! This is a reduced part of the original follow-XFF patchset from
! devel.squid-cache.org for use with the FreeBSD squid-2.5 port.
Index: src/acl.c
--- src/acl.c 13 May 2003 02:14:12 -0000 1.43.2.16
+++ src/acl.c 23 Nov 2003 14:20:12 -0000
@@ -2001,6 +2001,11 @@
cbdataLock(A);
if (request != NULL) {
checklist->request = requestLink(request);
+#if FOLLOW_X_FORWARDED_FOR
+ if (Config.onoff.acl_uses_indirect_client) {
+ checklist->src_addr = request->indirect_client_addr;
+ } else
+#endif /* FOLLOW_X_FORWARDED_FOR */
checklist->src_addr = request->client_addr;
checklist->my_addr = request->my_addr;
checklist->my_port = request->my_port;
Index: src/cf.data.pre
--- src/cf.data.pre 7 Nov 2003 03:14:30 -0000 1.49.2.46
+++ src/cf.data.pre 23 Nov 2003 14:20:17 -0000
@@ -2065,6 +2065,92 @@
NOCOMMENT_END
DOC_END
+NAME: follow_x_forwarded_for
+TYPE: acl_access
+IFDEF: FOLLOW_X_FORWARDED_FOR
+LOC: Config.accessList.followXFF
+DEFAULT: none
+DEFAULT_IF_NONE: deny all
+DOC_START
+ Allowing or Denying the X-Forwarded-For header to be followed to
+ find the original source of a request.
+
+ Requests may pass through a chain of several other proxies
+ before reaching us. The X-Forwarded-For header will contain a
+ comma-separated list of the IP addresses in the chain, with the
+ rightmost address being the most recent.
+
+ If a request reaches us from a source that is allowed by this
+ configuration item, then we consult the X-Forwarded-For header
+ to see where that host received the request from. If the
+ X-Forwarded-For header contains multiple addresses, and if
+ acl_uses_indirect_client is on, then we continue backtracking
+ until we reach an address for which we are not allowed to
+ follow the X-Forwarded-For header, or until we reach the first
+ address in the list. (If acl_uses_indirect_client is off, then
+ it's impossible to backtrack through more than one level of
+ X-Forwarded-For addresses.)
+
+ The end result of this process is an IP address that we will
+ refer to as the indirect client address. This address may
+ be treated as the client address for access control, delay
+ pools and logging, depending on the acl_uses_indirect_client,
+ delay_pool_uses_indirect_client and log_uses_indirect_client
+ options.
+
+ SECURITY CONSIDERATIONS:
+
+ Any host for which we follow the X-Forwarded-For header
+ can place incorrect information in the header, and Squid
+ will use the incorrect information as if it were the
+ source address of the request. This may enable remote
+ hosts to bypass any access control restrictions that are
+ based on the client's source addresses.
+
+ For example:
+
+ acl localhost src 127.0.0.1
+ acl my_other_proxy srcdomain .proxy.example.com
+ follow_x_forwarded_for allow localhost
+ follow_x_forwarded_for allow my_other_proxy
+DOC_END
+
+NAME: acl_uses_indirect_client
+COMMENT: on|off
+TYPE: onoff
+IFDEF: FOLLOW_X_FORWARDED_FOR
+DEFAULT: on
+LOC: Config.onoff.acl_uses_indirect_client
+DOC_START
+ Controls whether the indirect client address
+ (see follow_x_forwarded_for) is used instead of the
+ direct client address in acl matching.
+DOC_END
+
+NAME: delay_pool_uses_indirect_client
+COMMENT: on|off
+TYPE: onoff
+IFDEF: FOLLOW_X_FORWARDED_FOR && DELAY_POOLS
+DEFAULT: on
+LOC: Config.onoff.delay_pool_uses_indirect_client
+DOC_START
+ Controls whether the indirect client address
+ (see follow_x_forwarded_for) is used instead of the
+ direct client address in delay pools.
+DOC_END
+
+NAME: log_uses_indirect_client
+COMMENT: on|off
+TYPE: onoff
+IFDEF: FOLLOW_X_FORWARDED_FOR
+DEFAULT: on
+LOC: Config.onoff.log_uses_indirect_client
+DOC_START
+ Controls whether the indirect client address
+ (see follow_x_forwarded_for) is used instead of the
+ direct client address in the access log.
+DOC_END
+
NAME: http_access
TYPE: acl_access
LOC: Config.accessList.http
Index: src/client_side.c
--- src/client_side.c 2 Sep 2003 02:13:45 -0000 1.47.2.39
+++ src/client_side.c 23 Nov 2003 14:20:22 -0000
@@ -109,6 +109,11 @@
#if USE_IDENT
static IDCB clientIdentDone;
#endif
+#if FOLLOW_X_FORWARDED_FOR
+static void clientFollowXForwardedForStart(void *data);
+static void clientFollowXForwardedForNext(void *data);
+static void clientFollowXForwardedForDone(int answer, void *data);
+#endif /* FOLLOW_X_FORWARDED_FOR */
static int clientOnlyIfCached(clientHttpRequest * http);
static STCB clientSendMoreData;
static STCB clientCacheHit;
@@ -177,10 +182,179 @@
return ch;
}
+#if FOLLOW_X_FORWARDED_FOR
+/*
+ * clientFollowXForwardedForStart() copies the X-Forwarded-For
+ * header into x_forwarded_for_iterator and passes control to
+ * clientFollowXForwardedForNext().
+ *
+ * clientFollowXForwardedForNext() checks the indirect_client_addr
+ * against the followXFF ACL and passes the result to
+ * clientFollowXForwardedForDone().
+ *
+ * clientFollowXForwardedForDone() either grabs the next address
+ * from the tail of x_forwarded_for_iterator and loops back to
+ * clientFollowXForwardedForNext(), or cleans up and passes control to
+ * clientAccessCheck().
+ */
+
+static void
+clientFollowXForwardedForStart(void *data)
+{
+ clientHttpRequest *http = data;
+ request_t *request = http->request;
+ if (Config.accessList.followXFF
+ && httpHeaderHas(&request->header, HDR_X_FORWARDED_FOR))
+ {
+ request->x_forwarded_for_iterator = httpHeaderGetList(
+ &request->header, HDR_X_FORWARDED_FOR);
+ debug(33, 5) ("clientFollowXForwardedForStart: indirect_client_addr=%s XFF='%s'\n",
+ inet_ntoa(request->indirect_client_addr),
+ strBuf(request->x_forwarded_for_iterator));
+ clientFollowXForwardedForNext(http);
+ } else {
+ /* not configured to follow X-Forwarded-For, or nothing to follow */
+ debug(33, 5) ("clientFollowXForwardedForStart: nothing to do\n");
+ clientFollowXForwardedForDone(-1, http);
+ }
+}
+
+static void
+clientFollowXForwardedForNext(void *data)
+{
+ clientHttpRequest *http = data;
+ request_t *request = http->request;
+ debug(33, 5) ("clientFollowXForwardedForNext: indirect_client_addr=%s XFF='%s'\n",
+ inet_ntoa(request->indirect_client_addr),
+ strBuf(request->x_forwarded_for_iterator));
+ if (strLen(request->x_forwarded_for_iterator) != 0) {
+ /* check the acl to see whether to believe the X-Forwarded-For header */
+ http->acl_checklist = clientAclChecklistCreate(
+ Config.accessList.followXFF, http);
+ aclNBCheck(http->acl_checklist, clientFollowXForwardedForDone, http);
+ } else {
+ /* nothing left to follow */
+ debug(33, 5) ("clientFollowXForwardedForNext: nothing more to do\n");
+ clientFollowXForwardedForDone(-1, http);
+ }
+}
+
+static void
+clientFollowXForwardedForDone(int answer, void *data)
+{
+ clientHttpRequest *http = data;
+ request_t *request = http->request;
+ /*
+ * answer should be be ACCESS_ALLOWED or ACCESS_DENIED if we are
+ * called as a result of ACL checks, or -1 if we are called when
+ * there's nothing left to do.
+ */
+ if (answer == ACCESS_ALLOWED) {
+ /*
+ * The IP address currently in request->indirect_client_addr
+ * is trusted to use X-Forwarded-For. Remove the last
+ * comma-delimited element from x_forwarded_for_iterator and use
+ * it to to replace indirect_client_addr, then repeat the cycle.
+ */
+ const char *p;
+ const char *asciiaddr;
+ int l;
+ struct in_addr addr;
+ debug(33, 5) ("clientFollowXForwardedForDone: indirect_client_addr=%s is trusted\n",
+ inet_ntoa(request->indirect_client_addr));
+ p = strBuf(request->x_forwarded_for_iterator);
+ l = strLen(request->x_forwarded_for_iterator);
+
+ /*
+ * XXX x_forwarded_for_iterator should really be a list of
+ * IP addresses, but it's a String instead. We have to
+ * walk backwards through the String, biting off the last
+ * comma-delimited part each time. As long as the data is in
+ * a String, we should probably implement and use a variant of
+ * strListGetItem() that walks backwards instead of forwards
+ * through a comma-separated list. But we don't even do that;
+ * we just do the work in-line here.
+ */
+ /* skip trailing space and commas */
+ while (l > 0 && (p[l-1] == ',' || xisspace(p[l-1])))
+ l--;
+ strCut(request->x_forwarded_for_iterator, l);
+ /* look for start of last item in list */
+ while (l > 0 && ! (p[l-1] == ',' || xisspace(p[l-1])))
+ l--;
+ asciiaddr = p+l;
+ if (inet_aton(asciiaddr, &addr) == 0) {
+ /* the address is not well formed; do not use it */
+ debug(33, 3) ("clientFollowXForwardedForDone: malformed address '%s'\n",
+ asciiaddr);
+ goto done;
+ }
+ debug(33, 3) ("clientFollowXForwardedForDone: changing indirect_client_addr from %s to '%s'\n",
+ inet_ntoa(request->indirect_client_addr),
+ asciiaddr);
+ request->indirect_client_addr = addr;
+ strCut(request->x_forwarded_for_iterator, l);
+ if (! Config.onoff.acl_uses_indirect_client) {
+ /*
+ * If acl_uses_indirect_client is off, then it's impossible
+ * to follow more than one level of X-Forwarded-For.
+ */
+ goto done;
+ }
+ clientFollowXForwardedForNext(http);
+ return;
+ } else if (answer == ACCESS_DENIED) {
+ debug(33, 5) ("clientFollowXForwardedForDone: indirect_client_addr=%s not trusted\n",
+ inet_ntoa(request->indirect_client_addr));
+ } else {
+ debug(33, 5) ("clientFollowXForwardedForDone: indirect_client_addr=%s nothing more to do\n",
+ inet_ntoa(request->indirect_client_addr));
+ }
+done:
+ /* clean up, and pass control to clientAccessCheck */
+ debug(33, 6) ("clientFollowXForwardedForDone: cleanup\n");
+ if (Config.onoff.log_uses_indirect_client) {
+ /*
+ * Ensure that the access log shows the indirect client
+ * instead of the direct client.
+ */
+ ConnStateData *conn = http->conn;
+ conn->log_addr = request->indirect_client_addr;
+ conn->log_addr.s_addr &= Config.Addrs.client_netmask.s_addr;
+ debug(33, 3) ("clientFollowXForwardedForDone: setting log_addr=%s\n",
+ inet_ntoa(conn->log_addr));
+ }
+ stringClean(&request->x_forwarded_for_iterator);
+ request->flags.done_follow_x_forwarded_for = 1;
+ http->acl_checklist = NULL; /* XXX do we need to aclChecklistFree() ? */
+ clientAccessCheck(http);
+}
+#endif /* FOLLOW_X_FORWARDED_FOR */
+
void
clientAccessCheck(void *data)
{
clientHttpRequest *http = data;
+#if FOLLOW_X_FORWARDED_FOR
+ if (! http->request->flags.done_follow_x_forwarded_for
+ && httpHeaderHas(&http->request->header, HDR_X_FORWARDED_FOR))
+ {
+ /*
+ * There's an X-ForwardedFor header and we haven't yet tried
+ * to follow it to find the indirect_client_addr. Follow it now.
+ * clientFollowXForwardedForDone() will eventually pass control
+ * back to us.
+ *
+ * XXX perhaps our caller should have called
+ * clientFollowXForwardedForStart instead. Then we wouldn't
+ * need to do this little dance transferring control over
+ * there and then back here, and we wouldn't need the
+ * done_follow_x_forwarded_for flag.
+ */
+ clientFollowXForwardedForStart(data);
+ return;
+ }
+#endif /* FOLLOW_X_FORWARDED_FOR */
if (checkAccelOnly(http)) {
/* deny proxy requests in accel_only mode */
debug(33, 1) ("clientAccessCheck: proxy request denied in accel_only mode\n");
@@ -325,6 +499,9 @@
new_request->http_ver = old_request->http_ver;
httpHeaderAppend(&new_request->header, &old_request->header);
new_request->client_addr = old_request->client_addr;
+#if FOLLOW_X_FORWARDED_FOR
+ new_request->indirect_client_addr = old_request->indirect_client_addr;
+#endif /* FOLLOW_X_FORWARDED_FOR */
new_request->my_addr = old_request->my_addr;
new_request->my_port = old_request->my_port;
new_request->flags.redirected = 1;
@@ -3051,6 +3228,9 @@
safe_free(http->log_uri);
http->log_uri = xstrdup(urlCanonicalClean(request));
request->client_addr = conn->peer.sin_addr;
+#if FOLLOW_X_FORWARDED_FOR
+ request->indirect_client_addr = request->client_addr;
+#endif /* FOLLOW_X_FORWARDED_FOR */
request->my_addr = conn->me.sin_addr;
request->my_port = ntohs(conn->me.sin_port);
request->http_ver = http->http_ver;
Index: src/delay_pools.c
--- src/delay_pools.c 19 Jun 2003 02:13:57 -0000 1.5.54.6
+++ src/delay_pools.c 23 Nov 2003 14:20:23 -0000
@@ -318,6 +318,11 @@
r = http->request;
memset(&ch, '\0', sizeof(ch));
+#if FOLLOW_X_FORWARDED_FOR
+ if (Config.onoff.delay_pool_uses_indirect_client) {
+ ch.src_addr = r->indirect_client_addr;
+ } else
+#endif /* FOLLOW_X_FORWARDED_FOR */
ch.src_addr = r->client_addr;
ch.my_addr = r->my_addr;
ch.my_port = r->my_port;
*** src/structs.h.orig Sun Jun 26 12:45:58 2005
--- src/structs.h Sun Jun 26 12:48:45 2005
***************
*** 610,615 ****
--- 610,620 ----
int accel_uses_host_header;
int accel_no_pmtu_disc;
int global_internal_static;
+ #if FOLLOW_X_FORWARDED_FOR
+ int acl_uses_indirect_client;
+ int delay_pool_uses_indirect_client;
+ int log_uses_indirect_client;
+ #endif /* FOLLOW_X_FORWARDED_FOR */
} onoff;
acl *aclList;
struct {
***************
*** 631,636 ****
--- 636,644 ----
acl_access *reply;
acl_address *outgoing_address;
acl_tos *outgoing_tos;
+ #if FOLLOW_X_FORWARDED_FOR
+ acl_access *followXFF;
+ #endif /* FOLLOW_X_FORWARDED_FOR */
} accessList;
acl_deny_info_list *denyInfoList;
struct _authConfig {
***************
*** 1623,1628 ****
--- 1631,1641 ----
unsigned int body_sent:1;
unsigned int reset_tcp:1;
unsigned int must_keepalive:1;
+ #if FOLLOW_X_FORWARDED_FOR
+ /* XXX this flag could be eliminated;
+ * see comments in clientAccessCheck */
+ unsigned int done_follow_x_forwarded_for;
+ #endif /* FOLLOW_X_FORWARDED_FOR */
};
struct _link_list {
***************
*** 1666,1671 ****
--- 1679,1687 ----
int max_forwards;
/* these in_addr's could probably be sockaddr_in's */
struct in_addr client_addr;
+ #if FOLLOW_X_FORWARDED_FOR
+ struct in_addr indirect_client_addr; /* after following X-Forwarded-For */
+ #endif /* FOLLOW_X_FORWARDED_FOR */
struct in_addr my_addr;
unsigned short my_port;
HttpHeader header;
***************
*** 1677,1682 ****
--- 1693,1703 ----
const char *vary_headers; /* Used when varying entities are detected. Changes how the store key is calculated */
BODY_HANDLER *body_reader;
void *body_reader_data;
+ #if FOLLOW_X_FORWARDED_FOR
+ /* XXX a list of IP addresses would be a better data structure
+ * than this String */
+ String x_forwarded_for_iterator;
+ #endif /* FOLLOW_X_FORWARDED_FOR */
};
struct _cachemgr_passwd {
