Re: [PATCH ima-evm-utils] Improve memory handling for private keys and passwords

[Mimi Zohar <zohar@linux.ibm.com>]

On Fri, 2021-08-13 at 17:31 -0400, Mimi Zohar wrote:
> Hi Vitaly,
> 
> On Fri, 2021-08-13 at 00:46 +0300, Vitaly Chikunov wrote:
> > Hi,
> > 
> > On Fri, Aug 13, 2021 at 12:21:43AM +0300, Vitaly Chikunov wrote:
> > > After CRYPTO_secure_malloc_init OpenSSL will store private keys in
> > > secure heap. This facility is only available since OpenSSL_1_1_0-pre1
> > > and enabled for 'ima_sign', 'sign', 'sign_hash', and 'hmac'.
> 
> From the manpage:
> CRYPTO_secure_malloc_init() returns 0 on failure, 1 if successful, and
> 2 if successful but the heap could not be protected by memory mapping.
> 
> Not sure what we would do on failure ( 0, 2), but we should at least
> check the return code.
> > 
> > > setvbuf(3) _IONBF is used to hopefully avoid private key and password
> > > being stored inside of stdio buffers.
> > 
> > I should note that usefulness of this method (of avoiding buffering) is
> > not proven. I don't find other implementations doing it. So, I'm open to
> > suggestion of removing it.
> > 
> Probably would be better to split the patch.

According to the man page "OPENSSL_secure_malloc() allocates num bytes
from the heap.  If CRYPTO_secure_malloc_init() is not called, this is
equivalent to calling OPENSSL_malloc()".   OPENSSL_malloc() is
supported in the older openssl versions.

Does it make sense to replace allocating memory for the password via
malloc() with OPENSSL_secure_malloc()?  For older openssl versions,
define OPENSSL_secure_malloc() and OPENSSL_secure_free() as
OPENSSL_malloc() and OPENSSL_free().

This doesn't solve the memory handling for private keys and passwords
for older openssl versions, but it is a path forward.

thanks,

Mimi