Messages in this thread | | | Subject | Re: [PATCH v3 07/12] ima: Fail rule parsing when appraise_flag=blacklist is unsupportable | From | Nayna <> | Date | Mon, 20 Jul 2020 13:02:57 -0400 |
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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@linux.microsoft.com> >>> Cc: Nayna Jain <nayna@linux.ibm.com> >>> --- >>> >>> * 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@linux.ibm.com>
Tested-by: Nayna Jain<nayna@linux.ibm.com>
Thanks & Regards,
- Nayna
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