNOPSIS" +.HP 5n +\fBsudo\fR +\fB\-h\fR\ |\ \fB\-K\fR\ |\ \fB\-k\fR\ |\ \fB\-V\fR +.br +.PD 0 +.HP 5n +\fBsudo\fR +\fB\-v\fR +[\fB\-AknS\fR] +.if \n(BA [\fB\-a\fR\ \fItype\fR] +[\fB\-g\fR\ \fIgroup\fR] +[\fB\-h\fR\ \fIhost\fR] +[\fB\-p\fR\ \fIprompt\fR] +[\fB\-u\fR\ \fIuser\fR] +.br +.HP 5n +\fBsudo\fR +\fB\-l\fR +[\fB\-AknS\fR] +.if \n(BA [\fB\-a\fR\ \fItype\fR] +[\fB\-g\fR\ \fIgroup\fR] +[\fB\-h\fR\ \fIhost\fR] +[\fB\-p\fR\ \fIprompt\fR] +[\fB\-U\fR\ \fIuser\fR] +[\fB\-u\fR\ \fIuser\fR] +[\fIcommand\fR] +.br +.HP 5n +\fBsudo\fR +[\fB\-AbEHnPS\fR] +.if \n(BA [\fB\-a\fR\ \fItype\fR] +[\fB\-C\fR\ \fInum\fR] +.if \n(LC [\fB\-c\fR\ \fIclass\fR] +[\fB\-g\fR\ \fIgroup\fR] +[\fB\-h\fR\ \fIhost\fR] +[\fB\-p\fR\ \fIprompt\fR] +.if \n(SL [\fB\-r\fR\ \fIrole\fR] +.if \n(SL [\fB\-t\fR\ \fItype\fR] +[\fB\-T\fR\ \fItimeout\fR] +[\fB\-u\fR\ \fIuser\fR] +[\fIVAR\fR=\fIvalue\fR] +[\fB\-i\fR\ |\ \fB\-s\fR] +[\fIcommand\fR] +.br +.HP 9n +\fBsudoedit\fR +[\fB\-AknS\fR] +.if \n(BA [\fB\-a\fR\ \fItype\fR] +[\fB\-C\fR\ \fInum\fR] +.if \n(LC [\fB\-c\fR\ \fIclass\fR] +[\fB\-g\fR\ \fIgroup\fR] +[\fB\-h\fR\ \fIhost\fR] +[\fB\-p\fR\ \fIprompt\fR] +[\fB\-T\fR\ \fItimeout\fR] +[\fB\-u\fR\ \fIuser\fR] +\fIfile\ ...\fR +.PD +.SH "DESCRIPTION" +\fBsudo\fR +allows a permitted user to execute a +\fIcommand\fR +as the superuser or another user, as specified by the security +policy. +The invoking user's real +(\fInot\fR effective) +user ID is used to determine the user name with which +to query the security policy. +.PP +\fBsudo\fR +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 +\fBsudo\fR +front end. +The default security policy is +\fIsudoers\fR, +which is configured via the file +\fI@sysconfdir@/sudoers\fR, +or via LDAP. +See the +\fIPlugins\fR +section for more information. +.PP +The security policy determines what privileges, if any, a user has +to run +\fBsudo\fR. +The policy may require that users authenticate themselves with a +password or another authentication mechanism. +If authentication is required, +\fBsudo\fR +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 +\fIsudoers\fR +security policy is +\fR@password_timeout@\fR +minutes. +.PP +Security policies may support credential caching to allow the user +to run +\fBsudo\fR +again for a period of time without requiring authentication. +The +\fIsudoers\fR +policy caches credentials for +\fR@timeout@\fR +minutes, unless overridden in +sudoers(@mansectform@). +By running +\fBsudo\fR +with the +\fB\-v\fR +option, a user can update the cached credentials without running a +\fIcommand\fR. +.PP +When invoked as +\fBsudoedit\fR, +the +\fB\-e\fR +option (described below), is implied. +.PP +Security policies may log successful and failed attempts to use +\fBsudo\fR. +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: +.TP 12n +\fB\-A\fR, \fB\--askpass\fR +Normally, if +\fBsudo\fR +requires a password, it will read it from the user's terminal. +If the +\fB\-A\fR (\fIaskpass\fR) +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 +\fRSUDO_ASKPASS\fR +environment variable is set, it specifies the path to the helper +program. +Otherwise, if +sudo.conf(@mansectform@) +contains a line specifying the askpass program, that value will be +used. +For example: +.nf +.sp +.RS 16n +# Path to askpass helper program +Path askpass /usr/X11R6/bin/ssh-askpass +.RE +.fi +.RS 12n +.sp +If no askpass program is available, +\fBsudo\fR +will exit with an error. +.RE +.if \n(BA \{\ +.TP 12n +\fB\-a\fR \fItype\fR, \fB\--auth-type\fR=\fItype\fR +Use the specified +BSD +authentication +\fItype\fR +when validating the user, if allowed by +\fI/etc/login.conf\fR. +The system administrator may specify a list of sudo-specific +authentication methods by adding an +\(lqauth-sudo\(rq +entry in +\fI/etc/login.conf\fR. +This option is only available on systems that support +BSD +authentication. +.\} +.TP 12n +\fB\-b\fR, \fB\--background\fR +Run the given command in the background. +Note that it is not possible to use shell job control to manipulate +background processes started by +\fBsudo\fR. +Most interactive commands will fail to work properly in background +mode. +.TP 12n +\fB\-C\fR \fInum\fR, \fB\--close-from\fR=\fInum\fR +Close all file descriptors greater than or equal to +\fInum\fR +before executing a command. +Values less than three are not permitted. +By default, +\fBsudo\fR +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 +\fIsudoers\fR +policy only permits use of the +\fB\-C\fR +option when the administrator has enabled the +\fIclosefrom_override\fR +option. +.if \n(LC \{\ +.TP 12n +\fB\-c\fR \fIclass\fR, \fB\--login-class\fR=\fIclass\fR +Run the command with resource limits and scheduling priority of +the specified login +\fIclass\fR. +The +\fIclass\fR +argument can be either a class name as defined in +\fI/etc/login.conf\fR, +or a single +\(oq\-\(cq +character. +If +\fIclass\fR +is +\fB-\fR, +the default login class of the target user will be used. +Otherwise, the command must be run as the superuser (user ID 0), or +\fBsudo\fR +must be run from a shell that is already running as the superuser. +If the command is being run as a login shell, additional +\fI/etc/login.conf\fR +settings, such as the umask and environment variables, will +be applied, if present. +This option is only available on systems with +BSD +login classes. +.\} +.TP 12n +\fB\-E\fR, \fB\--preserve-env\fR +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. +.TP 12n +\fB\--preserve-env=list\fR +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. +.TP 12n +\fB\-e\fR, \fB\--edit\fR +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: +.RS 16n +.TP 5n +1.\& +Temporary copies are made of the files to be edited with the owner +set to the invoking user. +.TP 5n +2.\& +The editor specified by the policy is run to edit the temporary +files. +The +\fIsudoers\fR +policy uses the +\fRSUDO_EDITOR\fR, +\fRVISUAL\fR +and +\fREDITOR\fR +environment variables (in that order). +If none of +\fRSUDO_EDITOR\fR, +\fRVISUAL\fR +or +\fREDITOR\fR +are set, the first program listed in the +\fIeditor\fR +sudoers(@mansectform@) +option is used. +.TP 5n +3.\& +If they have been modified, the temporary files are copied back to +their original location and the temporary versions are removed. +.RE +.RS 12n +.sp +To help prevent the editing of unauthorized files, the following +restrictions are enforced unless explicitly allowed by the security policy: +.RS 16n +.TP 3n +\fB\(bu\fR +Symbolic links may not be edited (version 1.8.15 and higher). +.TP 3n +\fB\(bu\fR +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). +.TP 3n +\fB\(bu\fR +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). +.RE +.sp +Users are never allowed to edit device special files. +.sp +If the specified file does not exist, it will be created. +Note that unlike most commands run by +\fIsudo\fR, +the editor is run with the invoking user's environment unmodified. +If, for some reason, +\fBsudo\fR +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. +.RE +.TP 12n +\fB\-g\fR \fIgroup\fR, \fB\--group\fR=\fIgroup\fR +Run the command with the primary group set to +\fIgroup\fR +instead of the primary group specified by the target +user's password database entry. +The +\fIgroup\fR +may be either a group name or a numeric group ID +(GID) +prefixed with the +\(oq#\(cq +character (e.g., +\fR#0\fR +for GID 0). +When running a command as a GID, many shells require that the +\(oq#\(cq +be escaped with a backslash +(\(oq\e\(cq). +If no +\fB\-u\fR +option is specified, the command will be run as the invoking user. +In either case, the primary group will be set to +\fIgroup\fR. +The +\fIsudoers\fR +policy permits any of the target user's groups to be specified via +the +\fB\-g\fR +option as long as the +\fB\-P\fR +option is not in use. +.TP 12n +\fB\-H\fR, \fB\--set-home\fR +Request that the security policy set the +\fRHOME\fR +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. +.TP 12n +\fB\-h\fR, \fB\--help\fR +Display a short help message to the standard output and exit. +.TP 12n +\fB\-h\fR \fIhost\fR, \fB\--host\fR=\fIhost\fR +Run the command on the specified +\fIhost\fR +if the security policy plugin supports remote commands. +Note that the +\fIsudoers\fR +plugin does not currently support running remote commands. +This may also be used in conjunction with the +\fB\-l\fR +option to list a user's privileges for the remote host. +.TP 12n +\fB\-i\fR, \fB\--login\fR +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 +\fI.profile\fR, +\fI.bash_profile\fR +or +\fI.login\fR +will be read by the shell. +If a command is specified, it is passed to the shell for execution +via the shell's +\fB\-c\fR +option. +If no command is specified, an interactive shell is executed. +\fBsudo\fR +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 +\fICommand environment\fR +section in the +sudoers(@mansectform@) +manual documents how the +\fB\-i\fR +option affects the environment in which a command is run when the +\fIsudoers\fR +policy is in use. +.TP 12n +\fB\-K\fR, \fB\--remove-timestamp\fR +Similar to the +\fB\-k\fR +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. +.TP 12n +\fB\-k\fR, \fB\--reset-timestamp\fR +When used without a command, invalidates the user's cached credentials. +In other words, the next time +\fBsudo\fR +is run a password will be required. +This option does not require a password and was added to allow a +user to revoke +\fBsudo\fR +permissions from a +\fI.logout\fR +file. +.sp +When used in conjunction with a command or an option that may require +a password, this option will cause +\fBsudo\fR +to ignore the user's cached credentials. +As a result, +\fBsudo\fR +will prompt for a password (if one is required by the security +policy) and will not update the user's cached credentials. +.sp +Not all security policies support credential caching. +.TP 12n +\fB\-l\fR, \fB\--list\fR +If no +\fIcommand\fR +is specified, +list the allowed (and forbidden) commands for the +invoking user (or the user specified by the +\fB\-U\fR +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. +.sp +If a +\fIcommand\fR +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 +\fIcommand\fR +is specified but not allowed by the policy, +\fBsudo\fR +will exit with a status value of 1. +.TP 12n +\fB\-n\fR, \fB\--non-interactive\fR +Avoid prompting the user for input of any kind. +If a password is required for the command to run, +\fBsudo\fR +will display an error message and exit. +.TP 12n +\fB\-P\fR, \fB\--preserve-groups\fR +Preserve the invoking user's group vector unaltered. +By default, the +\fIsudoers\fR +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. +.TP 12n +\fB\-p\fR \fIprompt\fR, \fB\--prompt\fR=\fIprompt\fR +Use a custom password prompt with optional escape sequences. +The following percent +(\(oq%\(cq) +escape sequences are supported by the +\fIsudoers\fR +policy: +.PP +.RS 12n +.PD 0 +.TP 4n +\fR%H\fR +expanded to the host name including the domain name (on if the +machine's host name is fully qualified or the +\fIfqdn\fR +option is set in +sudoers(@mansectform@)) +.PD +.TP 4n +\fR%h\fR +expanded to the local host name without the domain name +.TP 4n +\fR%p\fR +expanded to the name of the user whose password is being requested +(respects the +\fIrootpw\fR, +\fItargetpw\fR, +and +\fIrunaspw\fR +flags in +sudoers(@mansectform@)) +.TP 4n +\fR\&%U\fR +expanded to the login name of the user the command will be run as +(defaults to root unless the +\fB\-u\fR +option is also specified) +.TP 4n +\fR%u\fR +expanded to the invoking user's login name +.TP 4n +\fR%%\fR +two consecutive +\(oq%\(cq +characters are collapsed into a single +\(oq%\(cq +character +.PP +The custom prompt will override the default prompt specified by either +the security policy or the +\fRSUDO_PROMPT\fR +environment variable. +On systems that use PAM, the custom prompt will also override the prompt +specified by a PAM module unless the +\fIpassprompt_override\fR +flag is disabled in +\fIsudoers\fR. +.RE +.if \n(SL \{\ +.TP 12n +\fB\-r\fR \fIrole\fR, \fB\--role\fR=\fIrole\fR +Run the command with an SELinux security context that includes +the specified +\fIrole\fR. +.\} +.TP 12n +\fB\-S\fR, \fB\--stdin\fR +Write the prompt to the standard error and read the password from the +standard input instead of using the terminal device. +.TP 12n +\fB\-s\fR, \fB\--shell\fR +Run the shell specified by the +\fRSHELL\fR +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 +\fB\-c\fR +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 \{\ +.TP 12n +\fB\-t\fR \fItype\fR, \fB\--type\fR=\fItype\fR +Run the command with an SELinux security context that includes +the specified +\fItype\fR. +If no +\fItype\fR +is specified, the default type is derived from the role. +.\} +.TP 12n +\fB\-U\fR \fIuser\fR, \fB\--other-user\fR=\fIuser\fR +Used in conjunction with the +\fB\-l\fR +option to list the privileges for +\fIuser\fR +instead of for the invoking user. +The security policy may restrict listing other users' privileges. +The +\fIsudoers\fR +policy only allows root or a user with the +\fRALL\fR +privilege on the current host to use this option. +.TP 12n +\fB\-T\fR \fItimeout\fR, \fB\--command-timeout\fR=\fItimeout\fR +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 +\fIsudoers\fR +policy requires that user-specified timeouts be explicitly enabled. +.TP 12n +\fB\-u\fR \fIuser\fR, \fB\--user\fR=\fIuser\fR +Run the command as a user other than the default target user +(usually +\fIroot\fR). +The +\fIuser\fR +may be either a user name or a numeric user ID +(UID) +prefixed with the +\(oq#\(cq +character (e.g., +\fR#0\fR +for UID 0). +When running commands as a UID, many shells require that the +\(oq#\(cq +be escaped with a backslash +(\(oq\e\(cq). +Some security policies may restrict UIDs +to those listed in the password database. +The +\fIsudoers\fR +policy allows UIDs that are not in the password database as long as the +\fItargetpw\fR +option is not set. +Other security policies may not support this. +.TP 12n +\fB\-V\fR, \fB\--version\fR +Print the +\fBsudo\fR +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 +\fB\-V\fR +option will display the arguments passed to configure when +\fBsudo\fR +was built and plugins may display more verbose information such as +default options. +.TP 12n +\fB\-v\fR, \fB\--validate\fR +Update the user's cached credentials, authenticating the user +if necessary. +For the +\fIsudoers\fR +plugin, this extends the +\fBsudo\fR +timeout for another +\fR@timeout@\fR +minutes by default, but does not run a command. +Not all security policies support cached credentials. +.TP 12n +\fB\--\fR +The +\fB\--\fR +option indicates that +\fBsudo\fR +should stop processing command line arguments. +.PP +Environment variables to be set for the command may also be passed +on the command line in the form of +\fIVAR\fR=\fIvalue\fR, +e.g., +\fRLD_LIBRARY_PATH\fR=\fI/usr/local/pkg/lib\fR. +Variables passed on the command line are subject to restrictions +imposed by the security policy plugin. +The +\fIsudoers\fR +policy subjects variables passed on the command line to the same +restrictions as normal environment variables with one important +exception. +If the +\fIsetenv\fR +option is set in +\fIsudoers\fR, +the command to be run has the +\fRSETENV\fR +tag set or the command matched is +\fRALL\fR, +the user may set variables that would otherwise be forbidden. +See +sudoers(@mansectform@) +for more information. +.SH "COMMAND EXECUTION" +When +\fBsudo\fR +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 +\fB\-P\fR +option was specified). +.PP +The following parameters may be specified by security policy: +.TP 3n +\fB\(bu\fR +real and effective user ID +.TP 3n +\fB\(bu\fR +real and effective group ID +.TP 3n +\fB\(bu\fR +supplementary group IDs +.TP 3n +\fB\(bu\fR +the environment list +.TP 3n +\fB\(bu\fR +current working directory +.TP 3n +\fB\(bu\fR +file creation mode mask (umask) +.if \n(SL \{\ +.TP 3n +\fB\(bu\fR +SELinux role and type +.\} +.if \n(PS \{\ +.TP 3n +\fB\(bu\fR +Solaris project +.\} +.if \n(PS \{\ +.TP 3n +\fB\(bu\fR +Solaris privileges +.\} +.if \n(LC \{\ +.TP 3n +\fB\(bu\fR +BSD +login class +.\} +.TP 3n +\fB\(bu\fR +scheduling priority (aka nice value) +.SS "Process model" +There are two distinct ways +\fBsudo\fR +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 +(\(lqpty\(rq) +is allocated and +fork(2) +is used to create a second +\fBsudo\fR +process, referred to as the +\fImonitor\fR. +The +\fImonitor\fR +creates a new terminal session with itself as the leader and the pty as its +controlling terminal, calls +fork(2), +sets up the execution environment as described above, and then uses the +execve(2) +system call to run the command in the child process. +The +\fImonitor\fR +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 +\(lqorphaned process group\(rq +and it would not receive any job control signals from the kernel. +When the command exits or is terminated by a signal, the +\fImonitor\fR +passes the command's exit status to the main +\fBsudo\fR +process and exits. +After receiving the command's exit status, the main +\fBsudo\fR +passes the command's exit status to the security policy's close function +and exits. +.PP +If no pty is used, +\fBsudo\fR +calls +fork(2), +sets up the execution environment as described above, and uses the +execve(2) +system call to run the command in the child process. +The main +\fBsudo\fR +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, +\fBsudo\fR +will execute the command directly instead of calling +fork(2) +first. +The +\fIsudoers\fR +policy plugin will only define a close function when I/O logging +is enabled, a pty is required, or the +\fIpam_session\fR +or +\fIpam_setcred\fR +options are enabled. +Note that +\fIpam_session\fR +and +\fIpam_setcred\fR +are enabled by default on systems using PAM. +.SS "Signal handling" +When the command is run as a child of the +\fBsudo\fR +process, +\fBsudo\fR +will relay signals it receives to the command. +The +\fRSIGINT\fR +and +\fRSIGQUIT\fR +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 +\fRSIGINT\fR +twice each time the user enters control-C. +Some signals, such as +\fRSIGSTOP\fR +and +\fRSIGKILL\fR, +cannot be caught and thus will not be relayed to the command. +As a general rule, +\fRSIGTSTP\fR +should be used instead of +\fRSIGSTOP\fR +when you wish to suspend a command being run by +\fBsudo\fR. +.PP +As a special case, +\fBsudo\fR +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 +reboot(@mansectsu@) +command sends +\fRSIGTERM\fR +to all non-system processes other than itself before rebooting +the system. +This prevents +\fBsudo\fR +from relaying the +\fRSIGTERM\fR +signal it received back to +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 +\fBsudo\fR +and not any other processes that the command may create. +As a result, running a script that calls +reboot(@mansectsu@) +or +shutdown(@mansectsu@) +via +\fBsudo\fR +may cause the system to end up in this undefined state unless the +reboot(@mansectsu@) +or +shutdown(@mansectsu@) +are run using the +\fBexec\fR() +family of functions instead of +\fBsystem\fR() +(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 +\fBclose\fR() +function, set a command timeout or required that the command be +run in a new pty, +\fBsudo\fR +may execute the command directly instead of running it as a child process. +.SS "Plugins" +Plugins may be specified via +\fRPlugin\fR +directives in the +sudo.conf(@mansectform@) +file. +They may be loaded as dynamic shared objects (on systems that support them), +or compiled directly into the +\fBsudo\fR +binary. +If no +sudo.conf(@mansectform@) +file is present, or it contains no +\fRPlugin\fR +lines, +\fBsudo\fR +will use the traditional +\fIsudoers\fR +security policy and I/O logging. +See the +sudo.conf(@mansectform@) +manual for details of the +\fI@sysconfdir@/sudo.conf\fR +file and the +sudo_plugin(@mansectform@) +manual for more information about the +\fBsudo\fR +plugin architecture. +.SH "EXIT VALUE" +Upon successful execution of a command, the exit status from +\fBsudo\fR +will be the exit status of the program that was executed. +If the command terminated due to receipt of a signal, +\fBsudo\fR +will send itself the same signal that terminated the command. +.PP +If the +\fB\-l\fR +option was specified without a command, +\fBsudo\fR +will exit with a value of 0 if the user is allowed to run +\fBsudo\fR +and they authenticated successfully (as required by the security policy). +If a command is specified with the +\fB\-l\fR +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, +\fBsudo\fR +exits with a value of 1. +In the latter case, the error string is printed to the standard error. +If +\fBsudo\fR +cannot +stat(2) +one or more entries in the user's +\fRPATH\fR, +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 +stat(2) +to return +\(lqpermission denied\(rq +is if you are running an automounter and one of the directories in +your +\fRPATH\fR +is on a machine that is currently unreachable. +.SH "SECURITY NOTES" +\fBsudo\fR +tries to be safe when executing external commands. +.PP +To prevent command spoofing, +\fBsudo\fR +checks "." and "" (both denoting current directory) last when +searching for a command in the user's +\fRPATH\fR +(if one or both are in the +\fRPATH\fR). +Note, however, that the actual +\fRPATH\fR +environment variable is +\fInot\fR +modified and is passed unchanged to the program that +\fBsudo\fR +executes. +.PP +Users should +\fInever\fR +be granted +\fBsudo\fR +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 +\fBsudo\fR +will normally only log the command it explicitly runs. +If a user runs a command such as +\fRsudo su\fR +or +\fRsudo sh\fR, +subsequent commands run from that shell are not subject to +\fBsudo\fR'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 +\fBsudo\fR +to verify that the command does not inadvertently give the user an +effective root shell. +For more information, please see the +\fIPreventing shell escapes\fR +section in +sudoers(@mansectform@). +.PP +To prevent the disclosure of potentially sensitive information, +\fBsudo\fR +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 +\fBsudo\fR +crashes, you may wish to re-enable core dumps by setting +\(lqdisable_coredump\(rq +to false in the +sudo.conf(@mansectform@) +file as follows: +.nf +.sp +.RS 6n +Set disable_coredump false +.RE +.fi +.PP +See the +sudo.conf(@mansectform@) +manual for more information. +.SH "ENVIRONMENT" +\fBsudo\fR +utilizes the following environment variables. +The security policy has control over the actual content of the command's +environment. +.TP 17n +\fREDITOR\fR +Default editor to use in +\fB\-e\fR +(sudoedit) mode if neither +\fRSUDO_EDITOR\fR +nor +\fRVISUAL\fR +is set. +.TP 17n +\fRMAIL\fR +Set to the mail spool of the target user when the +\fB\-i\fR +option is specified or when +\fIenv_reset\fR +is enabled in +\fIsudoers\fR +(unless +\fRMAIL\fR +is present in the +\fIenv_keep\fR +list). +.TP 17n +\fRHOME\fR +Set to the home directory of the target user when the +\fB\-i\fR +or +\fB\-H\fR +options are specified, when the +\fB\-s\fR +option is specified and +\fIset_home\fR +is set in +\fIsudoers\fR, +when +\fIalways_set_home\fR +is enabled in +\fIsudoers\fR, +or when +\fIenv_reset\fR +is enabled in +\fIsudoers\fR +and +\fIHOME\fR +is not present in the +\fIenv_keep\fR +list. +.TP 17n +\fRLOGNAME\fR +Set to the login name of the target user when the +\fB\-i\fR +option is specified, when the +\fIset_logname\fR +option is enabled in +\fIsudoers\fR +or when the +\fIenv_reset\fR +option is enabled in +\fIsudoers\fR +(unless +\fRLOGNAME\fR +is present in the +\fIenv_keep\fR +list). +.TP 17n +\fRPATH\fR +May be overridden by the security policy. +.TP 17n +\fRSHELL\fR +Used to determine shell to run with +\fB\-s\fR +option. +.TP 17n +\fRSUDO_ASKPASS\fR +Specifies the path to a helper program used to read the password +if no terminal is available or if the +\fB\-A\fR +option is specified. +.TP 17n +\fRSUDO_COMMAND\fR +Set to the command run by sudo. +.TP 17n +\fRSUDO_EDITOR\fR +Default editor to use in +\fB\-e\fR +(sudoedit) mode. +.TP 17n +\fRSUDO_GID\fR +Set to the group ID of the user who invoked sudo. +.TP 17n +\fRSUDO_PROMPT\fR +Used as the default password prompt unless +the +\fB\-p\fR +option was specified. +.TP 17n +\fRSUDO_PS1\fR +If set, +\fRPS1\fR +will be set to its value for the program being run. +.TP 17n +\fRSUDO_UID\fR +Set to the user ID of the user who invoked sudo. +.TP 17n +\fRSUDO_USER\fR +Set to the login name of the user who invoked sudo. +.TP 17n +\fRUSER\fR +Set to the same value as +\fRLOGNAME\fR, +described above. +.TP 17n +\fRVISUAL\fR +Default editor to use in +\fB\-e\fR +(sudoedit) mode if +\fRSUDO_EDITOR\fR +is not set. +.SH "FILES" +.TP 26n +\fI@sysconfdir@/sudo.conf\fR +\fBsudo\fR +front end configuration +.SH "EXAMPLES" +Note: the following examples assume a properly configured security +policy. +.PP +To get a file listing of an unreadable directory: +.nf +.sp +.RS 6n +$ sudo ls /usr/local/protected +.RE +.fi +.PP +To list the home directory of user yaz on a machine where the file +system holding ~yaz is not exported as root: +.nf +.sp +.RS 6n +$ sudo -u yaz ls ~yaz +.RE +.fi +.PP +To edit the +\fIindex.html\fR +file as user www: +.nf +.sp +.RS 6n +$ sudoedit -u www ~www/htdocs/index.html +.RE +.fi +.PP +To view system logs only accessible to root and users in the adm +group: +.nf +.sp +.RS 6n +$ sudo -g adm more /var/log/syslog +.RE +.fi +.PP +To run an editor as jim with a different primary group: +.nf +.sp +.RS 6n +$ sudoedit -u jim -g audio ~jim/sound.txt +.RE +.fi +.PP +To shut down a machine: +.nf +.sp +.RS 6n +$ sudo shutdown -r +15 "quick reboot" +.RE +.fi +.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 +\fRcd\fR +and file redirection work. +.nf +.sp +.RS 6n +$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" +.RE +.fi +.SH "DIAGNOSTICS" +Error messages produced by +\fBsudo\fR +include: +.TP 6n +\fRediting files in a writable directory is not permitted\fR +By default, +\fBsudoedit\fR +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 +\fIsudoedit_checkdir\fR +option in +sudoers(@mansectform@) +for more information. +.TP 6n +\fRediting symbolic links is not permitted\fR +By default, +\fBsudoedit\fR +does not follow symbolic links when opening files. +See the +\fIsudoedit_follow\fR +option in +sudoers(@mansectform@) +for more information. +.TP 6n +\fReffective uid is not 0, is sudo installed setuid root?\fR +\fBsudo\fR +was not run with root privileges. +The +\fBsudo\fR +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 +\(oqnosuid\(cq +option or on an NFS file system that maps uid 0 to an unprivileged uid. +.TP 6n +\fReffective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges?\fR +\fBsudo\fR +was not run with root privileges. +The +\fBsudo\fR +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 +\fBsudo\fR +binary is located on is mounted with the +\(oqnosuid\(cq +option or it is an NFS file system that maps uid 0 to an unprivileged uid. +.TP 6n +\fRfatal error, unable to load plugins\fR +An error occurred while loading or initializing the plugins specified in +sudo.conf(@mansectform@). +.TP 6n +\fRinvalid environment variable name\fR +One or more environment variable names specified via the +\fB\-E\fR +option contained an equal sign +(\(oq=\(cq). +The arguments to the +\fB\-E\fR +option should be environment variable names without an associated value. +.TP 6n +\fRno password was provided\fR +When +\fBsudo\fR +tried to read the password, it did not receive any characters. +This may happen if no terminal is available (or the +\fB\-S\fR +option is specified) and the standard input has been redirected from +\fI/dev/null\fR. +.TP 6n +\fRno tty present and no askpass program specified\fR +\fBsudo\fR +needs to read the password but there is no mechanism available to do so. +A terminal is not present to read the password from, +\fBsudo\fR +has not been configured to read from the standard input, +and no askpass program has been specified either via the +\fB\-A\fR +option or the +\fRSUDO_ASKPASS\fR +environment variable. +.TP 6n +\fRno writable temporary directory found\fR +\fBsudoedit\fR +was unable to find a usable temporary directory in which to store its +intermediate files. +.TP 6n +\fRsudo must be owned by uid 0 and have the setuid bit set\fR +\fBsudo\fR +was not run with root privileges. +The +\fBsudo\fR +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. +.TP 6n +\fRsudoedit is not supported on this platform\fR +It is only possible to run +\fBsudoedit\fR +on systems that support setting the effective user-ID. +.TP 6n +\fRtimed out reading password\fR +The user did not enter a password before the password timeout +(5 minutes by default) expired. +.TP 6n +\fRyou do not exist in the passwd database\fR +Your user ID does not appear in the system passwd database. +.TP 6n +\fRyou may not specify environment variables in edit mode\fR +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. +.SH "SEE ALSO" +su(1), +stat(2), +login_cap(3), +passwd(@mansectform@), +sudo.conf(@mansectform@), +sudo_plugin(@mansectform@), +sudoers(@mansectform@), +sudoreplay(@mansectsu@), +visudo(@mansectsu@) +.SH "HISTORY" +See the HISTORY file in the +\fBsudo\fR +distribution (https://www.sudo.ws/history.html) for a brief +history of sudo. +.SH "AUTHORS" +Many people have worked on +\fBsudo\fR +over the years; this version consists of code written primarily by: +.sp +.RS 6n +Todd C. Miller +.RE +.PP +See the CONTRIBUTORS file in the +\fBsudo\fR +distribution (https://www.sudo.ws/contributors.html) for an +exhaustive list of people who have contributed to +\fBsudo\fR. +.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 +\fBsudo\fR. +Also, many programs (such as editors) allow the user to run commands +via shell escapes, thus avoiding +\fBsudo\fR's +checks. +However, on most systems it is possible to prevent shell escapes with the +sudoers(@mansectform@) +plugin's +\fInoexec\fR +functionality. +.PP +It is not meaningful to run the +\fRcd\fR +command directly via sudo, e.g., +.nf +.sp +.RS 6n +$ sudo cd /usr/local/protected +.RE +.fi +.PP +since when the command exits the parent process (your shell) will +still be the same. +Please see the +\fIEXAMPLES\fR +section for more information. +.PP +Running shell scripts via +\fBsudo\fR +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 +\fBsudo\fR, +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" +\fBsudo\fR +is provided +\(lqAS IS\(rq +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 +\fBsudo\fR +or https://www.sudo.ws/license.html for complete details. |