How to Manually Validate a JWT Asp.Net Core?

How to Manually Validate a JWT Asp.Net Core?

In ASP.NET Core, you can manually validate a JSON Web Token (JWT) by following these steps:

  1. Install the System.IdentityModel.Tokens.Jwt package from NuGet if it is not already installed.

  2. Create an instance of the JwtSecurityTokenHandler class, which is used to validate and handle JWT tokens.

  3. Parse the JWT token string into a SecurityToken instance using the JwtSecurityTokenHandler class's ReadJwtToken method.

  4. Create an instance of the TokenValidationParameters class and set its properties as needed. This class contains the parameters used to validate the JWT token, such as the token's issuer, audience, signing key, and so on.

  5. Call the ValidateToken method of the JwtSecurityTokenHandler class and pass in the JWT token string, the TokenValidationParameters instance, and an output SecurityToken instance to receive the validated token.

  6. Check if the validation succeeded by checking if the SecurityToken instance received from the ValidateToken method is not null.

Here is some sample code that shows how to manually validate a JWT token:

using System.IdentityModel.Tokens.Jwt; using Microsoft.IdentityModel.Tokens; // The JWT token string to validate string jwtToken = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"; // Create an instance of the JwtSecurityTokenHandler class var tokenHandler = new JwtSecurityTokenHandler(); // Parse the JWT token string into a SecurityToken instance var securityToken = tokenHandler.ReadJwtToken(jwtToken); // Create an instance of the TokenValidationParameters class var validationParameters = new TokenValidationParameters { ValidateIssuer = true, ValidateAudience = true, ValidateIssuerSigningKey = true, ValidIssuer = "your-issuer", ValidAudience = "your-audience", IssuerSigningKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes("your-secret-key")) }; // Validate the JWT token SecurityToken validatedToken; var claimsPrincipal = tokenHandler.ValidateToken(jwtToken, validationParameters, out validatedToken); // Check if the validation succeeded if (validatedToken != null) { // The JWT token is valid } else { // The JWT token is invalid }

In this example, the ValidateToken method of the JwtSecurityTokenHandler class is used to validate the JWT token. The TokenValidationParameters instance contains the parameters used to validate the token, such as the issuer, audience, signing key, and so on. If the validation succeeds, the validatedToken variable will contain the validated token, and you can access its claims by accessing the claimsPrincipal variable.

Examples

  1. "ASP.NET Core JWT manual validation"

    • Description: Learn how to manually validate a JWT in ASP.NET Core without using built-in middleware.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters (Issuer, Audience, etc.) }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  2. "C# validate JWT signature manually"

    • Description: Understand how to manually validate the signature of a JWT in C#.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters including ValidateIssuerSigningKey ValidateIssuerSigningKey = true, IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("your-secret-key")) }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  3. "ASP.NET Core JWT validation without middleware"

    • Description: Explore how to perform JWT validation manually in ASP.NET Core without relying on middleware.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters (Issuer, Audience, etc.) }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  4. "C# JWT validate expiration manually"

    • Description: Learn how to manually validate the expiration of a JWT in C#.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters including ValidateLifetime ValidateLifetime = true, RequireExpirationTime = true, ClockSkew = TimeSpan.Zero // Optionally set clock skew }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  5. "JWT validate claims manually C#"

    • Description: Understand how to manually validate specific claims in a JWT in C#.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters including ValidateIssuer, ValidateAudience, etc. RoleClaimType = "roles" }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  6. "C# JWT validate issuer and audience manually"

    • Description: Explore how to manually validate the issuer and audience of a JWT in C#.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters including ValidateIssuer and ValidateAudience }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  7. "ASP.NET Core JWT validate multiple issuers manually"

    • Description: Learn how to manually validate JWTs from multiple issuers in ASP.NET Core.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters including ValidIssuers ValidIssuers = new[] { "issuer1", "issuer2" } }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  8. "C# JWT validate audience with multiple values manually"

    • Description: Understand how to manually validate the audience with multiple values in a JWT in C#.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters including ValidAudiences ValidAudiences = new[] { "audience1", "audience2" } }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  9. "C# JWT manual validation custom validation logic"

    • Description: Explore how to incorporate custom validation logic during manual JWT validation in C#.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters ValidateIssuer = true, IssuerValidator = (issuer, securityToken, validationParameters) => CustomIssuerValidation(issuer) }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

  10. "ASP.NET Core JWT manual validation with custom clock"

    • Description: Learn how to perform manual JWT validation in ASP.NET Core with a custom clock implementation.
    // Code Snippet var tokenHandler = new JwtSecurityTokenHandler(); var validationParameters = new TokenValidationParameters { // Set validation parameters including ClockSkew ClockSkew = TimeSpan.Zero, CustomLifetimeValidator = (before, expires, token, parameters) => CustomLifetimeValidation(before, expires) }; ClaimsPrincipal principal = tokenHandler.ValidateToken(token, validationParameters, out SecurityToken validatedToken);

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