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NAME | DESCRIPTION | Client Messages | Server Messages | Protocol flow of control | EVENT LOG VARIABLES | EXAMPLES | SEE ALSO | AUTHORS | BUGS | SUPPORT | DISCLAIMER | COLOPHON |
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SUDO_LOGSRV.PROTO(5) File Formats Manual SUDO_LOGSRV.PROTO(5)
sudo_logsrv.proto — Sudo log server protocol
Starting with version 1.9.0, sudo supports sending event and I/O
logs to a log server. The protocol used is written in Google's
Protocol Buffers domain specific language. The “EXAMPLES”
section includes a complete description of the protocol in
Protocol Buffers format.
Because there is no way to determine message boundaries when
using Protocol Buffers, the wire size of each message is sent
immediately preceding the message itself as a 32-bit unsigned
integer in network byte order. This is referred to as
“length-prefix framing” and is how Google suggests handling the
lack of message delimiters.
The protocol is made up of two basic messages, ClientMessage and
ServerMessage, described below. The server must accept messages
up to two megabytes in size. The server may return an error if
the client tries to send a message larger than two megabytes.
A ClientMessage is a container used to encapsulate all the
possible message types a client may send to the server.
message ClientMessage {
oneof type {
AcceptMessage accept_msg = 1;
RejectMessage reject_msg = 2;
ExitMessage exit_msg = 3;
RestartMessage restart_msg = 4;
AlertMessage alert_msg = 5;
IoBuffer ttyin_buf = 6;
IoBuffer ttyout_buf = 7;
IoBuffer stdin_buf = 8;
IoBuffer stdout_buf = 9;
IoBuffer stderr_buf = 10;
ChangeWindowSize winsize_event = 11;
CommandSuspend suspend_event = 12;
ClientHello hello_msg = 13;
}
}
The different ClientMessage sub-messages the client may sent to
the server are described below.
TimeSpec
message TimeSpec {
int64 tv_sec = 1;
int32 tv_nsec = 2;
}
A TimeSpec is the equivalent of a POSIX struct timespec,
containing seconds and nanoseconds members. The tv_sec member is
a 64-bit integer to support dates after the year 2038.
InfoMessage
message InfoMessage {
message StringList {
repeated string strings = 1;
}
message NumberList {
repeated int64 numbers = 1;
}
string key = 1;
oneof value {
int64 numval = 2;
string strval = 3;
StringList strlistval = 4;
NumberList numlistval = 5;
}
}
An InfoMessage is used to represent information about the
invoking user as well as the execution environment the command
runs in the form of key-value pairs. The key is always a string
but the value may be a 64-bit integer, a string, an array of
strings, or an array of 64-bit integers. The event log data is
composed of InfoMessage entries. See the “EVENT LOG VARIABLES”
section for more information.
ClientHello hello_msg
message ClientHello {
string client_id = 1;
}
A ClientHello message consists of client information that may be
sent to the server when the client first connects.
client_id
A free-form client description. This usually includes
the name and version of the client implementation.
AcceptMessage accept_msg
message AcceptMessage {
TimeSpec submit_time = 1;
repeated InfoMessage info_msgs = 2;
bool expect_iobufs = 3;
}
An AcceptMessage is sent by the client when a command is allowed
by the security policy. It contains the following members:
submit_time
The wall clock time when the command was submitted to the
security policy.
info_msgs
An array of InfoMessage describing the user who submitted
the command as well as the execution environment of the
command. This information is used to generate an event
log entry and may also be used by server to determine
where and how the I/O log is stored.
expect_iobufs
Set to true if the server should expect IoBuffer messages
to follow (for I/O logging) or false if the server should
only store the event log.
If an AcceptMessage is sent, the client must not send a
RejectMessage or RestartMessage.
RejectMessage reject_msg
message RejectMessage {
TimeSpec submit_time = 1;
string reason = 2;
repeated InfoMessage info_msgs = 3;
}
A RejectMessage is sent by the client when a command is denied by
the security policy. It contains the following members:
submit_time
The wall clock time when the command was submitted to the
security policy.
reason The reason the security policy gave for denying the
command.
info_msgs
An array of InfoMessage describing the user who submitted
the command as well as the execution environment of the
command. This information is used to generate an event
log entry.
If a RejectMessage is sent, the client must not send an
AcceptMessage or RestartMessage.
ExitMessage exit_msg
message ExitMessage {
TimeSpec run_time = 1;
int32 exit_value = 2;
bool dumped_core = 3;
string signal = 4;
string error = 5;
}
An ExitMessage is sent by the client after the command has exited
or has been terminated by a signal. It contains the following
members:
run_time
The total amount of elapsed time since the command
started, calculated using a monotonic clock where
possible. This is not the wall clock time.
exit_value
The command's exit value in the range 0-255.
dumped_core
True if the command was terminated by a signal and dumped
core.
signal If the command was terminated by a signal, this is set to
the name of the signal without the leading “SIG”. For
example, INT, TERM, KILL, SEGV.
error A message from the client indicating that the command was
terminated unexpectedly due to an error.
When performing I/O logging, the client should wait for a
commit_point corresponding to the final IoBuffer before closing
the connection unless the final commit_point has already been
received.
RestartMessage restart_msg
message RestartMessage {
string log_id = 1;
TimeSpec resume_point = 2;
}
A RestartMessage is sent by the client to resume sending an
existing I/O log that was previously interrupted. It contains
the following members:
log_id The the server-side name for an I/O log that was
previously sent to the client by the server. This may be
a path name on the server or some other kind of server-
side identifier.
resume_point
The point in time after which to resume the I/O log.
This is in the form of a TimeSpec representing the amount
of time since the command started, not the wall clock
time. The resume_point should correspond to a
commit_point previously sent to the client by the server.
If the server receives a RestartMessage containing a
resume_point it has not previously seen, an error will be
returned to the client and the connection will be
dropped.
If a RestartMessage is sent, the client must not send an
AcceptMessage or RejectMessage.
AlertMessage alert_msg
message AlertMessage {
TimeSpec alert_time = 1;
string reason = 2;
repeated InfoMessage info_msgs = 3;
}
An AlertMessage is sent by the client to indicate a problem
detected by the security policy while the command is running that
should be stored in the event log. It contains the following
members:
alert_time
The wall clock time when the alert occurred.
reason The reason for the alert.
info_msgs
An optional array of InfoMessage describing the user who
submitted the command as well as the execution
environment of the command. This information is used to
generate an event log entry.
IoBuffer ttyin_buf | ttyout_buf | stdin_buf | stdout_buf | stderr_buf
message IoBuffer {
TimeSpec delay = 1;
bytes data = 2;
}
An IoBuffer is used to represent data from terminal input,
terminal output, standard input, standard output, or standard
error. It contains the following members:
delay The elapsed time since the last record in the form of a
TimeSpec. The delay should be calculated using a
monotonic clock where possible.
data The binary I/O log data from terminal input, terminal
output, standard input, standard output, or standard
error.
ChangeWindowSize winsize_event
message ChangeWindowSize {
TimeSpec delay = 1;
int32 rows = 2;
int32 cols = 3;
}
A ChangeWindowSize message is sent by the client when the
terminal running the command changes size. It contains the
following members:
delay The elapsed time since the last record in the form of a
TimeSpec. The delay should be calculated using a
monotonic clock where possible.
rows The new number of terminal rows.
cols The new number of terminal columns.
CommandSuspend suspend_event
message CommandSuspend {
TimeSpec delay = 1;
string signal = 2;
}
A CommandSuspend message is sent by the client when the command
is either suspended or resumed. It contains the following
members:
delay The elapsed time since the last record in the form of a
TimeSpec. The delay should be calculated using a
monotonic clock where possible.
signal The signal name without the leading “SIG”. For example,
STOP, TSTP, CONT.
A ServerMessage is a container used to encapsulate all the
possible message types the server may send to a client.
message ServerMessage {
oneof type {
ServerHello hello = 1;
TimeSpec commit_point = 2;
string log_id = 3;
string error = 4;
string abort = 5;
}
}
The different ServerMessage sub-messages the server may sent to
the client are described below.
ServerHello hello
message ServerHello {
string server_id = 1;
string redirect = 2;
repeated string servers = 3;
bool subcommands = 4;
}
The ServerHello message consists of server information sent when
the client first connects. It contains the following members:
server_id
A free-form server description. Usually this includes
the name and version of the implementation running on the
log server. This member is always present.
redirect
A host and port separated by a colon (‘’): that the
client should connect to instead. The host may be a host
name, an IPv4 address, or an IPv6 address in square
brackets. This may be used for server load balancing.
The server will disconnect after sending the ServerHello
when it includes a redirect.
servers
A list of other known log servers. This can be used to
implement log server redundancy and allows the client to
discover all other log servers simply by connecting to
one known server. This member may be omitted when there
is only a single log server.
subcommands
If set, the server supports logging additional commands
during a session. The client may send an AcceptMessage
or RejectMessage when sudo is running in intercept mode.
In this mode, commands spawned from the initial command
authorized by sudo are subject to policy restrictions
and/or are logged. If subcommands is false, the client
must not attempt to log additional commands.
TimeSpec commit_point
A periodic time stamp sent by the server to indicate when I/O log
buffers have been committed to storage. This message is not sent
after every IoBuffer but rather at a server-configurable
interval. When the server receives an ExitMessage, it will
respond with a commit_point corresponding to the last received
IoBuffer before closing the connection.
string log_id
The server-side ID of the I/O log being stored, sent in response
to an AcceptMessage where expect_iobufs is true.
string error
A fatal server-side error. The server will close the connection
after sending the error message.
string abort
An abort message from the server indicates that the client should
kill the command and terminate the session. It may be used to
implement simple server-side policy. The server will close the
connection after sending the abort message.
The expected protocol flow is as follows:
1. Client connects to the first available server. If the
client is configured to use TLS, a TLS handshake will be
attempted.
2. Client sends ClientHello. This is currently optional but
allows the server to detect a non-TLS connection on the TLS
port.
3. Server sends ServerHello.
4. Client responds with either AcceptMessage, RejectMessage, or
RestartMessage.
5. If client sent a AcceptMessage with expect_iobufs set,
server creates a new I/O log and responds with a log_id.
6. Client sends zero or more IoBuffer messages.
7. Server periodically responds to IoBuffer messages with a
commit_point.
8. Client sends an ExitMessage when the command exits or is
killed.
9. Server sends the final commit_point if one is pending.
10. Server closes the connection. After receiving the final
commit_point, the client shuts down its side of the TLS
connection if TLS is in use, and closes the connection.
11. Server shuts down its side of the TLS connection if TLS is
in use, and closes the connection.
At any point, the server may send an error or abort message to
the client at which point the server will close the connection.
If an abort message is received, the client should terminate the
running command.
AcceptMessage, AlertMessage and RejectMessage classes contain an
array of InfoMessage that should contain information about the
user who submitted the command as well as information about the
execution environment of the command if it was accepted.
Some variables have a client, run, or submit prefix. These
prefixes are used to eliminate ambiguity for variables that could
apply to the client program, the user submitting the command, or
the command being run. Variables with a client prefix pertain to
the program performing the connection to the log server, for
example sudo. Variables with a run prefix pertain to the command
that the user requested be run. Variables with a submit prefix
pertain to the user submitting the request (the user running
sudo).
The following InfoMessage entries are required:
Key Type Description
command string command that was submitted
runuser string name of user the command was run as
submithost string name of host the command was
submitted
on
submituser string name of user submitting the command
The following InfoMessage entries are recognized, but not
required:
Key Type Description
clientargv StringList client's original argument vector
clientpid int64 client's process ID
clientppid int64 client's parent process ID
clientsid int64 client's terminal session ID
columns int64 number of columns in the terminal
lines int64 number of lines in the terminal
runargv StringList argument vector of command to run
runchroot string root directory of command to run
runcwd string running command's working directory
runenv StringList the running command's environment
rungid int64 primary group-ID of the command
rungids NumberList supplementary group-IDs for the
command
rungroup string primary group name of the command
rungroups StringList supplementary group names for the
command
runuid int64 run user's user-ID
submitcwd string submit user's current working
directory
submitenv StringList the submit user's environment
submitgid int64 submit user's primary group-ID
submitgids NumberList submit user's supplementary
group-IDs
submitgroup string submitting user's primary group name
submitgroups StringList submit user's supplementary group
names
submituid int64 submit user's user-ID
ttyname string the terminal the command was
submitted
from
The server must accept other variables not listed above but may
ignore them.
The Protocol Buffers description of the log server protocol,
using “proto3” syntax, is included in full below.
syntax = "proto3";
/*
* Client message to the server. Messages on the wire are
* prefixed with a 32-bit size in network byte order.
*/
message ClientMessage {
oneof type {
AcceptMessage accept_msg = 1;
RejectMessage reject_msg = 2;
ExitMessage exit_msg = 3;
RestartMessage restart_msg = 4;
AlertMessage alert_msg = 5;
IoBuffer ttyin_buf = 6;
IoBuffer ttyout_buf = 7;
IoBuffer stdin_buf = 8;
IoBuffer stdout_buf = 9;
IoBuffer stderr_buf = 10;
ChangeWindowSize winsize_event = 11;
CommandSuspend suspend_event = 12;
}
}
/* Equivalent of POSIX struct timespec */
message TimeSpec {
int64 tv_sec = 1; /* seconds */
int32 tv_nsec = 2; /* nanoseconds */
}
/* I/O buffer with keystroke data */
message IoBuffer {
TimeSpec delay = 1; /* elapsed time since last record */
bytes data = 2; /* keystroke data */
}
/*
* Key/value pairs, like Privilege Manager struct info.
* The value may be a number, a string, or a list of strings.
*/
message InfoMessage {
message StringList {
repeated string strings = 1;
}
message NumberList {
repeated int64 numbers = 1;
}
string key = 1;
oneof value {
int64 numval = 2;
string strval = 3;
StringList strlistval = 4;
NumberList numlistval = 5;
}
}
/*
* Event log data for command accepted by the policy.
*/
message AcceptMessage {
TimeSpec submit_time = 1; /* when command was submitted */
repeated InfoMessage info_msgs = 2; /* key,value event log data */
bool expect_iobufs = 3; /* true if I/O logging enabled */
}
/*
* Event log data for command rejected by the policy.
*/
message RejectMessage {
TimeSpec submit_time = 1; /* when command was submitted */
string reason = 2; /* reason command was rejected */
repeated InfoMessage info_msgs = 3; /* key,value event log data */
}
/* Message sent by client when command exits. */
/* Might revisit runtime and use end_time instead */
message ExitMessage {
TimeSpec run_time = 1; /* total elapsed run time */
int32 exit_value = 2; /* 0-255 */
bool dumped_core = 3; /* true if command dumped core */
string signal = 4; /* signal name if killed by signal */
string error = 5; /* if killed due to other error */
}
/* Alert message, policy module-specific. */
message AlertMessage {
TimeSpec alert_time = 1; /* time alert message occurred */
string reason = 2; /* policy alert error string */
repeated InfoMessage info_msgs = 3; /* key,value event log data */
}
/* Used to restart an existing I/O log on the server. */
message RestartMessage {
string log_id = 1; /* ID of log being restarted */
TimeSpec resume_point = 2; /* resume point (elapsed time) */
}
/* Window size change event. */
message ChangeWindowSize {
TimeSpec delay = 1; /* elapsed time since last record */
int32 rows = 2; /* new number of rows */
int32 cols = 3; /* new number of columns */
}
/* Command suspend/resume event. */
message CommandSuspend {
TimeSpec delay = 1; /* elapsed time since last record */
string signal = 2; /* signal that caused suspend/resume */
}
/*
* Server messages to the client. Messages on the wire are
* prefixed with a 32-bit size in network byte order.
*/
message ServerMessage {
oneof type {
ServerHello hello = 1; /* server hello message */
TimeSpec commit_point = 2; /* cumulative time of records stored */
string log_id = 3; /* ID of server-side I/O log */
string error = 4; /* error message from server */
string abort = 5; /* abort message, kill command */
}
}
/* Hello message from server when client connects. */
message ServerHello {
string server_id = 1; /* free-form server description */
string redirect = 2; /* optional redirect if busy */
repeated string servers = 3; /* optional list of known servers */
}
sudo_logsrvd.conf(5), sudoers(5), sudo(8), sudo_logsrvd(8)
Protocol Buffers,
https://developers.google.com/protocol-buffers/.
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.
If you believe you have found a bug in sudo, you can submit a bug
report at https://bugzilla.sudo.ws/
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.
sudo is provided “AS IS” and any express or implied warranties,
including, but not limited to, the implied warranties of
merchantability and fitness for a particular purpose are
disclaimed. See the LICENSE.md file distributed with sudo or
https://www.sudo.ws/about/license/ for complete details.
This page is part of the sudo (execute a command as another user)
project. Information about the project can be found at
https://www.sudo.ws/. If you have a bug report for this manual
page, see ⟨https://bugzilla.sudo.ws/⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/sudo-project/sudo⟩ on 2023-12-22. (At that
time, the date of the most recent commit that was found in the
repository was 2023-12-21.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Sudo 1.9.15p4 September 13, 2022 SUDO_LOGSRV.PROTO(5)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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