initial checkin with very basic functionality

checkcert/checkcert.py

@@ -0,0 +1,32 @@
+import ssl
+import sys
+import click
+import M2Crypto
+
+
+@click.command()
+@click.option("--san", is_flag=True, help="Output Subject Alternate Names")
+@click.option(
+    "--port", default=443, type=int, help="TCP port to connect to (default 443)"
+)
+@click.option("--expires", is_flag=True, help="Display the expiration date")
+@click.argument("domain")
+def main(san, port, expires, domain):
+    # handle a domain given with a : in it to specify the port
+    if ":" in domain:
+        uri = domain.split(":")
+        domain = uri[0]
+        port = uri[1]
+    cert = ssl.get_server_certificate((domain, port))
+    x509 = M2Crypto.X509.load_cert_string(cert)
+    if san:
+        all_sans = x509.get_ext("subjectAltName").get_value()
+        sans = all_sans.split(",")
+        for san in sans:
+            print(str(san).strip().removeprefix("DNS:"))
+        print(x509.get_subject().as_text())
+    print(f"Certificate for {domain}\nexpires after: {x509.get_not_after()}")
+
+
+if __name__ == "__main__":
+    main()