`maxRequestDepth` does not work if `depth` is not set

[gera2ld]

If depth header is not set or not a number, maxRequestDepth does not work as expected. Because in such cases depth will never meet 0:

npm-WebDAV-Server/src/server/v2/commands/Propfind.ts

Line 443 in 5f23762

if(depth !== 0)

[masx200]

@gera2ld

I also found this problem

curl http://foo.bar:1900/ -X PROPFIND -H depth:every --user root:root

curl http://foo.bar:1900/ -X PROPFIND -H depth:null --user root:root

curl http://foo.bar:1900/ -X PROPFIND --user root:root

[masx200]

@OpenMarshal

I found that as long as the "depth" in the request header is not a number or is not set, the server will treat it as "Infinity" and maxRequestDepth does not work.

[masx200]

@mholt
I found that this bug can cause serious and fatal server memory overflow and high CPU usage problems.

[masx200]

https://datatracker.ietf.org/doc/rfc4918/?include_text=1

9.1. PROPFIND Method

The PROPFIND method retrieves properties defined on the resource
identified by the Request-URI, if the resource does not have any
internal members, or on the resource identified by the Request-URI
and potentially its member resources, if the resource is a collection
that has internal member URLs. All DAV-compliant resources MUST
support the PROPFIND method and the propfind XML element
(Section 14.20) along with all XML elements defined for use with that
element.

A client MUST submit a Depth header with a value of "0", "1", or
"infinity" with a PROPFIND request. Servers MUST support "0" and "1"
depth requests on WebDAV-compliant resources and SHOULD support
"infinity" requests. In practice, support for infinite-depth
requests MAY be disabled, due to the performance and security
concerns associated with this behavior. Servers SHOULD treat a
request without a Depth header as if a "Depth: infinity" header was
included.

9.1.1.  PROPFIND Status Codes

This section, as with similar sections for other methods, provides
some guidance on error codes and preconditions or postconditions
(defined in Section 16) that might be particularly useful with
PROPFIND.

403 Forbidden - A server MAY reject PROPFIND requests on collections
with depth header of "Infinity", in which case it SHOULD use this
error with the precondition code 'propfind-finite-depth' inside the
error body.

[masx200]

The following are the steps to reproduce the bug

For example, if there is the existence of the following loop folder soft links:

$ pwd
/data/data/com.termux/files/home/test                      
 $ ls -l
total 7
drwx------ 2 u0_a261 u0_a261 3488 Sep  2 00:44 a
drwx------ 2 u0_a261 u0_a261 3488 Sep  2 00:44 b
$ ls -l b                                                  
 total 0
lrwxrwxrwx 1 u0_a261 u0_a261 42 Sep  2 00:38 a -> /data/data/com.termux/files/home/test/a
-rw------- 1 u0_a261 u0_a261  0 Sep  2 00:44 c.txt
$ ls -l a
total 0
lrwxrwxrwx 1 u0_a261 u0_a261 42 Sep  2 00:39 b -> /data/data/com.termux/files/home/test/b
-rw------- 1 u0_a261 u0_a261  0 Sep  2 00:44 d.txt
$

[masx200]

The following are the steps to reproduce the bug

Then I start the webdav service

npx webdav-cli --username root --password root --port=1900 --path=/data/data/com.termux/files/home

[masx200]

The following are the steps to reproduce the bug

Then initiate a request to the server, the server enters an endless loop, the memory overflows, and the server is down

curl http://127.0.0.1:1900 -X PROPFIND  --user root:root

<--- Last few GCs --->

[8419:0x745ce87a00]   797885 ms: Mark-sweep 920.1 (936.4) -> 916.2 (936.6) MB, 1737.1 / 0.8 ms  (average mu = 0.123, current mu = 0.014) allocation failure scavenge might not succeed
[8419:0x745ce87a00]   799605 ms: Mark-sweep 920.3 (936.9) -> 916.5 (936.4) MB, 1698.2 / 0.8 ms  (average mu = 0.071, current mu = 0.013) allocation failure scavenge might not succeed


<--- JS stacktrace --->

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory
error Command failed with signal "SIGABRT".
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
$

curl: (52) Empty reply from server

[masx200]

@AdrienCastex

The solution is as follows:

server.beforeRequest((arg, next) => {

    const { headers, method } = arg.request
    const { depth } = headers
    if (method === 'PROPFIND' && depth !== '0' && depth !== '1') {
        arg.setCode(403);
        arg.exit();
    }
    else {
        next();
    }
})