On Mon, 2022-03-14 at 08:58 -0300, Richard Dymond wrote: > On Mon, 14 Mar 2022 at 04:52, Tomas Mraz <tomas@xxxxxxxxxxx> wrote: > > The DSA_SIG_* functions are not deprecated including the i2d and > > d2i > > functions. So you can use d2i_DSA_SIG to decode the DER produced by > > the > > EVP_DigestSign() and then obtain the r and s values from the > > DSA_SIG. > > > > > Thank you, that works! For some reason it had escaped my notice that > that the DSA_SIG_* functions are not deprecated. > > By the way, the reason I need to get the 'r' and 's' values from the > DSA signature is that I am encoding them one after the other as 160- > bit unsigned integers, in network byte order, as required by SSH and > described in section 6.6 of RFC 4253 (dss_signature_blob)[1]. To do > this encoding I am calling BN_bn2bin() twice to write 'r' followed by > 's' at the appropriate locations in a 40-byte buffer. By any chance, > does OpenSSL 3.0 provide any support for encoding a DSA signature > like this from a DSA_SIG (i.e. without having to extract 'r' and 's' > first and then use BN_bn2bin())? No, there is no such function. However there is not much overhead in doing the two BN_bn2bin calls (should those be BN_bn2binpad actually?) once you already have a DSA_SIG object. > Richard > > [1] https://datatracker.ietf.org/doc/html/rfc4253#section-6.6 -- Tomáš Mráz, OpenSSL
