datamodel-code-generator: Authorization / request headers leaked to cross-origin redirect target when fetching remote schemas

Summary

When datamodel-code-generator fetches a remote schema and follows an HTTP redirect, it re-sends the original request headers, including any Authorization header, to the redirect target even when the redirect changes origin (host/port/scheme). Credentials that an operator scoped to a trusted schema host are therefore forwarded to an attacker-controlled or otherwise different host, leaking them.

Details

In src/datamodel_code_generator/http.py, get_body() follows redirects manually and re-issues each hop with the same headers argument, with no check that the origin is unchanged:

for redirect_count in range(MAX_HTTP_REDIRECTS + 1):
    _validate_url_for_fetch(current_url, allow_private_network=allow_private_network)
    response = httpx.get(current_url, headers=headers, follow_redirects=False, ...)  # same headers every hop
    if (redirect_url := _get_redirect_url(httpx, current_url, response)) is None:
        break
    current_url = redirect_url

Browsers and HTTP clients such as requests/httpx strip Authorization when a redirect crosses origin; here it is preserved unconditionally. Headers are operator-supplied via --http-headers (and credentials can also arrive through --url userinfo), so a redirect from the trusted host to any other host discloses them.

PoC

Self-contained reproducer: https://gist.github.com/thegr1ffyn/ade3035d7f2be95e16f11698259cdbc2
Host A (the trusted schema host) 302-redirects to host B (a different origin) which records received headers; the request carries an auth token scoped to A.

(The PoC uses loopback servers; allow_private_network=True is only to avoid the separate SSRF guard blocking loopback and has no bearing on the leak.)

Impact

Exposure of sensitive information to an unauthorized actor (CWE-200). Affects operators who pass authentication headers/credentials to fetch a remote schema (--http-headers, --url with userinfo) when the configured host issues a redirect to a different origin — e.g. a compromised or open-redirect-prone schema host, or a redirect chain influenced by an attacker-supplied $ref. The leaked credential can then be replayed against the trusted host. This is a credential-scoping weakness secondary to, and in the same component as, the project's other SSRF hardening.

Suggested remediation

When a redirect changes the origin (scheme/host/port), drop Authorization and other sensitive headers before following it, matching the behavior of mainstream HTTP clients.

Maintainer status

Confirmed by maintainer review and regression tests. The private fix PR was merged and released in 0.63.0: https://github.com/koxudaxi/datamodel-code-generator-ghsa-r5vv-ff45-prp2/pull/1

Fix summary: strip Authorization, Cookie, and Proxy-Authorization headers when a redirect crosses origin; preserve headers for same-origin redirects.

Release status: fixed in 0.63.0; 0.62.0 and earlier are affected.

Validation: uv run --group test --extra http pytest tests/test_http.py passed locally for the redirect regression coverage; uv run --group fix ruff check src/datamodel_code_generator/http.py tests/test_http.py passed.

Submitted by: Hamza Haroon (thegr1ffyn)