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Found at: raymii.org:70/haproxy_client_side_ssl_certificates.txt

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Title       : 	haproxy: client side ssl certificates
Author      : 	Remy van Elst
Date        : 	18-12-2013
URL         : 	https://raymii.org/s/tutorials/haproxy_client_side_ssl_certificates.html
Format      : 	Markdown/HTML
This tutorial shows you how to configure haproxy and client side ssl
You need at least haproxy 1.5 dev 16 for this to work. If you want to pass the
full sha 1 hash of a certificate to a backend you need at least 1.5 dev 19.

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Place the certificate chain file somewhere haproxy can access it and append the
following to your `bind` config line in the frontends where you want to use
client side certificates: `ca-file  verify required`.
If you want to also accept visitors without an ssl certificate change `verify
required` to `verify optional`. You might want this if you handle the
certificates in your application.
Below is an example which sends users to a different backend based on if there
is a client side certificate. It also sends users to a special error page if
there are validation errors with their client side certificate.
    frontend intranet
        mode http
        bind ssl crt /etc/haproxy/pem/server.pem ca-file /etc/haproxy/pem/client-chain.pem verify optional crt-ignore-err all crl-file /etc/haproxy/crl/haproxy.pem
        use_backend ssl-error unless { ssl_c_verify 0 }
        use_backend wiki if { ssl_fc_has_crt }
        default_backend helpdesk
    backend wiki
        mode http
        server wiki1 check
        server wiki2 check
    backend ssl-error
        mode http
        server helpdesk1 check
        server helpdesk2 check
    backend expired
        mode http
        option http-server-close
        redirect location /certificate-expired.html if { ssl_c_verify 10 } ! { path /certificate-expired.html }
        redirect location /certificate-revoked.html if { ssl_c_verify 23 } ! { path /certificate-revoked.html }
        redirect location /other-certificate-error.html unless { ssl_c_verify 0 } ! { path //other-certificate-error.html }
        server helpdesk3 check
Note that this example config also uses a CRL file to check for revocations. You
need to place that CRL file.
  * If the client did not provide a certificate, haproxy uses the `helpdesk` backend.
  * If the client provides a certificate, haproxy uses the `wiki` backend
  * If there is an error with the client certificate, haproxy uses the `ssl-error` backend. 
    * If the certificate is revoked, haproxy redirects the user to the `certificate-revoked.html` page on that backend server.
    * If the certificate is expired, haproxy redirects the user to the `certificate-expired.html` page on that backend server.
    * If there is any other error, haproxy redirects the user to the `other-certificate-error.html` page on that backend server.
I've had issues with a DER encoded CRL file for haproxy. To convert it to pem
you can use the following command:
    openssl crl -in example.crl -inform DER -outform PEM -out /etc/haproxy/crl/haproxy.crl
Combine this with a cronjob that downloads the CRL you are good to go:
    */5 * * * * wget -O /tmp/haproxy.crl http://example-ca.org/crl/example_crl.crl && openssl crl -in /tmp/example.crl -inform DER -outform PEM -out /etc/haproxy/crl/haproxy.crl
### Sending certificate details to backend application
You can also send specific details about a client certificate to your backend
application. You can then handle the verification of the certificate in your
backend application.
This example config sends all available certificate details to your backend
application as HTTP Headers:
    frontend intranet
        bind ssl crt /etc/haproxy/pem/server.pem ca-file /etc/haproxy/pem/client-chain.pem verify required
        http-request set-header X-SSL                       %[ssl_fc]
        http-request set-header X-SSL-Client-Verify         %[ssl_c_verify]
        http-request set-header X-SSL-Client-SHA1           %{+Q}[ssl_c_sha1]
        http-request set-header X-SSL-Client-DN             %{+Q}[ssl_c_s_dn]
        http-request set-header X-SSL-Client-CN             %{+Q}[ssl_c_s_dn(cn)]
        http-request set-header X-SSL-Issuer                %{+Q}[ssl_c_i_dn]
        http-request set-header X-SSL-Client-Not-Before     %{+Q}[ssl_c_notbefore]
        http-request set-header X-SSL-Client-Not-After      %{+Q}[ssl_c_notafter]
        default_backend example_backend
The `{+Q}` means that the data is quoted as a string. Otherwise it would be
binary or boolean.
In your backend the headers look like this:
    X-SSL: 1
    # 1 if client used a secure connection, 0 if not.
    X-SSL-Client-Verify: 0
    # The status code of the SSL client connection
    X-SSL-Client-SHA1: "a01b894d12579d88efce97d27107f380b05f5968"
    # The SHA 1 hash of the client certificate.
    X-SSL-Client-DN: "/C=NL/ST=Zuid Holland/L=Rotterdam/O=Sparkling Network/CN=exampleUserCertificate/emailAddress=example@example.org"
    # The full Distinguished Name of the client certificate.
    X-SSL-Client-CN: "exampleUserCertificate"
    # The full Common Name of the client certificate.
    X-SSL-Issuer: "/C=NL/ST=Zuid Holland/L=Rotterdam/O=Sparkling Network/CN=Sparkling Intermediate Client SSL CA 2"
    # The full Distinguished Name of the issuing certificate.
    X-SSL-Client-Not-Before: "120101100030Z"
    # Date from on which certificate is valid in format: YYMMDDhhmmss
    X-SSL-Client-Not-After: "160101100030Z"
    # Date from on which certificate is not valid anymore in format: YYMMDDhhmmss
### Testing it
You can use OpenSSL to test client side certificate authentication:
    openssl s_client -connect -cert ./client.pem -key ./client.key
### Links
  * [OpenSSL CRL][2]
  * [haproxy 1.5 ssl certificate data][3]
   [1]: https://www.digitalocean.com/?refcode=7435ae6b8212
   [2]: http://www.openssl.org/docs/apps/crl.html
   [3]: http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#7.3.3
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