mitmproxy/doc-src/certinstall/ssl.html
2015-03-18 00:29:54 -04:00

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SSL traffic poses a potential problem when using mitmproxy, as it is encrypted, it is opaque to inspection.
In order to be able to decrypt the traffic, you must use a certificate that the client, whose traffic you are intercepting, trusts.
This document outlines the different options you have for either using the certificate that mitmproxy generates or using your own.
Quick Setup
-----------
By far the easiest way to install the mitmproxy certificates is to use the built-in
web app. To do this, start mitmproxy and configure your target device with the
correct proxy settings. Now start a browser on the device, and visit the domain **mitm.it**.
You should see something like this:
<img src="@!urlTo("webapp.png")!@"></img>
Just click on the relevant icon, and then follow the setup instructions
for the platform you're on.
Certificates are installed via several different methods depending on the client.
There are too many to go into in this document, consult the documentation for
the client that you would to have trust the mitmproxy root certificate,
for specific installation instructions.
More On mitmproxy Certificates
------------------------------
The first time __mitmproxy__ or __mitmdump__ is run, the mitmproxy Certificate
Authority(CA) is created in the config directory (~/.mitmproxy by default).
This CA is used for on-the-fly generation of dummy certificates for each of the
SSL sites that your client visits. Since your browser won't trust the
__mitmproxy__ CA out of the box , you will see an SSL certificate
warning every time you visit a new SSL domain through __mitmproxy__. When
you are testing a single site through a browser, just accepting the bogus SSL
cert manually is not too much trouble, but there are a many circumstances where
you will want to configure your testing system or browser to trust the
__mitmproxy__ CA as a signing root authority.
CA and cert files
-----------------
The files created by mitmproxy in the .mitmproxy directory are as follows:
<table class="table">
<tr>
<td class="nowrap">mitmproxy-ca.pem</td>
<td>The private key and certificate in PEM format.</td>
</tr>
<tr>
<td class="nowrap">mitmproxy-ca-cert.pem</td>
<td>The certificate in PEM format. Use this to distribute to most
non-Windows platforms.</td>
</tr>
<tr>
<td class="nowrap">mitmproxy-ca-cert.p12</td>
<td>The certificate in PKCS12 format. For use on Windows.</td>
</tr>
<tr>
<td class="nowrap">mitmproxy-ca-cert.cer</td>
<td>Same file as .pem, but with an extension expected by some Android
devices.</td>
</tr>
</table>
Using a custom certificate
--------------------------
You can use your own certificate by passing the <kbd>--cert</kbd> option to mitmproxy. mitmproxy then uses the provided
certificate for interception of the specified domains instead of generating a certificate signed by its own CA.
The certificate file is expected to be in the PEM format.
You can include intermediary certificates right below your leaf certificate, so that you PEM file roughly looks like
this:
<pre>
-----BEGIN PRIVATE KEY-----
&lt;private key&gt;
-----END PRIVATE KEY-----
-----BEGIN CERTIFICATE-----
&lt;cert&gt;
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
&lt;intermediary cert (optional)&gt;
-----END CERTIFICATE-----
</pre>
For example, you can generate a certificate in this format using these instructions:
<pre class="terminal">
> openssl genrsa -out cert.key 2048
> openssl req -new -x509 -key cert.key -out cert.crt
(Specify the mitm domain as Common Name, e.g. *.google.com)
> cat cert.key cert.crt > cert.pem
> mitmproxy --cert=cert.pem
</pre>
Using a client side certificate
------------------------------------
You can use a client certificate by passing the <kbd>--client-certs DIRECTORY</kbd> option to mitmproxy.
If you visit example.org, mitmproxy looks for a file named example.org.pem in the specified directory
and uses this as the client cert. The certificate file needs to be in the PEM format and should contain
both the unencrypted private key as well as the certificate.
Using a custom certificate authority
------------------------------------
By default, mitmproxy will (generate and) use <samp>~/.mitmproxy/mitmproxy-ca.pem</samp> as the default certificate
authority to generate certificates for all domains for which no custom certificate is provided (see above).
You can use your own certificate authority by passing the <kbd>--confdir</kbd> option to mitmproxy.
mitmproxy will then look for <samp>mitmproxy-ca.pem</samp> in the specified directory. If no such file exists,
it will be generated automatically.