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227 lines
6.3 KiB
HTML
227 lines
6.3 KiB
HTML
<h6>Protocol Specification</h6>
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<p>All requests are HTTP GETs. As such, all parameters must be
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properly URL encoded. In particular, some base64 characters (such as
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"+") in the value fields needs to be escaped.</p>
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<p>Each response sent by Yubico is signed. To make sure the response
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has not been tampered with, you should verify the signature.</p>
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<p>To verify a <a name="signatures">signature</a> on a response message, follow
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the same procedure that was used to <a href="#generate_sig">sign the
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response message</a> and compare the signature in the response to the signature
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you generated. If the signature values are equal, the
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signature is correct.</p>
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Make sure you remove the signature itself from the values you generate
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the signature over for verification. If the incoming message is
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<pre>
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b=1&a=2&c=3&h=V5FkMYr9GCG9tQA9ihuuybWl99U=
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</pre>
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make sure to remove <code>h</code> before verifying:
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<pre>b=1&a=2&c=3 </pre>
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<br />
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<hr size="1" noshade color="#cccccc">
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<br />
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<h6 id="generate_sig">Generating signatures</h6>
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The Yubico API uses HMAC-SHA1 signatures with 160 bit key lengths
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(as defined by <a href="http://www.ietf.org/rfc/rfc3174.txt">RFC
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3174</a>). The HMAC key to use is the <a href="#api_key">API key</a>.
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<br /><br />
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<p>Generate the signature over the parameters in the message. Each
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message contains a set of key/value pairs, and the signature is always
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over the entire set (excluding the signature itself), sorted in
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alphabetical order of the keys.
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To generate a message signature:
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<ol>
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<li>Alphabetically sort the set of key/value pairs by key order.</li>
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<li>Construct a single line with each ordered key/value pair concatenated
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using '&', and each key and value contatenated with '='. Do not add any
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linebreaks. Do not add whitespace. For
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example: <code>a=2&b=1&c=3</code>.</li>
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<li>Apply the signature algorithm to the line's octet string (UTF-8 byte
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values according to
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<a href="http://www.ietf.org/rfc/rfc3629.txt">RFC 3629</a>) using
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the
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<a href="#api_key">API key</a> as key.</li>
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<li>Base 64 encode the resulting value according to
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<a href="http://www.ietf.org/rfc/rfc4648.html">RFC 4648</a>, for
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example, <code>t2ZMtKeValdA+H0jVpj3LIichn4=</code>.</li>
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<li>Append the value under key <code>h</code> to the message.
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</ol>
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<br /><br />
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<hr size="1" noshade color="#cccccc">
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<br />
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<h6>Verification</h6>
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There is one call to verify YubiKey OTPs: <code>verify</code>.
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<br /><br />
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<b>verify</b>
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The <code>verify</code> call lets you check whether an OTP is valid. Since the
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OTP itself contains identification information, all you have to do
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is to send the OTP.
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<br /><br />
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<hr size="1" noshade color="#cccccc">
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<br />
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<h6>Request</h6>
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Construct an HTTP GET call to
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<pre>http://api.yubico.com/wsapi/verify</pre>
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with the following parameters (note that this request need not be signed):
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<br></br>
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<table border="1">
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<th>parameter</th><th>type</th><th>required</th><th>purpose</th>
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<tr>
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<td><code>id</code></td>
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<td>string</td>
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<td>Yes</td>
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<td>Specifies the requestor so that the end-point can retrieve
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correct shared secret for signing the response.</td>
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</tr>
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<tr>
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<td><code>otp</code></td>
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<td>string</td>
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<td>Yes</td>
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<td>The OTP from the YubiKey.</td>
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</tr>
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<tr>
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<td><code>timestamp</td>
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<td>string</td>
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<td>No</td>
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<td>Timestamp=1 requests timestamp and session counter information the response</td>
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<tr>
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<td><code>h</code></td>
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<td>string</td>
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<td>No</td>
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<td>The optional HMAC-SHA1 signature for the request.</td>
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</tr>
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</table>
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<br></br>
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An example request (broken into two lines for legibility):
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<pre>
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http://api.yubico.com/wsapi/verify?otp=vvvvvvcucrlcietctc\
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kflvnncdgckubflugerlnr&id=87 </pre>
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<br />
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And if you require additional information on timestamp and session counters:
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<pre>
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http://api.yubico.com/wsapi/verify?otp=vvvvvvcucrlcietctc\
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kflvnncdgckubflugerlnr&id=87×tamp=1 </pre>
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<br />
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<hr size="1" noshade color="#cccccc">
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<br />
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<h6>Response</h6>
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The verification response tells you whether the OTP is valid.
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<br></br>
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The response has the following values:
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<br></br>
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<table border=1 width="100%">
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<th>parameter</th><th>type</th><th>purpose</th>
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<tr>
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<td><code>h</code></td>
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<td>string (base64)</td>
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<td>Signature as <a href="#signatures">described above</a>.</td>
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</tr>
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<tr>
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<td><code>t</code></td>
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<td>time stamp</td>
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<td>Timestamp in UTC.</td>
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</tr>
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<tr>
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<td><code>status</code></td>
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<td>string</td>
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<td>The status of the operation. The status are described
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in <a href="#verify_return_codes">return codes</a>.</td>
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</tr>
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<tr>
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<td><code>timestamp</code></td>
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<td>string</td>
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<td>YubiKey internal timestamp value when key was pressed</td>
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</tr>
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<tr>
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<td><code>sessioncounter</code></td>
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<td>string</td>
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<td>YubiKey internal usage counter when key was pressed</td>
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</tr>
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<tr>
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<td><code>sessionuse</code></td>
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<td>string</td>
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<td>YubiKey internal session usage counter when key was pressed</td>
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</tr>
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</table>
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<br /><br />
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<hr size="1" noshade color="#cccccc">
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<br />
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<h6 id="verify_return_codes">Return codes</h6>
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These are possible <code>status</code> values in a <code>verify</code>
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response:
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<table border=1 width="100%">
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<th>name</th><th>meaning</th>
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<tr>
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<td><code>OK</code></td>
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<td>The OTP is valid.</td>
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</tr>
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<tr>
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<td><code>BAD_OTP</code></td>
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<td>The OTP is invalid format.</td>
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</tr>
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<tr>
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<td><code>REPLAYED_OTP</code></td>
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<td>The OTP has already been seen by the service.</td>
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</tr>
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<tr>
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<td><code>BAD_SIGNATURE</code></td>
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<td>The HMAC signature verification failed.</td>
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</tr>
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<tr>
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<td><code>MISSING_PARAMETER</code></td>
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<td>The request lacks a parameter.</td>
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</tr>
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<tr>
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<td><code>NO_SUCH_CLIENT</code></td>
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<td>The request <code>id</code> does not exist.</td>
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</tr>
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<tr>
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<td><code>OPERATION_NOT_ALLOWED</code></td>
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<td>The request <code>id</code> is not allowed to verify OTPs.</td>
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</tr>
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<tr>
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<td><code>BACKEND_ERROR</code></td>
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<td>Unexpected error in our server. Please contact us if you see this
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error.</td>
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</tr>
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</table>
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