Snort mailing list archives
File preprocessor fails to capture files
From: Pablo Cantos Polaino <pcantos () redborder org>
Date: Fri, 8 May 2015 14:26:37 +0200
Hello all, I'm doing some tests over the file preprocessor and these are the conf options that I'm using related to file preprocessor: include file_magic.conf
config file:\ file_type_depth 4294967295, \ file_signature_depth 4294967295, \ file_capture_max 4294967295 preprocessor file_inspect:\ capture_queue_size 50000, \ signature, \ capture_disk /var/log/snort/files/ 50000
This time what I'm trying to do is to capture every file detected by file preprocessor in the directory /var/log/snort/files. For these tests, I've used the following files: wget ftp://ftp.hp.com/pub/information_storage/software/video/video1.avi wget ftp://ftp.hp.com/pub/information_storage/software/video/MakeUp.mov wget ftp://ftp.hp.com/pub/information_storage/software/video/Fighter.mpg wget http://releases.ubuntu.com/14.04/ubuntu-14.04.2-desktop-amd64.iso wget http://scholar.princeton.edu/sites/default/files/oversize_pdf_test_0.pdf wget https://10.0.70.110/client/VMware-viclient.exe --no-check-certificate wget http://cpansearch.perl.org/src/MIKEM/Device-SNP-1.3/datadesigner/tux-sw.bmp I addition, I've got a pcap traffic capture which includes all the 7 files above. When I run Snort reading this pcap, I got the following: Captured files:
# ls -lS
-rw------- 1 root root 24211979 May 8 11:14
8452B621DC334D1FD44470A80540CBEF2F6869AF851B9E8C684EF9402016F692 -rw------- 1 root root 13045613 May 8 11:14 5CF142947C2957EE648457A91B69FB82F088F31205030F9A77B2AD827228C6E9 -rw------- 1 root root 6352738 May 8 11:14 DB57C532919D9ABABAC127F29DBDC05ED832394880E46CAD81A5DDE713CCB4BE -rw------- 1 root root 2936119 May 8 11:14 B4127F43A3F455523B81179CC11AA4F28FC27F4C041D20E28AA08A32D85CB757 -rw------- 1 root root 495316 May 8 11:14 A294AA3D01CD8902BF842D320E7F2C043AF9EAD95D0E7198C3B71A0DBC9D253C -rw------- 1 root root 424526 May 8 11:14 8863DB1EC4B02D5BCC1FB4BD03D220F7458136342CDD47CE507A5B886C6BB56C -rw------- 1 root root 2817 May 8 11:14 D03CDB1F2584A2C06E866931EC5F31F141D9D08F237E04708C7C19D94FFA62F5 -rw------- 1 root root 1958 May 8 11:14 369FDD6FB34BB5E1F0EC79D063FE0115AEF35AA20972BE8E4739417594F692AA -rw------- 1 root root 1958 May 8 11:14 EF49069F43D349C83873A6784351F16ADC39B8358ACFAE3A30EA4DD684C29DCC
-rw------- 1 root root 446 May 8 11:14
8D490C71A27631CF6A476F68C409655CB63BF32C17846A3C3C125A79046DB2C1
Downloaded files:
# ls -l
-rw-r--r-- 1 root root 2187725 May 8 11:01 Fighter.mpg
-rw-r--r-- 1 root root 14955972 May 8 11:01 MakeUp.mov
-rw-r--r-- 1 root root 375187792 May 8 11:02 VMware-viclient.exe -rw-r--r-- 1 root root 101688487 Jul 10 2014 oversize_pdf_test_0.pdf
-rw-r--r-- 1 root root 446 Mar 22 2013 tux-sw.bmp -rw-r--r-- 1 root root 1044381696 Feb 18 20:12
ubuntu-14.04.2-desktop-amd64.iso -rw-r--r-- 1 root root 6094376 May 8 11:01 video1.avi # sha256sum *
55bdca20aa0ffd8fa3b12029d1e122696a936abc29dd4ec4a5bd878836a5d36f
Fighter.mpg
88a43830b006a4ade60874ffb10a0d5afd06245d0bc460da90015ed73df08d58 MakeUp.mov
57bc6123a563056e32fb317c20d1e3b96af723b2b2c9732033e3ab9ce8f8e625 VMware-viclient.exe fa43e683e94372d81210a275cc37112bf2df9c971d377506aab8ae47e5fb0d34 oversize_pdf_test_0.pdf 8d490c71a27631cf6a476f68c409655cb63bf32c17846a3c3c125a79046db2c1 tux-sw.bmp
39eeb28bdb8af630850e75e54b9864ca07640a2bb10bd10055763236b99f9b1d
ubuntu-14.04.2-desktop-amd64.iso bb13418aeb4535c0d1f5c491ad69dd87041a8a1ba7dacc6bc763337beaed7dca video1.avi
As you can see, Snort just captures correctly the smallest file, that fits in a single packet. The others captured files do not coincide with the captured files (in number and size, and hence in sha256) If I run Snort sniffing from my network interface and I download the 7 files by using the wget command, I got the following: Captured files:
-rw------- 1 root root 446 May 8 11:30
8D490C71A27631CF6A476F68C409655CB63BF32C17846A3C3C125A79046DB2C1
This case, Snort just captures the smallest file, that fits in a single packet. I've gone deep into the code and I've found out the problem could come from a strange behavior of the Frag3 preprocessor when dealing with packets that contain files. I see two different issues here: 1.- When sniffing from an interface, Snort is only able to capture files which fit in one single packet. 2.- When reading from a network capture file, Snort is able to capture files in general, but it does it in a wrong way when the file take up more than one packet. I'd like to know if you were aware of these strange behaviors. Best Regards, Pablo Cantos redborder.org / pcantos () redborder org
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Current thread:
- File preprocessor fails to capture files Pablo Cantos Polaino (May 08)
- Re: File preprocessor fails to capture files Hui Cao (huica) (May 08)
- Re: File preprocessor fails to capture files Pablo Cantos Polaino (May 08)
- Re: File preprocessor fails to capture files Hui cao (May 08)
- Re: File preprocessor fails to capture files Pablo Cantos Polaino (May 08)
- Re: File preprocessor fails to capture files Hui Cao (huica) (May 08)
- Re: File preprocessor fails to capture files Pablo Cantos Polaino (May 08)
- Re: File preprocessor fails to capture files Hui Cao (huica) (May 08)
- Re: File preprocessor fails to capture files Pablo Cantos Polaino (May 15)
- Re: File preprocessor fails to capture files Russ (May 15)
- Re: File preprocessor fails to capture files Pablo Cantos Polaino (May 16)
- Re: File preprocessor fails to capture files Pablo Cantos Polaino (May 08)
- Re: File preprocessor fails to capture files Hui Cao (huica) (May 08)