> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/server-administration/client-authentication/auth-cert.md).

# 20.12. Certificate Authentication \#

This authentication method uses SSL client certificates to perform authentication. It is therefore only available for SSL connections; see [Section 18.9.2](/server-administration/runtime/ssl-tcp.md#SSL-OPENSSL-CONFIG) for SSL configuration instructions. When using this authentication method, the server will require that the client provide a valid, trusted certificate. No password prompt will be sent to the client. The `cn` (Common Name) attribute of the certificate will be compared to the requested database user name, and if they match the login will be allowed. User name mapping can be used to allow `cn` to be different from the database user name.

The following configuration options are supported for SSL certificate authentication:

`map` : Allows for mapping between system and database user names. See [Section 20.2](/server-administration/client-authentication/auth-username-maps.md) for details.

It is redundant to use the `clientcert` option with `cert` authentication because `cert` authentication is effectively `trust` authentication with `clientcert=verify-full`.

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/auth-cert.html)（英文原文，待翻譯）


---

# 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 dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.postgresql.tw/server-administration/client-authentication/auth-cert.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

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.