ClamAV is an open source (GPLv2) anti-virus toolkit.
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<H3><A NAME="SECTION00074100000000000000">
Data scan functions</A>
</H3>
It's possible to scan a file or descriptor using:
<PRE>
int cl_scanfile(const char *filename, const char **virname,
unsigned long int *scanned, const struct cl_engine *engine,
const struct cl_limits *limits, unsigned int options);
int cl_scandesc(int desc, const char **virname, unsigned
long int *scanned, const struct cl_engine *engine, const
struct cl_limits *limits, unsigned int options);
</PRE>
Both functions will store a virus name under the pointer <code>virname</code>,
the virus name is part of the engine structure and must not be released
directly. If the third argument (<code>scanned</code>) is not NULL, the
functions will increase its value with the size of scanned data (in
<code>CL_COUNT_PRECISION</code> units). Both functions have support for archive
limits in order to protect against Denial of Service attacks.
<PRE>
struct cl_limits {
unsigned long int maxscansize; /* during the scanning of archives this
* size will never be exceeded
*/
unsigned long int maxfilesize; /* compressed files will only be
* decompressed and scanned up to this size
*/
unsigned int maxreclevel; /* maximum recursion level for archives */
unsigned int maxfiles; /* maximum number of files to be scanned
* within a single archive
*/
unsigned short archivememlim; /* limit memory usage for some unpackers */
};
</PRE>
The last argument (<code>options</code>) configures the scan engine and supports
the following flags (that can be combined using bit operators):
<UL>
<LI><SPAN CLASS="textbf">CL_SCAN_STDOPT</SPAN>
<BR>
This is an alias for a recommended set of scan options. You
should use it to make your software ready for new features
in the future versions of libclamav.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_RAW</SPAN>
<BR>
Use it alone if you want to disable support for special files.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_ARCHIVE</SPAN>
<BR>
This flag enables transparent scanning of various archive formats.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_BLOCKENCRYPTED</SPAN>
<BR>
With this flag the library will mark encrypted archives as viruses
(Encrypted.Zip, Encrypted.RAR).
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_MAIL</SPAN>
<BR>
Enable support for mail files.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_MAILURL</SPAN>
<BR>
The mail scanner will download and scan URLs listed in a mail
body. This flag should not be used on loaded servers. Due to
potential problems please do not enable it by default but make
it optional.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_OLE2</SPAN>
<BR>
Enables support for OLE2 containers (used by MS Office and .msi
files).
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_PDF</SPAN>
<BR>
Enables scanning within PDF files.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_PE</SPAN>
<BR>
This flag enables deep scanning of Portable Executable files and
allows libclamav to unpack executables compressed with run-time
unpackers.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_ELF</SPAN>
<BR>
Enable support for ELF files.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_BLOCKBROKEN</SPAN>
<BR>
libclamav will try to detect broken executables and mark them as
Broken.Executable.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_HTML</SPAN>
<BR>
This flag enables HTML normalisation (including ScrEnc
decryption).
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_ALGORITHMIC</SPAN>
<BR>
Enable algorithmic detection of viruses.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_PHISHING_BLOCKSSL</SPAN>
<BR>
Phishing module: always block SSL mismatches in URLs.
</LI>
<LI><SPAN CLASS="textbf">CL_SCAN_PHISHING_BLOCKCLOAK</SPAN>
<BR>
Phishing module: always block cloaked URLs.
</LI>
</UL>
All functions return 0 (<code>CL_CLEAN</code>) when the file seems clean,
<code>CL_VIRUS</code> when a virus is detected and another value on failure.
<PRE>
...
struct cl_limits limits;
const char *virname;
memset(&amp;limits, 0, sizeof(struct cl_limits));
limits.maxfiles = 10000;
limits.maxscansize = 100 * 1048576; /* 100 MB */
limits.maxfilesize = 10 * 1048576; /* 10 MB */
limits.maxreclevel = 16;
if((ret = cl_scanfile("/tmp/test.exe", &amp;virname, NULL, engine,
&amp;limits, CL_STDOPT)) == CL_VIRUS) {
printf("Virus detected: %s\n", virname);
} else {
printf("No virus detected.\n");
if(ret != CL_CLEAN)
printf("Error: %s\n", cl_strerror(ret));
}
</PRE>
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<ADDRESS>
Tomasz Kojm
2008-10-15
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