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Gentoo Linux Security Advisory GLSA 200402-07 |
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~ http://security.gentoo.org |
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~ Severity: Normal |
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~ Title: Clamav 0.65 DoS vulnerability |
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~ Date: February 11, 2004 |
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~ Bugs: #41248 |
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~ ID: 200402-07 |
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Synopsis |
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======== |
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|
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Oliver Eikemeier has reported a vulnerability in clamav, which can be |
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exploited by a malformed uuencoded message causing a denial of service |
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for programs that rely on the clamav daemon, such as SMTP daemons. |
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Background |
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========== |
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|
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Clam AntiVirus is a GPLed anti-virus toolkit, designed for integration |
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with mail servers to perform attachment scanning. Clam AV also provides |
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a command line scanner and a tool for fetching updates of the virus |
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database. |
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|
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Description |
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=========== |
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|
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Oliver Eikemeier of Fillmore Labs discovered the overflow in Clam AV |
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0.65 when it handled malformed UUEncoded messages, causing the daemon to |
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shut down. |
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|
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The problem originated in libclamav which calculates the line length of |
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an uuencoded message by taking the ASCII value of the first character |
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minus 64 while doing an assertion if the length is not in the allowed |
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range, effectively terminating the calling program as clamav would not |
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be available. |
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Impact |
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====== |
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|
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A malformed message such as the one below would cause a denial of |
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service, and depending on the server configuration this may impact other |
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daemons relying on Clam AV in a fatal manner. |
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|
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To exploit the vulnerability, you can add the following [ excluding the |
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two lines ] to ~/clamtest.mbox: |
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~From - |
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begin 644 byebye |
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byebye |
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end |
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Then do "clamscan --mbox -v ~/clamtest.mbox" or "clamdscan -v |
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~/clamtest.mbox; ps ax | grep clam": the former will cause an assertion |
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and a segmentation fault, the latter would cause the daemon to shut down. |
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Workaround |
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========== |
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There is no immediate workaround, a software upgrade is required. |
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Resolution |
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========== |
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All users are urged to upgrade their Clam AV installations to Clam AV 0.67: |
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~ # emerge sync |
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~ # emerge -pv ">=net-mail/clamav-0.6.7" |
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~ # emerge ">=net-mail/clamav-0.6.7" |
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|
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Concerns? |
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========= |
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|
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Security is a primary focus of Gentoo Linux and ensuring the |
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confidentiality and security of our users machines is of utmost |
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importance to us. Any security concerns should be addressed to |
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security@g.o or alternatively, you may file a bug at |
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http://bugs.gentoo.org. |
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|
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