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by Animats
2374 days ago
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"As of this writing, Cap’n Proto has not undergone a security review, therefore we suggest caution when handling messages from untrusted sources." Something like that has to be rigorously tested or proven to be free of buffer overflows. It's so easy to attack with malformed messages. Parsers for remote messages are a classic source of vulnerabilities. It's hard to test this, because it's a code generator. This looks promising as an attack vector for a big system built on microservices. If you can find an exploit in this that lets you overwrite memory, and can break into some service of a set of microservices by other means, you can leverage that into a break-in of other services that thought their input was a trusted source. The "zero overhead" claim goes away as soon as you send variable length items. Then there has to be some marshaling. |
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This is outdated, I should remove it. Cap'n Proto has been reviewed by multiple security experts, though not in a strictly formal setting. I trust it enough to rely on it for security in my own projects, but yeah, I am cautious about making promises to others...
> Something like that has to be rigorously tested or proven to be free of buffer overflows.
I've done a bunch of fuzz testing with AFL and by hand. I've also employed static analysis via template metaprogramming to catch some bugs. See:
https://capnproto.org/news/2015-03-02-security-advisory-and-...
(That was... almost five years ago.)
> The "zero overhead" claim goes away as soon as you send variable length items. Then there has to be some marshaling.
Space for messages is allocated in large blocks. The contents of the message are allocated sequentially in that space and constructed in-place. So once built, the message is already composed of a small number of contiguous memory segments (usually, one segment), which can then be written out easily. Or, if you're mmaping a file, you can have the blocks point directly into the memory-mapped space and avoid copying at all -- hence, zero-copy.
So no, there is no marshaling.