Re: [PATCH v3 07/12] ima: Fail rule parsing when appraise_flag=blacklist is unsupportable

[Nayna]

On 7/17/20 2:11 PM, Tyler Hicks wrote:
> On 2020-07-17 13:40:22, Nayna wrote:
> > On 7/9/20 2:19 AM, Tyler Hicks wrote:
> > > The "appraise_flag" option is only appropriate for appraise actions
> > > and its "blacklist" value is only appropriate when
> > > CONFIG_IMA_APPRAISE_MODSIG is enabled and "appraise_flag=blacklist" is
> > > only appropriate when "appraise_type=imasig|modsig" is also present.
> > > Make this clear at policy load so that IMA policy authors don't assume
> > > that other uses of "appraise_flag=blacklist" are supported.
> > >
> > > Fixes: 273df864cf74 ("ima: Check against blacklisted hashes for files with modsig")
> > > Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx>
> > > Cc: Nayna Jain <nayna@xxxxxxxxxxxxx>
> > > ---
> > >
> > > * v3
> > >     - New patch
> > >
> > >    security/integrity/ima/ima_policy.c | 13 ++++++++++++-
> > >    1 file changed, 12 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> > > index 81da02071d41..9842e2e0bc6d 100644
> > > --- a/security/integrity/ima/ima_policy.c
> > > +++ b/security/integrity/ima/ima_policy.c
> > > @@ -1035,6 +1035,11 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
> > >    		return false;
> > >    	}
> > > +	/* Ensure that combinations of flags are compatible with each other */
> > > +	if (entry->flags & IMA_CHECK_BLACKLIST &&
> > > +	    !(entry->flags & IMA_MODSIG_ALLOWED))
> > > +		return false;
> > > +
> > >    	return true;
> > >    }
> > > @@ -1371,8 +1376,14 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
> > >    				result = -EINVAL;
> > >    			break;
> > >    		case Opt_appraise_flag:
> > > +			if (entry->action != APPRAISE) {
> > > +				result = -EINVAL;
> > > +				break;
> > > +			}
> > > +
> > >    			ima_log_string(ab, "appraise_flag", args[0].from);
> > > -			if (strstr(args[0].from, "blacklist"))
> > > +			if (IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG) &&
> > > +			    strstr(args[0].from, "blacklist"))
> > >    				entry->flags |= IMA_CHECK_BLACKLIST;
> > If IMA_APPRAISE_MODSIG is disabled, it will allow the following rule to
> > load, which is not as expected.
> >
> > "appraise func=xxx_CHECK appraise_flag=blacklist appraise_type=imasig"
> >
> > Missing is the "else" condition to immediately reject the policy rule.
> Thanks for the review. You're right. This change is needed:
>
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 9842e2e0bc6d..cf3ddb38dfa8 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -1385,6 +1385,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>   			if (IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG) &&
>   			    strstr(args[0].from, "blacklist"))
>   				entry->flags |= IMA_CHECK_BLACKLIST;
> +			else
> +				result = -EINVAL;
>   			break;
>   		case Opt_permit_directio:
>   			entry->flags |= IMA_PERMIT_DIRECTIO;
Reviewed-by: Nayna Jain<nayna@xxxxxxxxxxxxx>

Tested-by: Nayna Jain<nayna@xxxxxxxxxxxxx>

Thanks & Regards,

ÂÂÂÂÂ - Nayna