Re: [PATCH ima-evm-utils v3] Use secure heap for private keys and passwords

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

Hi Vitaly,

On Sun, 2021-08-22 at 03:10 +0300, Vitaly Chikunov wrote:
> After CRYPTO_secure_malloc_init OpenSSL will store private keys 

^and passwords

> in
> secure heap. This facility is only available since OpenSSL_1_1_0-pre1.
> 
> Signed-off-by: Vitaly Chikunov <vt@altlinux.org>

Initially we started out discussing ways of protecting passwords, which
this patch does.  Thank you!  I'm not sure, however, it is protecting
the private keys.  Does read_priv_pkey()  also use the secure heap or
is PEM_read_PrivateKey() already safe?

> ---
>  src/evmctl.c | 148 +++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 121 insertions(+), 27 deletions(-)
> 
> diff --git a/src/evmctl.c b/src/evmctl.c
> 
> @@ -188,7 +207,9 @@ static int bin2file(const char *file, const char *ext, const unsigned char *data
>  	return err;
>  }
> 
> -static unsigned char *file2bin(const char *file, const char *ext, int *size)
> +/* Return data in OpenSSL secure heap if 'secure' is true. */
> +static unsigned char *file2bin(const char *file, const char *ext, int *size,
> +			       int secure)
>  {

The only caller of file2bin() that sets "secure" is evm_calc_hmac(),
but evm_calc_hmac() is a debugging tool, not meant for setting the real
security.evm xattr.

The kernel EVM HMAC key is an "encrypted" key type, which should be
based on a "trusted" key.  Neither of which are exposed to userspace
unencrypted. 

Enabling DEBUG by default was suppose to be temporary.  At this point,
should it be disabled?  As evm_calc_hmac() is only meant for debugging,
do we really care whether evm_calc_hmac() uses a secure heap or stack
for private keys or passwords?

thanks,

Mimi

>  	FILE *fp;
>  	size_t len;