I recently updated some certificate parsing routines/tests and ran them against the LetsEncrypt certificates.
I understand x1 and x2 are retired, but I have a question if these 2 files are technically valid. I could not find anything online about them.
Both PEM certificates use the following header/footer, in which the underscore (_) is a space.
I believe the formatting is supposed to conform to RFC 7468 (RFC 7468 - Textual Encodings of PKIX, PKCS, and CMS Structures), which provides for ignoring whitespace between the encapsulation boundaries and outside of them, but defines the encapsulation boundaries as the entirety of a line -- which suggests to me the space is non-conformant. Perhaps another RFC covers this though?
No other LetsEncrypt/ISRG certs present this detail. Running the certs through a handful of random libraries showed them both passing and failing due to the space; without the space they always parse.
I'm adjusting my tools to support this variant, but I still wonder if this is correct.