init

LICENSE

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+MIT License
+Copyright (c) 2017 Stephen McQuay
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# certexp
+
+report certificate expiry for a collection of servers, which yields equivalent
+information to:
+
+```bash
+$ echo | openssl s_client -connect $hostname:$port 2> /dev/null | openssl x509 -noout -dates | grep notAfter
+```
+
+## example usage
+
+```bash
+$ cat sites.txt
+apple.com
+google.com
+amazon.com
+imap.gmail.com:993
+$ cat sites.txt | certexp
+apple.com                2018-10-31 23:59:59 +0000 UTC
+google.com               2018-02-13 15:19:00 +0000 UTC
+amazon.com               2018-09-21 23:59:59 +0000 UTC
+imap.gmail.com           2018-02-27 09:29:00 +0000 UTC
+```

main.go

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+package main
+
+import (
+	"bufio"
+	"crypto/tls"
+	"fmt"
+	"log"
+	"net"
+	"os"
+)
+
+func main() {
+	s := bufio.NewScanner(os.Stdin)
+	for s.Scan() {
+		line := s.Text()
+		if line == "" {
+			continue
+		}
+
+		host, port := line, "443"
+		if h, p, err := net.SplitHostPort(line); err == nil {
+			host, port = h, p
+		}
+
+		c, err := tls.Dial("tcp", fmt.Sprintf("%v:%v", host, port), nil)
+		if err != nil {
+			log.Fatalf("dial: %v", err)
+		}
+		if err := c.Handshake(); err != nil {
+			log.Fatalf("handshake: %v", err)
+		}
+		if err := c.Close(); err != nil {
+			log.Fatalf("close: %v", err)
+		}
+
+		for _, chain := range c.ConnectionState().VerifiedChains {
+			for _, cert := range chain {
+				if cert.DNSNames != nil {
+					fmt.Printf("%-24v %v\n", host, cert.NotAfter)
+				}
+			}
+		}
+	}
+}