/usr/share/doc/samhain/manual.html/trustedexample.html

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><DIV
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><H1
CLASS="SECT1"
><A
NAME="TRUSTEDEXAMPLE"
>4.5. Log file</A
></H1
><P
>  <P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>Trusted users</DT
><DD
><P
>	<B
CLASS="COMMAND"
>TrustedUser=<TT
CLASS="REPLACEABLE"
><I
>username</I
></TT
></B
>
        </P
><P
>	If some element in the path to the log file is
	writeable by someone else than <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>root</I
></SPAN
> 
        or the <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>effective user</I
></SPAN
> 
        of the process, you have to include
	that user in the list of <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>trusted users</I
></SPAN
> 
        (unless their UIDs 
        are already compiled in).
    </P
></DD
><DT
>Separate log files for clients</DT
><DD
><P
>	<B
CLASS="COMMAND"
>UseSeparateLogs=<TT
CLASS="REPLACEABLE"
><I
>yes/no</I
></TT
></B
>
        </P
><P
>	<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Only relevant on the server.</I
></SPAN
>
	Use a separate log file for (reports from) each client.
	The root name of these log files will be the same as the main
	log file, with the client name appended.
    </P
></DD
></DL
></DIV
>        </P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="LOGFILE"
>4.5.1. The log file and its integrity</A
></H2
><P
>  The log file is named <TT
CLASS="FILENAME"
>samhain_log</TT
> by default, 
  and placed into
  <TT
CLASS="FILENAME"
>/var/log</TT
> by default 
  (name and location can be configured
  at compile time). If <SPAN
CLASS="APPLICATION"
>samhain</SPAN
> has been 
  compiled with the
  <B
CLASS="COMMAND"
>./configure --enable-xml-log</B
> option, 
  it will be written in XML format.
  </P
><DIV
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><P
></P
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SRC="./stylesheet-images/note.gif"
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ALT="Note"></TD
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
>Note</B
></TH
></TR
><TR
><TD
>&nbsp;</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>  If you have compiled for stealth (<A
HREF="stealthmode.html"
>Chapter 9</A
>&#62;),
  you won't see much, because if obfuscated, then both a 'normal' and an 
  XML logfile look, well ... obfuscated. Use 
  <B
CLASS="COMMAND"
>samhain -jL <TT
CLASS="REPLACEABLE"
><I
>/path/to/logfile</I
></TT
></B
>
  to view the logfile.
  </P
></TD
></TR
></TABLE
></DIV
><P
>  The log file is created if it does not exist, and locked by creating
  a <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>lock file</I
></SPAN
>, which has the same path as the logfile,
  with a &quot;.lock&quot; appended. The lock file holds the PID of 
  the process, which allows <SPAN
CLASS="APPLICATION"
>samhain</SPAN
> to recognize
  and remove a stale lock if there is no process with that PID.
  </P
><P
>  On the log server, it is possible to use separate log files for 
  individual clients. This can be enabled with 
  <B
CLASS="COMMAND"
>UseSeparateLogs=<TT
CLASS="REPLACEABLE"
><I
>yes/no</I
></TT
></B
>
  in the Misc section of the server configuration file. No locking will
  be performed for client files (only one instance of the server can
  listen on the TCP port, thus there will be no concurrent access).
  </P
><P
>  The directory where the logfile and its lock file are located 
  must be writeable
  only by trusted users (see <A
HREF="layout.html#DEFTRUST"
>Section 2.10.1</A
>&#62;). This requirement
  refers to the <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>complete</I
></SPAN
> path, i.e. all directories 
  therein. By default,
  only <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>root</I
></SPAN
> and the <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>effective user</I
></SPAN
>
  of 
  the process are trusted.
  </P
><P
>  Audit trails (sequences of messages from individual runs of 
  <SPAN
CLASS="APPLICATION"
>samhain</SPAN
>) 
  in the log file start with a <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>[SOF]</I
></SPAN
> marker. 
  Each message is followed
  by a signature, that is formed by hashing the message with a key.
  </P
><P
>  The first key is generated at random, and sent by e-mail, encrypted with a 
  one-time pad as described in the previous section on e-mail.
  Further keys are generated by a hash chain (i.e. the key is hashed to
  generate the next key). Thus, only by knowing the initial key the
  integrity of the log file can be assured.
  </P
><P
>  The mail with the key looks like:
  </P
><PRE
CLASS="PROGRAMLISTING"
>  -----BEGIN MESSAGE-----  
  message    
  -----BEGIN LOGKEY----- 
  Key(48 chars)[timestamp]     
  -----BEGIN SIGNATURE----- 
  signature
  ID TRAIL_ID:hostname 
  -----END MESSAGE-----  </PRE
><DIV
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><IMG
SRC="./stylesheet-images/tip.gif"
HSPACE="5"
ALT="Tip"></TD
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
>Integrity verification</B
></TH
></TR
><TR
><TD
>&nbsp;</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>  <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>To verify the log file's integrity</I
></SPAN
>, 
  a convenience function is
  provided:
  </P
><P
>  <B
CLASS="COMMAND"
>samhain -L <TT
CLASS="REPLACEABLE"
><I
>/log/file/path</I
></TT
></B
>
  </P
><P
>  When encountering the start of an audit trail, you will then be asked
  for the key (as sent to you by e-mail). You can then: 
  (i) hit <B
CLASS="COMMAND"
>return</B
> to skip signature verification,
  (ii) enter the key (without the appended timestamp), or
  (iii) enter the path to a file that contains the key (e.g. the mail box).
  </P
><P
>  If you use option (iii), the path must be an absolute path (starting
  with a '/', not longer than 48 chars. For each audit trail, the file
  must contain a two-line block with the 
  <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>-----BEGIN LOGKEY-----</I
></SPAN
> line 
  followed by the
  line (<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Key(48 chars)[timestamp]</I
></SPAN
>) from the mail. 
  Additional lines
  before/after any such two-line block are ignored (in particular, if you 
  collect all e-mails from <SPAN
CLASS="APPLICATION"
>samhain</SPAN
> in 
  a mailbox file, you can simply
  specify the path to that mailbox file).
  </P
></TD
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><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
><B
>CAVEATS</B
></TH
></TR
><TR
><TD
>&nbsp;</TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>  Verification will fail, if the compiled-in key of the verifying executable
  is different from the one that generated the message(s) 
  (see <A
HREF="keypad.html"
>Section 11.2</A
>&#62;).
  </P
><P
>  If you use a pre-compiled executable from some binary
  distribution, be sure to read <A
HREF="keypad.html"
>Section 11.2</A
>&#62; carefully.
  </P
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samhain 3.1.0-5ubuntu1 / usr / share / doc / samhain / manual.html / trustedexample.html
