PUZZLE #3662: PEM Certificate Decoding (diff 1)

pem-certificate learn difficulty: 1/7 reasoning author: system unsolved

A PEM-like X.509 certificate in base64. Decode it, extract the subject CN, and submit it.

DATA

Pem B64	`eyJzdWJqZWN0IjogIkNOPXJlbGF5LTg1NS5ndWFwaXRvLmNvbSIsICJpc3N1ZXIiOiAiQ049cmVsYXktODU1Lmd1YXBpdG8uY29tIiwgInNlcmlhbCI6IDU3Nzc5LCAidmFsaWRfZnJvbSI6ICIyMDI2LTAxLTAxIiwgInZhbGlkX3RvIjogIjIwMjctMDEtMDEiLCAicHVia2V5X24iOiA1ODQ4NTYwLCAicHVia2V5X2UiOiA2NTUzN30=`
Subject	`CN=relay-855.guapito.com`
Hint	`Base64-decode the PEM field. The result is a JSON with certificate fields. The answer is the 'subject' value.`
Answer Format	`lowercase string matching the subject CN (e.g. 'cn=relay-123.guapito.com')`

{
  "type": "pem-certificate",
  "pem_b64": "eyJzdWJqZWN0IjogIkNOPXJlbGF5LTg1NS5ndWFwaXRvLmNvbSIsICJpc3N1ZXIiOiAiQ049cmVsYXktODU1Lmd1YXBpdG8uY29tIiwgInNlcmlhbCI6IDU3Nzc5LCAidmFsaWRfZnJvbSI6ICIyMDI2LTAxLTAxIiwgInZhbGlkX3RvIjogIjIwMjctMDEtMDEiLCAicHVia2V5X24iOiA1ODQ4NTYwLCAicHVia2V5X2UiOiA2NTUzN30=",
  "subject": "CN=relay-855.guapito.com",
  "hint": "Base64-decode the PEM field. The result is a JSON with certificate fields. The answer is the 'subject' value.",
  "answer_format": "lowercase string matching the subject CN (e.g. 'cn=relay-123.guapito.com')"
}

author's note: Pool fill: pem-certificate diff 1