44 lines
2.4 KiB
Markdown
44 lines
2.4 KiB
Markdown
# GoogleAuthenticator
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Simple, easy to use server-side two-factor authentication library for .NET that works with Google Authenticator
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[](https://dev.azure.com/brandon-potter/GoogleAuthenticator/_build/latest?definitionId=1&branchName=master)
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[](https://www.nuget.org/packages/GoogleAuthenticator/)
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[`Install-Package GoogleAuthenticator`](https://www.nuget.org/packages/GoogleAuthenticator)
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## 1.x Usage
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See blog post for usage instructions *(1.x only)*:
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https://csharprookie.wordpress.com/2015/03/17/implementing-free-two-factor-authentication-in-net-using-google-authenticator/
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## 2.x Usage
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*Additional examples at [Google.Authenticator.WinTest](https://github.com/BrandonPotter/GoogleAuthenticator/tree/master/Google.Authenticator.WinTest) and [Google.Authenticator.WebSample](https://github.com/BrandonPotter/GoogleAuthenticator/tree/master/Google.Authenticator.WebSample)*
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```csharp
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using Google.Authenticator;
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string key = Guid.NewGuid().ToString().Replace("-", "").Substring(0, 10);
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TwoFactorAuthenticator tfa = new TwoFactorAuthenticator();
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SetupCode setupInfo = tfa.GenerateSetupCode("Test Two Factor", "user@example.com", key, false, 3);
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string qrCodeImageUrl = setupInfo.QrCodeSetupImageUrl;
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string manualEntrySetupCode = setupInfo.ManualEntryKey;
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imgQrCode.ImageUrl = qrCodeImageUrl;
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lblManualSetupCode.Text = manualEntrySetupCode;
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// verify
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TwoFactorAuthenticator tfa = new TwoFactorAuthenticator();
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bool result = tfa.ValidateTwoFactorPIN(key, txtCode.Text)
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```
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## Common Pitfalls
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* Old documentation indicated specifying width and height for the QR code, but changes in QR generation now uses pixels per module (QR "pixel") so using a value too high will result in a huge image that can overrun memory allocations
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* Don't use the secret key and `ManualEntryKey` interchangeably. `ManualEntryKey` is used to enter into the authenticator app when scanning a QR code is impossible and is derived from the secret key ([discussion example](https://github.com/BrandonPotter/GoogleAuthenticator/issues/54))
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# Notes
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On linux, you need to ensure `libgdiplus` is installed if you want to generate QR Codes. See [https://github.com/codebude/QRCoder/issues/227](https://github.com/codebude/QRCoder/issues/227).
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