how to download the ssl certificate from a website?

Question

I want to download the ssl certificate from, say https://www.google.com, using wget or any other commands. Any unix command line? wget or openssl?

Answer 1

In order to download the certificate, you need to use the client built into openssl like so:

</dev/null openssl s_client -connect $HOST:$PORTNUMBER -servername $SERVERNAME \
    | openssl x509 > /tmp/$SERVERNAME.cert

That will save the certificate to /tmp/$SERVERNAME.cert.

The -servername is used to select the correct certificate when multiple are presented, in the case of SNI.

You can use -showcerts if you want to download all the certificates in the chain. But if you just want to download the server certificate, there is no need to specify -showcerts. The x509 at the end will strip out the intermediate certs, you will need to use sed -n '/-----BEGIN/,/-----END/p' instead of the x509 at the end.

</dev/null indicates that nothing should be sent to the server, so that the connection is released.

openssl x509 removes information about the certificate chain and connection details. This is the preferred format to import the certificate into other keystores.

Answer 2

I found the answer. Openssl provides it.

openssl s_client -connect ${REMHOST}:${REMPORT}

Answer 3

The GNUTLS client tool, gnutls-cli, can also make this easy:

gnutls-cli --print-cert www.example.com \
        < /dev/null \
        > www.example.com.certs

The program is designed to provide an interactive client to the site, so you need to give it empty input (in this example, from /dev/null) to end the interactive session.

Answer 4

true | openssl s_client -connect google.com:443 2>/dev/null | openssl x509

this mode of openssl expects stdin, so we provide it via true |, this connects to the server specified in the -connect parameter. 2>/dev/null silences errors (optional), we can pass the whole output into the x509 parser, specifying /dev/stdin to use the shell pipe as the input file. And that will output just the -----BEGIN CERTIFICATE----- to -----END CERTIFICATE----- portion of the s_client output. You can redirect that to a file by adding > google.com.pem to the end of the command.

---

As best I can tell, this does not verify the certificate chain, it only can tell you what ssl identity the end server provides.

Answer 5

based on @bignose answer, here is a self-contained version that fits well in e.g. a chef recipe:

sudo apt-get install gnutls-bin 
gnutls-cli --print-cert myserver.com </dev/null| sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > myserver.crt
sudo cp myserver.crt /usr/local/share/ca-certificates/myserver.crt
sudo update-ca-certificates

Answer 6

Alternative syntax using Ex and process substitution:

ex +'/BEGIN CERTIFICATE/,/END CERTIFICATE/p' <(echo | openssl s_client -showcerts -connect example.com:443) -scq > file.crt

Answer 7

Try Bash shell functions

I made two shell functions.

• getcert() will dump PEM cert to STDOUT.
• dumpcert() will dump PEM cert to file.

You get the default openssl debug messages on STDERR.

getcert()

$ getcert() { true | openssl s_client -connect "$1:443" -servername "$1" | openssl x509; }
$ getcert example.com > example.com.cer
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert Global Root G2
verify return:1
depth=1 C = US, O = DigiCert Inc, CN = DigiCert Global G2 TLS RSA SHA256 2020 CA1
verify return:1
depth=0 C = US, ST = California, L = Los Angeles, O = Internet\C2\A0Corporation\C2\A0for\C2\A0Assigned\C2\A0Names\C2\A0and\C2\A0Numbers, CN = www.example.org
verify return:1
DONE
$ cat example.com.cer
-----BEGIN CERTIFICATE-----
MIIHbjCCBlagAwIBAgIQB1vO8waJyK3fE+Ua9K/hhzANBgkqhkiG9w0BAQsFADBZ
MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMTMwMQYDVQQDEypE
aWdpQ2VydCBHbG9iYWwgRzIgVExTIFJTQSBTSEEyNTYgMjAyMCBDQTEwHhcNMjQw
MTMwMDAwMDAwWhcNMjUwMzAxMjM1OTU5WjCBljELMAkGA1UEBhMCVVMxEzARBgNV
BAgTCkNhbGlmb3JuaWExFDASBgNVBAcTC0xvcyBBbmdlbGVzMUIwQAYDVQQKDDlJ
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oE51bWJlcnMxGDAWBgNVBAMTD3d3dy5leGFtcGxlLm9yZzCCASIwDQYJKoZIhvcN
AQEBBQADggEPADCCAQoCggEBAIaFD7sO+cpf2fXgCjIsM9mqDgcpqC8IrXi9wga/
9y0rpqcnPVOmTMNLsid3INbBVEm4CNr5cKlh9rJJnWlX2vttJDRyLkfwBD+dsVvi
vGYxWTLmqX6/1LDUZPVrynv/cltemtg/1Aay88jcj2ZaRoRmqBgVeacIzgU8+zmJ
7236TnFSe7fkoKSclsBhPaQKcE3Djs1uszJs8sdECQTdoFX9I6UgeLKFXtg7rRf/
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hzId/R43jlAAAAGNW9L8XwAABAMASDBGAiEA4Koh/VizdQU1tjZ2E2VGgWSXXkwn
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BgkqhkiG9w0BAQsFAAOCAQEABOFuAj4N4yNG9OOWNQWTNSICC4Rd4nOG1HRP/Bsn
rz7KrcPORtb6D+Jx+Q0amhO31QhIvVBYs14gY4Ypyj7MzHgm4VmPXcqLvEkxb2G9
Qv9hYuEiNSQmm1fr5QAN/0AzbEbCM3cImLJ69kP5bUjfv/76KB57is8tYf9sh5ik
LGKauxCM/zRIcGa3bXLDafk5S2g5Vr2hs230d/NGW1wZrE+zdGuMxfGJzJP+DAFv
iBfcQnFg4+1zMEKcqS87oniOyG+60RMM0MdejBD7AS43m9us96Gsun/4kufLQUTI
FfnzxLutUV++3seshgefQOy5C/ayi8y1VTNmujPCxPCi6Q==
-----END CERTIFICATE-----

dumpcert()

Dumps to file. File name is domain-name (minus any ugly characters).

$ dumpcert() { true | openssl s_client -connect "$1:443" -servername "$1" | openssl x509 > "${1//[^a-Z0-9.-]}.cer"; }
$ dumpcert example.net
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert Global Root G2
verify return:1
depth=1 C = US, O = DigiCert Inc, CN = DigiCert Global G2 TLS RSA SHA256 2020 CA1
verify return:1
depth=0 C = US, ST = California, L = Los Angeles, O = Internet\C2\A0Corporation\C2\A0for\C2\A0Assigned\C2\A0Names\C2\A0and\C2\A0Numbers, CN = www.example.org
verify return:1
DONE
$ cat example.net.cer
-----BEGIN CERTIFICATE-----
MIIHbjCCBlagAwIBAgIQB1vO8waJyK3fE+Ua9K/hhzANBgkqhkiG9w0BAQsFADBZ
MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMTMwMQYDVQQDEypE
aWdpQ2VydCBHbG9iYWwgRzIgVExTIFJTQSBTSEEyNTYgMjAyMCBDQTEwHhcNMjQw
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BAgTCkNhbGlmb3JuaWExFDASBgNVBAcTC0xvcyBBbmdlbGVzMUIwQAYDVQQKDDlJ
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AQEBBQADggEPADCCAQoCggEBAIaFD7sO+cpf2fXgCjIsM9mqDgcpqC8IrXi9wga/
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FfnzxLutUV++3seshgefQOy5C/ayi8y1VTNmujPCxPCi6Q==
-----END CERTIFICATE-----