x5c

A pass-by-query-param online x509 certificate decoder, written in Go.

• Demo
• Usage
• Install
• API
• Build

Demo

https://x5c.bnna.net/

Note: until this is a paid service, there's no guarantee of uptime.

Usage

x5c-server --web-root ./public/ --port 8080 --rate-limit 50

• --web-root can be used to override index.html
• --rate-limit limits the number of request per ip per 5m window

Install

go install github.com/therootcompany/x5c/cmd/x5c-server

API

GET /api/x509?cert=<pem|rfc-base64|url-base64|hex>

{
    "issuer": "CN=example.com",
    "subject": "CN=example.com",
    "serial_number": "588847758906910965042193239346229823033307348532",
    "valid_from": "2024-09-07T07:50:45Z",
    "valid_to": "2025-09-07T07:50:45Z",
    "sha1_fingerprint": "D3480B4AFC14E72DAFE350173995967CC5A10AD6",
    "sha256_fingerprint": "5832B347806271E1B341EF364A5C73849B8CB30EECB66C8A2EC8AC7D04CAD74F"
}

Example certificate:

-----BEGIN CERTIFICATE-----
MIIBQDCB86ADAgECAhRnJNjDOT2MzyPw0YgyhI2ziwS+NDAFBgMrZXAwFjEUMBIG
A1UEAwwLZXhhbXBsZS5jb20wHhcNMjQwOTA3MDc1MDQ1WhcNMjUwOTA3MDc1MDQ1
WjAWMRQwEgYDVQQDDAtleGFtcGxlLmNvbTAqMAUGAytlcAMhAFe8ERQZwaGP7UCi
HDcKnCGI8EzOlqEcuGa502FzqDzdo1MwUTAdBgNVHQ4EFgQUcOjieH3j0OY4nrtP
BdDO4XN/rLEwHwYDVR0jBBgwFoAUcOjieH3j0OY4nrtPBdDO4XN/rLEwDwYDVR0T
AQH/BAUwAwEB/zAFBgMrZXADQQBFOO8xhfMbZ2iJbS/mgkOyund5/FVorMZsu/j5
jCjcURccZOG6+gh1ahTGk20QmRLmE2Cf/+WTpfrAa5l6x6cN
-----END CERTIFICATE-----

Build

GOOS=linux GOARCH=amd64 go build -o x5c-server ./cmd/x5c-server/