PuTTY bug pageant-backwards-compatibility

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summary: 0.61-style Pageant does not work with 0.60-style PuTTY
class: bug: This is clearly an actual problem we want fixed.
difficulty: fun: Just needs tuits, and not many of them.
priority: high: This should be fixed in the next release.
present-in: 0.61
fixed-in: r9264 52e5dae242e331ae34106eb3cc260067902d091d 0.62

Pageant ensures that other concurrent users of the same Windows machine do not connect to it by checking that a SID on the file mapping object passed to it in each request matches its own. In 0.60, it checked the SID against its default one, which caused some troubles with Cygwin (see cygwin-clobbers-pageant) which does something odd to the default SID. In 0.61, it was reworked to check the SID against the one identifying the running user, and all the Pageant clients were correspondingly modified to make that SID the owner of the file mapping.

Unfortunately, this has the side effect that Pageant 0.61 will not talk to PuTTY 0.60, and (perhaps even more importantly) not to any other program that still uses 0.60's SID selection, such as WinSCP.

The fix is to allow Pageant to accept either the default or user SID as the owner of the file mapping. We think this is still safe in terms of keeping other users out of Pageant.

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Audit trail for this bug.

(last revision of this bug record was at 2017-04-28 16:52:45 +0100)