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Rob Hague
fe65570ebc
* Use System.Security.Cryptography for DSA
This is the analogue of the RSA change #1373 for DSA. This has a couple of caveats:
- The BCL supports only FIPS 186-compliant keys, that is, public (P, Q) lengths
of (512 <= P <= 1024, 160) for FIPS 186-1/186-2; and (2048, 256), (3072, 256)
for FIPS 186-3/186-4. The latter also specifies (2048, 224) but due to a quirk
in the Windows API, the BCL does not support Q values of length 224[^1].
- OpenSSH, based on the SSH spec, only supports (supported) Q values of length 160,
but appears to also work in non-FIPS-compliant cases such as in our integration
tests with a (2048, 160) host key. That test now fails and I changed that host key
to (1024, 160).
This basically means that (1024, 160) is the largest DSA key size supported by both
SSH.NET and OpenSSH. However, given that OpenSSH deprecated DSA in 2015[^2], and the
alternative that I have been considering is just to delete support for DSA in the
library, this change seems reasonable to me. I don't think we can justify keeping the
current handwritten code around.
I think we may still consider dropping DSA from the library, I just had this branch
laying around and figured I'd finish it off.
[^1]: https://github.com/dotnet/runtime/blob/fadd8313653f71abd0068c8bf914be88edb2c8d3/src/libraries/Common/src/System/Security/Cryptography/DSACng.ImportExport.cs#L259-L265
[^2]: https://www.openssh.com/txt/release-7.0
* Appease mono
* test experiment
* Revert "Appease mono"
This reverts commit 881eefe5e8.