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 and other sensitive headers before following it, matching the behavior of mainstream HTTP clients.