PuTTY bug ppk-longline-crash

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summary: Long lines in PPK files (e.g. long key comments) can cause crash
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: 0.52 0.53 0.53b 0.54 0.55 0.56 0.57 2005-03-01
fixed-in: 2005-03-02 ec76c24084e544a850785eb1d74c7a82189eea3f (0.58)

Long lines in PuTTY SSH-2 private key (.PPK) files could cause a one-byte buffer overflow, potentially leading to a crash. ("Long" here means header values or other lines of 128 characters or more.)

In practice, this is most likely to occur if a very long comment field is specified - I don't think there are any other circumstances under which PuTTYgen will generate keys with lines that long.

Although this fault has been present ever since SSH-2 public-key support was added to PuTTY, the report that led to its discovery indicated that it only failed in 0.57. This may be down to a change in the compiler version we used between 0.56 and 0.57.

Until the next release, if you want to continue to use release versions of the PuTTY tools, a workaround is to load any affected key into a snapshot version of PuTTYgen, trim the key comment, and then save the key back out - it should then work with 0.57 tools. (The key format hasn't changed since 0.57.)

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Audit trail for this bug.
(last revision of this bug record was at 2016-12-27 11:40:22 +0000)