view tests/test-http-protocol.t @ 30766:d7bf7d2bd5ab

hgweb: support Content Security Policy

Content-Security-Policy (CSP) is a web security feature that allows
servers to declare what loaded content is allowed to do. For example,
a policy can prevent loading of images, JavaScript, CSS, etc unless
the source of that content is whitelisted (by hostname, URI scheme,
hashes of content, etc). It's a nifty security feature that provides
extra mitigation against some attacks, notably XSS.

Mitigation against these attacks is important for Mercurial because
hgweb renders repository data, which is commonly untrusted. While we
make attempts to escape things, etc, there's the possibility that
malicious data could be injected into the site content. If this happens
today, the full power of the web browser is available to that
malicious content. A restrictive CSP policy (defined by the server
operator and sent in an HTTP header which is outside the control of
malicious content), could restrict browser capabilities and mitigate
security problems posed by malicious data.

CSP works by emitting an HTTP header declaring the policy that browsers
should apply. Ideally, this header would be emitted by a layer above
Mercurial (likely the HTTP server doing the WSGI "proxying"). This
works for some CSP policies, but not all.

For example, policies to allow inline JavaScript may require setting
a "nonce" attribute on <script>. This attribute value must be unique
and non-guessable. And, the value must be present in the HTTP header
and the HTML body. This means that coordinating the value between
Mercurial and another HTTP server could be difficult: it is much
easier to generate and emit the nonce in a central location.

This commit introduces support for emitting a
Content-Security-Policy header from hgweb. A config option defines
the header value. If present, the header is emitted. A special
"%nonce%" syntax in the value triggers generation of a nonce and
inclusion in <script> elements in templates. The inclusion of a
nonce does not occur unless "%nonce%" is present. This makes this
commit completely backwards compatible and the feature opt-in.

The nonce is a type 4 UUID, which is the flavor that is randomly
generated. It has 122 random bits, which should be plenty to satisfy
the guarantees of a nonce.

  $ cat >> $HGRCPATH << EOF
  > [web]
  > push_ssl = false
  > allow_push = *
  > EOF

  $ hg init server
  $ cd server
  $ touch a
  $ hg -q commit -A -m initial
  $ cd ..

  $ hg -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid >> $DAEMON_PIDS

compression formats are advertised in compression capability

#if zstd
  $ get-with-headers.py 127.0.0.1:$HGPORT '?cmd=capabilities' | tr ' ' '\n' | grep compression
  compression=zstd,zlib
#else
  $ get-with-headers.py 127.0.0.1:$HGPORT '?cmd=capabilities' | tr ' ' '\n' | grep compression
  compression=ZL
#endif

  $ killdaemons.py

server.compressionengines can replace engines list wholesale

  $ hg --config server.compressionengines=none -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid > $DAEMON_PIDS
  $ get-with-headers.py 127.0.0.1:$HGPORT '?cmd=capabilities' | tr ' ' '\n' | grep compression
  compression=none

  $ killdaemons.py

Order of engines can also change

  $ hg --config server.compressionengines=none,zlib -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid > $DAEMON_PIDS
  $ get-with-headers.py 127.0.0.1:$HGPORT '?cmd=capabilities' | tr ' ' '\n' | grep compression
  compression=none,zlib

  $ killdaemons.py

Start a default server again

  $ hg -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid > $DAEMON_PIDS

Server should send application/mercurial-0.1 to clients if no Accept is used

  $ get-with-headers.py --headeronly 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000' -
  200 Script output follows
  content-type: application/mercurial-0.1
  date: * (glob)
  server: * (glob)
  transfer-encoding: chunked

Server should send application/mercurial-0.1 when client says it wants it

  $ get-with-headers.py --hgproto '0.1' --headeronly 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000' -
  200 Script output follows
  content-type: application/mercurial-0.1
  date: * (glob)
  server: * (glob)
  transfer-encoding: chunked

Server should send application/mercurial-0.2 when client says it wants it

  $ get-with-headers.py --hgproto '0.2' --headeronly 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000' -
  200 Script output follows
  content-type: application/mercurial-0.2
  date: * (glob)
  server: * (glob)
  transfer-encoding: chunked

  $ get-with-headers.py --hgproto '0.1 0.2' --headeronly 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000' -
  200 Script output follows
  content-type: application/mercurial-0.2
  date: * (glob)
  server: * (glob)
  transfer-encoding: chunked

Requesting a compression format that server doesn't support results will fall back to 0.1

  $ get-with-headers.py --hgproto '0.2 comp=aa' --headeronly 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000' -
  200 Script output follows
  content-type: application/mercurial-0.1
  date: * (glob)
  server: * (glob)
  transfer-encoding: chunked

#if zstd
zstd is used if available

  $ get-with-headers.py --hgproto '0.2 comp=zstd' 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000' > resp
  $ f --size --hexdump --bytes 36 --sha1 resp
  resp: size=248, sha1=4d8d8f87fb82bd542ce52881fdc94f850748
  0000: 32 30 30 20 53 63 72 69 70 74 20 6f 75 74 70 75 |200 Script outpu|
  0010: 74 20 66 6f 6c 6c 6f 77 73 0a 0a 04 7a 73 74 64 |t follows...zstd|
  0020: 28 b5 2f fd                                     |(./.|

#endif

application/mercurial-0.2 is not yet used on non-streaming responses

  $ get-with-headers.py --hgproto '0.2' 127.0.0.1:$HGPORT '?cmd=heads' -
  200 Script output follows
  content-length: 41
  content-type: application/mercurial-0.1
  date: * (glob)
  server: * (glob)
  
  e93700bd72895c5addab234c56d4024b487a362f

Now test protocol preference usage

  $ killdaemons.py
  $ hg --config server.compressionengines=none,zlib -R server serve -p $HGPORT -d --pid-file hg.pid
  $ cat hg.pid > $DAEMON_PIDS

No Accept will send 0.1+zlib, even though "none" is preferred b/c "none" isn't supported on 0.1

  $ get-with-headers.py --headeronly 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000' Content-Type
  200 Script output follows
  content-type: application/mercurial-0.1

  $ get-with-headers.py 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000'  > resp
  $ f --size --hexdump --bytes 28 --sha1 resp
  resp: size=227, sha1=35a4c074da74f32f5440da3cbf04
  0000: 32 30 30 20 53 63 72 69 70 74 20 6f 75 74 70 75 |200 Script outpu|
  0010: 74 20 66 6f 6c 6c 6f 77 73 0a 0a 78             |t follows..x|

Explicit 0.1 will send zlib because "none" isn't supported on 0.1

  $ get-with-headers.py --hgproto '0.1' 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000'  > resp
  $ f --size --hexdump --bytes 28 --sha1 resp
  resp: size=227, sha1=35a4c074da74f32f5440da3cbf04
  0000: 32 30 30 20 53 63 72 69 70 74 20 6f 75 74 70 75 |200 Script outpu|
  0010: 74 20 66 6f 6c 6c 6f 77 73 0a 0a 78             |t follows..x|

0.2 with no compression will get "none" because that is server's preference
(spec says ZL and UN are implicitly supported)

  $ get-with-headers.py --hgproto '0.2' 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000'  > resp
  $ f --size --hexdump --bytes 32 --sha1 resp
  resp: size=432, sha1=ac931b412ec185a02e0e5bcff98dac83
  0000: 32 30 30 20 53 63 72 69 70 74 20 6f 75 74 70 75 |200 Script outpu|
  0010: 74 20 66 6f 6c 6c 6f 77 73 0a 0a 04 6e 6f 6e 65 |t follows...none|

Client receives server preference even if local order doesn't match

  $ get-with-headers.py --hgproto '0.2 comp=zlib,none' 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000'  > resp
  $ f --size --hexdump --bytes 32 --sha1 resp
  resp: size=432, sha1=ac931b412ec185a02e0e5bcff98dac83
  0000: 32 30 30 20 53 63 72 69 70 74 20 6f 75 74 70 75 |200 Script outpu|
  0010: 74 20 66 6f 6c 6c 6f 77 73 0a 0a 04 6e 6f 6e 65 |t follows...none|

Client receives only supported format even if not server preferred format

  $ get-with-headers.py --hgproto '0.2 comp=zlib' 127.0.0.1:$HGPORT '?cmd=getbundle&heads=e93700bd72895c5addab234c56d4024b487a362f&common=0000000000000000000000000000000000000000'  > resp
  $ f --size --hexdump --bytes 33 --sha1 resp
  resp: size=232, sha1=a1c727f0c9693ca15742a75c30419bc36
  0000: 32 30 30 20 53 63 72 69 70 74 20 6f 75 74 70 75 |200 Script outpu|
  0010: 74 20 66 6f 6c 6c 6f 77 73 0a 0a 04 7a 6c 69 62 |t follows...zlib|
  0020: 78                                              |x|