Subject: Re: [PATCH 2/2] receive-pack: use find_commit_header() in check_nonce()

From: Junio C Hamano <[email-masked]>
Date: Fri, 09 Feb 2024 14:18:22 -0800

René Scharfe <[email-masked]> writes:

> @@ -620,17 +605,18 @@ static int constant_memequal(const char *a, const char *b, size_t n)
>  	for (i = 0; i < n; i++)
>  		res |= a[i] ^ b[i];
>  	return res;
>  }
>
> -static const char *check_nonce(const char *buf, size_t len)
> +static const char *check_nonce(const char *buf)
>  {
> -	char *nonce = find_header(buf, len, "nonce", NULL);
> +	size_t noncelen;
> +	const char *found = find_commit_header(buf, "nonce", &noncelen);
> +	char *nonce = found ? xmemdupz(found, noncelen) : NULL;

OK, the changes to this function are all quite trivially correct.

>  	timestamp_t stamp, ostamp;
>  	char *bohmac, *expect = NULL;
>  	const char *retval = NONCE_BAD;
> -	size_t noncelen;
>
>  	if (!nonce) {
>  		retval = NONCE_MISSING;
>  		goto leave;
>  	} else if (!push_cert_nonce) {
> @@ -668,11 +654,10 @@ static const char *check_nonce(const char *buf, size_t len)
>  	if (bohmac == nonce || bohmac[0] != '-') {
>  		retval = NONCE_BAD;
>  		goto leave;
>  	}
>
> -	noncelen = strlen(nonce);
>  	expect = prepare_push_cert_nonce(service_dir, stamp);
>  	if (noncelen != strlen(expect)) {
>  		/* This is not even the right size. */
>  		retval = NONCE_BAD;
>  		goto leave;
> @@ -765,11 +750,11 @@ static void prepare_push_cert_sha1(struct child_process *proc)
>  		sigcheck.payload = xmemdupz(push_cert.buf, bogs);
>  		sigcheck.payload_len = bogs;
>  		check_signature(&sigcheck, push_cert.buf + bogs,
>  				push_cert.len - bogs);
>
> -		nonce_status = check_nonce(push_cert.buf, bogs);
> +		nonce_status = check_nonce(sigcheck.payload);

Hmph.  sigc->payload is used as a read-only member in
check_signature(), and the xmemdupz() copy we made earlier is
readily available as a replacement for the counted (push_cert.buf,
bogs) string.  Very nice finding.

>  	}
>  	if (!is_null_oid(&push_cert_oid)) {
>  		strvec_pushf(&proc->env, "GIT_PUSH_CERT=%s",
>  			     oid_to_hex(&push_cert_oid));
>  		strvec_pushf(&proc->env, "GIT_PUSH_CERT_SIGNER=%s",
> --
> 2.43.0