AWS Lambda

// Generated by ChatGPT
def lambda_handler(event, context):
    # Accessing event data
    print("Received event:", event)
    
    # Accessing context data
    print("Request ID:", context.aws_request_id)
    print("Function Name:", context.function_name)

    # Your processing logic here
    return {
        'statusCode': 200,
        'body': 'Hello from Lambda!'
    }

cd <to-the-created-folder>
dotnet nuget add source https://api.nuget.org/v3/index.json -n nuget.org
dotnet new --install Amazon.Lambda.Templates
dotnet new lambda.EmptyFunction --name SymKeyGen
cd SymKeyGen
cd src
notepad SymKeyGen.csproj 
// make the following changes

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework> //Change here
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
    <AWSProjectType>Lambda</AWSProjectType>
    <!-- This property makes the build directory similar to a publish directory and helps the AWS .NET Lambda Mock Test Tool find project dependencies. -->
    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
    <!-- Generate ready to run images during publishing to improve cold start time. -->
    <PublishReadyToRun>false</PublishReadyToRun> //Change here
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Amazon.Lambda.Core" Version="2.3.0" />
  </ItemGroup>
</Project>

dotnet add package Amazon.Lambda.Core
dotnet add package Amazon.Lambda.APIGatewayEvents
dotnet add package AWSSDK.S3
dotnet add package Newtonsoft.Json
notepad Function.cs

//Generated by ChatGPT

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using Amazon.Lambda.Core;
using Amazon.Lambda.APIGatewayEvents;
using Amazon.S3;
using Amazon.S3.Model;
using Newtonsoft.Json;
using System.Text.RegularExpressions;

[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]

public class Function
{
    private readonly string bucketName = "radifineuniquebucketname"; // Update with your S3 bucket name
    private readonly IAmazonS3 s3Client;

    public Function()
    {
        s3Client = new AmazonS3Client();
    }

    // Entry point for the Lambda function
    public APIGatewayProxyResponse FunctionHandler(APIGatewayProxyRequest request, ILambdaContext context)
    {
        return GenerateKey(request, context);
    }

    public APIGatewayProxyResponse GenerateKey(APIGatewayProxyRequest request, ILambdaContext context)
    {
        // Parse input parameters from the request
        if (request.QueryStringParameters == null || 
            !request.QueryStringParameters.TryGetValue("input", out var hexInput))
        {
            return new APIGatewayProxyResponse
            {
                StatusCode = 400,
                Body = JsonConvert.SerializeObject(new { Error = "Input parameter is required." }),
                Headers = new System.Collections.Generic.Dictionary<string, string>
                {
                    { "Content-Type", "application/json" }
                }
            };
        }

        // Decode hex input to original string
        string inputParam = HexToString(hexInput);

        // Validate the input
        if (!IsValidInput(inputParam))
        {
            return new APIGatewayProxyResponse
            {
                StatusCode = 400,
                Body = JsonConvert.SerializeObject(new { Error = "Invalid input parameter." }),
                Headers = new System.Collections.Generic.Dictionary<string, string>
                {
                    { "Content-Type", "application/json" }
                }
            };
        }

        // Generate a symmetric key based on the input parameter
        byte[] symmetricKey = GenerateKeyFromInput(inputParam);
        var base64Key = Convert.ToBase64String(symmetricKey);

        // Save the key to S3
        string fileName = $"{inputParam}.txt"; // Name the file using the input string
        var putRequest = new PutObjectRequest
        {
            BucketName = bucketName,
            Key = fileName,
            ContentBody = base64Key,
            ContentType = "text/plain"
        };

        // Upload the key to S3
        s3Client.PutObjectAsync(putRequest).Wait();

        // Return the key and success message
        var response = new
        {
            Key = base64Key,
            Message = "Key generated and saved successfully."
        };

        return new APIGatewayProxyResponse
        {
            StatusCode = 200,
            Body = JsonConvert.SerializeObject(response),
            Headers = new System.Collections.Generic.Dictionary<string, string>
            {
                { "Content-Type", "application/json" }
            }
        };
    }

    private bool IsValidInput(string input)
    {
        // Check for null or empty
        if (string.IsNullOrWhiteSpace(input))
            return false;

        // Check length (e.g., maximum length of 255 characters)
        if (input.Length > 255)
            return false;

        // Validate against a regex pattern (adjust as necessary)
        string pattern = @"^[a-zA-Z0-9\-\.]+$"; // Example pattern: allows alphanumeric, hyphens, and dots
        return Regex.IsMatch(input, pattern);
    }

    private byte[] GenerateKeyFromInput(string input)
    {
        using (var sha256 = SHA256.Create())
        {
            // Hash the input to create a fixed-length key
            return sha256.ComputeHash(Encoding.UTF8.GetBytes(input));
        }
    }

    private string HexToString(string hex)
    {
        StringBuilder result = new StringBuilder(hex.Length / 2);
        for (int i = 0; i < hex.Length; i += 2)
        {
            result.Append((char)Convert.ToByte(hex.Substring(i, 2), 16));
        }
        return result.ToString();
    }
}

dotnet build
dotnet publish -c Release -o ./publish
Compress-Archive -Path * -DestinationPath ../SymKeyGenSrc.zip