Hi Anderson, thanks a lot for the information, I will try your suggestion. However, in case I cannot sue the legacy key format for whatever reason, is there a simple way of detecting what crypto library libssh was compiled with? I could not find anything in libssh.h.
Regards, Michal On Thursday, January 23, 2020 11:49 CET, Anderson Sasaki <[email protected]> wrote: > > ----- Original Message ----- > > From: "Michal Vaško" <[email protected]> > > To: [email protected] > > Sent: Thursday, January 23, 2020 10:47:49 AM > > Subject: Importing hostkey > > > > Hello, > > we have recently found an issue with importing RSA host key of length 2048 > > but presumably the problem may occur also with other key types/lengths. It > > seems to work fine when libssh is compiled with OpenSSL but not with gcrypt. > > The problem is tracked on GitHub [1]. My query is whether anyone can tell me > > more about this/had the same problem and fixed it somehow. It would be best > > if there was a format compatible with both backend libraries. Thanks for any > > input. > > > > Some more details regarding the problem, the key is generated by: > > openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -outform PEM > > > > Then, the header and footer is removed only to be added later [2] and stored > > back into a file. This file is then imported [3], which fails. > > > > Regards, > > Michal > > > > [1] https://github.com/CESNET/Netopeer2/issues/534 > > [2] > > https://github.com/CESNET/libnetconf2/blob/devel/src/session_server_ssh.c#L43 > > [3] > > https://github.com/CESNET/libnetconf2/blob/devel/src/session_server_ssh.c#L1291 > > > > > > Hello, > > This happens because OpenSSL uses the PKCS#8 format when writing RSA keys to > PEM files by default. When compiled with OpenSSL we use its parser, which > supports PKCS#8 format. > > Unfortunately, AFAIK, libgcrypt does not have a PEM file parser; what we use > is an internally implemented parser which only supports the legacy OpenSSL > format (also called "SSLeay format" or "traditional format"). > > You can convert the PKCS#8 PEM file to the legacy format by running: > > $ openssl rsa -in pkcs8-file.pem -out legacy.pem > > Then such key in legacy format can be used both with OpenSSL and libgcrypt. > > Regards, > Anderson > >
