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SubjectRe: [PATCH 3/4] ima: Improvements in ima_appraise_measurement()
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Hello Serge,

Thanks for quickly reviewing these patches!

Serge E. Hallyn <serge@hallyn.com> writes:

> Quoting Thiago Jung Bauermann (bauerman@linux.vnet.ibm.com):
>> From: Mimi Zohar <zohar@linux.vnet.ibm.com>
>> @@ -241,16 +241,20 @@ int ima_appraise_measurement(enum ima_hooks func,
>> }
>>
>> status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
>> - if ((status != INTEGRITY_PASS) &&
>> - (status != INTEGRITY_PASS_IMMUTABLE) &&
>> - (status != INTEGRITY_UNKNOWN)) {
>> - if ((status == INTEGRITY_NOLABEL)
>> - || (status == INTEGRITY_NOXATTRS))
>> - cause = "missing-HMAC";
>> - else if (status == INTEGRITY_FAIL)
>> - cause = "invalid-HMAC";
>> + switch (status) {
>> + case INTEGRITY_PASS:
>> + case INTEGRITY_PASS_IMMUTABLE:
>> + case INTEGRITY_UNKNOWN:
>
> Wouldn't it be more future-proof to replace this with a 'default', or
> to at least add a "default: BUG()" to catch new status values?

I agree. I like the "default: BUG()" option.

>> + break;
>> + case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */
>> + case INTEGRITY_NOLABEL: /* No security.evm xattr. */
>> + cause = "missing-HMAC";
>> + goto out;
>> + case INTEGRITY_FAIL: /* Invalid HMAC/signature. */
>> + cause = "invalid-HMAC";
>> goto out;
>> }
>> +
>> switch (xattr_value->type) {
>> case IMA_XATTR_DIGEST_NG:
>> /* first byte contains algorithm id */
>> @@ -316,17 +320,20 @@ int ima_appraise_measurement(enum ima_hooks func,
>> integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
>> op, cause, rc, 0);
>> } else if (status != INTEGRITY_PASS) {
>> + /* Fix mode, but don't replace file signatures. */
>> if ((ima_appraise & IMA_APPRAISE_FIX) &&
>> (!xattr_value ||
>> xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
>> if (!ima_fix_xattr(dentry, iint))
>> status = INTEGRITY_PASS;
>> - } else if ((inode->i_size == 0) &&
>> - (iint->flags & IMA_NEW_FILE) &&
>> - (xattr_value &&
>> - xattr_value->type == EVM_IMA_XATTR_DIGSIG)) {
>> + }
>> +
>> + /* Permit new files with file signatures, but without data. */
>> + if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
>
> This may be correct, but it's not identical to what you're replacing.
> Since in either case you're setting status to INTEGRITY_PASS the final
> result is the same, but with a few extra possible steps. Not sure
> whether that matters.

Good point. I'll have to defer this one to Mimi though.

>
>> + xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) {
>> status = INTEGRITY_PASS;
>> }
>> +
>> integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
>> op, cause, rc, 0);
>> } else {


--
Thiago Jung Bauermann
IBM Linux Technology Center

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