rsa_sign example is not working

[Oldes]

Summary

When trying rsa_sign.exe, I get this output:

  . Reading private key from rsa_priv.txt
  . Checking the private key
  . Generating the RSA/SHA-256 signature failed
  ! mbedtls_rsa_pkcs1_sign returned -0x4080

  + Press Enter to exit this program.

It is failing at this line:
https://github.com/ARMmbed/mbedtls/blob/d1d0b41fc0b9e3d4012ccf9796ef9e641079cea2/library/rsa.c#L1887
because of this check:
https://github.com/ARMmbed/mbedtls/blob/d1d0b41fc0b9e3d4012ccf9796ef9e641079cea2/library/rsa.c#L918-L919

I suppose, that there cannot be NULL for the random function here:
https://github.com/ARMmbed/mbedtls/blob/d1d0b41fc0b9e3d4012ccf9796ef9e641079cea2/programs/pkey/rsa_sign.c#L145-L146

NOTE:
It was tested with the version 3.1.0.

[ronald-cron-arm]

Thanks for reporting this issue. The documentation of mbedtls_rsa_pkcs1_sign says that the RNG function parameter is mandatory thus you are right, the call to it in rsa_sign.c is not correct.