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Rename plugin.pod -> sudo_plugin.pod and wire into Makefile

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Todd C. Miller
2010-02-21 21:24:20 -05:00
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SUDO_PLUGIN(1m) MAINTENANCE COMMANDS SUDO_PLUGIN(1m)
SSuuddoo PPlluuggiinn AAPPII
Starting with version 1.8, ssuuddoo supports a plugin API for policy and
session logging. By default, the _s_u_d_o_e_r_s policy plugin and an
associated I/O logging plugin are used. Via the plugin API, ssuuddoo can
be configured to use alternate policy and/or I/O logging plugins
provided by third parties. The plugins to be used are specified via
the _/_e_t_c_/_s_u_d_o_._c_o_n_f file.
The API is versioned with a major and minor number. The minor version
number is incremented when additions are made. The major number is
incremented when incompatible changes are made. A plugin should be
check the version passed to it and make sure that the major version
matches.
The plugin API is defined by the sudo_plugin.h header file.
TThhee ssuuddoo..ccoonnff FFiillee
The _/_e_t_c_/_s_u_d_o_._c_o_n_f file contains plugin configuration directives.
Currently, the only supported keyword is the Plugin directive, which
causes a plugin plugin to be loaded.
A Plugin line consists of the Plugin keyword, followed by the
_s_y_m_b_o_l___n_a_m_e and the _p_a_t_h to the shared object containing the plugin.
The _s_y_m_b_o_l___n_a_m_e is the name of the struct policy_plugin or struct
io_plugin in the plugin shared object. The _p_a_t_h may be fully qualified
or relative. If not fully qualified it is relative to the
$prefix/libexec directory where the prefix is specified at build time
(/usr/local by default).
The same shared object may contain multiple plugins, each with a
different symbol name. The shared object file must be owned by uid 0
and only writable by its owner. Because of ambiguities that arise from
composite policies, only a single policy plugin may be specified. This
limitation does not apply to I/O plugins.
#
# Default /etc/sudo.conf file
#
# Format:
# Plugin plugin_name plugin_path
#
# The plugin_path relative to prefix/libexec unless fully qualified
# The plugin_name corresponds to a global symbol in the plugin
# that contains the plugin interface.
#
Plugin policy_plugin sudoers.so
Plugin io_plugin sudoers.so
PPoolliiccyy PPlluuggiinn AAPPII
A policy plugin must declare and populate a policy_plugin struct in the
global scope. This structure contains pointers to the functions that
implement the ssuuddoo policy checks. The name of the symbol should be
specified in _/_e_t_c_/_s_u_d_o_._c_o_n_f along with a path to the plugin so that
ssuuddoo can load it.
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struct policy_plugin {
#define SUDO_POLICY_PLUGIN 1
unsigned int type; /* always SUDO_POLICY_PLUGIN */
unsigned int version; /* always SUDO_API_VERSION */
int (*open)(unsigned int version, sudo_conv_t conversation,
char * const settings[], char * const user_info[],
char * const user_env[]);
void (*close)(int exit_status, int error);
int (*show_version)(int verbose);
int (*check_policy)(int agrc, char * const argv[],
char *env_add[], char **command_info[],
char **argv_out[], char **user_env_out[]);
int (*list)(int argc, char * const argv[], int verbose,
const char *list_user);
int (*validate)(void);
void (*invalidate)(int remove);
};
The policy_plugin struct has the following fields:
type
The type field should always be set to SUDO_POLICY_PLUGIN
version
The version field should be set to SUDO_API_VERSION.
This allows ssuuddoo to determine the API version the plugin was built
against.
open
int (*open)(unsigned int version, sudo_conv_t conversation,
char * const settings[], char * const user_info[],
char * const user_env[]);
Returns 1 on success, 0 on failure and -1 on error. On error, the
plugin may optionally call the conversation function with
SUDO_CONF_ERROR_MSG to present additional error information to the
user.
The function arguments are as follows:
version
The version passed in by ssuuddoo allows the plugin to determine
the major and minor version number of the plugin API supported
by ssuuddoo.
conversation
A pointer to the conversation function that can be used by the
plugin to interact with the user (see below).
settings
A vector of user-supplied ssuuddoo settings in the form of
"name=value" strings. The vector is terminated by a NULL
pointer. These settings correspond to flags the user specified
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when running ssuuddoo. As such, they will only be present when the
corresponding flag has been specified on the command line.
When parsing _s_e_t_t_i_n_g_s, the plugin should split on the ffiirrsstt
equal sign ('=') since the _n_a_m_e field will never include one
itself but the _v_a_l_u_e might.
runas_user=string
The user name or uid to to run the command as, if specified
via the -u flag.
runas_group=string
The group name or gid to to run the command as, if
specified via the -g flag.
prompt=string
The prompt to use when requesting a password, if specified
via the -p flag.
set_home=bool
Set to true if the user specified the -H flag. If true,
set the HOME environment variable to the target user's home
directory.
preserve_environment=bool
Set to true if the user specified the -E flag, indicating
that the user wishes to preserve the environment.
login_shell=bool
Set to true if the user specified the -i flag, indicating
that the user wishes to run a login shell.
preserve_groups=bool
Set to true if the user specified the -P flag, indicating
that the user wishes to preserve the group vector instead
of setting it based on the runas user.
ignore_ticket=bool
Set to true if the user specified the -k flag along with a
command, indicating that the user wishes to ignore any
cached authentication credentials.
login_class=string
BSD login class to use when setting resource limits and
nice value, if specified by the -c flag.
selinux_role=string
SELinux role to use when executing the command, if
specified by the -r flag.
selinux_type=string
SELinux type to use when executing the command, if
specified by the -t flag.
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bsdauth_type=string
Authentication type, if specified by the -a flag, to use on
systems where BSD authentication is supported.
Additional settings may be added in the future so the plugin
should silently ignore settings that it does not recognize.
user_info
A vector of information about the user running the command in
the form of "name=value" strings. The vector is terminated by
a NULL pointer.
When parsing _u_s_e_r___i_n_f_o, the plugin should split on the ffiirrsstt
equal sign ('=') since the _n_a_m_e field will never include one
itself but the _v_a_l_u_e might.
user=string
The name of the user invoking ssuuddoo.
uid=uid_t
The real user ID of the user invoking ssuuddoo.
gid=gid_t
The real group ID of the user invoking ssuuddoo.
groups=list
The user's supplementary group list formatted as a string
of comma-separated group IDs.
cwd=string
The user's current working directory.
tty=string
The path to the user's terminal device. If the user has no
terminal device associated with the session, the value will
be empty, as in tty=.
host=string
The local machine's hostname as returned by the
gethostname() system call.
user_env
The user's environment in the form of a NULL-terminated vector
of "name=value" strings.
When parsing _u_s_e_r___e_n_v, the plugin should split on the ffiirrsstt
equal sign ('=') since the _n_a_m_e field will never include one
itself but the _v_a_l_u_e might.
close
void (*close)(int exit_status, int error);
The close function is called when the command being run by ssuuddoo
finishes.
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The function arguments are as follows:
exit_status
The command's exit status, as returned by the _w_a_i_t(2) system
call. The value of exit_status is undefined if error is non-
zero.
error
If the command could not be executed, this is set to the value
of errno set by the _e_x_e_c_v_e(2) system call. The plugin is
responsible for displaying error information via the
conversation function. If the command was successfully
executed, the value of error is 0.
show_version
int (*show_version)(int verbose);
The show_version function is called by ssuuddoo when the user specifies
the -V option. The plugin may display its version information to
the user via the conversation function using SUDO_CONV_INFO_MSG.
If the user requests detailed version information, the verbose flag
will be set.
check_policy
int (*check_policy)(int argc, char * const argv[]
char *env_add[], char **command_info[],
char **argv_out[], char **user_env_out[]);
The _c_h_e_c_k___p_o_l_i_c_y function is called by ssuuddoo to determine whether
the user is allowed to run the specified commands. Returns 1 if
the command is allowed, 0 if not and -1 on error. On error, the
plugin may optionally call the conversation function with
SUDO_CONF_ERROR_MSG to present additional error information to the
user.
The function arguments are as follows:
argc
The number of elements in _a_r_g_v, not counting the final NULL
pointer.
argv
The argument vector describing the command the user wishes to
run, in the same form as what would be passed to the _e_x_e_c_v_e_(_)
system call. The vector is terminated by a NULL pointer.
env_add
Additional environment variables specified by the user on the
command line in the form of a NULL-terminated vector of
"name=value" strings. The plugin may reject the command if one
or more variables are not allowed to be set, or it may silently
ignore such variables.
When parsing _e_n_v___a_d_d, the plugin should split on the ffiirrsstt
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equal sign ('=') since the _n_a_m_e field will never include one
itself but the _v_a_l_u_e might.
command_info
Information about the command being run in the form of
"name=value" strings. These values are used by ssuuddoo to set the
execution environment when running a command. The plugin is
responsible for creating and populating the vector, which must
be terminated with a NULL pointer. The following values are
recognized by ssuuddoo:
command=string
Fully qualified path to the command to be executed.
runas_uid=uid
User ID to run the command as.
runas_euid=uid
Effective user ID to run the command as. If not specified,
the value of _r_u_n_a_s___u_i_d is used.
runas_gid=gid
Group ID to run the command as.
runas_egid=gid
Effective group ID to run the command as. If not
specified, the value of _r_u_n_a_s___g_i_d is used.
runas_groups=list
The supplementary group vector to use for the command in
the form of a comma-separated list of group IDs. If
_p_r_e_s_e_r_v_e___g_r_o_u_p_s is set, this option is ignored.
login_class=login_class
BSD login class to use when setting resource limits and
nice value (optional). This option is only set on systems
that support login classes.
preserve_groups=bool
If set, ssuuddoo will preserve the user's group vector instead
of initializing the group vector based on runas_user.
cwd=string
The current working directory to change to when executing
the command.
noexec=bool
If set, prevent the command from executing other programs.
chroot=string
The root directory to use when running the command.
nice=int
Nice value (priority) to use when executing the command.
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The nice value, if specified, overrides the priority
associated with the _l_o_g_i_n___c_l_a_s_s on BSD systems.
umask=octal
The file creation mask to use when executing the command.
selinux_role=string
SELinux role to use when executing the command.
selinux_type=string
SELinux type to use when executing the command.
timeout=int
Command timeout. If non-zero then when the timeout expires
the command will be killed.
Unsupported values will be ignored.
argv_out
The NULL-terminated argument vector to pass to the _e_x_e_c_v_e_(_)
system call when executing the command. The plugin is
responsible for allocating and populating the vector.
user_env_out
The NULL-terminated environment vector to use when executing
the command. The plugin is responsible for allocating and
populating the vector.
list
int (*list)(int verbose, const char *list_user,
int argc, char * const argv[]);
List available privileges for the invoking user. Returns 1 on
success, 0 on failure and -1 on error. On error, the plugin may
optionally call the conversation function with SUDO_CONF_ERROR_MSG
to present additional error information to the user.
Privileges should be output via the conversation function using
SUDO_CONV_INFO_MSG.
verbose
Flag indicating whether to list in verbose mode or not.
list_user
The name of a different user to list privileges for if the
policy allows it. If NULL, the plugin should list the
privileges of the invoking user.
argc
The number of elements in _a_r_g_v, not counting the final NULL
pointer.
argv
If non-NULL, an argument vector describing a command the user
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wishes to check against the policy in the same form as what
would be passed to the _e_x_e_c_v_e_(_) system call. If the command is
permitted by the policy, the fully-qualified path to the
command should be displayed along with any command line
arguments.
validate
int (*validate)(void);
The validate function is called when ssuuddoo is run with the -v flag.
For policy plugins such as _s_u_d_o_e_r_s that cache authentication
credentials, this function will validate and cache the credentials.
The validate function should be NULL if the plugin does not support
credential caching.
Returns 1 on success, 0 on failure and -1 on error. On error, the
plugin may optionally call the conversation function with
SUDO_CONF_ERROR_MSG to present additional error information to the
user.
invalidate
void (*invalidate)(int remove);
The invalidate function is called when ssuuddoo is called with the -k
or -K flag. For policy plugins such as _s_u_d_o_e_r_s that cache
authentication credentials, this function will invalidate the
credentials. If the _r_e_m_o_v_e flag is set, the plugin may remove the
credentials instead of simply invalidating them.
The invalidate function should be NULL if the plugin does not
support credential caching.
_C_o_n_v_e_r_s_a_t_i_o_n _A_P_I
If the plugin needs to interact with the user or display informational
or error messages, it may do so via the conversation function. A
plugin should not attempt to read directly from the standard input or
the user's tty.
struct sudo_conv_message {
#define SUDO_CONV_PROMPT_ECHO_OFF 1
#define SUDO_CONV_PROMPT_ECHO_ON 2
#define SUDO_CONV_ERROR_MSG 3
#define SUDO_CONV_INFO_MSG 4
int msg_type;
int timeout;
const char *msg;
};
struct sudo_conv_reply {
char *reply;
};
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typedef int (*sudo_conv_t)(int num_msgs,
const struct sudo_conv_message msgs[],
struct sudo_conv_reply replies[]);
A conversation function is passed in to the plugin's open function when
the plugin is initialized. The plugin passes in a struct
sudo_conv_message and struct sudo_conv_reply for each message in the
conversation. The plugin is responsible for freeing the actual reply
buffer in struct sudo_conv_reply.
See the sample plugin for an example of the conversation function
usage.
II//OO PPlluuggiinn AAPPII
struct io_plugin {
#define SUDO_IO_PLUGIN 2
unsigned int type; /* always SUDO_IO_PLUGIN */
unsigned int version; /* always SUDO_API_VERSION */
int (*open)(unsigned int version, sudo_conv_t conversation
char * const settings[], char * const user_info[],
char * const user_env[]);
void (*close)(int exit_status, int error); /* wait status or error */
int (*show_version)(int verbose);
int (*log_input)(const char *buf, unsigned int len);
int (*log_output)(const char *buf, unsigned int len);
};
When an I/O plugin is loaded, ssuuddoo runs the command in a pseudo-tty.
This makes it possible to log the input and output from the user's
session. If the log_input function is defined, it will receive the raw
user input (note that this will include input even when echo is
disabled, such as passwords). The log_output function receives output
from the pseudo-tty that is suitable for replaying the user's session
at a later time. Either log_input or log_output may be NULL. If the
open function returns 0, no I/O will be sent to the plugin.
The io_plugin struct has the following fields:
type
The type field should always be set to SUDO_IO_PLUGIN
version
The version field should be set to SUDO_API_VERSION.
This allows ssuuddoo to determine the API version the plugin was built
against.
open
int (*open)(unsigned int version, sudo_conv_t conversation
char * const settings[], char * const user_info[],
char * const user_env[]);
Returns 1 on success, 0 if the command should not be logged and -1
on error. On error, the plugin may optionally call the
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conversation function with SUDO_CONF_ERROR_MSG to present
additional error information to the user.
The function arguments are as follows:
version
The version passed in by ssuuddoo allows the plugin to determine
the major and minor version number of the plugin API supported
by ssuuddoo.
conversation
A pointer to the conversation function that may be used by the
_s_h_o_w___v_e_r_s_i_o_n function to display version information (see
show_version below). The conversation function may also be
used to display additional error message to the user.
settings
A vector of user-supplied ssuuddoo settings in the form of
"name=value" strings. The vector is terminated by a NULL
pointer. These settings correspond to flags the user specified
when running ssuuddoo. As such, they will only be present when the
corresponding flag has been specified on the command line.
When parsing _s_e_t_t_i_n_g_s, the plugin should split on the ffiirrsstt
equal sign ('=') since the _n_a_m_e field will never include one
itself but the _v_a_l_u_e might.
See the "Policy Plugin API" section for a list of all possible
settings.
user_info
A vector of information about the user running the command in
the form of "name=value" strings. The vector is terminated by
a NULL pointer.
When parsing _u_s_e_r___i_n_f_o, the plugin should split on the ffiirrsstt
equal sign ('=') since the _n_a_m_e field will never include one
itself but the _v_a_l_u_e might.
See the "Policy Plugin API" section for a list of all possible
strings.
user_env
The user's environment in the form of a NULL-terminated vector
of "name=value" strings.
When parsing _u_s_e_r___e_n_v, the plugin should split on the ffiirrsstt
equal sign ('=') since the _n_a_m_e field will never include one
itself but the _v_a_l_u_e might.
close
void (*close)(int exit_status, int error);
The close function is called when the command being run by ssuuddoo
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finishes.
The function arguments are as follows:
exit_status
The command's exit status, as returned by the _w_a_i_t(2) system
call. The value of exit_status is undefined if error is non-
zero.
error
If the command could not be executed, this is set to the value
of errno set by the _e_x_e_c_v_e(2) system call. If the command was
successfully executed, the value of error is 0.
show_version
int (*show_version)(int verbose);
The show_version function is called by ssuuddoo when the user specifies
the -V option. The plugin may display its version information to
the user via the conversation function using SUDO_CONV_INFO_MSG.
If the user requests detailed version information, the verbose flag
will be set.
log_input
int (*log_input)(const char *buf, unsigned int len);
The _l_o_g___i_n_p_u_t function is called whenever data can be read from the
user but before it is passed to the running command. This allows
the plugin to reject data if it chooses to (for instance if the
input contains banned content). Returns 1 if the data should be
passed to the command, 0 if the data is rejected (which will
terminate the command) or -1 if an error occurred.
The function arguments are as follows:
buf The buffer containing user input.
len The length of _b_u_f in bytes.
log_output
int (*log_output)(const char *buf, unsigned int len);
The _l_o_g___o_u_t_p_u_t function is called whenever data can be read from
the command but before it is written to the user's terminal. This
allows the plugin to reject data if it chooses to (for instance if
the input contains banned content). Returns 1 if the data should
be passed to the user, 0 if the data is rejected (which will
terminate the command) or -1 if an error occurred.
The function arguments are as follows:
buf The buffer containing command output.
len The length of _b_u_f in bytes.
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UUnnhhaannddlleedd ccoommmmaanndd lliinnee ooppttiioonnss
The -L command line option has been deprecated as its output is covered
by the _s_u_d_o_e_r_s manual page.
SSuuddoo iimmpplleemmeennttaattiioonn ddeettaaiillss
Version macros:
#define SUDO_API_VERSION_GET_MAJOR(v) ((v) >> 16)
#define SUDO_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
#define SUDO_API_VERSION_SET_MAJOR(vp, n) do { \
*(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
} while(0)
#define SUDO_VERSION_SET_MINOR(vp, n) do { \
*(vp) = (*(vp) & 0xffff0000) | (n); \
} while(0)
#define SUDO_API_VERSION_MAJOR 1
#define SUDO_API_VERSION_MINOR 0
#define SUDO_API_VERSION ((SUDO_API_VERSION_MAJOR << 16) | SUDO_API_VERSION_MINOR)
Sudo will cast the plugin symbol to the following when determining the
plugin type.
union sudo_plugin {
struct policy_plugin policy;
struct io_plugin io;
};
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