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81 lines
3.4 KiB
81 lines
3.4 KiB
3 years ago
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From e09a28a30e13e5c22b481010f26b4a7743a09280 Mon Sep 17 00:00:00 2001
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From: John Dennis <jdennis@redhat.com>
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Date: Tue, 5 Mar 2019 10:15:48 +0100
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Subject: [PATCH] Modify am_handler setup to run before mod_proxy
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The way the ECP flow works is that when a client initiates the flow, the
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SP's response is HTTP 200, but not the requested content, but a signed XML
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document that contains the "samlp:AuthnRequest" element. The idea is that
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the ECP client would then determine the IDP and send the document to the
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IDP, get a samlp:Response and convey that to the SP to get access to the
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protected resource.
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Internally, the auth check which is normally done with am_check_uid() set to
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apache's ap_hook_check_user_id() hook, just responds with OK, so it pretends
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to authenticate the user. Then in the usual flow, the request reaches the
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ap_hook_handler which handles the request. There in the pipeline, mellon
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registers functions am_handler() which should run first (APR_HOOK_FIRST),
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determine that this request is an ECP one and return the ECP AuthnRequest
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document. But in case the proxy module is also in the picture, the proxy
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module "races" for who gets to be the first to handle the request in the
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pipeline and wins. Therefore, the request reaches the protected resource
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via mod_proxy and returns it.
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This fix modifies the ap_hook_handler() call to explicitly run before
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handlers from mod_proxy.c
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To reproduce the bug:
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0) Have a SP with mellon connected to a Keycloak IDP (or any other IDP I
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guess). In the example below, my SAML SP is saml.federation.test
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1) Set a Location protected by mellon that proxies requests to another
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URL. For example:
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ProxyPass /sp-proxy http://app.federation.test/example_app/
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<Location /sp-proxy>
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AuthType Mellon
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MellonEnable auth
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Require valid-user
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</Location>
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2) call:
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curl -L -H "Accept: application/vnd.paos+xml" \
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-H 'PAOS: ver="urn:liberty:paos:2003-08";"urn:oasis:names:tc:SAML:2.0:profiles:SSO:ecp"' \
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http://saml.federation.test/sp-proxy
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Before the patch, you would see whatever is served from the proxied
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page. With the patch, you should get back a XML document with a
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samlp:AuthnRequest.
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---
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mod_auth_mellon.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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diff --git a/mod_auth_mellon.c b/mod_auth_mellon.c
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index 74bd328..5330f48 100644
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--- a/mod_auth_mellon.c
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+++ b/mod_auth_mellon.c
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@@ -207,6 +207,12 @@ static int am_create_request(request_rec *r)
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static void register_hooks(apr_pool_t *p)
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{
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+ /* Our handler needs to run before mod_proxy so that it can properly
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+ * return ECP AuthnRequest messages when running as a reverse proxy.
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+ * See: https://github.com/Uninett/mod_auth_mellon/pull/196
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+ */
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+ static const char * const run_handler_before[]={ "mod_proxy.c", NULL };
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+
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ap_hook_access_checker(am_auth_mellon_user, NULL, NULL, APR_HOOK_MIDDLE);
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ap_hook_check_user_id(am_check_uid, NULL, NULL, APR_HOOK_MIDDLE);
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ap_hook_post_config(am_global_init, NULL, NULL, APR_HOOK_MIDDLE);
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@@ -222,7 +228,7 @@ static void register_hooks(apr_pool_t *p)
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* Therefore this hook must run before any handler that may check
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* r->handler and decide that it is the only handler for this URL.
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*/
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- ap_hook_handler(am_handler, NULL, NULL, APR_HOOK_FIRST);
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+ ap_hook_handler(am_handler, NULL, run_handler_before, APR_HOOK_FIRST);
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#ifdef ENABLE_DIAGNOSTICS
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ap_hook_open_logs(am_diag_log_init,NULL,NULL,APR_HOOK_MIDDLE);
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--
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2.19.2
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