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Sudo Upgrade Notes

  • Upgrading from a version prior to 1.9.15:

    The sudoers plugin now uses a time stamp path name that is based on the user-ID instead of the user name. For example, a time stamp file that was /var/run/sudo/ts/root in sudo 1.9.14 will now be /var/run/sudo/ts/0. The lecture flag file name is now also based on the user-ID, which will result in users receiving the sudo lecture again on upgrade to sudo 1.9.15.

  • Upgrading from a version prior to 1.9.14:

    Sudo now runs commands in a new pseudo-terminal by default. This can prevent a malicious program run via sudo from accessing the user’s terminal device after the command completes.

    When sudo runs a command in a new pseudo-terminal, an additional process is created to monitor the command’s status and pass terminal control signals between the two terminals. See the “Process model” subsection in the sudo manual and the description of the “use_pty” option in the sudoers manual for more information.

    A side effect of running the command in a new pseudo-terminal is that sudo must pass input from the user’s terminal to the pseudo-terminal, even if the command being run does not require the input. The “exec_background” option in sudoers can be used to prevent this, but some screen-oriented commands may not operate properly when run as a background process.

    To restore the historic behavior where a command is run in the user’s terminal, add the following line to the sudoers file:

    Defaults !use_pty
  • Upgrading from a version prior to 1.9.13:

    Sudo now builds AIX-style shared libraries and dynamic shared objects by default instead of svr4-style. This means that the default sudo plugins are now .a (archive) files that contain a .so shared object file instead of bare .so files. This was done to improve compatibility with the AIX Freeware ecosystem, specifically, the AIX Freeware build of OpenSSL. When loading a .a file as a plugin the name of the included .so file must also be specified, for example /usr/libexec/sudo/sudoers.a(

    Sudo is still capable of loading svr4-style .so plugins and if a .so file is requested, either via sudo.conf or the sudoers file, and only the .a file is present, sudo will convert the path from to plugin.a( This ensures compatibility with existing configurations. To restore the old, pre-1.9.13 behavior, run configure using the –with-aix-soname=svr4 option.

  • Upgrading from a version prior to 1.9.10:

    Sudo now interprets a command line argument in sudoers that begins with a ‘^’ character as a regular expression. To start a command argument with a literal ‘^’ character, it must be escaped with a backslash (’'). This may result in a syntax error after upgrading for existing sudoers rules where the command line arguments begin with a ‘^’.

    A user may now only run “sudo -U otheruser -l” if they have a “sudo ALL” privilege where the RunAs user contains either “root” or “otheruser”. Previously, having “sudo ALL” was sufficient, regardless of the RunAs user.

  • Upgrading from a version prior to 1.9.9:

    Sudo now runs commands with the core limit resource limit set to 0 by default. While most operating systems restrict core dumps of set-user-ID programs like sudo, this protection is lost when sudo executes a command. By disabling core dumps by default, it is possible to avoid potential security problems such as those seen with the Linux logrotate utility, which could interpret a core dump as a valid configuration file.

    To restore the historic core dump file size behavior, add the following line to the sudoers file:

    Defaults rlimit_core=default
  • Upgrading from a version prior to 1.9.7:

    Sudo now links with OpenSSL 1.0.1 or higher by default if it is present on the system unless it is explicitly disabled (via --disable-openssl), or unless the sudo log client and server code is disabled (via --disable-log-client and --disable-log-server). As a result, the sudo log server (and the client built into the sudoers plugin) now support TLS connections by default.

  • Upgrading from a version prior to 1.9.3:

    Due to the addition of the CHROOT and CWD options, it is no longer possible to declare an alias with one of those names. If a sudoers file has an alias with one of those names, sudo and visudo will report a syntax error with a message like “syntax error: unexpected CHROOT, expecting ALIAS”.

    Starting with version 1.9.3, sudoers rules must end in either a newline or the end-of-file. This makes it possible to provide better error messages. Previously, it was possible to include multiple rules on a single line, separated by white space.

    Starting with version 1.9.3, sudo will attempt to recover from a syntax error in the sudoers file by discarding the portion of the line that contains the error until the end of the line. To restore the historic behavior of refusing to run when a syntax error is encountered, add error_recovery=false as a plugin option in sudo.conf for the “sudoers_audit” plugin, (or “sudoers_policy” if there is no “sudoers_audit” plugin configured).

  • Upgrading from a version prior to 1.9.1:

    Starting with version 1.9.1, sudoers plugin arguments in sudo.conf should be specified for the “sudoers_audit” plugin, not “sudoers_policy”. This is because the sudoers file is now opened and parsed by the “sudoers_audit” plugin. Previously, this was done by the “sudoers_policy” plugin. The use of an audit plugin makes it possible for the sudoers module to detect when a command has been rejected by an approval plugin and only log commands that are allowed by both policy and approval plugins.

  • Upgrading from a version prior to 1.8.30:

    Starting with version 1.8.30, sudo will no longer allow commands to be run as a user or group ID that is not in the password or group databases by default. Previously, sudo would always allow unknown user or group IDs if the sudoers entry permitted it, including via the ALL alias. The old behavior can be restored by setting the new “allow_unknown_runas_id” Defaults setting in the sudoers file.

  • Upgrading from a version prior to 1.8.29:

    Starting with version 1.8.29, if the umask is explicitly set in sudoers, that value is used regardless of the umask specified by PAM or login.conf. However, if the umask is not explicitly set in sudoers, PAM, or login.conf may now override the default sudoers umask. Previously, the sudoers umask always overrode the umask set by PAM, which was not the documented behavior.

  • Upgrading from a version prior to 1.8.28:

    Starting with version 1.8.28, sudo stores the signal that caused a command to be suspended or resumed as a string in the I/O log timing file. The version of sudoreplay included with sudo 1.8.28 can process either type of I/O log file but older versions of sudoreplay are unable to replay the newer logs.

    Starting with version 1.8.28, sudoedit honors the umask and umask_override settings in sudoers. Previously, the user’s umask was used as-is.

  • Upgrading from a version prior to 1.8.26:

    Starting with version 1.8.26, sudo no long sets the USERNAME environment variable when running commands. This is a non-standard environment variable that was set on some older Linux systems. Sudo still sets the LOGNAME, USER, and, on AIX systems, LOGIN environment variables.

    Handling of the LOGNAME, USER (and on AIX, LOGIN) environment variables has changed slightly in version 1.8.26. Sudo now treats those variables as a single unit. This means that if one variable is preserved or removed from the environment using env_keep, env_check, or env_delete, the others are too.

  • Upgrading from a version prior to 1.8.23:

    In sudo 1.8.23 the “sudoers2ldif” script and the visudo -x functionality has been superseded by the “cvtsudoers” utility. The cvtsudoers utility is intended to be a drop-in replacement for “sudoers2ldif”. Because it uses the same parser as sudo and visudo, cvtsudoers can perform a more accurate conversion than sudoers2ldif could.

    To convert a sudoers file to JSON, the format option must be specified. For example, instead of:

    visudo -f sudoers_file -x output_file

    one would use:

    cvtsudoers -f json -o output_file sudoers_file

    Unlike “visudo -x”, “cvtsudoers” reads from the standard input by default. Also, the base DN may be specified on the command line, if desired, using the -b option.

  • Upgrading from a version prior to 1.8.20:

    Due to the addition of the TIMEOUT, NOTBEFORE, and NOTAFTTER options, it is no longer possible to declare an alias with one of those names. If a sudoers file has an alias with one of those names, sudo, and visudo will report a syntax error with a message like “syntax error: unexpected TIMEOUT, expecting ALIAS”.

    Prior to version 1.8.20, when log_input, log_output, or use_pty were enabled, if any of the standard input, output, or error were not connected to a terminal, sudo would use a pipe. The pipe allows sudo to interpose itself between the old standard input, output, or error and log the contents. Beginning with version 1.8.20, a pipe is only used when I/O logging is enabled. If use_pty is set without log_input or log_output, no pipe will be used. Additionally, if log_input is set without log_output, a pipe is only used for the standard input. Likewise, if log_output is set without log_input, a pipe is only used for the standard output and standard error. This results in a noticeable change in behavior if the use_pty flag is set and no terminal is present when running commands such as scripts that execute other commands asynchronously (in the background). Previously, sudo would exit immediately, causing background commands to terminate with a broken pipe if they attempt to write to the standard output or standard error. As of version 1.8.20, a pipe will not be used in this case so the command will no longer be terminated.

  • Upgrading from a version prior to 1.8.16:

    When editing files with sudoedit, files in a directory that is writable by the invoking user may no longer be edited by default. Also, sudoedit will refuse to follow a symbolic link in the path to be edited if that directory containing the link is writable by the user. This behavior can be disabled by negating the sudoedit_checkdir sudoers option, which is now enabled by default.

  • Upgrading from a version prior to 1.8.15:

    Prior to version 1.8.15, when env_reset was enabled (the default) and the -s option was not used, the SHELL environment variable was set to the shell of the invoking user. In 1.8.15 and above, when env_reset is enabled and the -s option is not used, SHELL is set based on the target user.

    When editing files with sudoedit, symbolic links will no longer be followed by default. The old behavior can be restored by enabling the sudoedit_follow option in sudoers or on a per-command basis with the FOLLOW and NOFOLLOW tags.

    Prior to version 1.8.15, groups listed in sudoers that were not found in the system group database were passed to the group plugin, if any. Starting with 1.8.15, only groups of the form %:group are resolved via the group plugin by default. The old behavior can be restored by using the always_query_group_plugin sudoers option.

    Locking of the time stamp file has changed in sudo 1.8.15. Previously, the user’s entire time stamp file was locked while retrieving and updating a time stamp record. Now, only a single record, specific to the tty or parent process ID, is locked. This lock is held while the user enters their password. If sudo is suspended at the password prompt (or run in the background), the lock is dropped until sudo is resumed, at which point it will be reacquired. This allows sudo to be used in a pipeline even when a password is required–only one instance of sudo will prompt for a password.

  • Upgrading from a version prior to 1.8.14:

    On HP-UX, sudo will no longer check for “” if “” is specified but does not exist. This was a temporary hack for backward compatibility with Sudo 1.8.6 and below when the plugin path name was not listed in sudo.conf. A plugin path name that explicitly ends in “.sl” will still work as expected.

  • Upgrading from a version prior to 1.8.12:

    On Solaris, sudo is now able to determine the NIS domain name. As a result, if you had previously been using netgroups that do not include the domain, you will need to either set the domain in the entry or leave the domain part of the tuple blank.

    For example, the following will no longer work:

     my-hosts (foo,-,-) (bar,-,-) (baz,-,-)

    and should be changed to:

     my-hosts (foo,-,) (bar,-,) (baz,-,)
  • Upgrading from a version prior to 1.8.10:

    The time stamp file format has changed in sudo 1.8.10. There is now a single time stamp file for each user, even when tty-based time stamps are used. Each time stamp file may contain multiple records to support tty-based time stamps as well as multiple authentication users. On systems that support it, monotonic time is stored instead of wall clock time. As a result, it is important that the time stamp files not persist when the system reboots. For this reason, the default location for the time stamp files has changed back to a directory located in /var/run. Systems that do not have /var/run (e.g. AIX) or that do not clear it on boot (e.g. HP-UX) will need to clear the time stamp directory via a start up script. Such a script is installed by default on AIX and HP-UX systems.

    Because there is now a single time stamp file per user, the -K option will remove all of the user’s time stamps, not just the time stamp for the current terminal.

    Lecture status is now stored separately from the time stamps in a separate directory: /var/db/sudo/lectured, /var/lib/sudo/lectured or /var/adm/sudo/lectured depending on what is present on the system.

    LDAP-based sudoers now uses a default search filter of (objectClass=sudoRole) for more efficient queries. It is possible to disable the default search filter by specifying SUDOERS_SEARCH_FILTER in ldap.conf but omitting a value.

  • Upgrading from a version prior to 1.8.7:

    Sudo now stores its libexec files in a “sudo” sub-directory instead of in libexec itself. For backward compatibility, if the plugin is not found in the default plugin directory, sudo will check the parent directory default directory ends in /sudo.

    The default sudo plugins now all use the .so extension, regardless of the extension used by system shared libraries. For backward compatibility, sudo on HP-UX will also search for a plugin with an .sl extension if the .so version is not found.

    Handling of users belonging to a large number of groups has changed. Previously, sudo would only use the group list from the kernel unless the system_group plugin was enabled in sudoers. Now, sudo will query the groups database if the user belongs to the maximum number of groups supported by the kernel. See the group_source and max_groups settings in the sudo.conf manual for details.

  • Upgrading from a version prior to 1.8.2:

    When matching Unix groups in the sudoers file, sudo will now match based on the name of the group as it appears in sudoers instead of the group-ID. This can substantially reduce the number of group lookups for sudoers files that contain a large number of groups. There are a few side effects of this change.

    1. Unix groups with different names but the same group-ID are can no longer be used interchangeably. Sudo will look up all of a user’s groups by group-ID and use the resulting group names when matching sudoers entries. If there are multiple groups with the same ID, the group name returned by the system getgrgid() library function is the name that will be used when matching sudoers entries.

    2. Unix group names specified in the sudoers file that are longer than the system maximum will no longer match. For instance, if there is a Unix group “fireflie” on a system where group names are limited to eight characters, “%fireflies” in sudoers will no longer match “fireflie”. Previously, a lookup by name of the group “fireflies” would have matched the “fireflie” group on most systems.

    The legacy group matching behavior may be restored by enabling the match_group_by_gid Defaults option in sudoers available in sudo 1.8.18 and higher.

  • Upgrading from a version prior to 1.8.1:

    Changes in the sudoers parser could result in parse errors for existing sudoers file. These changes cause certain erroneous entries to be flagged as errors where before they allowed. Changes include:

    Combining multiple Defaults entries with a backslash. E.g.

     Defaults set_path \
     Defaults syslog

    which should be:

     Defaults set_path
     Defaults syslog

    Also, double-quoted strings with a missing end-quote are now detected and result in an error. Previously, text starting a double quote and ending with a newline was ignored. E.g.

     Defaults set_path"foo

    In previous versions of sudo, the “foo portion would have been ignored.

    To avoid problems, sudo 1.8.1’s make install will not install a new sudo binary if the existing sudoers file has errors.

    In Sudo 1.8.1 the noexec functionality has moved out of the sudoers policy plugin and into the sudo front-end. As a result, the path to the noexec file is now specified in the sudo.conf file instead of the sudoers file. If you have a sudoers file that uses the “noexec_file” option, you will need to move the definition to the sudo.conf file instead.

    Old style in /etc/sudoers:

     Defaults noexec_file=/usr/local/libexec/

    New style in /etc/sudo.conf:

     Path noexec /usr/local/libexec/
  • Upgrading from a version prior to 1.8.0:

    Starting with version 1.8.0, sudo uses a modular framework to support policy and I/O logging plugins. The default policy plugin is “sudoers” which provides the traditional sudoers evaluation and I/O logging. Plugins are typically located in /usr/libexec or /usr/local/libexec, though this is system-dependent. The sudoers plugin is named “” on most systems.

    The sudo.conf file, usually stored in /etc, is used to configure plugins. This file is optional–if no plugins are specified in sudo.conf, the “sudoers” plugin is used. See the example sudo.conf file in the docs directory or refer to the updated sudo manual to see how to configure sudo.conf.

    The “askpass” setting has moved from the sudoers file to the sudo.conf file. If you have a sudoers file that uses the “askpass” option, you will need to move the definition to the sudo.conf file.

    Old style in /etc/sudoers:

     Defaults askpass=/usr/X11R6/bin/ssh-askpass

    New style in /etc/sudo.conf:

     Path askpass /usr/X11R6/bin/ssh-askpass
  • Upgrading from a version prior to 1.7.5:

    Sudo 1.7.5 includes an updated LDAP schema with support for the sudoNotBefore, sudoNotAfter, and sudoOrder attributes.

    The sudoNotBefore and sudoNotAfter attribute support is only used when the SUDOERS_TIMED setting is enabled in ldap.conf. If enabled, those attributes are used directly when constructing an LDAP filter. As a result, your LDAP server must have the updated schema if you want to use sudoNotBefore and sudoNotAfter.

    The sudoOrder support does not affect the LDAP filter sudo constructs and so there is no need to explicitly enable it in ldap.conf. If the sudoOrder attribute is not present in an entry, a value of 0 is used. If no entries contain sudoOrder attributes, the results are in whatever order the LDAP server returns them, as in past versions of sudo.

    Older versions of sudo will simply ignore the new attributes if they are present in an entry. There are no compatibility problems using the updated schema with older versions of sudo.

  • Upgrading from a version prior to 1.7.4:

    Starting with sudo 1.7.4, the time stamp files have moved from /var/run/sudo to either /var/db/sudo, /var/lib/sudo, or /var/adm/sudo. The directories are checked for existence in that order. This prevents users from receiving the sudo lecture every time the system reboots. Time stamp files older than the boot time are ignored on systems where it is possible to determine this.

    Additionally, the tty_tickets sudoers option is now enabled by default. To restore the old behavior (single time stamp per user), add a line like:

     Defaults !tty_tickets

    to sudoers or use the --without-tty-tickets configure option.

    The HOME and MAIL environment variables are now reset based on the target user’s password database entry when the env_reset sudoers option is enabled (which is the case in the default configuration). Users wishing to preserve the original values should use a sudoers entry like:

     Defaults env_keep += HOME

    to preserve the old value of HOME and

     Defaults env_keep += MAIL

    to preserve the old value of MAIL.

    Preserving HOME has security implications since many programs use it when searching for configuration files. Adding HOME to env_keep may enable a user to run unrestricted commands via sudo.

    The default syslog facility has changed from “local2” to “authpriv” (or “auth” if the operating system doesn’t have “authpriv”). The --with-logfac configure option can be used to change this or it can be changed in the sudoers file.

  • Upgrading from a version prior to 1.7.0:

    Starting with sudo 1.7.0, comments in the sudoers file must not have a digit or minus sign immediately after the comment character (’#’). Otherwise, the comment may be interpreted as a user or group-ID.

    When sudo is build with LDAP support the /etc/nsswitch.conf file is now used to determine the sudoers sea ch order. sudo will default to only using /etc/sudoers unless /etc/nsswitch.conf says otherwise. This can be changed with an nsswitch.conf line, e.g.:

    sudoers: ldap files

    Would case LDAP to be searched first, then the sudoers file. To restore the pre-1.7.0 behavior, run configure with the --with-nsswitch=no flag.

    Sudo now ignores user .ldaprc files as well as system LDAP defaults. All LDAP configuration is now in /etc/ldap.conf (or whichever file was specified by configure’s --with-ldap-conf-file option). If you are using TLS, you may now need to specify:

     tls_checkpeer no

    in sudo’s ldap.conf unless ldap.conf references a valid certificate authority file(s).

  • Upgrading from a version prior to 1.6.9:

    Starting with sudo 1.6.9, if an OS supports a modular authentication method such as PAM, it will be used by default by configure.

    Environment variable handling has changed significantly in sudo 1.6.9. Prior to version 1.6.9, sudo would preserve the user’s environment, pruning out potentially dangerous variables. Beginning with sudo 1.6.9, the environment is reset to a default set of values with only a small number of “safe” variables preserved. To preserve specific environment variables, add them to the “env_keep” list in sudoers. E.g.

     Defaults env_keep += "EDITOR"

    The old behavior can be restored by negating the “env_reset” option in sudoers. E.g.

     Defaults !env_reset

    There have also been changes to how the “env_keep” and “env_check” options behave.

    Prior to sudo 1.6.9, the TERM and PATH environment variables would always be preserved even if the env_keep option was redefined. That is no longer the case. Consequently, if env_keep is set with “=” and not simply appended to (i.e. using “+=”), PATH and TERM must be explicitly included in the list of environment variables to keep. The LOGNAME, SHELL, USER, and USERNAME environment variables are still always set.

    Additionally, the env_check setting previously had no effect when env_reset was set (which is now on by default). Starting with sudo 1.6.9, environment variables listed in env_check are also preserved in the env_reset case, provided that they do not contain a ‘/’ or ‘%’ character. It is not necessary to also list a variable in env_keep–having it in env_check is sufficient.

    The default lists of variables to be preserved and/or checked are displayed when sudo is run by root with the -V flag.

  • Upgrading from a version prior to 1.6.8:

    Prior to sudo 1.6.8, if /var/run did not exist, sudo would put the time stamp files in /tmp/.odus. As of sudo 1.6.8, the time stamp files will be placed in /var/adm/sudo or /usr/adm/sudo if there is no /var/run directory. This directory will be created if it does not already exist.

    Previously, a sudoers entry that explicitly prohibited running a command as a certain user did not override a previous entry allowing the same command. This has been fixed in sudo 1.6.8 such that the last match is now used (as it is documented). Hopefully no one was depending on the previous (buggy) behavior.

  • Upgrading from a version prior to 1.6:

    As of sudo 1.6, parsing of runas entries and the NOPASSWD tag has changed. Prior to 1.6, a runas specifier applied only to a single command directly following it. Likewise, the NOPASSWD tag only allowed the command directly following it to be run without a password. Starting with sudo 1.6, both the runas specifier and the NOPASSWD tag are “sticky” for an entire command list. So, given the following line in sudo < 1.6

     millert ALL=(daemon) NOPASSWD:/usr/bin/whoami,/bin/ls

    millert would be able to run /usr/bin/whoami as user daemon without a password and /bin/ls as root with a password.

    As of sudo 1.6, the same line now means that millert is able to run both /usr/bin/whoami and /bin/ls as user daemon without a password. To expand on this, take the following example:

     millert ALL=(daemon) NOPASSWD:/usr/bin/whoami, (root) /bin/ls, \

    millert can run /usr/bin/whoami as daemon and /bin/ls and /sbin/dump as root. No password need be given for either command. In other words, the “(root)” sets the default runas user to root for the rest of the list. If we wanted to require a password for /bin/ls and /sbin/dump the line could be written as:

     millert ALL=(daemon) NOPASSWD:/usr/bin/whoami, \
         (root) PASSWD:/bin/ls, /sbin/dump

    Additionally, sudo now uses a per-user time stamp directory instead of a time stamp file. This allows tty time stamps to simply be files within the user’s time stamp dir. For the default, non-tty case, the time stamp on the directory itself is used.

    Also, the temporary file used by visudo is now /etc/sudoers.tmp since some versions of vipw on systems with shadow passwords use /etc/stmp for the temporary shadow file.

  • Upgrading from a version prior to 1.5:

    By default, sudo expects the sudoers file to be mode 0440 and to be owned by user and group 0. This differs from version 1.4 and below which expected the sudoers file to be mode 0400 and to be owned by root. Doing a make install will set the sudoers file to the new mode and group. If sudo encounters a sudoers file with the old permissions it will attempt to update it to the new scheme. You cannot, however, use a sudoers file with the new permissions with an old sudo binary. It is suggested that if have a means of distributing sudo you distribute the new binaries first, then the new sudoers file (or you can leave sudoers as is and sudo will fix the permissions itself as long as sudoers is on a local file system).