[max@xxxxxxxxxxxxx: sredird vulnerabilities]

Hi auditors,

this is still unfixed (#267098) as of today.

Cheers,
Max

----- Forwarded message from Max Vozeler <max@xxxxxxxxxxxxx> -----

From: Max Vozeler <max@xxxxxxxxxxxxx>
To: russell@xxxxxxxxxxxx
Cc: team@xxxxxxxxxxxxxxxxxxx
Subject: sredird vulnerabilities
Date: Fri, 30 Jul 2004 14:52:24 +0200
User-Agent: Mutt/1.5.6+20040523i

Hi Russell,

[ CCing Security Team for vulns in the testing version ]

there are two bugs in sredird that can introduce security problems,
potentially leading to a remote root compromise. Affected in Debian is
the testing/unstable sredird 2.2.1-1.

Feel free to forward this info as you like. Unless you want me to delay
disclosure to the BTS for some reason, or the fixed package has already
entered testing by then, I'll file +security bugs in 10 days or so.

There are two bugs:

LogMsg() format string bug
--------------------------

sredird-2.2.1/sredird.c:

   458  /* Generic log function with log level control. Uses the same log levels
   459  of the syslog(3) system call */
   460  void LogMsg(int LogLevel, const char * const Msg)
   461    {
   462      if (LogLevel <= MaxLogLevel)
   463        syslog(LogLevel,Msg);
   464    }

The log buffer in Msg is given to syslog() as format control string. This
can lead to overwriting of any memory locations in case the content of Msg
is controllable by an attacker. There is in fact one such place where the
input to LogMsg() is constructed from data as supplied by the client:

  1365  /* Handling of COM Port Control specific commands */
  1366  void HandleCPCCommand(BufferType *SockB, int PortFd, unsigned char * 
Command, size_t CSize)
  1367    {
  1368      char LogStr[TmpStrLen];
  1369      char SigStr[TmpStrLen];

  ..

  1376      /* Check wich command has been requested */
  1377      switch (Command[3])
  1378        {
  1379          /* Signature */
  1380          case TNCAS_SIGNATURE:

  ..

  1391                /* Received client signature */
  1392                strncpy(SigStr,(char *) &Command[4],CSize - 6);
  1393                sprintf(LogStr,"Received client signature: %s",SigStr);
  1394                LogMsg(LOG_INFO,LogStr);

The canonical fix would be to add an explicit "%s" format string to the
syslog() call in LogMsg(). (See attached sredird-log-fmt.diff)

HandleCPCCommand() stack overflow
---------------------------------

Affected is the last chunk of code in HandleCPCCommand() shown above.
LogStr is not large enough to store the largest possible output from
sprintf(). CSize is limited to 254 by the caller, minus 6, makes a max.
SigStr length of 248 bytes. After the sprintf() with 27 or so non-format
characters, the output can grow to

  27 + 248 = 275 bytes
  
.. which is too much for LogStr[255], by 20 bytes or so. This may be 
enough to overwrite precious stuff on the stack like saved eip depending
on stack layout.

Why not just replace it with snprintf()? This would solve this problem
for good. See attached patch sredird-hcpcc-bof.diff for example.

(There should be a LogStr[sizeof(LogStr)-1] = 0; after the snprintf in
the patch which I forgot to add)

Cheers,
Max

-- 
308E81E7B97963BCA0E6ED889D5BD511B7CDA2DC

--- sredird.c.orig      2004-05-01 21:45:49.000000000 +0200
+++ sredird.c   2004-05-01 21:46:05.000000000 +0200
@@ -460,7 +460,7 @@
 void LogMsg(int LogLevel, const char * const Msg)
   {
     if (LogLevel <= MaxLogLevel)
-      syslog(LogLevel,Msg);
+      syslog(LogLevel,"%s",Msg);
   }
 
 /* Try to lock the file given in LockFile as pid LockPid using the classical

--- sredird.c.orig      2004-05-01 22:09:28.000000000 +0200
+++ sredird.c   2004-05-01 22:10:10.000000000 +0200
@@ -1390,7 +1390,7 @@
             {
               /* Received client signature */
               strncpy(SigStr,(char *) &Command[4],CSize - 6);
-              sprintf(LogStr,"Received client signature: %s",SigStr);
+              snprintf(LogStr,sizeof(LogStr)-1,"Received client signature: 
%s",SigStr);
               LogMsg(LOG_INFO,LogStr);
             }
         break;




----- End forwarded message -----

-- 
308E81E7B97963BCA0E6ED889D5BD511B7CDA2DC