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

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><A
NAME="KEYPAD"
>11.2. Integrity of the samhain executable</A
></H1
><P
>  Each samhain executable contains a compiled-in key, that is used
  when the signatures of emails and/or logfile entries are verified.
  By default, a  cryptographically strong random key 
  is generated by the <B
CLASS="COMMAND"
>configure</B
> script at compile time.
  Thus, each build is unique, and signature verification will fail
  if a different build is used, except if the compiled-in key was set
  to a common value for both builds.
  </P
><P
>  To set a 
  user-defined key, there is an option
  </P
><P
>  <B
CLASS="COMMAND"
>./configure --enable-base=<TT
CLASS="REPLACEABLE"
><I
>B1,B2</I
></TT
></B
>
  </P
><P
>  where B1,B2 should be two integers in the range 0...2147483647.
  </P
><P
>  The key generated by <B
CLASS="COMMAND"
>configure</B
> is printed in 
  the configure script's output. It is recommended that you save this key
  and use it for further builds.
  </P
><P
>  Whenever you try to verify the integrity of e-mails or log file entries,
  this compiled-in key is used (to be more specific: the signature key
  is encrypted with a one-time pad generated from the message itself and
  the compiled-in key). As a result, if executable B is used to
  verify the integrity of e-mails sent by executable A, <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>integrity 
  verification
  will fail</I
></SPAN
> if the compiled-in keys of A and B do not match. 
  This can be used to
  check the integrity of A in a straightforward way (check e-mails on another
  host, using a different executable compiled with  the same key).
  </P
><P
>  Obviously, this scheme can be broken, but it requires an intruder to 
  disassemble/decompile and analyze the existing 
  <SPAN
CLASS="APPLICATION"
>samhain</SPAN
> executable, rather 
  than simply replace it with a precompiled trojan.
  </P
><P
>  However, if you use a <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>precompiled</I
></SPAN
> 
  <SPAN
CLASS="APPLICATION"
>samhain</SPAN
> executable (e.g. from a
  binary distribution), in principle a prospective intruder could easily 
  obtain a copy of the executable and analyze it in advance. This will
  enable her/him to generate fake audit trails and/or generate
  a trojan for this particular binary distribution.
  </P
><P
>  For this reason, it is possible for the user to add more key material into 
  the binary executable. This is done with the command:
  </P
><P
>  <B
CLASS="COMMAND"
>samhain --add-key=<TT
CLASS="REPLACEABLE"
><I
>key@/path/to/samhain_executable</I
></TT
></B
>
  </P
><P
>  This will read the file <TT
CLASS="FILENAME"
>/path/to/samhain_executable</TT
>, 
  add the key <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>key</I
></SPAN
>,
  which can be a string of arbitrary length, except that it should not 
  contain a '@' (because it has a special meaning, separating
  key from path), and write the new binary to the location 
  <TT
CLASS="FILENAME"
>/path/to/executable.out</TT
> (i.e.
  with .out appended). 
  </P
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>For Clarification</B
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><P
>Please note that --add-key does not replace a compiled-in key but only
adds to it. Integrity verification depends on both the compiled-in and
any added key material, and integrity verification using different binaries
will therefore only work if all were compiled with the same key and 
had the same extra key material (if any) added in.
  </P
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>WARNING</B
></TH
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><TD
>&nbsp;</TD
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><P
>  Using a precompiled samhain executable from a binary
  package distribution is not recommended unless you add in key material as
  described above.
  </P
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samhain 3.1.0-5ubuntu1 / usr / share / doc / samhain / manual.html / keypad.html
