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AFFLIB(TM): Multiple Format String Injections



AFFLIB(TM): Multiple Format String Injections
AFFLIB(TM): Multiple Format String Injections



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                     Virtual Security Research, LLC.
http://www.vsecurity.com/ 
                            Security Advisory

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Advisory Name: Multiple Format String Injections in AFFLIB
 Release Date: 2007-04-27
  Application: AFFLIB(TM)
     Versions: 2.2.0-2.2.5 and likely earlier. 
               2.2.6-2.2.8 contain a subset of these vulnerabilities.
     Severity: Medium to Low
       Author: Timothy D. Morgan 
Vendor Status: Vendor Notified, Limited Fixes Available
CVE Candidate: CVE-2007-2054
    Reference: 
http://www.vsecurity.com/bulletins/advisories/2007/afflib-fmtstr.txt 
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Product Description:

> From the forensicswiki.org website[1]:

  "The Advanced Forensics Format (AFF) is an extensible open format for
   the storage of disk images and related forensic metadata. It was
   developed by Simson Garfinkel and Basis Technology."

AFFLIB(TM) is the reference implementation of the AFF(TM) format,
written primarily by Simson Garfinkel.  It comes in the form of an open
source library and a set of command line tools used to manipulate
AFF(TM) files.



Vulnerability Overview:

In mid-March, 2007 Virtual Security Research, LLC (VSR) performed a
security code review of AFFLIB(TM) as a part of an internal tool
assessment process.  As a result, multiple vulnerabilities of varying
severities were discovered. The most significant of these
vulnerabilities are being announced publicly to raise awareness and help
end-users secure themselves against potential attack.

Several command line utilities included in AFFLIB(TM) pass command line
arguments to warn() and err() calls as part of the format string
argument.  If an attacker could influence these command line parameters,
these could be exploited to execute arbitrary code.  

Some of the listed vulnerabilities have been fixed in versions 2.2.6 and 
later, but others remain in the latest release (2.2.8).  All line numbers 
listed below are from version 2.2.0.


Vulnerability Details:

The following sections include detailed descriptions of the format
string injection vulnerabilities found during the assessment.


* Format String Injection in s3 *
File: lib/s3.cpp
Line: 207

Description:
A command line parameter is used as the format string in the err()
call. If an attacker could control this name, a format string injection
vulnerability could be exploited.  Lines 192-207 are included to
illustrate the problem:

 void s3_cp(const char *fname,string key)
 {
    struct s3headers meta[2] = {{0,0},{0,0}};
    char buf[64];

    if(opt_flag){
    snprintf(buf,sizeof(buf),"%d",opt_flag);
    meta[0].name = AMAZON_METADATA_PREFIX "arg";
    meta[0].value = buf;
    }

    /* Read from fname into a buffer.
     * Note that we do this with read, so that we can read from stdin
     */
    FILE *f = fopen(fname,"r");
    if(!f) err(1,fname);

An attacker could exploit this problem if the s3 binary were
setuid/setgid, or if the s3 program were executed in a CGI script or
something similar.



* Format String Injections in afconvert *
File: tools/afconvert.cpp
Lines: 226, 263, and 305

Description:
A command line parameter is used as the format string in three err()
calls. If an attacker could control this name, a format string injection
vulnerability could be exploited. 



* Format String Injection in afcopy *
File: tools/afcopy.cpp
Lines: 202 and 250

Description:
A command line parameter is used as the format string in two err()
calls. If an attacker could control this name, a format string injection
vulnerability could be exploited.



* Format String Injection in afinfo *
File: tools/afinfo.cpp
Line: 584

Description:
A command line parameter is used as the format string in the err()
call. If an attacker could control this name, a format string injection
vulnerability could be exploited.



* Format String Injection in aimage *
File: aimage/aimage.cpp
Line: 577

Description:
A command line parameter is used as the format string in the err()
call. If an attacker could control this name, a format string injection
vulnerability could be exploited. Lines 548-577 are included below to
help illustrate the problem:

 int getlock(class imager *im)
 {
    /* If the file exists and the PID in the file is running,
     * can't get the lock.
     */
    char lockfile[MAXPATHLEN];
    sprintf(lockfile,"/tmp/aimge.%s.lock",im->infile);
    if(access(lockfile,F_OK)==0){
    /* Lockfile exists. Get it's pid */
    char buf[1024];
    FILE *f = fopen(lockfile,"r");
    if(!f){
        perror(lockfile);		// can't read lockfile...
            return -1;
            }
            fgets(buf,sizeof(buf),f);
            buf[sizeof(buf)-1] = 0;
            int pid = atoi(buf);
            if(checkpid(pid)==0){
                /* PID is not running; we can delete the lockfile */
                    if(unlink(lockfile)){
                    	err(1,"could not delete lockfile %s: ",lockfile);
                            }
                            }
                            /* PID is running; generate error */
                            errx(1,"%s is locked by process %d\n",im->infile,pid);
    }
    FILE *f = fopen(lockfile,"w");
    if(!f){
    err(1,lockfile);

Since the im->infile value could be specified by a user, the lockfile
string could contain format string characters.  An attacker could
exploit this problem if the aimage binary were setuid/setgid, or if the
aimage program were executed in a CGI script or something similar.



* Format String Injection in imager *
File: aimage/imager.cpp
Line: 265

Description:
A command line parameter is used as the format string in the err()
call. If an attacker could control this name, a format string injection
vulnerability could be exploited.



* Format String Injection in afxml *
File: tools/afxml.cpp
Line: 101

Description:
A command line parameter is used as the format string in the err()
call. If an attacker could control this name, a format string injection
vulnerability could be exploited.




Vendor Response:

Simson Garfinkel was first contacted on 2007-03-31. The following
timeline outlines the responses from the vendor regarding this issue:

 2007-04-01 - Vendor provided details of all vulnerabilities
              identified.  
 2007-04-03 - Continued vendor communication.
 2007-04-05 - Vendor released version 2.2.6, containing multiple
              security fixes.
 2007-04-06 - Vendor notified VSR that fixes were released.
 2007-04-09 - VSR notified vendor that 9 vulnerability instances still 
              remained in latest release.
 2007-04-12 - Vendor confirmed that remaining vulnerabilities would be
              fixed in next release.
 2007-04-25 - Vendor released versions 2.2.7 and 2.2.8.  Vendor did not 
              notify VSR.
 2007-04-27 - VSR discovered new versions were released.  VSR inspected 
              version 2.2.8 and found that no additional vulnerabilities
              were fixed.  VSR advisories published.


Recommendation:

AFFLIB(TM) users should upgrade to the newest version.  Third-party
projects which rely on AFFLIB(TM) should encourage users to upgrade,
and/or incorporate fixes into their distribution of the library.

The update is available via:

http://www.afflib.org/downloads/ 

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Common Vulnerabilities and Exposures (CVE) Information:

The Common Vulnerabilities and Exposures (CVE) project has assigned
the following name to these issues.  This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for 
security problems.

  CVE-2007-2054

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References:

1. AFF - Forensics Wiki
http://www.forensicswiki.org/wiki/AFF 

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This advisory is distributed for educational purposes only, and comes
with absolutely NO WARRANTY; not even the implied warranty of
merchantability or fitness for a particular purpose.  Virtual Security
Research, LLC nor the author accepts any liability for any direct,
indirect, or consequential loss or damage arising from use of, or
reliance on, this information.

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Vulnerability Disclosure Policy:

http://www.vsecurity.com/disclosurepolicy.html 

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AFF(TM) and AFFLIB(TM) are trademarks of Simson Garfinkel and Basis
Technology Corp.

Included source code excerpts are copyright Simson Garfinkel and Basis
Technology Corp.

This advisory is copyright (C) 2007 Virtual Security Research, LLC. All
rights reserved.
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