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    SubjectRe: [PATCH v2 05/11] ima: Fail rule parsing when the KEXEC_CMDLINE hook is combined with an invalid cond
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    On 6/26/20 3:38 PM, Tyler Hicks wrote:
    > The KEXEC_CMDLINE hook function only supports the pcr conditional. Make
    > this clear at policy load so that IMA policy authors don't assume that
    > other conditionals are supported.
    >
    > Since KEXEC_CMDLINE's inception, ima_match_rules() has always returned
    > true on any loaded KEXEC_CMDLINE rule without any consideration for
    > other conditionals present in the rule. Make it clear that pcr is the
    > only supported KEXEC_CMDLINE conditional by returning an error during
    > policy load.
    >
    > An example of why this is a problem can be explained with the following
    > rule:
    >
    > dont_measure func=KEXEC_CMDLINE obj_type=foo_t
    >
    > An IMA policy author would have assumed that rule is valid because the
    > parser accepted it but the result was that measurements for all
    > KEXEC_CMDLINE operations would be disabled.
    >
    > Fixes: b0935123a183 ("IMA: Define a new hook to measure the kexec boot command line arguments")
    > Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
    > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
    > ---
    >
    > * v2
    > - Added Mimi's Reviewed-by
    >
    > security/integrity/ima/ima_policy.c | 21 +++++++++++++++++++++
    > 1 file changed, 21 insertions(+)
    >
    > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
    > index 166124d67774..676d5557af1a 100644
    > --- a/security/integrity/ima/ima_policy.c
    > +++ b/security/integrity/ima/ima_policy.c
    > @@ -343,6 +343,17 @@ static int ima_lsm_update_rule(struct ima_rule_entry *entry)
    > return 0;
    > }
    >
    > +static bool ima_rule_contains_lsm_cond(struct ima_rule_entry *entry)
    > +{
    > + int i;
    > +
    > + for (i = 0; i < MAX_LSM_RULES; i++)
    > + if (entry->lsm[i].args_p)
    > + return true;
    > +
    > + return false;
    > +}
    > +
    > /*
    > * The LSM policy can be reloaded, leaving the IMA LSM based rules referring
    > * to the old, stale LSM policy. Update the IMA LSM based rules to reflect
    > @@ -993,6 +1004,16 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
    > case POLICY_CHECK:
    > break;
    > case KEXEC_CMDLINE:
    > + if (entry->action & ~(MEASURE | DONT_MEASURE))
    > + return false;
    > +
    > + if (entry->flags & ~(IMA_FUNC | IMA_PCR))
    > + return false;
    > +
    > + if (ima_rule_contains_lsm_cond(entry))
    > + return false;
    > +
    > + break;
    > case KEY_CHECK:
    > if (entry->action & ~(MEASURE | DONT_MEASURE))
    > return false;
    >

    Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

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