Fix PEM encoding for RSA private keys

[davidben]

The originally generator code systematically encoded RSA private keys in PEM wrong. Fixes #178.

import base64
import json
import sys

def key_to_pem(key: bytes) -> str:
    ret = "-----BEGIN PRIVATE KEY-----\n"
    b64 = base64.b64encode(key).decode("ascii")
    while b64:
        l = min(len(b64), 64)
        ret += b64[:l]
        ret += "\n"
        b64 = b64[l:]
    ret += "-----END PRIVATE KEY-----\n"
    return ret

def fix(path: str):
    with open(path) as f:
        orig = f.read()
        j = json.loads(orig)
    changed = False
    for g in j["testGroups"]:
        if g["type"] not in ("RsaesOaepDecrypt", "RsaesPkcs1Decrypt"):
            continue
        pk8 = bytes.fromhex(g["privateKeyPkcs8"])
        # Spot-check that this is a PKCS #8 blob and not, say, RSAPrivateKey.
        # This is the rsaEncryption OID.
        assert bytes.fromhex("2a864886f70d010101") in pk8
        g["privateKeyPem"] = key_to_pem(pk8)
        changed = True
    if changed:
        with open(path, "w") as f:
            json.dump(j, f, indent=2, separators=(",", " : "))
            f.write("\n")

for arg in sys.argv[1:]:
    fix(arg)

[cpu]

Thank you 🙇 LGTM