58 lines
3.6 KiB
Text
58 lines
3.6 KiB
Text
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=== OTP Policies
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{{book.project.name}} has a number of policies you can set up for your FreeOTP or Google Authenticator One-Time Password
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generator. Click on the `Authentication` left menu item and got to the `OTP Policy` tab.
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.OTP Policy
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image:../../{{book.images}}/otp-policy.png[]
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Any policies you set here will be used to validate one-time passwords. When configuring OTP, FreeOTP and Google Authenticator
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can scan in a bar code that is generated on the OTP set up page that {{book.project.name}} has. The bar code is also
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generated from information configured on the `OTP Policy` tab.
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==== TOTP vs. HOTP
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There are two different algorithms to choose from for your OTP generators. Time Based (TOTP) and Counter Based (HOTP) based.
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For TOTP, your token generator will hash the current time and a share secret. The server validates the OTP by comparing
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the all hashes within a certain window of time to the submitted value. So, TOTPs are valid only for a short window of time (usually 30 seconds).
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For HOTP a shared counter is used instead of the current time. The server increments the counter each successful OTP login. So, valid OTPs only
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change after a successful login.
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TOTP is considered a little more secure because the matchable OTP is only valid for a short window of time while the OTP for HOTP can
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be valid for an indeterminate amount of time. HOTP is much more user friendly as the user won't have to hurry to enter in their
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OTP before the time interval is up. With the way {{book.project.name}} has implement TOTP this distinction becomes a little more
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blurry. HOTP requires a database update every time the server wants to increment the counter. This can be a performance drain
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on the authentication server when there is heavy load. So, to provide a more efficient alternative, TOTP does not remember passwords
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used. This bypasses the need to do any DB updates, but the downside is that TOTPs can be re-used in the valid time interval. For future
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versions of {{book.project.name}} it is planned that you will be able to configure whether TOTP checks older OTPs in the time interval.
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==== TOTP Configuration Options
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Hashing Algorithm::
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Default is SHA1, more secure options are SHA256 and SHA512.
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Number of Digits::
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How many characters is the OTP? Short means more user friendly as it is less the user has to type. More means more security.
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Look Ahead Window::
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How many intervals ahead should the server try and match the hash? This exists so just in case the clock of the TOTP generator
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or authentication server get out of sync. The default value of 1 is usually good enough. For example, if the time interval
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for a new token is every 30 seconds, the default value of 1 means that it will only accept valid tokens in that 30 second window.
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Each increment of this config value will increase the valid window by 30 seconds.
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OTP Token Period::
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Time interval in seconds a new TOTP will be generated by the token generator. And, the time window the server is matching a hash.
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==== HOTP Configuration Options
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Hashing Algorithm::
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Default is SHA1, more secure options are SHA256 and SHA512.
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Number of Digits::
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How many characters is the OTP? Short means more user friendly as it is less the user has to type. More means more security.
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Look Ahead Window::
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How many counters ahead should the server try and match the hash? The default value is 1. This exists to cover the case
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where the user's counter gets ahead of the server's. This can often happen as users often increment the counter
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manually too many times by accident. This value really should be increased to like a value of 10 or so.
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Initial Counter::
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What is the value of the initial counter?
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