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| 1 | +namespace Giraffe |
| 2 | + |
| 3 | +/// <summary> |
| 4 | +/// CSRF (Cross-Site Request Forgery) protection helpers for Giraffe. |
| 5 | +/// Provides anti-forgery token generation and validation. |
| 6 | +/// </summary> |
| 7 | +[<RequireQualifiedAccess>] |
| 8 | +module Csrf = |
| 9 | + open System |
| 10 | + open System.Security.Cryptography |
| 11 | + open System.Text |
| 12 | + open System.Threading.Tasks |
| 13 | + open Microsoft.AspNetCore.Http |
| 14 | + open Microsoft.Extensions.Logging |
| 15 | + open Microsoft.AspNetCore.Antiforgery |
| 16 | + |
| 17 | + // Defaults are selected to what developers would expect from ASP.NET Core application. |
| 18 | + |
| 19 | + /// <summary> |
| 20 | + /// Default CSRF token header name |
| 21 | + /// </summary> |
| 22 | + [<Literal>] |
| 23 | + let DefaultCsrfTokenHeaderName = "X-CSRF-TOKEN" |
| 24 | + |
| 25 | + /// <summary> |
| 26 | + /// Default CSRF token form field name |
| 27 | + /// </summary> |
| 28 | + [<Literal>] |
| 29 | + let DefaultCsrfTokenFormFieldName = "__RequestVerificationToken" |
| 30 | + |
| 31 | + /// <summary> |
| 32 | + /// Validates the CSRF token from the request. |
| 33 | + /// Checks for token in header (X-CSRF-TOKEN) or form field (__RequestVerificationToken). |
| 34 | + /// </summary> |
| 35 | + /// <param name="invalidTokenHandler">Optional custom handler for invalid tokens. If None, returns 403 Forbidden with logged warning.</param> |
| 36 | + /// <param name="next">The next HttpFunc</param> |
| 37 | + /// <param name="ctx">The HttpContext</param> |
| 38 | + /// <returns>HttpFuncResult</returns> |
| 39 | + let validateCsrfTokenExt (invalidTokenHandler: HttpHandler option) : HttpHandler = |
| 40 | + fun (next: HttpFunc) (ctx: HttpContext) -> |
| 41 | + task { |
| 42 | + let antiforgery = ctx.GetService<IAntiforgery>() |
| 43 | + |
| 44 | + try |
| 45 | + let! isValid = antiforgery.IsRequestValidAsync ctx |
| 46 | + |
| 47 | + if isValid then |
| 48 | + return! next ctx |
| 49 | + else |
| 50 | + let defaultHandler = |
| 51 | + fun (next: HttpFunc) (ctx: HttpContext) -> |
| 52 | + let logger = ctx.GetLogger("Giraffe.Csrf") |
| 53 | + |
| 54 | + logger.LogWarning( |
| 55 | + "CSRF token validation failed for request to {Path}", |
| 56 | + ctx.Request.Path |
| 57 | + ) |
| 58 | + |
| 59 | + ctx.Response.StatusCode <- 403 |
| 60 | + Task.FromResult(Some ctx) |
| 61 | + |
| 62 | + let handler = invalidTokenHandler |> Option.defaultValue defaultHandler |
| 63 | + return! handler earlyReturn ctx |
| 64 | + with ex -> |
| 65 | + let defaultHandler = |
| 66 | + fun (next: HttpFunc) (ctx: HttpContext) -> |
| 67 | + let logger = ctx.GetLogger("Giraffe.Csrf") |
| 68 | + logger.LogWarning(ex, "CSRF token validation error for request to {Path}", ctx.Request.Path) |
| 69 | + ctx.Response.StatusCode <- 403 |
| 70 | + Task.FromResult(Some ctx) |
| 71 | + |
| 72 | + let handler = invalidTokenHandler |> Option.defaultValue defaultHandler |
| 73 | + return! handler earlyReturn ctx |
| 74 | + } |
| 75 | + |
| 76 | + /// <summary> |
| 77 | + /// Validates the CSRF token from the request with default error handling. |
| 78 | + /// Checks for token in header (X-CSRF-TOKEN) or form field (__RequestVerificationToken). |
| 79 | + /// Uses default error handling (403 Forbidden) for invalid tokens. |
| 80 | + /// </summary> |
| 81 | + /// <param name="next">The next HttpFunc</param> |
| 82 | + /// <param name="ctx">The HttpContext</param> |
| 83 | + /// <returns>HttpFuncResult</returns> |
| 84 | + let validateCsrfToken: HttpHandler = validateCsrfTokenExt None |
| 85 | + |
| 86 | + /// <summary> |
| 87 | + /// Alias for validateCsrfToken - validates anti-forgery tokens from requests. |
| 88 | + /// </summary> |
| 89 | + let requireAntiforgeryToken = validateCsrfToken |
| 90 | + |
| 91 | + /// <summary> |
| 92 | + /// Alias for validateCsrfTokenExt - validates anti-forgery tokens from requests with custom error handler. |
| 93 | + /// </summary> |
| 94 | + let requireAntiforgeryTokenExt = validateCsrfTokenExt |
| 95 | + |
| 96 | + /// <summary> |
| 97 | + /// Generates a CSRF token and adds it to the HttpContext items for use in views. |
| 98 | + /// The token can be accessed via ctx.Items["CsrfToken"] and ctx.Items["CsrfTokenHeaderName"]. |
| 99 | + /// </summary> |
| 100 | + /// <param name="next">The next HttpFunc</param> |
| 101 | + /// <param name="ctx">The HttpContext</param> |
| 102 | + /// <returns>HttpFuncResult</returns> |
| 103 | + let generateCsrfToken: HttpHandler = |
| 104 | + fun (next: HttpFunc) (ctx: HttpContext) -> |
| 105 | + task { |
| 106 | + let antiforgery = ctx.GetService<IAntiforgery>() |
| 107 | + let tokens = antiforgery.GetAndStoreTokens ctx |
| 108 | + |
| 109 | + // Store token for view rendering |
| 110 | + ctx.Items.["CsrfToken"] <- tokens.RequestToken |
| 111 | + ctx.Items.["CsrfTokenHeaderName"] <- tokens.HeaderName |
| 112 | + |
| 113 | + return! next ctx |
| 114 | + } |
| 115 | + |
| 116 | + /// <summary> |
| 117 | + /// Returns the CSRF token as JSON for AJAX requests. |
| 118 | + /// Response format: { "token": "...", "headerName": "X-CSRF-TOKEN" } |
| 119 | + /// </summary> |
| 120 | + /// <param name="next">The next HttpFunc</param> |
| 121 | + /// <param name="ctx">The HttpContext</param> |
| 122 | + /// <returns>HttpFuncResult</returns> |
| 123 | + let csrfTokenJson: HttpHandler = |
| 124 | + fun (next: HttpFunc) (ctx: HttpContext) -> |
| 125 | + task { |
| 126 | + let antiforgery = ctx.GetService<IAntiforgery>() |
| 127 | + let tokens = antiforgery.GetAndStoreTokens ctx |
| 128 | + |
| 129 | + let response = |
| 130 | + {| |
| 131 | + token = tokens.RequestToken |
| 132 | + headerName = tokens.HeaderName |
| 133 | + |} |
| 134 | + |
| 135 | + return! Core.json response next ctx |
| 136 | + } |
| 137 | + |
| 138 | + /// <summary> |
| 139 | + /// Returns the CSRF token as an HTML hidden input field. |
| 140 | + /// Can be included directly in forms. |
| 141 | + /// </summary> |
| 142 | + /// <param name="next">The next HttpFunc</param> |
| 143 | + /// <param name="ctx">The HttpContext</param> |
| 144 | + /// <returns>HttpFuncResult</returns> |
| 145 | + let csrfTokenHtml: HttpHandler = |
| 146 | + fun (next: HttpFunc) (ctx: HttpContext) -> |
| 147 | + task { |
| 148 | + let antiforgery = ctx.GetService<IAntiforgery>() |
| 149 | + let tokens = antiforgery.GetAndStoreTokens(ctx) |
| 150 | + |
| 151 | + let html = |
| 152 | + sprintf "<input type=\"hidden\" name=\"%s\" value=\"%s\" />" tokens.HeaderName tokens.RequestToken |
| 153 | + |
| 154 | + return! Core.htmlString html next ctx |
| 155 | + } |
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