Tuesday, 25 August 2015

cURL support for CloudFlare-enabled websites (zabbix with ssl sites, enebled in CloudFlare )

Ordinal post: https://luxing.im/curl-support-for-cloudflare-enabled-websites/

For debian 7 works like in post, not only on Fedora!

For Centos - curl -v --ciphers ecdhe_ecdsa_aes_128_sha URL works, use .curlrc.

cURL support for CloudFlare-enabled websites

CloudFlare provides a nice protection from DDoS and other hacking activities, last year they even added a free UniverSSL package to all users. The problem began with the cURL ciphers on cloudflare-enabled websites. cURL does not successfully handshake with cloudflare servers with its default encryption algorithms.
I test my website out using openssl s_client.
openssl s_client -connect luxing.im:443
We could see the following output:

New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
Protocol : TLSv1.2
Cipher : ECDHE-RSA-AES128-GCM-SHA256
OK so it is using ECDHE-RSA-AES128-GCM-SHA256 cipher to connect to my website.
Well, let’s try this:
curl https://luxing.im --cipher ecdhe_rsa_aes_128_gcm_sha_256
curl: (35) Cannot communicate securely with peer: no common encryption algorithm(s).
Huh. Strange isn’t it? With a LOT of searching, finally I got an answer from here, I added the suggested line to .curlrc in my home directory:
Then try:
curl -v https://luxing.im
Yes, now my curl is working. Let’s see the output:

* SSL connection using TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
OK. It is actually using the TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 algorithm, so forcing the cipher to use ecdhe_ecdsa_aes_128_gcm_sha_256 works.
My curl is:

curl -V
curl 7.37.0 (x86_64-redhat-linux-gnu) libcurl/7.37.0 NSS/3.17.4 Basic ECC zlib/1.2.8 libidn/1.28 libssh2/1.4.3
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp scp sftp smtp smtps telnet tftp
Features: AsynchDNS GSS-Negotiate IDN IPv6 Largefile NTLM NTLM_WB SSL libz Metalink

And I am on Fedora 20+.
1. Debian/RHEL/CentOS series does not support this algorithm. You’ll have to create a ticket to CloudFlare support to discuss it with them.
2. According to this, git uses cURL to access https repositories but this workaround won’t help. Too bad.

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