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SubjectRe: [PATCH 3/4] ima: Improvements in ima_appraise_measurement()
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On Wed, 2018-03-14 at 21:03 -0300, Thiago Jung Bauermann wrote:
> 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.

Agreed.  I would put it at the end after INTEGRITY_FAIL.

>
> >> + 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.

The end result is the same, but add some needed comments.

Mimi

>
> >
> >> + 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 {
>
>

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