illumos: manual page: audit

AUDIT_REMOTE(7) Standards, Environments, and Macros AUDIT_REMOTE(7)

NAME

audit_remote - send audit logs to a remote server

SYNOPSIS

/usr/lib/security/audit_remote.so

DESCRIPTION

The audit_remote plugin module for audit,
/usr/lib/security/audit_remote.so, sends binary audit records
(audit.log(5)) to audit servers specified in the plugin's attributes
configured by auditconfig(8).

Object Attributes

The following attributes specify the configuration of the audit_remote
plugin:

p_hosts

host1[:[port1][:mech1]][,host2[:[port2][:mech2]],... \
hostn[:[portn][:mechn]]]

A list of audit hosts/servers. Audit records are sent to the first
available host. If a host is unreachable or a timeout occurs while
sending data, the next host in the list is tried. If connection to
all hosts fails, the list is tried again from the beginning.

The host part of a p_hosts entry can be in any form acceptable to
getipnodebyname(3SOCKET).

The port part of a p_hosts entry is the port on host that is
contacted to initiate an audit server connection. If not specified,
the port number is that assigned to the solaris-audit service. See
getservbyname(3XNET).

The mech part of a p_host entry is the GSS-API mechanism name
(mech(5)). If not specified, the local host's default mechanism is
used. The recommended mechanism is kerberos_v5.

p_retries

The number of retries for connecting to and sending data to a server.

The default value is 3.

p_timeout

The number of seconds in which a connection/sending data timeouts.

The default value is 5 seconds.

qsize

The maximum number of outstanding audit records to keep.

The default is the value of the kernel queue control high water mark.
See auditconfig(8).

GSS SESSION

The audit_remote plugin is a TCP client that authenticates configured
audit servers using the GSS-API (libgss(3LIB)). Binary Audit records are
sent with integrity and confidentiality protection as per-message tokens
generated by gss_wrap(3GSS).

The plugin initiates a TCP connection to an audit server (host:port:mech)
and establishes a GSS security context (with gss_init_sec_context(3GSS)),
with appropriate security mechanism (mech(5)).

If no port is specified, the service name solaris-audit is looked up to
obtain a TCP port number. If no mechanism is specified, the GSS_C_NO_OID
is used as a mech_type parameter of gss_init_sec_context(3GSS), and
causes the underlying GSS-API to use the local default mechanism.

gss_init_sec_context(3GSS) uses GSS_C_NO_CREDENTIAL as the initiator
credential handle and a target name of the form audit@<ost_fqdn>. The
server is expected to use gss_accept_sec_context(3GSS) to complete the
context establishment.

Once the security context is established, the client (audit_remote
plugin) calls gss_wrap(3GSS) to achieve the confidentiality of the
transferred payload - the audit records. The server is expected to use
gss_unwrap(3GSS) to unwrap the received data and gss_get_mic(3GSS) to
obtain the MIC (Message Integrity Code) to be later sent back to the
plugin as a message retrieval acknowledgment.

For example, if the kerberos_v5 mechanism is configured as GSS_API
mechanism on the client and both sides agree on using this mechanism, the
client side has to be eligible to non-interactively gain session keys for
the audit/<host_fqdn>@<REALM> principal from the Kerberos KDC/TGS. At
the same time the identity running the audit server application has to
have the long term keys associated with the audit/<host_fqdn>@<REALM>
principal stored in the keytab file (krb5.conf(5)) to be able to decrypt
the session keys.

The audit_remote plugin initiates a connection to first server in the
p_hosts list. If the connection fails or audit record sends are not
responded to in p_timeout seconds, after p_retries attempts the plugin
tries to connect to the next server. If the connection to the last server
fails, the plugin retries to connect to the first host in the list.
audit_warn(8) is executed at every unsuccessful attempt to connect to the
server or send timeout with the plugin option plugin audit_remote.so
retry <count> <error>.<error> is connection <host:port> <the network
error>. An EPROTO network error indicates that the client plugin did not
get a successful protocol version handshake.

PROTOCOL DESCRIPTION

All protocol messages are preceded by the 4 octets of the size of the
data to follow. This size is in network byte order.

The protocol begins with version negotiation followed by a GSS-API
security context token exchange. On error the connection is closed (and
any output token optionally sent).

The version negotiation takes place in the clear with the plugin sending
an octet array of the comma (,) separated list of versions supported. The
current version number is the characters 01. The receiver is expected to
respond with the version that they accept (in the current case that is
the characters 01). A mismatch is considered an error and the connection
is closed.

The version octet array sent by the plugin and the version characters
accepted by the receiver are concatenated together to make up the
application data field of the channel bindings of the GSS security
context establishment.

<plugin version characters> || <server accepted version characters>"
||" represents concatenation

Subsequent tokens contain a 64 bit sequence number in network byte order
and a single audit record (audit.log(5)); the client uses confidentiality
protection. wrap (64 bit sequence number || audit record)

The server acknowledges the receipt (and is then responsible for any data
loss) with the received 64 bit sequence number and a MIC token of the
unwrapped 64 bit sequence number and audit record. MIC verification on
the client side acknowledges the audit record can be freed and not saved
for possible retransmission.

64 bit sequence number || mic (64 bit sequence number || audit record)

Secure remote audit client/server communication flow:

1) Client <--> Server - TCP handshake

2) Client <--> Server - protocol version negotiation:
a) Client --> Server - send data size - uint32_t value (2)
b) Client --> Server - send clear text message of the versions
supported comma separated, e.g.,
"01,02,03" for versions 1 and 2 and 3.
The only version supported at present is
"01"
c) Client <-- Server - send data size - uint32_t value (2)
d) Client <-- Server - send clear text version selected
("01")
:no version match; close connection; try next host

3) Security context initiation:
a) Client - Construct channel bindings application data value
(4 octets "0101")
b) Client --> Server - send token (data) size - uint32_t value
c) Client --> Server - GSS-API per-context token
d) Client <-- Server - send token (data) size
e) Client <-- Server - GSS-API per-context token
:repeat a-e until security context is initialized; if unsuccessful,
close connection; try next host

4) Client - transmit thread, when audit record to be sent:
a) Client --> Server - send data size
b) Client --> Server - GSS-API per-message token
wrap (sequence number || audit record)
:repeat a-b while less than max (qsize) outstanding records

5) Client - receive thread:
a) Client <-- Server - receive data size - uint32_t value
b) Client <-- Server - receive sequence number - uint64_t value
c) Client <-- Server - receive MIC
d) Client - MIC verification - OK
e) Client - remove particular audit record
pointed by the sequence number from the
retransmit buffer
:repeat a-e, on error close connection; try next host;
retransmit unacknowledged audit records

6) Server - receive thread:
a) Client --> Server - receive data size
b) Client --> Server - GSS-API receive, uwrap, store
per-message token

7) Server - transmit thread:
a) Server - MIC generation - message integrity code
mic (sequence number || audit record)
b) Client <-- Server - send data size
c) Client < -- Server - send sequence number
d) Client <-- Server - send MIC

EXAMPLES

Example 1: Activating audit_remote.so and Specifying attributes

The following commands cause audit_remote.so to be activated and set the
p_retries and p_timeout attributes. Note that using auditconfig(8) only
allows one attribute to be set at a time.

# auditconfig -setplugin audit_remote active p_retries=2
# auditconfig -setplugin audit_remote active p_timeout=90

Example 2: Activating audit_remote.so and Specifying the Remote Audit

Servers

The following command causes audit_remote.so to be activated and
specifies the remote audit servers to where the audit records are sent.
The kerberos_v5 security mechanism is defined to be used when
communicating with the servers.

# auditconfig -setplugin audit_remote active \
p_hosts=eggplant.eng.example.com::kerberos_v5,\
purple.ebay.example.com:4592:kerberos_v5

Example 3: Using the Configuration of Usage Default Security Mechanism

The following example shows the configuration of usage of default
security mechanism. It also shows use of default port on one of the
configured servers:

# auditconfig -setplugin audit_remote active \
p_hosts=jedger.eng.example.com,\
jbadams.ebay.example.com:4592

ATTRIBUTES

See attributes(7) for a description of the following attributes:

+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|MT Level | MT-Safe |
+--------------------+-----------------+
|Interface Stability | See below. |
+--------------------+-----------------+

The plugin configuration parameters are Committed. The client/server
protocol (version "01") is Contracted Project Private. See audit.log(5)
for the audit record format and content stability.

NOTES

audit_remote authenticates itself to the remote audit service by way of
GSS-API (libgss(3LIB)). Default gss credentials are used as provided by
the gss implementation mechanism, such as Kerberos.

The solaris-audit service port assigned by IANA is 16162.

November 22, 2021 AUDIT_REMOTE(7)