Updated to enforce nonce in example and documentaion

Introduces security-model guidance covering provider invariants, expected auth failure modes, and integration-safe handling.

README.md

@@ -40,7 +40,7 @@ In the consuming application's `composer.json`:
     }
   ],
   "require": {
-    "dixon/blackwall-auth-sdk": "*"
+    "andydixon/blackwall-auth-sdk": "*"
   }
 }
 ```
@@ -77,12 +77,20 @@ $config = Config::fromArray([
 $client = new AuthClient($config);
 
 // Step 1: redirect user to provider
-$auth = $client->buildAuthorisationUrl();
+$auth = $client->buildAuthorisationUrl([
+    'extra' => [
+        // Include nonce in the authorisation request for OIDC.
+        'nonce' => rtrim(strtr(base64_encode(random_bytes(32)), '+/', '-_'), '='),
+    ],
+]);
 header('Location: ' . $auth['url']);
 exit;
 ```
 
+The generated authorisation request URL will include `nonce=...` alongside `state`, `scope`, and the PKCE parameters.
+
 For callback handling, see `docs/INTEGRATION_GUIDE.md`.
+For provider-side threat/invariant assumptions, see `docs/SECURITY_MODEL.md`.
 
 Minimal callback example:
 
@@ -123,10 +131,33 @@ This wrapper now delegates to `BlackWall\Auth\AuthClient`.
 ## Security notes
 
 - Always validate OAuth `state` in callback handlers.
+- Handle provider callback errors (`error`, `error_description`) explicitly; treat `access_denied` as an expected user/authorisation outcome rather than a transport failure.
+- Treat `invalid_scope` as a client-configuration mismatch: requested scopes must be a subset of scopes allowed on the provider client.
+- Expect `access_denied` even after the consent page is displayed if provider-side project membership or tenant scope changes before consent submission.
+- Expect provider token introspection to return `active=false` when user/project/client state is no longer active.
+- Expect revoked JWT access tokens to be rejected by provider `userinfo` even before token expiry.
+- Register only HTTPS redirect URIs in provider client settings (HTTP should be used only for localhost loopback during development).
+- Use OAuth/portal authentication endpoints for end users; provider admin login endpoints enforce separate admin scope checks.
+- For provider admin enrolment URL export operations, use `POST` with CSRF protection; do not automate them via unauthenticated `GET` links.
+- Handle provider CSV exports with formula-injection safety in mind if opening them in spreadsheet applications.
+- Treat generated enrolment URLs as secrets and keep them out of URL query strings and request logs.
+- For reverse-proxy deployments, harden trusted proxy/IP forwarding configuration to prevent spoofed client IP headers.
+- Prefer narrowly scoped trusted-proxy entries (explicit IPs/CIDR ranges) instead of broad network trust.
+- Keep client-side admin mutation retries idempotent; approval workflows can be lock-serialised and should not be assumed to execute twice.
+- Do not submit parallel approve/reject/cancel decisions for the same approval request ID.
+- Apply bounded CSV import sizes and row counts for admin bulk-user operations.
+- Never place client secrets, refresh tokens, or access tokens in URL query strings.
+- For OIDC providers, include a per-request `nonce` in authorisation requests.
+- Ensure requested `scope` values in SDK config/examples (for example `offline_access`) are enabled on the provider-side client before rollout.
+- Expect refresh-token exchange to fail (`invalid_grant`) if provider-side client scopes were tightened and the refresh token now carries disallowed scopes.
+- For direct Cryptbin API usage, send `key_b64url` on unwrap calls; provider rejects key-mismatch unwrap attempts with `403 Forbidden`.
+- For newly created Cryptbin items, continue using the creating WebAuthn credential for unwrap/update/delete flows.
 - Always use HTTPS in production.
 - Store refresh tokens securely.
 - Keep access tokens out of logs and browser-visible output.
 - Use short session lifetimes where possible.
+- `Config::fromArray()` enforces HTTPS URLs by default.
+- For localhost-only development over HTTP, set `allowInsecureHttp => true`.
 
 ## Repository layout
 

docs/INTEGRATION_GUIDE.md

@@ -25,7 +25,15 @@ $client = new AuthClient(Config::fromArray([
 ]));
 
 if (!isset($_SESSION['user'])) {
-    $auth = $client->buildAuthorisationUrl();
+    $auth = $client->buildAuthorisationUrl([
+        'extra' => [
+            // Include nonce in the authorisation request for OIDC.
+            'nonce' => rtrim(strtr(base64_encode(random_bytes(32)), '+/', '-_'), '='),
+        ],
+    ]);
+    // Prevent stale redirects from being reused from cache.
+    header('Cache-Control: no-store, no-cache, must-revalidate, max-age=0');
+    header('Pragma: no-cache');
     header('Location: ' . $auth['url']);
     exit;
 }
@@ -33,6 +41,8 @@ if (!isset($_SESSION['user'])) {
 echo 'Already signed in.';
 ```
 
+The resulting redirect request includes `nonce=...` in the provider authorisation URL, together with `state`, `code_challenge`, and the rest of the OAuth/OIDC query parameters.
+
 ## 2. Handle callback
 
 ```php
@@ -54,6 +64,16 @@ $client = new AuthClient(Config::fromArray([
     'redirectUri' => 'https://your-app.example/callback.php',
 ]));
 
+if (isset($_GET['error'])) {
+    $error = (string) $_GET['error'];
+    $description = isset($_GET['error_description']) ? (string) $_GET['error_description'] : 'Unknown provider error';
+    // access_denied is a normal authorisation outcome (for example, membership
+    // revoked, privilege changed, or user denied consent between request and submit).
+    // invalid_scope usually means the app requested scopes not enabled on the provider client.
+    http_response_code(in_array($error, ['access_denied', 'invalid_scope'], true) ? 403 : 400);
+    exit('Authorisation failed: ' . $description);
+}
+
 $result = $client->handleCallback($_GET);
 
 $_SESSION['user'] = [
@@ -117,10 +137,45 @@ try {
 }
 ```
 
+`UserInfoException` with `invalid_token` can occur when provider-side subject scope is no longer active (for example user/project disabled) between token issuance and userinfo retrieval.
+`TokenExchangeException` with `invalid_grant` can also occur when provider-side client/user/project state is inactive at exchange time.
+Token introspection can return `active=false` when the token subject (user/project) or client has since been disabled.
+Provider JWT access tokens are now revocation-aware at `userinfo`; revoked JWTs can fail before natural expiry.
+Refresh-token exchange can return `invalid_grant` when provider client scope policy has been tightened and stored refresh scopes are no longer allowed.
+Provider login/authorisation steps can also fail with `access_denied` when account status is disabled before completion.
+WebAuthn-based login verification can return credential-style failures for disabled accounts even when authenticator assertions are otherwise valid.
+Existing authenticated sessions may also be invalidated when account status changes to disabled.
+OAuth authorisation consent submission can return `access_denied` if the account becomes inactive between session establishment and consent completion.
+OAuth authorisation can also return `invalid_scope` if requested scopes are not explicitly allowed on the provider client configuration.
+Provider user/project assignment views may exclude disabled projects even if historical assignments exist.
+
 ## Operational guidance
 
 - Keep provider URLs in environment variables, not hard-coded.
 - Avoid printing tokens in production pages.
+- Expect `429 Too Many Requests` from provider control endpoints under abuse protection; implement backoff/retry instead of tight loops.
+- Apply the same backoff strategy for provider `userinfo` calls that return `429 Too Many Requests`.
+- For token exchange and refresh, apply bounded retry/backoff on transient provider failures instead of immediate repeated retries.
+- Use exactly one client authentication method per token/control request (do not send both HTTP Basic and `client_secret` form fields together).
+- If you call provider WebAuthn login challenge/verify endpoints directly, use `POST` only.
+- Treat admin enrolment URL export as a state-changing operation: call it with `POST` and include a valid CSRF token.
+- Treat provider CSV exports as untrusted input in spreadsheet tools; prefer importing into systems that neutralise formula cells.
+- Treat enrolment URLs as sensitive bearer material: do not place them in redirect query parameters, logs, or analytics tags; keep them in one-time server-side flash/session state.
+- If your deployment runs behind reverse proxies, ensure trusted-proxy configuration is strict so spoofed forwarding headers cannot bypass IP-based abuse controls.
+- Trusted proxy allowlists may be expressed as explicit IPs or CIDR ranges; avoid broad ranges and keep proxy chains minimal.
+- For approval-driven admin mutations, assume provider-side execution is serialised per approval item; client retries should still be idempotent and bounded.
+- This serialisation applies across approval actions (approve/reject/cancel), so clients should avoid parallel decision submissions for the same request ID.
+- For provider CSV-based user import operations, enforce strict file-size and row-count limits in automation tooling and surface clear operator errors on limit breaches.
+- Configure OAuth client redirect URIs as HTTPS in production; reserve HTTP for localhost loopback testing only.
+- Assume provider rate limits are enforced per source identity (for example IP) and shared across related auth endpoints.
+- Treat report/export-style provider endpoints as high-cost and expect stricter rate limits.
 - Rotate client secrets for confidential clients.
+- Do not transport secrets or tokens in URL query parameters; keep them in server-side session or secure storage only.
+- Add a unique `nonce` to each OIDC authorisation request.
+- Keep `state`, `nonce`, and PKCE values within standard URL-safe formats/lengths; malformed values can be rejected by provider validation.
 - Validate `state` on every callback request.
 - Use secure session cookies (`Secure`, `HttpOnly`, `SameSite=Lax` or stricter).
+- HTTPS URLs are enforced by default in `Config::fromArray()`.
+- For localhost-only HTTP testing, explicitly set `allowInsecureHttp => true`.
+- If you call Cryptbin unwrap APIs directly, include the original share key as `key_b64url`; unwrap now returns `403 Forbidden` when key proof does not match metadata verifier.
+- New Cryptbin items may also bind unwrap/update/delete operations to the creating WebAuthn credential; use the same authenticator for follow-up operations.

docs/MIGRATION.md

@@ -26,6 +26,7 @@ $user = $client->getUserInfo($tokens->accessToken);
 ## Key differences
 
 - Method spelling uses British English in the new API: `buildAuthorisationUrl()`.
+- The legacy method name `getAuthorizationUrl()` is unchanged for backwards compatibility.
 - Token responses are strongly typed via `TokenSet`.
 - Errors are represented by specific exception classes.
 - HTTP transport is swappable via `HttpClientInterface`.

docs/SECURITY_MODEL.md

@@ -0,0 +1,27 @@
+# BlackWall Provider Security Model (SDK View)
+
+Last reviewed: 2026-02-26
+
+This document summarises provider-side security guarantees that SDK integrators should design around.
+
+## Threat Assumptions
+
+- Provider is internet-exposed.
+- Attackers can register and attempt tenant-boundary abuse.
+- OAuth/WebAuthn endpoints are abuse targets and may rate limit.
+
+## Invariants Integrators Should Assume
+
+1. Tenant/project/user/client scope is enforced server-side and can change between request steps.
+2. OAuth authorize can fail with `invalid_scope` if requested scopes are not currently allowed for the client.
+3. Token/refresh exchange can fail with `invalid_grant` when subject/client state or scope policy changes.
+4. UserInfo can fail for revoked/invalid/inactive subjects even before nominal token expiry.
+5. Admin and portal workflows are distinct scope domains; do not mix them in client UX flows.
+
+## Integration Guidance
+
+- Keep requested scopes minimal and aligned to the provider client configuration.
+- Treat `access_denied`, `invalid_scope`, and `invalid_grant` as expected security outcomes, not transport errors.
+- Build retries only for transient failures; do not blindly retry authz/authn denials.
+- Keep enrolment URLs/tokens and OAuth tokens out of URLs, logs, and analytics tags.
+- Use strict HTTPS and secure session-cookie handling in the relying party app.

public_html/callback.php

@@ -16,6 +16,7 @@ foreach ($autoloadCandidates as $file) {
 }
 
 use BlackWallSDK\BlackWallAuth;
+use BlackWall\Auth\Exception\UserInfoException;
 
 $auth = new BlackWallAuth([
     'clientId' => '94d228c4-d4c6-4479-9b02-793e6a73e3f2',
@@ -25,6 +26,15 @@ $auth = new BlackWallAuth([
     'redirectUri' => 'https://test.dixon.cx/callback.php',
 ]);
 
+if (isset($_GET['error'])) {
+    $error = (string) $_GET['error'];
+    $description = isset($_GET['error_description']) ? (string) $_GET['error_description'] : 'Authorisation was denied.';
+    $status = $error === 'access_denied' ? 403 : 400;
+    http_response_code($status);
+    echo 'Authorisation failed: ' . htmlspecialchars($description, ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');
+    exit;
+}
+
 try {
     $result = $auth->handleCallback($_GET);
     $_SESSION['access_token'] = $result['tokens']['access_token'] ?? null;
@@ -33,6 +43,9 @@ try {
 
     header('Location: /');
     exit;
+} catch (UserInfoException $e) {
+    http_response_code(403);
+    echo 'User info access failed: ' . htmlspecialchars($e->getMessage(), ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');
 } catch (Throwable $e) {
     http_response_code(500);
     echo 'Auth failed: ' . htmlspecialchars($e->getMessage(), ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');

public_html/index.php

@@ -39,7 +39,11 @@ if (isset($_GET['logout'])) {
 }
 
 if (!isset($_SESSION['user'])) {
-    $authData = $auth->getAuthorizationUrl();
+    $authData = $auth->getAuthorizationUrl([
+        'extra' => [
+            'nonce' => rtrim(strtr(base64_encode(random_bytes(32)), '+/', '-_'), '='),
+        ],
+    ]);
     header('Location: ' . $authData['url']);
     exit;
 }

src/Auth/Config.php

@@ -13,7 +13,8 @@ final class Config
         public readonly string $redirectUri,
         public readonly ?string $userInfoUrl = null,
         public readonly ?string $clientSecret = null,
-        public readonly string $defaultScope = 'openid profile email'
+        public readonly string $defaultScope = 'openid profile email',
+        public readonly bool $allowInsecureHttp = false
     ) {
     }
 
@@ -28,14 +29,57 @@ final class Config
             }
         }
 
+        $allowInsecureHttp = isset($config['allowInsecureHttp']) && (bool) $config['allowInsecureHttp'];
+        $authorizeUrl = rtrim(trim((string) $config['authorizeUrl']), '/');
+        $tokenUrl = rtrim(trim((string) $config['tokenUrl']), '/');
+        $redirectUri = trim((string) $config['redirectUri']);
+        $userInfoUrl = isset($config['userInfoUrl']) ? rtrim(trim((string) $config['userInfoUrl']), '/') : null;
+
+        self::assertSecureUrl($authorizeUrl, 'authorizeUrl', $allowInsecureHttp);
+        self::assertSecureUrl($tokenUrl, 'tokenUrl', $allowInsecureHttp);
+        self::assertSecureUrl($redirectUri, 'redirectUri', $allowInsecureHttp);
+        if ($userInfoUrl !== null && $userInfoUrl !== '') {
+            self::assertSecureUrl($userInfoUrl, 'userInfoUrl', $allowInsecureHttp);
+        }
+
         return new self(
             clientId: $config['clientId'],
-            authorizeUrl: rtrim($config['authorizeUrl'], '/'),
+            authorizeUrl: $authorizeUrl,
-            tokenUrl: rtrim($config['tokenUrl'], '/'),
+            tokenUrl: $tokenUrl,
-            redirectUri: $config['redirectUri'],
+            redirectUri: $redirectUri,
-            userInfoUrl: isset($config['userInfoUrl']) ? rtrim((string) $config['userInfoUrl'], '/') : null,
+            userInfoUrl: $userInfoUrl,
             clientSecret: isset($config['clientSecret']) ? (string) $config['clientSecret'] : null,
-            defaultScope: isset($config['scope']) ? (string) $config['scope'] : 'openid profile email'
+            defaultScope: isset($config['scope']) ? (string) $config['scope'] : 'openid profile email',
+            allowInsecureHttp: $allowInsecureHttp
         );
     }
+
+    private static function assertSecureUrl(string $url, string $field, bool $allowInsecureHttp): void
+    {
+        $parts = parse_url($url);
+        if ($parts === false || !isset($parts['scheme'])) {
+            throw new \InvalidArgumentException("{$field} must be a valid absolute URL");
+        }
+
+        $scheme = strtolower((string) $parts['scheme']);
+        if (!in_array($scheme, ['https', 'http'], true)) {
+            throw new \InvalidArgumentException("{$field} must use http or https");
+        }
+
+        if ($scheme === 'https') {
+            return;
+        }
+
+        if ($allowInsecureHttp && self::isLocalHost((string) ($parts['host'] ?? ''))) {
+            return;
+        }
+
+        throw new \InvalidArgumentException("{$field} must use https (set allowInsecureHttp=true for localhost development)");
+    }
+
+    private static function isLocalHost(string $host): bool
+    {
+        $normalized = strtolower(trim($host));
+        return in_array($normalized, ['localhost', '127.0.0.1', '::1'], true);
+    }
 }

src/Auth/Http/CurlHttpClient.php

@@ -8,15 +8,19 @@ use BlackWall\Auth\Exception\TransportException;
 
 final class CurlHttpClient implements HttpClientInterface
 {
-    public function __construct(private readonly int $timeoutSeconds = 20)
+    public function __construct(
+        private readonly int $timeoutSeconds = 20,
+        private readonly int $connectTimeoutSeconds = 10
+    )
     {
     }
 
     public function postForm(string $url, array $fields, array $headers = []): array
     {
+        $this->assertValidUrl($url);
         $ch = curl_init($url);
         if ($ch === false) {
-            throw new TransportException('Unable to initialise cURL for POST request');
+            throw new TransportException('Unable to initialise cURL for POST request', 'curl_init_failed');
         }
 
         $headerLines = $this->normaliseHeaders(array_merge([
@@ -29,16 +33,31 @@ final class CurlHttpClient implements HttpClientInterface
             CURLOPT_POSTFIELDS => http_build_query($fields, '', '&', PHP_QUERY_RFC3986),
             CURLOPT_HTTPHEADER => $headerLines,
             CURLOPT_RETURNTRANSFER => true,
+            CURLOPT_CONNECTTIMEOUT => $this->connectTimeoutSeconds,
             CURLOPT_TIMEOUT => $this->timeoutSeconds,
+            CURLOPT_SSL_VERIFYPEER => true,
+            CURLOPT_SSL_VERIFYHOST => 2,
+            CURLOPT_FOLLOWLOCATION => false,
+            CURLOPT_MAXREDIRS => 0,
         ]);
+        if (defined('CURLOPT_PROTOCOLS')) {
+            curl_setopt($ch, CURLOPT_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);
+        }
+        if (defined('CURLOPT_REDIR_PROTOCOLS')) {
+            curl_setopt($ch, CURLOPT_REDIR_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);
+        }
 
         $body = curl_exec($ch);
         $status = (int) curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
+        $errno = curl_errno($ch);
         $error = curl_error($ch);
         curl_close($ch);
 
         if ($body === false) {
-            throw new TransportException($error !== '' ? $error : 'Unknown cURL POST error');
+            throw new TransportException(
+                $error !== '' ? $error : 'Unknown cURL POST error',
+                $errno > 0 ? ('curl_errno_' . $errno) : 'curl_post_failed'
+            );
         }
 
         return ['status' => $status, 'body' => $body];
@@ -46,9 +65,10 @@ final class CurlHttpClient implements HttpClientInterface
 
     public function get(string $url, array $headers = []): array
     {
+        $this->assertValidUrl($url);
         $ch = curl_init($url);
         if ($ch === false) {
-            throw new TransportException('Unable to initialise cURL for GET request');
+            throw new TransportException('Unable to initialise cURL for GET request', 'curl_init_failed');
         }
 
         $headerLines = $this->normaliseHeaders(array_merge([
@@ -58,16 +78,31 @@ final class CurlHttpClient implements HttpClientInterface
         curl_setopt_array($ch, [
             CURLOPT_HTTPHEADER => $headerLines,
             CURLOPT_RETURNTRANSFER => true,
+            CURLOPT_CONNECTTIMEOUT => $this->connectTimeoutSeconds,
             CURLOPT_TIMEOUT => $this->timeoutSeconds,
+            CURLOPT_SSL_VERIFYPEER => true,
+            CURLOPT_SSL_VERIFYHOST => 2,
+            CURLOPT_FOLLOWLOCATION => false,
+            CURLOPT_MAXREDIRS => 0,
         ]);
+        if (defined('CURLOPT_PROTOCOLS')) {
+            curl_setopt($ch, CURLOPT_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);
+        }
+        if (defined('CURLOPT_REDIR_PROTOCOLS')) {
+            curl_setopt($ch, CURLOPT_REDIR_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);
+        }
 
         $body = curl_exec($ch);
         $status = (int) curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
+        $errno = curl_errno($ch);
         $error = curl_error($ch);
         curl_close($ch);
 
         if ($body === false) {
-            throw new TransportException($error !== '' ? $error : 'Unknown cURL GET error');
+            throw new TransportException(
+                $error !== '' ? $error : 'Unknown cURL GET error',
+                $errno > 0 ? ('curl_errno_' . $errno) : 'curl_get_failed'
+            );
         }
 
         return ['status' => $status, 'body' => $body];
@@ -81,9 +116,30 @@ final class CurlHttpClient implements HttpClientInterface
     {
         $result = [];
         foreach ($headers as $name => $value) {
+            if (
+                str_contains((string) $name, "\r")
+                || str_contains((string) $name, "\n")
+                || str_contains((string) $value, "\r")
+                || str_contains((string) $value, "\n")
+            ) {
+                throw new TransportException('Header names/values must not contain CR/LF characters', 'invalid_header');
+            }
             $result[] = sprintf('%s: %s', $name, $value);
         }
 
         return $result;
     }
+
+    private function assertValidUrl(string $url): void
+    {
+        $parts = parse_url($url);
+        if ($parts === false || !isset($parts['scheme'])) {
+            throw new TransportException('Request URL must be an absolute URL', 'invalid_url');
+        }
+
+        $scheme = strtolower((string) $parts['scheme']);
+        if (!in_array($scheme, ['http', 'https'], true)) {
+            throw new TransportException('Only http/https URLs are supported', 'invalid_url_scheme');
+        }
+    }
 }

tests/ConfigSecurityTest.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace BlackWall\Auth\Tests;
+
+use BlackWall\Auth\Config;
+use PHPUnit\Framework\TestCase;
+
+final class ConfigSecurityTest extends TestCase
+{
+    public function testRejectsInsecureHttpForNonLocalhostByDefault(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        Config::fromArray([
+            'clientId' => 'client-123',
+            'authorizeUrl' => 'http://provider.example/oauth/authorize',
+            'tokenUrl' => 'https://provider.example/oauth/token',
+            'userInfoUrl' => 'https://provider.example/oauth/userinfo',
+            'redirectUri' => 'https://app.example/callback.php',
+        ]);
+    }
+
+    public function testAllowsInsecureHttpForLocalhostWhenExplicitlyEnabled(): void
+    {
+        $config = Config::fromArray([
+            'clientId' => 'client-123',
+            'authorizeUrl' => 'http://localhost/oauth/authorize',
+            'tokenUrl' => 'http://127.0.0.1/oauth/token',
+            'userInfoUrl' => 'http://localhost/oauth/userinfo',
+            'redirectUri' => 'http://localhost/callback.php',
+            'allowInsecureHttp' => true,
+        ]);
+
+        self::assertTrue($config->allowInsecureHttp);
+        self::assertSame('http://localhost/oauth/authorize', $config->authorizeUrl);
+    }
+}
+

tests/CurlHttpClientSecurityTest.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace BlackWall\Auth\Tests;
+
+use BlackWall\Auth\Exception\TransportException;
+use BlackWall\Auth\Http\CurlHttpClient;
+use PHPUnit\Framework\TestCase;
+
+final class CurlHttpClientSecurityTest extends TestCase
+{
+    public function testRejectsUnsupportedUrlScheme(): void
+    {
+        $client = new CurlHttpClient();
+
+        $this->expectException(TransportException::class);
+        $client->get('file:///etc/passwd');
+    }
+
+    public function testRejectsHeaderInjectionAttempt(): void
+    {
+        $client = new CurlHttpClient();
+
+        $this->expectException(TransportException::class);
+        $client->get('https://example.com', [
+            'X-Test' => "ok\r\nInjected: yes",
+        ]);
+    }
+}
+