From 58727ec088e55f739b146cff3baa955f8d1b2a3e Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Wed, 25 May 2016 16:23:59 +0200 Subject: [PATCH] BUG/MAJOR: http: fix breakage of "reqdeny" causing random crashes Commit 108b1dd ("MEDIUM: http: configurable http result codes for http-request deny") introduced in 1.6-dev2 was incomplete. It introduced a new field "rule_deny_status" into struct http_txn, which is filled only by actions "http-request deny" and "http-request tarpit". It's then used in the deny code path to emit the proper error message, but is used uninitialized when the deny comes from a "reqdeny" rule, causing random behaviours ranging from returning a 200, an empty response, or crashing the process. Often upon startup only 200 was returned but after the fields are used the crash happens. This can be sped up using -dM. There's no need at all for storing this status in the http_txn struct anyway since it's used immediately after being set. Let's store it in a temporary variable instead which is passed as an argument to function http_req_get_intercept_rule(). As an extra benefit, removing it from struct http_txn reduced the size of this struct by 8 bytes. This fix must be backported to 1.6 where the bug was detected. Special thanks to Falco Schmutz for his detailed report including an exploitable core and a reproducer. --- include/types/proto_http.h | 1 - src/proto_http.c | 21 +++++++++++++-------- 2 files changed, 13 insertions(+), 9 deletions(-) diff --git a/include/types/proto_http.h b/include/types/proto_http.h index 7e8f2cbbc..935be8ce6 100644 --- a/include/types/proto_http.h +++ b/include/types/proto_http.h @@ -366,7 +366,6 @@ struct http_txn { unsigned int flags; /* transaction flags */ enum http_meth_t meth; /* HTTP method */ /* 1 unused byte here */ - short rule_deny_status; /* HTTP status from rule when denying */ short status; /* HTTP status from the server, negative if from proxy */ char *uri; /* first line if log needed, NULL otherwise */ diff --git a/src/proto_http.c b/src/proto_http.c index 416504247..d79a78219 100644 --- a/src/proto_http.c +++ b/src/proto_http.c @@ -3276,10 +3276,12 @@ static int http_transform_header(struct stream* s, struct http_msg *msg, * further processing of the request (auth, deny, ...), and defaults to * HTTP_RULE_RES_STOP if it executed all rules or stopped on an allow, or * HTTP_RULE_RES_CONT if the last rule was reached. It may set the TX_CLTARPIT - * on txn->flags if it encounters a tarpit rule. + * on txn->flags if it encounters a tarpit rule. If is not NULL + * and a deny/tarpit rule is matched, it will be filled with this rule's deny + * status. */ enum rule_result -http_req_get_intercept_rule(struct proxy *px, struct list *rules, struct stream *s) +http_req_get_intercept_rule(struct proxy *px, struct list *rules, struct stream *s, int *deny_status) { struct session *sess = strm_sess(s); struct http_txn *txn = s->txn; @@ -3325,12 +3327,14 @@ http_req_get_intercept_rule(struct proxy *px, struct list *rules, struct stream return HTTP_RULE_RES_STOP; case ACT_ACTION_DENY: - txn->rule_deny_status = rule->deny_status; + if (deny_status) + *deny_status = rule->deny_status; return HTTP_RULE_RES_DENY; case ACT_HTTP_REQ_TARPIT: txn->flags |= TX_CLTARPIT; - txn->rule_deny_status = rule->deny_status; + if (deny_status) + *deny_status = rule->deny_status; return HTTP_RULE_RES_DENY; case ACT_HTTP_REQ_AUTH: @@ -4090,6 +4094,7 @@ int http_process_req_common(struct stream *s, struct channel *req, int an_bit, s struct redirect_rule *rule; struct cond_wordlist *wl; enum rule_result verdict; + int deny_status = HTTP_ERR_403; if (unlikely(msg->msg_state < HTTP_MSG_BODY)) { /* we need more data */ @@ -4110,7 +4115,7 @@ int http_process_req_common(struct stream *s, struct channel *req, int an_bit, s /* evaluate http-request rules */ if (!LIST_ISEMPTY(&px->http_req_rules)) { - verdict = http_req_get_intercept_rule(px, &px->http_req_rules, s); + verdict = http_req_get_intercept_rule(px, &px->http_req_rules, s, &deny_status); switch (verdict) { case HTTP_RULE_RES_YIELD: /* some data miss, call the function later. */ @@ -4156,7 +4161,7 @@ int http_process_req_common(struct stream *s, struct channel *req, int an_bit, s /* parse the whole stats request and extract the relevant information */ http_handle_stats(s, req); - verdict = http_req_get_intercept_rule(px, &px->uri_auth->http_req_rules, s); + verdict = http_req_get_intercept_rule(px, &px->uri_auth->http_req_rules, s, &deny_status); /* not all actions implemented: deny, allow, auth */ if (verdict == HTTP_RULE_RES_DENY) /* stats http-request deny */ @@ -4285,9 +4290,9 @@ int http_process_req_common(struct stream *s, struct channel *req, int an_bit, s manage_client_side_cookies(s, req); txn->flags |= TX_CLDENY; - txn->status = http_err_codes[txn->rule_deny_status]; + txn->status = http_err_codes[deny_status]; s->logs.tv_request = now; - http_reply_and_close(s, txn->status, http_error_message(s, txn->rule_deny_status)); + http_reply_and_close(s, txn->status, http_error_message(s, deny_status)); stream_inc_http_err_ctr(s); sess->fe->fe_counters.denied_req++; if (sess->fe != s->be)