Re: [PATCH v7 3/5] certs: Make blacklist_vet_description() more strict

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On 21/04/2022 17:57, Jarkko Sakkinen wrote:
On Thu, Apr 21, 2022 at 05:27:42PM +0200, Mickaël Salaün wrote:

On 21/04/2022 17:12, Jarkko Sakkinen wrote:
On Wed, Apr 20, 2022 at 11:29:08AM +0100, David Howells wrote:
Mickaël Salaün <mic@xxxxxxxxxxx> wrote:

+	/* The following algorithm only works if prefix lengths match. */
+	BUILD_BUG_ON(sizeof(tbs_prefix) != sizeof(bin_prefix));
+	prefix_len = sizeof(tbs_prefix) - 1;
+	for (i = 0; *desc; desc++, i++) {
+		if (*desc == ':') {
+			if (tbs_step == prefix_len)
+				goto found_colon;
+			if (bin_step == prefix_len)
+				goto found_colon;
+			return -EINVAL;
+		}
+		if (i >= prefix_len)
+			return -EINVAL;
+		if (*desc == tbs_prefix[i])
+			tbs_step++;
+		if (*desc == bin_prefix[i])
+			bin_step++;
+	}

I wonder if:

	static const char tbs_prefix[] = "tbs:";
	static const char bin_prefix[] = "bin:";

	if (strncmp(desc, tbs_prefix, sizeof(tbs_prefix) - 1) == 0 ||
	    strncmp(desc, bin_prefix, sizeof(bin_prefix) - 1) == 0)
		goto found_colon;

might be better.

David

I think it'd be.

BR, Jarkko

I'm confused. Didn't you plan to send this patch series before v5.18-rc2?
It's been a while since I started working on this.

That was my original plan but due to some other things, I've sent
a PR for rc4. I CC'd you to the PR.

OK, I missed it. My micro-optimization isn't worth it, strncmp is much simple indeed.



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