ruby -- $SAFE escaping vulnerability about Exception#to_s/NameError#to_s

2012-08-21T00:00:00
ID 2A093853-2495-11E2-B0C7-000D601460A4
Type freebsd
Reporter FreeBSD
Modified 2012-08-21T00:00:00

Description

The official ruby site reports:

Vulnerabilities found for Exception#to_s, NameError#to_s, and name_err_mesg_to_s() which is Ruby interpreter-internal API. A malicious user code can bypass $SAFE check by utilizing one of those security holes. Ruby's $SAFE mechanism enables untrusted user codes to run in $SAFE >= 4 mode. This is a kind of sandboxing so some operations are restricted in that mode to protect other data outside the sandbox. The problem found was around this mechanism. Exception#to_s, NameError#to_s, and name_err_mesg_to_s() interpreter-internal API was not correctly handling the $SAFE bits so a String object which is not tainted can destructively be marked as tainted using them. By using this an untrusted code in a sandbox can modify a formerly-untainted string destructively. Ruby 1.8 once had a similar security issue. It fixed Exception#to_s and NameError#to_s, but name_err_mesg_to_str() issue survived previous security fix