[PATCH] Added warning about redefinition of listen socket protocol options
Sergey Kandaurov
pluknet at nginx.com
Mon Jan 23 10:21:33 UTC 2023
> On 31 Dec 2022, at 18:35, Maxim Dounin <mdounin at mdounin.ru> wrote:
>
> # HG changeset patch
> # User Maxim Dounin <mdounin at mdounin.ru>
> # Date 1672497248 -10800
> # Sat Dec 31 17:34:08 2022 +0300
> # Node ID c215d5cf25732ece1819cf1cd48ebb480bb642c7
> # Parent 07b0bee87f32be91a33210bc06973e07c4c1dac9
> Added warning about redefinition of listen socket protocol options.
>
> The "listen" directive in the http module can be used multiple times
> in different server blocks. Originally, it was supposed to be specified
> once with various socket options, and without any parameters in virtual
> server blocks. For example:
>
> server { listen 80 backlog=1024; server_name foo; ... }
> server { listen 80; server_name bar; ... }
> server { listen 80; server_name bazz; ... }
>
> The address part of the syntax ("address[:port]" / "port" / "unix:path")
> uniquely identifies the listening socket, and therefore is enough for
> name-based virtual servers (to let nginx know that the virtual server
> accepts requests on the listening socket in question).
>
> To ensure that listening options do not conflict between virtual servers,
> they were allowed only once. For example, the following configuration
> will be rejected ("duplicate listen options for 0.0.0.0:80 in ..."):
>
> server { listen 80 backlog=1024; server_name foo; ... }
> server { listen 80 backlog=512; server_name bar; ... }
>
> At some point it was, however, noticed, that it is sometimes convenient
> to repeat some options for clarity. In nginx 0.8.51 the "ssl" parameter
> was allowed to be specified multiple times, e.g.:
>
> server { listen 443 ssl backlog=1024; server_name foo; ... }
> server { listen 443 ssl; server_name bar; ... }
> server { listen 443 ssl; server_name bazz; ... }
>
> This approach makes configuration more readable, since SSL sockets are
> immediately visible in the configuration. If this is not needed, just the
> address can still be used.
>
> Later, additional protocol-specific options similar to "ssl" were
> introduced, notably "http2" and "proxy_protocol". With these options,
> one can write:
>
> server { listen 443 ssl backlog=1024; server_name foo; ... }
> server { listen 443 http2; server_name bar; ... }
> server { listen 443 proxy_protocol; server_name bazz; ... }
>
> The resulting socket will use ssl, http2, and proxy_protocol, but this
> is not really obvious from the configuration.
>
> To ensure such misleading configurations are not allowed, nginx now
> warns as long as the "listen" directive is used with options different
nitpicking:
"ensure .. are not allowed" and "warns" don't seem to be equally strong.
As such, I'd rewrite to something like:
To emphasize such misleading configurations are discouraged, nginx now
> from the options previously used if these are potentially confusing.
Not really confident what "these" refers to.
s/these/they/ ?
>
> In particular, the following configurations are allowed:
>
> server { listen 8401 ssl backlog=1024; server_name foo; }
> server { listen 8401 ssl; server_name bar; }
> server { listen 8401 ssl; server_name bazz; }
>
> server { listen 8402 ssl http2 backlog=1024; server_name foo; }
> server { listen 8402 ssl; server_name bar; }
> server { listen 8402 ssl; server_name bazz; }
>
> server { listen 8403 ssl; server_name bar; }
> server { listen 8403 ssl; server_name bazz; }
> server { listen 8403 ssl http2; server_name foo; }
>
> server { listen 8404 ssl http2 backlog=1024; server_name foo; }
> server { listen 8404 http2; server_name bar; }
> server { listen 8404 http2; server_name bazz; }
>
> server { listen 8405 ssl http2 backlog=1024; server_name foo; }
> server { listen 8405 ssl http2; server_name bar; }
> server { listen 8405 ssl http2; server_name bazz; }
>
> server { listen 8406 ssl; server_name foo; }
> server { listen 8406; server_name bar; }
> server { listen 8406; server_name bazz; }
>
> And the following configurations will generate warnings:
>
> server { listen 8501 ssl http2 backlog=1024; server_name foo; }
> server { listen 8501 http2; server_name bar; }
> server { listen 8501 ssl; server_name bazz; }
>
> server { listen 8502 backlog=1024; server_name foo; }
> server { listen 8502 ssl; server_name bar; }
>
> server { listen 8503 ssl; server_name foo; }
> server { listen 8503 http2; server_name bar; }
>
> server { listen 8504 ssl; server_name foo; }
> server { listen 8504 http2; server_name bar; }
> server { listen 8504 proxy_protocol; server_name bazz; }
>
> server { listen 8505 ssl http2 proxy_protocol; server_name foo; }
> server { listen 8505 ssl http2; server_name bar; }
> server { listen 8505 ssl; server_name bazz; }
>
> server { listen 8506 ssl http2; server_name foo; }
> server { listen 8506 ssl; server_name bar; }
> server { listen 8506; server_name bazz; }
>
> server { listen 8507 ssl; server_name bar; }
> server { listen 8507; server_name bazz; }
> server { listen 8507 ssl http2; server_name foo; }
>
> server { listen 8508 ssl; server_name bar; }
> server { listen 8508; server_name bazz; }
> server { listen 8508 ssl backlog=1024; server_name foo; }
>
> server { listen 8509; server_name bazz; }
> server { listen 8509 ssl; server_name bar; }
> server { listen 8509 ssl backlog=1024; server_name foo; }
>
15 examples of dos and don'ts looks slightly excessive.
The accurate description (such as provided by you below) allows
to reduce most of them to e.g. four common invalid configurations:
A lesser option set with socket option:
server { listen 8443 backlog=1024; server_name foo; }
server { listen 8443 http2; server_name bar; }
The main option set is repeated at least twice:
server { listen 127.0.0.1:8443; server_name foo; }
server { listen 127.0.0.1:8443 ssl; server_name bar; }
server { listen 127.0.0.1:8443 ssl; server_name baz; }
Option sets partially overlap:
server { listen 127.0.0.1:8443 ssl; server_name foo; }
server { listen 127.0.0.1:8443 http2; server_name bar; }
More than two option sets:
server { listen 127.0.0.1:8443 http2 ssl; server_name foo; }
server { listen 127.0.0.1:8443 http2; server_name bar; }
server { listen 127.0.0.1:8443 ssl; server_name baz; }
> The basic idea is that at most two sets of protocol options are allowed:
> the main one (with socket options, if any), and a shorter one, with options
> being a subset of the main options, repeated for clarity. As long as the
> shorter set of protocol options is used, all listen directives except the
> main one should use it.
I'd move this paragraph somewhere before examples, as this is the most
specific description of things actually changed.
BTW, while reviewing I caught sort of a bug.
As I understand the above explanation, if there are both full and short
sets present, then at most one listen directive can have the full set,
while shorter sets can be repeated. If so, then with the proposed patch
the next configuration is expectedly invalid:
server { listen 127.0.0.1:8443 ssl; server_name foo; }
server { listen 127.0.0.1:8443 ssl; server_name bar; }
server { listen 127.0.0.1:8443; server_name baz; }
This is expected since first two servers with same options are
interpreted as a short form (with full form seen potentially later on),
but 3rd server has lesser options, which is caught by this check:
(addr[i].protocols_set && protocols != addr[i].protocols)
Which is interpreted as:
"this server has a lesser set that doesn't match a a shorter set".
Now, if 3rd server is moved first, configuration starts to pass:
server { listen 127.0.0.1:8443; server_name baz; }
server { listen 127.0.0.1:8443 ssl; server_name foo; }
server { listen 127.0.0.1:8443 ssl; server_name bar; }
This is because after (now) 2nd server, it is parsed as:
1st server has a short form, and 2nd server has a full form.
Then 3rd server goes to "the same options" case. This also
overwrites the remembered shorter set in addr[i].protocols.
I guess an additional check should be added to address this.
It is similar to the "options removed" case and ensures that
the repeated options set actually matches a shorter set:
diff --git a/src/http/ngx_http.c b/src/http/ngx_http.c
--- a/src/http/ngx_http.c
+++ b/src/http/ngx_http.c
@@ -1345,7 +1345,9 @@ ngx_http_add_addresses(ngx_conf_t *cf, n
/* the same options */
- if (lsopt->set && addr[i].protocols_changed) {
+ if ((lsopt->set && addr[i].protocols_changed)
+ || (addr[i].protocols_set && protocols != addr[i].protocols))
+ {
ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
"protocol options redefined for %V",
&addr[i].opt.addr_text);
>
> diff --git a/src/http/ngx_http.c b/src/http/ngx_http.c
> --- a/src/http/ngx_http.c
> +++ b/src/http/ngx_http.c
> @@ -1228,7 +1228,8 @@ static ngx_int_t
> ngx_http_add_addresses(ngx_conf_t *cf, ngx_http_core_srv_conf_t *cscf,
> ngx_http_conf_port_t *port, ngx_http_listen_opt_t *lsopt)
> {
> - ngx_uint_t i, default_server, proxy_protocol;
> + ngx_uint_t i, default_server, proxy_protocol,
> + protocols, protocols_prev;
> ngx_http_conf_addr_t *addr;
> #if (NGX_HTTP_SSL)
> ngx_uint_t ssl;
> @@ -1264,12 +1265,18 @@ ngx_http_add_addresses(ngx_conf_t *cf, n
> default_server = addr[i].opt.default_server;
>
> proxy_protocol = lsopt->proxy_protocol || addr[i].opt.proxy_protocol;
> + protocols = lsopt->proxy_protocol;
> + protocols_prev = addr[i].opt.proxy_protocol;
>
> #if (NGX_HTTP_SSL)
> ssl = lsopt->ssl || addr[i].opt.ssl;
> + protocols |= lsopt->ssl << 1;
> + protocols_prev |= addr[i].opt.ssl << 1;
> #endif
> #if (NGX_HTTP_V2)
> http2 = lsopt->http2 || addr[i].opt.http2;
> + protocols |= lsopt->http2 << 2;
> + protocols_prev |= addr[i].opt.http2 << 2;
> #endif
>
> if (lsopt->set) {
> @@ -1299,6 +1306,55 @@ ngx_http_add_addresses(ngx_conf_t *cf, n
> addr[i].default_server = cscf;
> }
>
> + /* check for conflicting protocol options */
> +
> + if ((protocols | protocols_prev) != protocols_prev) {
> +
> + /* options added */
> +
> + if ((addr[i].opt.set && !lsopt->set)
> + || addr[i].protocols_changed
> + || (protocols | protocols_prev) != protocols)
> + {
> + ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
> + "protocol options redefined for %V",
> + &addr[i].opt.addr_text);
> + }
> +
> + addr[i].protocols = protocols_prev;
> + addr[i].protocols_set = 1;
> + addr[i].protocols_changed = 1;
> +
> + } else if ((protocols_prev | protocols) != protocols) {
> +
> + /* options removed */
> +
> + if (lsopt->set
> + || (addr[i].protocols_set && protocols != addr[i].protocols))
> + {
> + ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
> + "protocol options redefined for %V",
> + &addr[i].opt.addr_text);
> + }
> +
> + addr[i].protocols = protocols;
> + addr[i].protocols_set = 1;
> + addr[i].protocols_changed = 1;
> +
> + } else {
> +
> + /* the same options */
> +
> + if (lsopt->set && addr[i].protocols_changed) {
> + ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
> + "protocol options redefined for %V",
> + &addr[i].opt.addr_text);
> + }
> +
> + addr[i].protocols = protocols;
> + addr[i].protocols_set = 1;
> + }
> +
> addr[i].opt.default_server = default_server;
> addr[i].opt.proxy_protocol = proxy_protocol;
> #if (NGX_HTTP_SSL)
> @@ -1355,6 +1411,9 @@ ngx_http_add_address(ngx_conf_t *cf, ngx
> }
>
> addr->opt = *lsopt;
> + addr->protocols = 0;
> + addr->protocols_set = 0;
> + addr->protocols_changed = 0;
> addr->hash.buckets = NULL;
> addr->hash.size = 0;
> addr->wc_head = NULL;
> diff --git a/src/http/ngx_http_core_module.h b/src/http/ngx_http_core_module.h
> --- a/src/http/ngx_http_core_module.h
> +++ b/src/http/ngx_http_core_module.h
> @@ -274,6 +274,10 @@ typedef struct {
> typedef struct {
> ngx_http_listen_opt_t opt;
>
> + unsigned protocols:3;
> + unsigned protocols_set:1;
> + unsigned protocols_changed:1;
> +
> ngx_hash_t hash;
> ngx_hash_wildcard_t *wc_head;
> ngx_hash_wildcard_t *wc_tail;
--
Sergey Kandaurov
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