cmd/jwk: check return from jose_jwk_thp_buf() properly

[sergio-correia]

jose_jwk_thp_buf() returns, on success, the number of bytes written; otherwise, it returns SIZE_MAX.

We now check its return properly, from jcmd_jwk_thp(), which is used by the CLI utility.

Fixes: #170

[sarroutbi]

I would follow an if/else if approach to ease code readibility. Something like:

           size_t nbytes = jose_jwk_thp_buf(NULL, jwk, opt.hash, dec, sizeof(dec)); // dec is the output buffer
+            if (nbytes == SIZE_MAX) {
+                fprintf(stderr, "Error making thumbprint: Reached %ul (SIZE_MAX) nbytes\n", SIZE_MAX); // Please, not %ul might be adjusted here
+                return EXIT_FAILURE;
+            } else if (nbytes == 0) {
                 fprintf(stderr, "Error making thumbprint: nbytes equals 0.\n");
                 return EXIT_FAILURE;
             }

This way, in case error takes place, it will be clear where it is taking place

[sergio-correia]

This way, in case error takes place, it will be clear where it is taking place

It doesn't look like a big (if at all) improvement in this case. I will just check for the SIZE_MAX instead and make it simpler.

[sarroutbi]

This way, in case error takes place, it will be clear where it is taking place

It doesn't look like a big (if at all) improvement in this case. I will just check for the SIZE_MAX instead and make it simpler.

👍 OTOH ... is it feasible to add a unit test to cover this? I am just wondering

[sergio-correia]

Good point. Yeah, we can add the example from the issue report, I believe. Let me do that.

[sarroutbi]

Thanks for including the unit test. LGTM