1018064 - Replace mozilla::pkix::der::Input::MatchBytes with a variant that requires the match to be at the end of the input

Status: RESOLVED FIXED

(Core :: Security: PSM, defect)

Description

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

Attachment: replace-MatchBytes-with-MatchRest.patch

All of our uses of MatchBytes, including the future uses I'm about to add, follow the pattern:

   if (input.MatchBytes(x) && input.AtEnd()) {
     // consider it a match
   } else {
     // it's not really a match
   }

In some places, this logic is less clear than it should be and generally this pattern is much more error prone than the use of a function that checks that the match occurs at the end of the input.

Comment 1

[[:mmc] Monica Chew (no longer reading bugmail)]

Comment on attachment 8431407 [details] [diff] [review]
replace-MatchBytes-with-MatchRest.patch

Review of attachment 8431407 [details] [diff] [review]:
-----------------------------------------------------------------

::: security/pkix/lib/pkixder.h
@@ +155,4 @@
>    {
> +    // Normally we use EnsureLength which compares (input + len < end), but
> +    // here we want to be sure that there is nothing following the matched
> +    // bytes

Cleaner to do input.AtEnd() before returning?

Comment 2

[Brian Smith (:briansmith, :bsmith, use NEEDINFO?)]

[:mmc] Monica Chew (please use needinfo) from comment #1)
> Cleaner to do input.AtEnd() before returning?

We can't do that, because we need to avoid changing any state of the Input object if it isn't a complete match, so we have to check that we're at the end first.

Thanks for the review!

https://hg.mozilla.org/integration/mozilla-inbound/rev/c470f879b8c8(In reply to

Comment 3

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/c470f879b8c8