While fixing legacy/trac#14013, nikkolasg realized thatif we did in fact use `!= DIGEST256_LEN` it caused a failure in the test: ``` // XXX Should it not be always DIGEST256_LEN ? Running the tests with // the condition ` != DIGEST256_LEN` fails. if (base16_decode(digests->d[alg], DIGEST256_LEN, hexdigest, strlen(hexdigest)) < 0) { ``` Turns out that `alg` here is actually `sha1` thus of size `DIGEST_LEN`. The base16 decode is safe with a larger length but this check (just above in the code) could resolved in unwanted behavior: ``` if (!tor_mem_is_zero(digests->d[alg], DIGEST256_LEN)) { ``` `tor_mem_is_zero` does make sure that the full length is zeroes thus here looking for 12 extra bytes out of bound to be 0... (DIGEST_LEN vs DIGEST256_LEN). The length we used should be set according to the algorithm in `alg` Patch coming soon.