details: http://hg.nginx.org/nginx/rev/a30ea5c6451d
branches:
changeset: 5226:a30ea5c6451d
user: Ruslan Ermilov <ru@nginx.com>
date: Thu May 23 16:26:10 2013 +0400
description:
Memcached: stricten header validation.

An invalid memcached reply that started with '\n' could cause
segmentation fault.

An invalid memcached reply "VALUE / 0 2\r?ok\r\nEND\r\n" was
considered as a valid response.

In addition, if memcached reports that the key was not found,
set u->headers_in.content_length_n to 0. This ensures that
ngx_http_memcached_filter() will not be called while previous
code relied on always intercepting 404. Initialization of
ctx->rest was moved to where it belongs.

diffstat:

src/http/modules/ngx_http_memcached_module.c | 26 +++++++++++++++++---------
1 files changed, 17 insertions(+), 9 deletions(-)

diffs (75 lines):

diff -r 15a7deeaa19a -r a30ea5c6451d src/http/modules/ngx_http_memcached_module.c
--- a/src/http/modules/ngx_http_memcached_module.c Thu May 23 15:47:58 2013 +0400
+++ b/src/http/modules/ngx_http_memcached_module.c Thu May 23 16:26:10 2013 +0400
@@ -197,7 +197,6 @@ ngx_http_memcached_handler(ngx_http_requ
return NGX_HTTP_INTERNAL_SERVER_ERROR;
}

- ctx->rest = NGX_HTTP_MEMCACHED_END;
ctx->request = r;

ngx_http_set_ctx(r, ctx, ngx_http_memcached_module);
@@ -309,10 +308,15 @@ ngx_http_memcached_process_header(ngx_ht

found:

+ line.data = u->buffer.pos;
+ line.len = p - u->buffer.pos;
+
+ if (line.len == 0 || *(p - 1) != CR) {
+ goto no_valid;
+ }
+
*p = '\0';
-
- line.len = p - u->buffer.pos - 1;
- line.data = u->buffer.pos;
+ line.len--;

ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
"memcached: \"%V\"", &line);
@@ -387,10 +391,9 @@ found:
length:

start = p;
+ p = line.data + line.len;

- while (*p && *p++ != CR) { /* void */ }
-
- u->headers_in.content_length_n = ngx_atoof(start, p - start - 1);
+ u->headers_in.content_length_n = ngx_atoof(start, p - start);
if (u->headers_in.content_length_n == -1) {
ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
"memcached sent invalid length in response \"%V\" "
@@ -401,7 +404,7 @@ found:

u->headers_in.status_n = 200;
u->state->status = 200;
- u->buffer.pos = p + 1;
+ u->buffer.pos = p + sizeof(CRLF) - 1;

return NGX_OK;
}
@@ -410,8 +413,10 @@ found:
ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
"key: \"%V\" was not found by memcached", &ctx->key);

+ u->headers_in.content_length_n = 0;
u->headers_in.status_n = 404;
u->state->status = 404;
+ u->buffer.pos = p + sizeof("END" CRLF) - 1;
u->keepalive = 1;

return NGX_OK;
@@ -435,7 +440,10 @@ ngx_http_memcached_filter_init(void *dat

u = ctx->request->upstream;

- u->length += NGX_HTTP_MEMCACHED_END;
+ if (u->headers_in.status_n != 404) {
+ u->length += NGX_HTTP_MEMCACHED_END;
+ ctx->rest = NGX_HTTP_MEMCACHED_END;
+ }

return NGX_OK;
}

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