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Short version: I'm seeing an SSL certificate chain that's different based on how I access the https server. What's going on, and how do I verify the certificate under these circumstances?
I'm trying to use libcurl to verify the certificate of an SSL connection. The server I'm connecting to is Amazon S3.
When I access Amazon S3 in Firefox, I get this certificate chain:
When I access the same URL via the OpenSSL command line tool, I get this certificate chain:
The "*.s3.amazonaws.com" and "VeriSign Class 3 Secure Server CA - G3" certificates appear to be the same, but the one after that is different! It's named "VeriSign Class 3 Public Primary Certification Authority - G5" in both chains, but the certificate serial number is different. (Other information is different as well; let me know if you want a longer dump.)
I believe that this difference is the reason that I can't get libcurl to verify the SSL certificate. The certificate with serial number "18:DA:D1..." is in my CACERT.PEM file, but the certificate with serial number "35:97:31..." is not.
Obviously, the simple fix would be to add certificate "35:97:31..." to my CACERT.PEM file, but I want to make the right change here, not just a quick fix.
I'm using libcurl with OpenSSL to download from Amazon S3. Libcurl is returning "SSL certificate problem: unable to get local issuer certificate", which I know means that the root certificate isn't listed in my CACERT.PEM file. (I'm using the one downloaded from curl's website, which is converted from Mozilla's certificate store.) I am able to verify certificates on other SSL connections, so I know my libcurl setup is correct.
To see what was going on, and why the certificate didn't verify, I pulled up the same URL in Firefox. Firefox didn't show any SSL certificate warnings. Here's the certification path Firefox shows. The root certificate, "VeriSign Class 3 Public Primary Certification Authority - G5", is listed in my CACERT.PEM file, and the serial number of the certificate matches what's shown in the screenshot.
Here's the serial numbers of all three certificates in the chain:
On a different platform (different OS, different version of OpenSSL, etc.), I tried accessing the same URL using the OpenSSL command line tool, and I got a different certification path!
$ openssl s_client -showcerts -connect stackoverflowtest.s3.amazonaws.com:443
CONNECTED(00000003)
depth=3 C = US, O = "VeriSign, Inc.", OU = Class 3 Public Primary Certification Authority
verify return:1
depth=2 C = US, O = "VeriSign, Inc.", OU = VeriSign Trust Network, OU = "(c) 2006 VeriSign, Inc. - For authorized use only", CN = VeriSign Class 3 Public Primary Certification Authority - G5
verify return:1
depth=1 C = US, O = "VeriSign, Inc.", OU = VeriSign Trust Network, OU = Terms of use at https://www.verisign.com/rpa (c)10, CN = VeriSign Class 3 Secure Server CA - G3
verify return:1
depth=0 C = US, ST = Washington, L = Seattle, O = Amazon.com Inc., OU = S3-A, CN = *.s3.amazonaws.com
verify return:1
---
Certificate chain
0 s:/C=US/ST=Washington/L=Seattle/O=Amazon.com Inc./OU=S3-A/CN=*.s3.amazonaws.com
i:/C=US/O=VeriSign, Inc./OU=VeriSign Trust Network/OU=Terms of use at https://www.verisign.com/rpa (c)10/CN=VeriSign Class 3 Secure Server CA - G3
-----BEGIN CERTIFICATE-----
MIIFOTCCBCGgAwIBAgIQQ/u6wmYn4JceHBHgMMNrZjANBgkqhkiG9w0BAQUFADCB
tTELMAkGA1UEBhMCVVMxFzAVBgNVBAoTDlZlcmlTaWduLCBJbmMuMR8wHQYDVQQL
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RbV4ir5EI2EPKxIy30YDvpCQ0WQvYLWFV0qQOuOXkMC2M2IsBmVn2/9GQ7eP
-----END CERTIFICATE-----
1 s:/C=US/O=VeriSign, Inc./OU=VeriSign Trust Network/OU=Terms of use at https://www.verisign.com/rpa (c)10/CN=VeriSign Class 3 Secure Server CA - G3
i:/C=US/O=VeriSign, Inc./OU=VeriSign Trust Network/OU=(c) 2006 VeriSign, Inc. - For authorized use only/CN=VeriSign Class 3 Public Primary Certification Authority - G5
-----BEGIN CERTIFICATE-----
MIIF7DCCBNSgAwIBAgIQbsx6pacDIAm4zrz06VLUkTANBgkqhkiG9w0BAQUFADCB
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bWFnZS9naWYwITAfMAcGBSsOAwIaBBSP5dMahqyNjmvDz4Bq1EgYLHsZLjAlFiNo
dHRwOi8vbG9nby52ZXJpc2lnbi5jb20vdnNsb2dvLmdpZjAoBgNVHREEITAfpB0w
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HSCrJfQBY9i+eaUwHwYDVR0jBBgwFoAUf9Nlp8Ld7LvwMAnzQzn6Aq8zMTMwDQYJ
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Rs/iGAZeqa6ogZpHFt4MKGwlJ7net4RYxh84HqTEy2Y=
-----END CERTIFICATE-----
2 s:/C=US/O=VeriSign, Inc./OU=VeriSign Trust Network/OU=(c) 2006 VeriSign, Inc. - For authorized use only/CN=VeriSign Class 3 Public Primary Certification Authority - G5
i:/C=US/O=VeriSign, Inc./OU=Class 3 Public Primary Certification Authority
-----BEGIN CERTIFICATE-----
MIIExjCCBC+gAwIBAgIQNZcxh/OHOgcyfs5YDJt+2jANBgkqhkiG9w0BAQUFADBf
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CPMr3u00HUSe0gST9MsFFy0JLS1j7/YmC3s=
-----END CERTIFICATE-----
---
Server certificate
subject=/C=US/ST=Washington/L=Seattle/O=Amazon.com Inc./OU=S3-A/CN=*.s3.amazonaws.com
issuer=/C=US/O=VeriSign, Inc./OU=VeriSign Trust Network/OU=Terms of use at https://www.verisign.com/rpa (c)10/CN=VeriSign Class 3 Secure Server CA - G3
---
No client certificate CA names sent
Server Temp Key: ECDH, prime256v1, 256 bits
---
SSL handshake has read 4624 bytes and written 399 bytes
---
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-SHA
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
SSL-Session:
Protocol : TLSv1.2
Cipher : ECDHE-RSA-AES128-SHA
Session-ID: B642ED1E6FE32F7A374B5A62847DEC63C2F37DCA7A18FD669B8F0FCDC98C49BF
Session-ID-ctx:
Master-Key: EE2D31F43D341A0895B36E0BCCE7557B221F1469AC1B7B0BA22D843C75F25F949822B0D0E22E967A1F373F034E9624E4
Key-Arg : None
Krb5 Principal: None
PSK identity: None
PSK identity hint: None
Start Time: 1430871883
Timeout : 300 (sec)
Verify return code: 0 (ok)
---
closed
When I decode the certificates it lists, I get a different certificate chain than Firefox gave me.
The cert in use, and its immediate parent cert are the same, but the next one up has the same name, but a different serial number.
Here's my version information:
> curld --version curl 7.40.0 (i386-pc-win32ce) libcurl/7.40.0 OpenSSL/1.0.1e Protocols: dict ftp ftps gopher http https imap imaps pop3 pop3s rtsp smb smbs smtp smtps tftp Features: NTLM SSL
> curld --version curl 7.40.0 (i386-pc-win32) libcurl/7.40.0 OpenSSL/1.0.1c Protocols: dict ftp ftps gopher http https imap imaps pop3 pop3s rtsp smb smbs smtp smtps tftp Features: AsynchDNS Largefile NTLM SSL
$ cat /etc/redhat-release CentOS release 6.6 (Final) $ openssl version OpenSSL 1.0.1e-fips 11 Feb 2013 $ yum list openssl Installed Packages openssl.x86_64 1.0.1e-30.el6.8 @updates
Firefox: 37.0.2, running on Windows 7 x64.
I did review this question: SSL Certificate - Certification Path in browser different from Certificate Chain File, but my problem appears to be different: In that case, the certificate chain in the OpenSSL command line tool went 1 - 2 - 3 - 4, and in IE it was 1 - 2 - 3. Because IE considered "3" to be a root certificate, the chain stopped early. In my case, Firefox is reporting 1 - 2 - 3, and OpenSSL is reporting 1 - 2 - 4; The chain is different.
544
To check an SSL certificate on any website, all you need to do is follow two simple steps. First, check if the URL of the website begins with HTTPS, where S indicates it has an SSL certificate. Second, click on the padlock icon on the address bar to check all the detailed information related to the certificate.
To resolve the chain issue: Search your Certificate Authority's (CA) website to download their intermediate CA file. This file links all of the trusted CA certificates needed to reach the root certificate. When this Intermediate CA file has been downloaded, you must upload it to the LoadMaster.
certificate_list This is a sequence (chain) of certificates. The sender's certificate MUST come first in the list. Each following certificate MUST directly certify the one preceding it.
The server sends the same chain certificates to firefox and s_client:
But the way the certificates will be verified differs depending on the SSL stack and the trusted root certificates of the client. And in case of curl you run into an old OpenSSL validation problem. Details:
The solution is probably to use a CA store for curl which still includes the old deprecated 1024bit CA's so that it contains the trust anchor "/C=US/O=VeriSign, Inc./OU=Class 3 Public Primary Certification Authority"
For even more details about this problem see
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