Ankur Mhatre
e9381dc5be
Three modules on Spring Boot 4.1.1 with Spring Authorization Server 7.1.1: the provider
itself, a relying party, and an API that trusts its tokens. Client registration, PKCE,
a custom consent page and token customisation, with profiles that make each failure
reproducible.
Every claim is backed by captured output in docs/output/as-*.txt, regenerated by
authorization-server/scripts/run-all.sh. Notable findings, verified against the jars:
- OAuth2AuthorizationServerConfiguration.applyDefaultSecurity(HttpSecurity) was deleted
in 7.0, and both configuration classes moved into spring-security-config
- ClientSettings.requireProofKey flipped from false to true, on the authorization server
(1.5.8 -> 7.1.1) and on the OAuth2 client (6.5.1 -> 7.1.1)
- requireProofKey(false) does not make PKCE optional for a public client; the code
verifier is that client's only authentication at the token endpoint
- MediaTypeRequestMatcher(TEXT_HTML) matches Accept: */*, so the token endpoint answers
API callers with 302 -> /login unless setIgnoredMediaTypes(ALL) is called
Also renames the repository to spring-auth-demo and cross-links the new chapter set from
the existing documentation.
72 lines
2.7 KiB
Markdown
72 lines
2.7 KiB
Markdown
[← 08 The relying party](08-client.md) · [index](README.md) · next: [10 — Should you run one at all](10-should-you.md)
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# The entry point and the Accept header
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## The symptom
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A failed token request answers `302 -> /login` instead of a JSON `401`. Your API client
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follows the redirect, gets 200 and an HTML login page, and reports “the token endpoint
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returned HTML”.
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## The cause
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The authorization server chain needs two behaviours from one entry point: send a *browser*
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hitting `/oauth2/authorize` to the login page, and send a *machine* hitting `/oauth2/token`
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a protocol error. The documented way to express that is:
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```java
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.exceptionHandling(ex -> ex.defaultAuthenticationEntryPointFor(
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new LoginUrlAuthenticationEntryPoint("/login"),
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new MediaTypeRequestMatcher(MediaType.TEXT_HTML)))
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```
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On its own, that does not work. `MediaTypeRequestMatcher` treats `*/*` as matching
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`text/html`, and `*/*` is what curl, most HTTP clients, and anything that does not set
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`Accept` send. So the matcher fires for API callers too.
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## The fix
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```java
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MediaTypeRequestMatcher matcher = new MediaTypeRequestMatcher(MediaType.TEXT_HTML);
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matcher.setIgnoredMediaTypes(Set.of(MediaType.ALL));
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```
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## The difference, measured
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[`as-entrypoint-accept.txt`](../output/as-entrypoint-accept.txt), same request three ways
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against both configurations:
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| `Accept` | without `setIgnoredMediaTypes` | with it |
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|---|---|---|
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| `*/*` | **302 → /login** | **401** |
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| `application/json` | 401 | 401 |
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| `text/html` | 302 → /login | 302 → /login |
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The browser case is preserved either way. Only the `*/*` case changes, and that is the case
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every API client falls into.
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## Why only public clients hit it
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A confidential client presenting a wrong secret never reaches the entry point at all:
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`OAuth2ClientAuthenticationFilter` writes the error itself, so the `Accept` header makes no
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difference and you get a clean 401. It is the *public* client — whose only
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authentication mechanism is the code verifier — that falls through to the entry point
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when there is nothing to authenticate with. Which means the bug is invisible until you add
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your first SPA.
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## The mirror image in the test suite
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```java
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this.mvc.perform(post("/oauth2/token")
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.accept(MediaType.ALL)
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.param("grant_type", "authorization_code")
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.param("code", "bogus")
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.param("client_id", "demo-spa"))
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.andExpect(status().isUnauthorized());
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```
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Pinning it as a test matters because the fix is one line in an `exceptionHandling` lambda
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and is exactly the kind of thing a later refactor drops.
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Next: [10 — Should you run one at all](10-should-you.md)
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