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Posted to bugs@httpd.apache.org by bu...@apache.org on 2002/08/31 02:13:17 UTC
DO NOT REPLY [Bug 12202] New: -
If-None-Match requests always return 304 with FileETag None directive
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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=12202
If-None-Match requests always return 304 with FileETag None directive
Summary: If-None-Match requests always return 304 with FileETag
None directive
Product: Apache httpd-1.3
Version: 1.3.26
Platform: All
OS/Version: All
Status: NEW
Severity: Critical
Priority: Other
Component: core
AssignedTo: bugs@httpd.apache.org
ReportedBy: andrew@tellme.com
If Apache has the FileETag directive set to "None" and an If-None-Match header
is sent in a request, Apache always sends back a 304 Not Modified response,
regardless of the content of the ETag(s) sent in the If-None-Match header.
This bug is pretty high priority, because it means that if a site running
Apache normally serves ETags but then stops serving them by setting FileETag
None, any downstream caches which understand ETags and send If-None-Match
requests will stop getting updated content.
How to reproduce:
1. Make a regular HTTP request to Apache for any static file,
and note its ETag.
2. Make another HTTP request for that file, sending an If-None-Match
header (for example, if the ETag from step 1 is "abcdef", send
the header If-None-Match: "abcdef"). Apache should correctly
return a 304 Not Modified response.
3. Make a new If-None-Match request with a bogus ETag, for example
by sending If-None-Match: "xxx". Apache should correctly return
a 200 OK and include an entity body.
4. Add a FileETag None directive to the Apache configuration,
and restart Apache.
5. Make the same If-None-Match request as in step 2. Again, Apache
should correctly return a 304 Not Modified response.
6. Make the same bogus If-None-Match request as in step 3 (or any
other If-None-Match request with a bogus ETag). Apache will
incorrectly return a 304 Not Modified response.
Steps 4 and 6 are enough to reproduce the bug but the other steps give a little
context by showing the correct behavior.
We have reproduced this bug with Apache 1.3.23 on OpenBSD and Apache 1.3.26 on
Solaris x86. We strongly suspect the bug to be platform independent; a quick
perusal of the code makes it look like the culprit is the strstr() inside
ap_meets_conditions() in src/main/http_protocol.c (line 612 of the Apache
1.3.26 distribution):
if_nonematch = ap_table_get(r->headers_in, "If-None-Match");
if (if_nonematch != NULL) {
if (r->method_number == M_GET) {
if (if_nonematch[0] == '*')
return HTTP_NOT_MODIFIED;
if (etag != NULL) {
if (ap_table_get(r->headers_in, "Range")) {
if (etag[0] != 'W' &&
ap_find_list_item(r->pool, if_nonematch, etag)) {
return HTTP_NOT_MODIFIED;
}
}
/* here */ else if (strstr(if_nonematch, etag)) {
return HTTP_NOT_MODIFIED;
}
The problem appears to be that when FileETag None is set, the If-None-Match
header is set to "" because ap_make_etag() returns "" in that case.
Unfortunately, strstr(str, "") always returns true, so Apache incorrectly
returns 304 Not Modified for all requests.
A quick hack would be to have ap_make_etag() return an impossible sentinel
value instead of "" when FileETag None is set. A better fix would be to ignore
the If-None-Match logic altogether if FileETag None is set, as there is no
other sensible behavior.
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