Chain get all certificates; intermediate and root
Neil Traft:
I'm using Apache's HTTPClient in Java and trying to connect to graph.facebook.com. I get the "SSLPeerUnverifiedException: No peer certificate" error, so I guess Facebook's CA is not in the default keystore. So I need to create my own keystore with all the certificates I want to trust, right? So I found the following command to get the certificate:
echo | openssl s_client -connect graph.facebook.com:443 2>&1 | \
sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > mycert.pem
Not sure what happened, but this seems to work. I added the certificate to the keystore in Bouncy Castle format. I created the SSLSocketFactory with the new keystore, but it still doesn't work.
My first guess is that maybe I don't have all the certificates in the chain (apparently these things are in the chain). So how do I know if a so called "intermediate" CA is involved? How do I get these certificates? Am I on the right track?
Neil Traft:
I finally had time to look into this and it turned out to be super easy! I'm just missing one option to the openssl command: the showcerts option. Below is an example of getting a certificate suitable for connecting to Facebook's image server.
Note: I also found that to verify the SSL connection, you don't want to add the certificate of the endpoint you are connecting to in the keystore. You only need intermediate and root certificate authorities. In some cases only the root CA, otherwise you will get an exception. See this excellent blog post for more info .
$ openssl s_client -connect graph.facebook.com:443 -showcerts
CONNECTED(00000003)
depth=2 /C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
verify error:num=20:unable to get local issuer certificate
verify return:0
---
Certificate chain
0 s:/C=US/ST=California/L=Palo Alto/O=Facebook, Inc./CN=*.facebook.com
i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance CA-3
-----BEGIN CERTIFICATE-----
MIIFgjCCBGqgAwIBAgIQDKKbZcnESGaLDuEaVk6fQjANBgkqhkiG9w0BAQUFADBm
MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3
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a1BHnLLP4mxTHL6faAXYd05IxNn/IA==
-----END CERTIFICATE-----
1 s:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance CA-3
i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
-----BEGIN CERTIFICATE-----
MIIGVTCCBT2gAwIBAgIQCFH5WYFBRcq94CTiEsnCDjANBgkqhkiG9w0BAQUFADBs
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9ZKNu8BVIASm2LAXFszj0Mi0PeXZhMbT9m5teMl5Q+h6N/9cNUm/ocU=
-----END CERTIFICATE-----
2 s:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
i:/C=US/O=Entrust.net/OU=www.entrust.net/CPS incorp. by ref. (limits liab.)/OU=(c) 1999 Entrust.net Limited/CN=Entrust.net Secure Server Certification Authority
-----BEGIN CERTIFICATE-----
MIIEQjCCA6ugAwIBAgIEQodApTANBgkqhkiG9w0BAQUFADCBwzELMAkGA1UEBhMC
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-----END CERTIFICATE-----
---
Server certificate
subject=/C=US/ST=California/L=Palo Alto/O=Facebook, Inc./CN=*.facebook.com
issuer=/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance CA-3
---
No client certificate CA names sent
---
SSL handshake has read 4285 bytes and written 309 bytes
---
New, TLSv1/SSLv3, Cipher is RC4-MD5
Server public key is 1024 bit
Compression: NONE
Expansion: NONE
SSL-Session:
Protocol : TLSv1
Cipher : RC4-MD5
Session-ID: A2AD56513E9EB36D5E4EC193977882BEEC5EC64D07D8E4310C562CC3A4571913
Session-ID-ctx:
Master-Key: 3AC56DD593C864A17D00B08CEFEDB299607491C5E2ABAFE14E2AABADDC8A734B888CC6389BDBE40782EA5ED6E3EAFE4A
Key-Arg : None
Start Time: 1300747299
Timeout : 300 (sec)
Verify return code: 0 (ok)
---