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Re: [anti-XSS]about CERT/CC:malicious_code_mitigation
From: Valdis.Kletnieks () vt edu
Date: Tue, 10 Aug 2004 00:17:40 -0400
On Mon, 09 Aug 2004 19:45:07 PDT, dd said:
Real solution is to have "per input" input validation which will always let some "potentially bad" things through, but help mitigate exposures and then do things "right".
Actually, you should be doing "per input" validation on each field, which tries to totally eliminate the "potentially bad" for each field, as appropriate for the field in question - my example of alphanumeric, space, hyphen, and underscore may not be suitable for all fields (as one clued person pointed out to me in private mail). A real program will almost certainly end up with a separate filter for each field type.... The *important* part is that you're *not* using 's/[list-of-known-bad]//g', but that you use 's/[^list-of-known-good]//g'. Making the known-good list for each field is the programmer's problem. How many CGI scripts have had directory traversal issues that would have been completely and totally prevented if they had done the filtering right and dropped the '/' character (and probably '.' too) out? ;)
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Current thread:
- [anti-XSS]about CERT/CC:malicious_code_mitigation bitlance winter (Aug 07)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation Valdis . Kletnieks (Aug 09)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation dd (Aug 09)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation Valdis . Kletnieks (Aug 09)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation dd (Aug 09)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation Dave Horsfall (Aug 10)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation Valdis . Kletnieks (Aug 10)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation dd (Aug 09)
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation Valdis . Kletnieks (Aug 09)
- <Possible follow-ups>
- Re: [anti-XSS]about CERT/CC:malicious_code_mitigation auto269562 (Aug 10)