| Date: Sat, 24 Jun 2006 19:04:19 +0100 (IST)
| From: paul at clubi.ie
|[... gcc's SSP (also called "ProPolice") is ] simply the insertion
| of guard values in the frame 'preamble' to protect the return address
| by overflow of variables local to the frame - by having the compiler
| emit code to check the guard is still valid when returning from a
and the rearrangement of local (auto) variables,
and the duplication of certain parameters; see
or (horribly long url)
| (Note that if the guard is a well-known value, and the attacker can
| inject full values (rather than say, ASCII restricted ones), the
| attacker can defeat SSP easily. I guess though compilers can easily
| randomise the guard value somewhat on a per-object file basis.).
yes. the value, sometimes called a canary, is
nominally random (per execution, not per compile),
albeit there is a fixed fallback.
Experienced (20+ yrs) kernel/software Eng: | Brian Foster Montpellier,
• Unix, embedded, &tc; • Linux; • doc; | blf at utvinternet.ie FRANCE
• IDL, automated testing, process, &tc. | Stop E$$o (ExxonMobile)!
Résumé (CV) http://www.blf.utvinternet.ie | http://www.stopesso.com
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