linux-kernel - Re: [PATCH v10 09/12] ima: Implement support for module-style appended signatures

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Date:   Tue, 28 May 2019 16:06:09 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Jessica Yu <jeyu@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Corbet <corbet@....net>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>
Subject: Re: [PATCH v10 09/12] ima: Implement support for module-style
 appended signatures

On Tue, 2019-05-28 at 16:23 -0300, Thiago Jung Bauermann wrote:
> Mimi Zohar <zohar@...ux.ibm.com> writes:
> 
> > Hi Thiago,
> >
> >> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> >> index fca7a3f23321..a7a20a8c15c1 100644
> >> --- a/security/integrity/ima/ima_policy.c
> >> +++ b/security/integrity/ima/ima_policy.c
> >> @@ -1144,6 +1144,12 @@ void ima_delete_rules(void)
> >>  	}
> >>  }
> >>
> >> +#define __ima_hook_stringify(str)	(#str),
> >> +
> >> +const char *const func_tokens[] = {
> >> +	__ima_hooks(__ima_hook_stringify)
> >> +};
> >> +
> >>  #ifdef	CONFIG_IMA_READ_POLICY
> >>  enum {
> >>  	mask_exec = 0, mask_write, mask_read, mask_append
> >> @@ -1156,12 +1162,6 @@ static const char *const mask_tokens[] = {
> >>  	"MAY_APPEND"
> >>  };
> >>
> >> -#define __ima_hook_stringify(str)	(#str),
> >> -
> >> -static const char *const func_tokens[] = {
> >> -	__ima_hooks(__ima_hook_stringify)
> >> -};
> >> -
> >>  void *ima_policy_start(struct seq_file *m, loff_t *pos)
> >>  {
> >>  	loff_t l = *pos;
> >
> > Is moving this something left over from previous versions or there is
> > a need for this change?
> 
> Well, it's not a strong need, but it's still relevant in the current
> version. I use func_tokens in ima_read_modsig() in order to be able to
> mention the hook name in mod_check_sig()'s error message:
> 
> In ima_read_modsig():
> 
> 	rc = mod_check_sig(sig, buf_len, func_tokens[func]);
> 
> And in mod_check_sig():
> 
> 		pr_err("%s: Module is not signed with expected PKCS#7 message\n",
> 		       name);
> 
> If you think it's not worth it to expose func_tokens, I can make
> ima_read_modsig() pass a more generic const string such as "IMA modsig"
> for example.

This is fine.  I somehow missed moving func_tokens[] outside of the
ifdef was in order to make it independent of "CONFIG_IMA_READ_POLICY".

thanks,

Mimi