tor/changes/bug7352

  o Major bugfixes:
    - Tor tries to wipe potentially sensitive data after using it, so
      that if some subsequent security failure exposes Tor's memory,
      the damage will be limited. But we had a bug where the compiler
      was eliminating these wipe operations when it decided that the
      memory was no longer visible to a (correctly running) program,
      hence defeating our attempt at defense in depth. We fix that
      by using OpenSSL's OPENSSL_cleanse() operation, which a compiler
      is unlikely to optimize away. Future versions of Tor may use
      a less ridiculously heavy approach for this. Fixes bug 7352.
      Reported in an article by Andrey Karpov.
Add and use and unlikely-to-be-eliminated memwipe() Apparently some compilers like to eliminate memset() operations on data that's about to go out-of-scope. I've gone with the safest possible replacement, which might be a bit slow. I don't think this is critical path in any way that will affect performance, but if it is, we can work on that in 0.2.4. Fixes bug 7352. 2012-11-07 22:09:58 +01:00			`o Major bugfixes:`
			`- Tor tries to wipe potentially sensitive data after using it, so`
			`that if some subsequent security failure exposes Tor's memory,`
			`the damage will be limited. But we had a bug where the compiler`
			`was eliminating these wipe operations when it decided that the`
			`memory was no longer visible to a (correctly running) program,`
			`hence defeating our attempt at defense in depth. We fix that`
			`by using OpenSSL's OPENSSL_cleanse() operation, which a compiler`
			`is unlikely to optimize away. Future versions of Tor may use`
			`a less ridiculously heavy approach for this. Fixes bug 7352.`
			`Reported in an article by Andrey Karpov.`