NFC-99 Web eID for mobile support by SanderKondratjevNortal · Pull Request #64 · web-eid/web-eid-authtoken-validation-dotnet

SanderKondratjevNortal · 2025-11-27T11:05:15Z

Signed-off-by: Sander Kondratjev sander.kondratjev@nortal.com

example/src/WebEid.AspNetCore.Example/Controllers/Api/AuthController.cs

mrts · 2026-02-12T19:02:28Z

example/src/WebEid.AspNetCore.Example/Pages/WebEidCallback.cshtml

+
+        const path = window.location.pathname;
+        let endpoint;
+        if (path === "/sign/mobile/certificate") {


As discussed during Java code review, you can just validate the path and then reuse it directly:

const path = window.location.pathname; const allowedEndpoints = ["/sign/mobile/certificate", "/sign/mobile/signature"]; if (!allowedEndpoints.includes(path)) { const error = new Error("Unexpected callback path: " + path); error.code = "INVALID_CALLBACK_PATH"; throw error; }

This remains yet to be updated.

example/src/WebEid.AspNetCore.Example/Pages/WebEidLogin.cshtml

example/src/WebEid.AspNetCore.Example/Signing/MobileSigningService.cs

example/src/WebEid.AspNetCore.Example/WebEid.AspNetCore.Example.csproj

src/WebEid.Security/AuthToken/SupportedSignatureAlgorithm.cs

src/WebEid.Security/Validator/CertValidators/ISubjectCertificateValidator.cs

src/WebEid.Security/Validator/CertValidators/SubjectCertificateNotRevokedValidator.cs

src/WebEid.Security/Validator/CertValidators/SubjectCertificatePolicyValidator.cs

src/WebEid.Security/Validator/CertValidators/SubjectCertificateTrustedValidator.cs

src/WebEid.Security/Validator/CertValidators/SubjectCertificateValidatorBatch.cs

src/WebEid.Security/Validator/VersionValidators/AuthTokenVersion1Validator.cs

src/WebEid.Security/Validator/VersionValidators/AuthTokenVersion11Validator.cs

mrts · 2026-03-05T15:13:14Z

example/src/WebEid.AspNetCore.Example/Controllers/Api/AuthController.cs

            AddNewClaimIfCertificateHasData(claims, ClaimTypes.Name, certificate.GetSubjectCn);

-            var claimsIdentity = new ClaimsIdentity(claims, CookieAuthenticationDefaults.AuthenticationScheme);
+            if (!string.IsNullOrEmpty(authToken.UnverifiedSigningCertificate))


You need a v1.1 format check here to avoid the following attack (also in Java):

Attacker gets a valid web-eid:1 auth token from client-side flow to log in normally

Before posting to /auth/login, attacker edits JSON and adds:

unverifiedSigningCertificate: any base64 cert they want

supportedSignatureAlgorithms: any list

Server validates token as v1, v1 validator ignores these two fields and authentication succeeds

AuthController stores those untrusted values into auth cookie claims (signingCertificate, supportedSignatureAlgorithms)

Later attacker calls /sign/mobile/init; MobileSigningService sees those claims, skips certificate initialization and builds mobile sign request directly from injected claim values

Signing flow now runs with attacker-chosen signing certificate metadata, not server-validated metadata

This is not immediately dangerous, but it bypasses v1.1 safety checks and may introduce some subtle attacks against real systems that we cannot even foresee at the moment.

A simple

var isV11 = authToken.Format?.StartsWith("web-eid:1.1", StringComparison.OrdinalIgnoreCase) == true;

check and using isV11 in the if block would guard against this.

This is not implemented yet.

mrts · 2026-03-05T15:19:15Z

src/WebEid.Security/Validator/VersionValidators/AuthTokenVersion11Validator.cs

+
+            bool hasInvalid =
+                algorithms.Any(a =>
+                    !SupportedSigningCryptoAlgorithms.Contains(a.CryptoAlgorithm) ||


a can be null here, then a.CryptoAlgorithm will fail with NullReferenceException.

src/WebEid.Security.Tests/Validator/VersionValidators/AuthTokenV11CertificateTest.cs

…eid example Signed-off-by: Sander Kondratjev <sander.kondratjev@nortal.com>

…bile auth error layout

Signed-off-by: Sander Kondratjev <sander.kondratjev@nortal.com>

mrts · 2026-03-05T15:33:40Z

src/WebEid.Security/Validator/CertValidators/SubjectCertificatePurposeValidator.cs

    /// Validates the purpose of the user certificate from the authentication token.
    /// </summary>
-    public class SubjectCertificatePurposeValidator : ISubjectCertificateValidator
+    internal class SubjectCertificatePurposeValidator : ISubjectCertificateValidator


Can this be sealed as others?

Suggested change

internal class SubjectCertificatePurposeValidator : ISubjectCertificateValidator

internal sealed class SubjectCertificatePurposeValidator : ISubjectCertificateValidator

mrts · 2026-04-02T13:59:49Z

example/src/WebEid.AspNetCore.Example/Pages/WebEidCallback.cshtml

+
+        const path = window.location.pathname;
+        let endpoint;
+        if (path === "/sign/mobile/certificate") {


This remains yet to be updated.

mrts · 2026-04-02T14:08:04Z

example/src/WebEid.AspNetCore.Example/Pages/Welcome.cshtml

+        }
+    });
+
+    function isMobileDevice() {


We should extract this function to a separate module and reuse it to make code more DRY.

mrts · 2026-04-02T14:14:31Z

example/src/WebEid.AspNetCore.Example/Controllers/Api/AuthController.cs

            AddNewClaimIfCertificateHasData(claims, ClaimTypes.Name, certificate.GetSubjectCn);

-            var claimsIdentity = new ClaimsIdentity(claims, CookieAuthenticationDefaults.AuthenticationScheme);
+            if (!string.IsNullOrEmpty(authToken.UnverifiedSigningCertificate))


This is not implemented yet.

mrts · 2026-04-02T14:41:06Z

example/src/WebEid.AspNetCore.Example/Controllers/Api/AuthController.cs

-            var claimsIdentity = new ClaimsIdentity(claims, CookieAuthenticationDefaults.AuthenticationScheme);
+            var signingCertificate = authToken.UnverifiedSigningCertificates != null &&
+                                     authToken.UnverifiedSigningCertificates.Count > 0
+                ? authToken.UnverifiedSigningCertificates[0]


Noting that currently a user authenticating with multiple signing certificates cannot choose a non-first certificate during signing, but I guess this is intended.

mrts · 2026-04-02T14:47:04Z

example/src/WebEid.AspNetCore.Example/WebEid.AspNetCore.Example.csproj

+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation" Version="10.0.3" />
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="10.0.3" />
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.OpenIdConnect" Version="10.0.3" />
    <PackageReference Include="Microsoft.Identity.Web" Version="3.8.4" />


Should we update other packages as well?

mrts · 2026-04-02T14:50:34Z

src/WebEid.Security/Validator/AuthTokenValidator.cs

    using Exceptions;
    using Microsoft.Extensions.Logging;
-    using Microsoft.IdentityModel.Tokens;
    using Newtonsoft.Json;


Let's use System.Text.Json instead of Newtonsoft.Json and remove Newtonsoft.Json from project. Also update project dependencies and .NET version to 10 like with example.

SanderKondratjevNortal changed the base branch from main to web-eid-mobile November 27, 2025 11:05

SanderKondratjevNortal force-pushed the NFC-99 branch 2 times, most recently from 0315bc1 to 076734c Compare November 27, 2025 12:55

SanderKondratjevNortal force-pushed the NFC-99 branch 2 times, most recently from 46c9709 to 025a58c Compare January 27, 2026 09:07

mrts requested changes Feb 12, 2026

View reviewed changes

mrts requested changes Feb 13, 2026

View reviewed changes

SanderKondratjevNortal force-pushed the NFC-99 branch from 8561d8d to dba0714 Compare February 17, 2026 16:01

mrts requested changes Mar 5, 2026

View reviewed changes

SanderKondratjevNortal added 3 commits March 9, 2026 15:13

NFC-99 Add web-eid-1.1 token support with Web eID for Mobile for web-…

df10605

…eid example Signed-off-by: Sander Kondratjev <sander.kondratjev@nortal.com>

NFC-118 Switch request/response JSON fields to camelCase and unify mo…

8911767

…bile auth error layout

NFC-127 Bump project from .NET 8 to .NET 10

15e35e1

Signed-off-by: Sander Kondratjev <sander.kondratjev@nortal.com>

SanderKondratjevNortal force-pushed the NFC-99 branch from d50a7c8 to 15e35e1 Compare March 9, 2026 13:13

SanderKondratjevNortal added 2 commits March 23, 2026 17:01

NFC-115 Implement minimal multiple signing certification solution

9245610

NFC-135 Update EU funding logo

265952a

SanderKondratjevNortal force-pushed the NFC-99 branch from bd1edc8 to 265952a Compare March 23, 2026 15:01

mrts requested changes Apr 2, 2026

View reviewed changes

mrts reviewed Apr 2, 2026

View reviewed changes

	internal class SubjectCertificatePurposeValidator : ISubjectCertificateValidator
	internal sealed class SubjectCertificatePurposeValidator : ISubjectCertificateValidator

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mrts Mar 5, 2026 •

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