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;
Making this change does not conflict with any later patches in the
series.
Mimi, I've rebased and force pushed to my fixup branch with this change,
for your comparison:
https://git.kernel.org/pub/scm/linux/kernel/git/tyhicks/linux.git/log/?h=next-integrity-testing-fixup
Tyler
>
> Thanks & Regards,
>
> - Nayna
>
