Sudo: Unterschied zwischen den Versionen

Aus Foxwiki
Versionsgeschichte interaktiv durchsuchen
← Zum vorherigen Versionsunterschied
VisuellWikitext
K Textersetzung - „= Umgebungsvariablen =“ durch „= Umgebung =“
 
(25 dazwischenliegende Versionen desselben Benutzers werden nicht angezeigt)
Zeile 1: Zeile 1:
{{DISPLAYTITLE:sudo}}
{{DISPLAYTITLE:sudo}}
'''sudo''' führt Kommandos mit der Identität eines anderen Benutzers aus
'''sudo''' führt Kommandos mit der Identität eines anderen Benutzers aus


== Beschreibung ==
== Beschreibung ==
* Der Befehl sudo kann Programmaufrufen vorangestellt werden.
* Der Befehl sudo kann Programmaufrufen vorangestellt werden
* Er ermöglicht berechtigten Benutzern, das Programm im Namen und mit den Rechten eines anderen Benutzers auszuführen.
* Er ermöglicht berechtigten Benutzern, das Programm im Namen und mit den Rechten eines anderen Benutzers auszuführen.
* sudo, sudoedit — execute a command as another user
* sudo, sudoedit — execute a command as another user
Zeile 22: Zeile 21:


Sicherheitsrichtlinien können das Zwischenspeichern von Anmeldeinformationen unterstützen, damit der Benutzer sudo für eine gewisse Zeit erneut ausführen kann, ohne dass eine Authentifizierung erforderlich ist.  
Sicherheitsrichtlinien können das Zwischenspeichern von Anmeldeinformationen unterstützen, damit der Benutzer sudo für eine gewisse Zeit erneut ausführen kann, ohne dass eine Authentifizierung erforderlich ist.  
* Durch De-
 
Die sudoers-Richtlinie zwischenspeichert Anmeldeinformationen für jedes Terminal für 15 Minuten.  
Die sudoers-Richtlinie zwischenspeichert Anmeldeinformationen für jedes Terminal für 15 Minuten.  
* Weitere Informationen finden Sie unter den Optionen timestamp_type und timestamp_timeout in sudoers(5).  
* Weitere Informationen finden Sie unter den Optionen timestamp_type und timestamp_timeout in sudoers(5).  
Zeile 28: Zeile 27:


Auf Systemen, auf denen sudo die primäre Methode zur Erlangung von Superuser-Rechten ist, müssen unbedingt Syntaxfehler in den Konfigurationsdateien der Sicherheitsrichtlinien vermieden werden.
Auf Systemen, auf denen sudo die primäre Methode zur Erlangung von Superuser-Rechten ist, müssen unbedingt Syntaxfehler in den Konfigurationsdateien der Sicherheitsrichtlinien vermieden werden.
tionsdateien zu vermeiden.
 
 
* Für die Standard-Sicherheitsrichtlinie sudoers(5) sollten Änderungen an den Konfigurationsdateien mit dem Dienstprogramm visudo(8) vorgenommen werden.
* Für die Standard-Sicherheitsrichtlinie sudoers(5) sollten Änderungen an den Konfigurationsdateien mit dem Dienstprogramm visudo(8) vorgenommen werden.
das sicherstellt, dass keine Syntaxfehler eingeführt werden.


Wenn es als sudoedit aufgerufen wird, ist die Option -e (siehe unten) impliziert.
Wenn es als sudoedit aufgerufen wird, ist die Option -e (siehe unten) impliziert.
Zeile 38: Zeile 37:


== Installation ==
== Installation ==
# apt-get install sudo
== Syntax ==
== Syntax ==
  sudo -h | -K | -k | -V
  sudo -h | -K | -k | -V
Zeile 47: Zeile 48:
=== Parameter ===
=== Parameter ===
=== Optionen ===
=== Optionen ===
=== Umgebungsvariablen ===
=== Umgebung ===
=== Exit-Status ===
=== Rückgabewert ===


== Konfiguration ==
== Konfiguration ==
* Zuerst muss man sich als Superuser einloggen
Nach der Installation muss jeder Benutzer, der SuperUser-Rechte erhalten soll, der Gruppe "sudo" hinzugefügt werden
* das funktioniert mit dem Befehl "su",
* dort gibt man das bei der Installation festgelegte Passwort ein
* und wenn die Anmeldung erfolgreich war, kann das Paket "sudo" installiert werden mit dem Befehl:
# apt-get install sudo
 
* Nach der Installation muss nur noch der Benutzer, der SuperUser-Rechte erhalten soll, der Gruppe "sudo" hinzugefügt werden.
* Das funktioniert mit dem Befehl
  # usermod -G sudo -a BENUTZERNAME
  # usermod -G sudo -a BENUTZERNAME


Ausführen von sudo ohne Passwort.
; Ausführen von sudo ohne Passwort
   # visudo
   # visudo
In der sudoers.d Datei in der letzten Zeile folgenden Befehl einfügen:
In der sudoers.d Datei in der letzten Zeile folgenden Befehl einfügen:
  User ALL=(ALL) NOPASSWD:ALL
  'USER' ALL=(ALL) NOPASSWD:ALL
 
* User ist der Name des Users, den das betreffen soll.
 
; Einzelne Befehle auszuschließen
* in der Klammer die Befehle listen, die gewünscht sind, in diesem Fall sind das alle Befehle (ALL)


* User ist der Name des User, den das betreffen soll.
* Es ist möglich, einzelne Befehle davon auszuschließen in der Klammer die Befehle listen die gewünscht sind, in diesem Fall sind das alle Befehle (ALL)
=== Dateien ===
=== Dateien ===


== Anwendungen ==
== Anwendung ==
* Beispielsweise um Aufgaben auszuführen, die Administratoren vorbehalten sind:
* Beispielsweise um Aufgaben auszuführen, die Administratoren vorbehalten sind:
** Programme installieren (sudo apt-get install ...)
** Programme installieren (sudo apt-get install ...)
Zeile 91: Zeile 89:


== Sicherheit ==
== Sicherheit ==
; "could not open display"
;/etc/sudoers.d
Defaults env_keep += "DISPLAY"
This will allow sudo to pass the DISPLAY environment variable to the program it runs, and those programs will then be able to connect to the correct DISPLAY.
xhost +
== Dokumentation ==
== Dokumentation ==
=== RFC ===
=== Man-Pages ===
=== Man-Pages ===
=== Info-Pages ===
=== Info-Pages ===
Zeile 100: Zeile 106:
=== Projekt-Homepage ===
=== Projekt-Homepage ===
=== Weblinks ===
=== Weblinks ===
=== Einzelnachweise ===
<references />
== Testfragen ==
<div class="toccolours mw-collapsible mw-collapsed">
''Testfrage 1''
<div class="mw-collapsible-content">'''Antwort1'''</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
''Testfrage 2''
<div class="mw-collapsible-content">'''Antwort2'''</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
''Testfrage 3''
<div class="mw-collapsible-content">'''Antwort3'''</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
''Testfrage 4''
<div class="mw-collapsible-content">'''Antwort4'''</div>
</div>
<div class="toccolours mw-collapsible mw-collapsed">
''Testfrage 5''
<div class="mw-collapsible-content">'''Antwort5'''</div>
</div>
= TMP 1 =
*
*
= Links =
== Intern ==
# TODO
== Web ==
# https://wiki.ubuntuusers.de/sudo/
= TMP2 =
== Options ==
-A, --askpass
Normally, if sudo requires a password, it will read it from the user's terminal.  If the -A (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 SUDO_ASKPASS en‐
vironment variable is set, it specifies the path to the helper program.  Otherwise, if sudo.conf(5) contains a line specifying the askpass
program, that value will be used.  For example:
# Path to askpass helper program
Path askpass /usr/X11R6/bin/ssh-askpass
If no askpass program is available, sudo will exit with an error.
-B, --bell  Ring the bell as part of the password prompt when a terminal is present.  This option has no effect if an askpass program is used.
-b, --background
Run the given command in the background.  It is not possible to use shell job control to manipulate background processes started by sudo.
Most interactive commands will fail to work properly in background mode.
-C num, --close-from=num
Close all file descriptors greater than or equal to num before executing a command.  Values less than three are not permitted.  By default,
sudo will close all open file descriptors other than standard input, standard output, and standard error when executing a command.  The se‐
curity policy may restrict the user's ability to use this option.  The sudoers policy only permits use of the -C option when the adminis‐
trator has enabled the closefrom_override option.
-D directory, --chdir=directory
Run the command in the specified directory instead of the current working directory.  The security policy may return an error if the user
does not have permission to specify the working directory.
-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.
--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.  This option
may be specified multiple times.
-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:
1.  Temporary copies are made of the files to be edited with the owner set to the invoking user.
2.  The editor specified by the policy is run to edit the temporary files.  The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR en‐
vironment variables (in that order).  If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor
sudoers(5) option is used.
3.  If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed.
To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security pol‐
icy:
•  Symbolic links may not be edited (version 1.8.15 and higher).
•  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).
•  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).
Users are never allowed to edit device special files.
If the specified file does not exist, it will be created.  Unlike most commands run by sudo, the editor is run with the invoking user's en‐
vironment unmodified.  If the temporary file becomes empty after editing, the user will be prompted before it is installed.  If, for some
reason, sudo is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a tem‐
porary file.
-g group, --group=group
Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry.
The group may be either a group name or a numeric group-ID (GID) prefixed with the ‘#’ character (e.g., #0 for GID 0).  When running a com‐
mand as a GID, many shells require that the ‘#’ be escaped with a backslash (‘\’).  If no -u option is specified, the command will be run
as the invoking user.  In either case, the primary group will be set to group.  The sudoers policy permits any of the target user's groups
to be specified via the -g option as long as the -P option is not in use.
-H, --set-home
Request that the security policy set the 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.
-h, --help  Display a short help message to the standard output and exit.
-h host, --host=host
Run the command on the specified host if the security policy plugin supports remote commands.  The sudoers plugin does not currently sup‐
port running remote commands.  This may also be used in conjunction with the -l option to list a user's privileges for the remote host.
-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 .profile, .bash_profile, or .login will be read by the shell.  If a command is specified, it is passed to the shell as a simple command
using the -c option.  The command and any arguments are concatenated, separated by spaces, after escaping each character (including white
space) with a backslash (‘\’) except for alphanumerics, underscores, hyphens, and dollar signs.  If no command is specified, an interactive
shell is executed.  sudo 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.  Most shells behave differently when a command is specified as compared to an interac‐
tive session; consult the shell's manual for details.  The Command environment section in the sudoers(5) manual documents how the -i option
affects the environment in which a command is run when the sudoers policy is in use.
-K, --remove-timestamp
Similar to the -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.
-k, --reset-timestamp
When used without a command, invalidates the user's cached credentials.  In other words, the next time sudo is run a password will be re‐
quired.  This option does not require a password, and was added to allow a user to revoke sudo permissions from a .logout file.
When used in conjunction with a command or an option that may require a password, this option will cause sudo to ignore the user's cached
credentials.  As a result, sudo will prompt for a password (if one is required by the security policy) and will not update the user's
cached credentials.
Not all security policies support credential caching.
-l, --list  If no command is specified, list the allowed (and forbidden) commands for the invoking user (or the user specified by the -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.
If a command is specified and is permitted by the security policy, the fully-qualified path to the command is displayed along with any com‐
mand line arguments.  If a command is specified but not allowed by the policy, sudo will exit with a status value of 1.
-n, --non-interactive
Avoid prompting the user for input of any kind.  If a password is required for the command to run, sudo will display an error message and
exit.
-P, --preserve-groups
Preserve the invoking user's group vector unaltered.  By default, the 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.
-p prompt, --prompt=prompt
Use a custom password prompt with optional escape sequences.  The following percent (‘%’) escape sequences are supported by the sudoers
policy:
%H  expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in
sudoers(5))
%h  expanded to the local host name without the domain name
%p  expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5))
%U  expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified)
%u  expanded to the invoking user's login name
%%  two consecutive ‘%’ characters are collapsed into a single ‘%’ character
The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable.  On
systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is dis‐
abled in sudoers.
-R directory, --chroot=directory
Change to the specified root directory (see chroot(8)) before running the command.  The security policy may return an error if the user
does not have permission to specify the root directory.
-r role, --role=role
Run the command with an SELinux security context that includes the specified role.
-S, --stdin
Write the prompt to the standard error and read the password from the standard input instead of using the terminal device.
-s, --shell
Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database en‐
try.  If a command is specified, it is passed to the shell as a simple command using the -c option.  The command and any arguments are con‐
catenated, separated by spaces, after escaping each character (including white space) with a backslash (‘\’) except for alphanumerics, un‐
derscores, hyphens, and dollar signs.  If no command is specified, an interactive shell is executed.  Most shells behave differently when a
command is specified as compared to an interactive session; consult the shell's manual for details.
-t type, --type=type
Run the command with an SELinux security context that includes the specified type.  If no type is specified, the default type is derived
from the role.
-U user, --other-user=user
Used in conjunction with the -l option to list the privileges for user instead of for the invoking user.  The security policy may restrict
listing other users' privileges.  When using the sudoers policy, only root or a user with the ability to run any command as either root or
the specified user on the current host may use this option.
-T timeout, --command-timeout=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 sudoers policy requires that user-specified timeouts be explicitly enabled.
-u user, --user=user
Run the command as a user other than the default target user (usually root).  The user may be either a user name or a numeric user-ID (UID)
prefixed with the ‘#’ character (e.g., #0 for UID 0).  When running commands as a UID, many shells require that the ‘#’ be escaped with a
backslash (‘\’).  Some security policies may restrict UIDs to those listed in the password database.  The sudoers policy allows UIDs that
are not in the password database as long as the targetpw option is not set.  Other security policies may not support this.
-V, --version
Print the sudo version string as well as the version string of any configured plugins.  If the invoking user is already root, the -V option
will display the arguments passed to configure when sudo was built; plugins may display additional information such as default options.
-v, --validate
Update the user's cached credentials, authenticating the user if necessary.  For the sudoers plugin, this extends the sudo timeout for an‐
other 15 minutes by default, but does not run a command.  Not all security policies support cached credentials.
--          The -- option indicates that sudo should stop processing command line arguments.
Options that take a value may only be specified once unless otherwise indicated in the description.  This is to help guard against problems caused by
poorly written scripts that invoke sudo with user-controlled input.
Environment variables to be set for the command may also be passed on the command line in the form of VAR=value, e.g.,
LD_LIBRARY_PATH=/usr/local/pkg/lib.  Variables passed on the command line are subject to restrictions imposed by the security policy plugin.  The
sudoers policy subjects variables passed on the command line to the same restrictions as normal environment variables with one important exception.  If
the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would
otherwise be forbidden.  See sudoers(5) for more information.
COMMAND EXECUTION
When sudo 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 -P option was specified).
The following parameters may be specified by security policy:
•  real and effective user-ID
•  real and effective group-ID
•  supplementary group-IDs
•  the environment list
•  current working directory
•  file creation mode mask (umask)
•  SELinux role and type
•  scheduling priority (aka nice value)
Process model
There are two distinct ways sudo can run a command.
If an I/O logging plugin is configured or if the security policy explicitly requests it, a new pseudo-terminal (“pty”) is allocated and fork(2) is used
to create a second sudo process, referred to as the monitor.  The monitor 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 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 “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 monitor passes the com‐
mand's exit status to the main sudo process and exits.  After receiving the command's exit status, the main sudo passes the command's exit status to
the security policy's close function and exits.
If no pty is used, sudo 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 sudo 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, sudo will execute the command directly instead of call‐
ing fork(2) first.  The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is
specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled.  Both pam_session and pam_setcred are enabled
by default on systems using PAM.
On systems that use PAM, the security policy's close function is responsible for closing the PAM session.  It may also log the command's exit status.
Signal handling
When the command is run as a child of the sudo process, sudo will relay signals it receives to the command.  The SIGINT and 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 re‐
ceiving SIGINT twice each time the user enters control-C.  Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to
the command.  As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by sudo.
As a special case, sudo will not relay signals that were sent by the command it is running.  This prevents the command from accidentally killing it‐
self.  On some systems, the reboot(8) command sends SIGTERM to all non-system processes other than itself before rebooting the system.  This prevents
sudo from relaying the SIGTERM signal it received back to reboot(8), 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 sudo and not any other processes that
the command may create.  As a result, running a script that calls reboot(8) or shutdown(8) via sudo may cause the system to end up in this undefined
state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the com‐
mand and the calling process).
If no I/O logging plugins are loaded and the policy plugin has not defined a close() function, set a command timeout, or required that the command be
run in a new pty, sudo may execute the command directly instead of running it as a child process.
Plugins
Plugins may be specified via Plugin directives in the sudo.conf(5) file.  They may be loaded as dynamic shared objects (on systems that support them),
or compiled directly into the sudo binary.  If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, sudo will use sudoers(5) for
the policy, auditing, and I/O logging plugins.  See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for
more information about the sudo plugin architecture.
EXIT VALUE
Upon successful execution of a command, the exit status from sudo will be the exit status of the program that was executed.  If the command terminated
due to receipt of a signal, sudo will send itself the same signal that terminated the command.
If the -l option was specified without a command, sudo will exit with a value of 0 if the user is allowed to run sudo and they authenticated success‐
fully (as required by the security policy).  If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by
the security policy, otherwise it will be 1.
If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, sudo exits with a value of 1.
In the latter case, the error string is printed to the standard error.  If sudo cannot stat(2) one or more entries in the user's 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 stat(2) to return “permission denied” is if you are running an auto‐
mounter and one of the directories in your PATH is on a machine that is currently unreachable.
SECURITY NOTES
sudo tries to be safe when executing external commands.
To prevent command spoofing, sudo checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or
both are in the PATH).  Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the
program that sudo executes.
Users should never be granted sudo 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.
By default, sudo will only log the command it explicitly runs.  If a user runs a command such as sudo su or sudo sh, subsequent commands run from that
shell are not subject to sudo'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 sudo to verify that the command does not inadvertently give the user an effective root
shell.  For information on ways to address this, see the Preventing shell escapes section in sudoers(5).
To prevent the disclosure of potentially sensitive information, sudo 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 set-user-ID processes to dump core by default.
To aid in debugging sudo crashes, you may wish to re-enable core dumps by setting “disable_coredump” to false in the sudo.conf(5) file as follows:
Set disable_coredump false
See the sudo.conf(5) manual for more information.
ENVIRONMENT
sudo utilizes the following environment variables.  The security policy has control over the actual content of the command's environment.
EDITOR          Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set.
MAIL            Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is
present in the env_keep list).
HOME            Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is
set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the
env_keep list.
LOGNAME          Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when
the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list).
PATH            May be overridden by the security policy.
SHELL            Used to determine shell to run with -s option.
SUDO_ASKPASS    Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified.
SUDO_COMMAND    Set to the command run by sudo, including command line arguments.  The command line arguments are truncated at 4096 characters to pre‐
vent a potential execution error.
SUDO_EDITOR      Default editor to use in -e (sudoedit) mode.
SUDO_GID        Set to the group-ID of the user who invoked sudo.
SUDO_PROMPT      Used as the default password prompt unless the -p option was specified.
SUDO_PS1        If set, PS1 will be set to its value for the program being run.
SUDO_UID        Set to the user-ID of the user who invoked sudo.
SUDO_USER        Set to the login name of the user who invoked sudo.
USER            Set to the same value as LOGNAME, described above.
VISUAL          Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set.
FILES
/etc/sudo.conf            sudo front-end configuration
EXAMPLES
The following examples assume a properly configured security policy.
To get a file listing of an unreadable directory:
$ sudo ls /usr/local/protected
To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root:
$ sudo -u yaz ls ~yaz
To edit the index.html file as user www:
$ sudoedit -u www ~www/htdocs/index.html
To view system logs only accessible to root and users in the adm group:
$ sudo -g adm more /var/log/syslog
To run an editor as jim with a different primary group:
$ sudoedit -u jim -g audio ~jim/sound.txt
To shut down a machine:
$ sudo shutdown -r +15 "quick reboot"
To make a usage listing of the directories in the /home partition.  The commands are run in a sub-shell to allow the cd command and file redirection to
work.
$ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE"
DIAGNOSTICS
Error messages produced by sudo include:
editing files in a writable directory is not permitted
By default, 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 sudoedit_checkdir option in sudoers(5) for more information.
editing symbolic links is not permitted
By default, sudoedit does not follow symbolic links when opening files.  See the sudoedit_follow option in sudoers(5) for more information.
effective uid is not 0, is sudo installed setuid root?
sudo was not run with root privileges.  The sudo 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 ‘nosuid’ option or on an NFS file system that maps uid 0 to an unprivileged uid.
effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges?
sudo was not run with root privileges.  The sudo 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 sudo binary is located on is mounted with the ‘nosuid’ option or it is an NFS file system
that maps uid 0 to an unprivileged uid.
fatal error, unable to load plugins
An error occurred while loading or initializing the plugins specified in sudo.conf(5).
invalid environment variable name
One or more environment variable names specified via the -E option contained an equal sign (‘=’).  The arguments to the -E option should be envi‐
ronment variable names without an associated value.
no password was provided
When sudo tried to read the password, it did not receive any characters.  This may happen if no terminal is available (or the -S option is speci‐
fied) and the standard input has been redirected from /dev/null.
a terminal is required to read the password
sudo needs to read the password but there is no mechanism available for it to do so.  A terminal is not present to read the password from, sudo
has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the
sudo.conf(5) file or the SUDO_ASKPASS environment variable.
no writable temporary directory found
sudoedit was unable to find a usable temporary directory in which to store its intermediate files.
The “no new privileges” flag is set, which prevents sudo from running as root.
sudo was run by a process that has the Linux “no new privileges” flag is set.  This causes the set-user-ID bit to be ignored when running an exe‐
cutable, which will prevent sudo from functioning.  The most likely cause for this is running sudo within a container that sets this flag.  Check
the documentation to see if it is possible to configure the container such that the flag is not set.
sudo must be owned by uid 0 and have the setuid bit set
sudo was not run with root privileges.  The sudo 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.
sudoedit is not supported on this platform
It is only possible to run sudoedit on systems that support setting the effective user-ID.
timed out reading password
The user did not enter a password before the password timeout (5 minutes by default) expired.
you do not exist in the passwd database
Your user-ID does not appear in the system passwd database.
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.
SEE ALSO
su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8)
HISTORY
See the HISTORY.md file in the sudo distribution (https://www.sudo.ws/about/history/) for a brief history of sudo.
AUTHORS
Many people have worked on sudo over the years; this version consists of code written primarily by:
Todd C. Miller
See the CONTRIBUTORS.md file in the sudo distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed
to sudo.


CAVEATS
# <nowiki>https://wiki.ubuntuusers.de/sudo/</nowiki>
There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via sudo. Also, many programs (such
as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks.  However, on most systems it is possible to prevent shell
escapes with the sudoers(5) plugin's noexec functionality.


It is not meaningful to run the cd command directly via sudo, e.g.,


$ sudo cd /usr/local/protected


since when the command exits the parent process (your shell) will still be the same.  See the EXAMPLES section for more information.


Running shell scripts via sudo can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a
[[Kategorie:Linux/Benutzer]]
/dev/fd/ directory, set-user-ID shell scripts are generally safe).
[[Kategorie:Linux/Befehl]]


[[Kategorie:Linux:Benutzer]]
{{DEFAULTSORT:sudo}}
{{DEFAULTSORT:sudo}}

Aktuelle Version vom 8. September 2024, 10:33 Uhr

sudo führt Kommandos mit der Identität eines anderen Benutzers aus

Beschreibung

  • Der Befehl sudo kann Programmaufrufen vorangestellt werden
  • Er ermöglicht berechtigten Benutzern, das Programm im Namen und mit den Rechten eines anderen Benutzers auszuführen.
  • sudo, sudoedit — execute a command as another user

sudo ermöglicht es einem zugelassenen Benutzer, einen Befehl als Superuser oder als ein anderer Benutzer auszuführen, wie in der Sicherheitsrichtlinie angegeben.

  • Die echte (nicht effektive) Benutzer-ID des aufrufenden Benutzers wird verwendet, um den Benutzernamen zu bestimmen, mit dem die Sicherheitsrichtlinie abgefragt wird.

sudo unterstützt eine Plugin-Architektur für Sicherheitsrichtlinien, Auditing und Input/Output-Logging.

  • Dritte können ihre eigenen Plugins entwickeln und vertreiben, die nahtlos mit dem sudo-Frontend zusammenarbeiten.
  • Die Standard-Sicherheitsrichtlinie ist sudoers, die über die Datei /etc/sudoers oder über LDAP konfiguriert wird.
  • Weitere Informationen finden Sie im Abschnitt Plugins.

Die Sicherheitsrichtlinie bestimmt, ob und welche Rechte ein Benutzer hat, um sudo auszuführen.

  • Die Richtlinie kann verlangen, dass sich die Benutzer mit einem Passwort oder einem anderen Authentifizierungsmechanismus authentifizieren.
  • Wenn eine Authentifizierung erforderlich ist, wird sudo beendet, wenn das Passwort des Benutzers nicht innerhalb einer konfigurierbaren Zeitspanne eingegeben wird.
  • Dieses Zeitlimit ist richtlinienspezifisch; das Standardzeitlimit für die Kennworteingabeaufforderung für die Sicherheitsrichtlinie sudoers beträgt 0 Minuten.

Sicherheitsrichtlinien können das Zwischenspeichern von Anmeldeinformationen unterstützen, damit der Benutzer sudo für eine gewisse Zeit erneut ausführen kann, ohne dass eine Authentifizierung erforderlich ist.

Die sudoers-Richtlinie zwischenspeichert Anmeldeinformationen für jedes Terminal für 15 Minuten.

  • Weitere Informationen finden Sie unter den Optionen timestamp_type und timestamp_timeout in sudoers(5).
  • Wenn Sie sudo mit der Option -v ausführen, kann ein Benutzer die zwischengespeicherten Anmeldeinformationen aktualisieren, ohne einen Befehl auszuführen.

Auf Systemen, auf denen sudo die primäre Methode zur Erlangung von Superuser-Rechten ist, müssen unbedingt Syntaxfehler in den Konfigurationsdateien der Sicherheitsrichtlinien vermieden werden.


  • Für die Standard-Sicherheitsrichtlinie sudoers(5) sollten Änderungen an den Konfigurationsdateien mit dem Dienstprogramm visudo(8) vorgenommen werden.

Wenn es als sudoedit aufgerufen wird, ist die Option -e (siehe unten) impliziert.

Sicherheitsrichtlinien und Audit-Plugins können erfolgreiche und fehlgeschlagene Versuche, sudo auszuführen, protokollieren.

  • Wenn ein E/A-Plugin konfiguriert ist, können auch die Ein- und Ausgaben des laufenden Befehls protokolliert werden.

Installation

# apt-get install sudo

Syntax

sudo -h | -K | -k | -V
sudo -v [-ABknS] [-g group] [-h host] [-p prompt] [-u user]
sudo -l [-ABknS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command]
sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-r role] [-t type] [-T timeout] [-u user] [VAR=value] [-i | -s] [command]
sudoedit [-ABknS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-r role] [-t type] [-T timeout] [-u user] file ...

Parameter

Optionen

Umgebung

Rückgabewert

Konfiguration

Nach der Installation muss jeder Benutzer, der SuperUser-Rechte erhalten soll, der Gruppe "sudo" hinzugefügt werden 

# usermod -G sudo -a BENUTZERNAME
Ausführen von sudo ohne Passwort
 # visudo

In der sudoers.d Datei in der letzten Zeile folgenden Befehl einfügen: 

'USER' ALL=(ALL) NOPASSWD:ALL
  • User ist der Name des Users, den das betreffen soll.
Einzelne Befehle auszuschließen
  • in der Klammer die Befehle listen, die gewünscht sind, in diesem Fall sind das alle Befehle (ALL)

Dateien

Anwendung

  • Beispielsweise um Aufgaben auszuführen, die Administratoren vorbehalten sind:
    • Programme installieren (sudo apt-get install ...)
    • Systemkonfigurationen ändern (sudo nano /etc/fstab)
  • Der Linux-Befehl sudo ermöglicht einem Benutzer, einen Befehl als Superuser oder als ein anderer Benutzer auszuführen.
  • sudo erfordert die Angabe eines Passworts.
  • Dies ist normalerweise das Benutzerpasswort, nicht das Root-Passwort
Beispiel
usermod -G sudo -a Otto

Jetzt gehört der User Otto der Gruppe sudo an. 

sudo apt update

Und kann mit sudo root Befehle ausführen, ohne sich als root anzumelden. 

less /etc/group

Mit diesem Befehl lassen sich Gruppen anzeigen und nachvollziehen, wer zu sudo gehört. Siehe /etc/groups

Sicherheit

"could not open display"
/etc/sudoers.d
Defaults env_keep += "DISPLAY"

This will allow sudo to pass the DISPLAY environment variable to the program it runs, and those programs will then be able to connect to the correct DISPLAY. 

xhost +

Dokumentation

Man-Pages

Info-Pages

Siehe auch

Links

Projekt-Homepage

Weblinks

  1. https://wiki.ubuntuusers.de/sudo/


Abgerufen von „https://wiki.foxtom.de/index.php?title=Sudo&oldid=107625“