view tests/test-merge-local.t @ 36755:ff4bc0ab6740 stable

wireproto: check permissions when executing "batch" command (BC) (SEC)

For as long as the "batch" command has existed (introduced by
bd88561afb4b and first released as part of Mercurial 1.9), that command
(like most wire commands introduced after 2008) lacked an entry in
the hgweb permissions table. And since we don't verify permissions if
an entry is missing from the permissions table, this meant that
executing a command via "batch" would bypass all permissions
checks.

The security implications are significant: a Mercurial HTTP server
would allow writes via "batch" wire protocol commands as long as
the HTTP request were processed by Mercurial and the process running
the Mercurial HTTP server had write access to the repository. The
Mercurial defaults of servers being read-only and the various web.*
config options to define access control were bypassed.

In addition, "batch" could be used to exfiltrate data from servers
that were configured to not allow read access.

Both forms of permissions bypass could be mitigated to some extent
by using HTTP authentication. This would prevent HTTP requests from
hitting Mercurial's server logic. However, any authenticated request
would still be able to bypass permissions checks via "batch" commands.

The easiest exploit was to send "pushkey" commands via "batch" and
modify the state of bookmarks, phases, and obsolescence markers.
However, I suspect a well-crafted HTTP request could trick the server
into running the "unbundle" wire protocol command, effectively
performing a full `hg push` to create new changesets on the remote.

This commit plugs this gaping security hole by having the "batch"
command perform permissions checking on each sub-command that is
being batched. We do this by threading a permissions checking
callable all the way to the protocol handler. The threading is a
bit hacky from a code perspective. But it preserves API compatibility,
which is the proper thing to do on the stable branch.

One of the subtle things we do is assume that a command with an
undefined permission is a "push" command. This is the safest thing to
do from a security perspective: we don't want to take chances that
a command could perform a write even though the server is configured
to not allow writes.

As the test changes demonstrate, it is no longer possible to bypass
permissions via the "batch" wire protocol command.

.. bc::

   The "batch" wire protocol command now enforces permissions of
   each invoked sub-command. Wire protocol commands must define
   their operation type or the "batch" command will assume they
   can write data and will prevent their execution on HTTP servers
   unless the HTTP request method is POST, the server is configured
   to allow pushes, and the (possibly authenticated) HTTP user is
   authorized to perform a push.

  $ hg init

Revision 0:

  $ echo "unchanged" > unchanged
  $ echo "remove me" > remove
  $ echo "copy me" > copy
  $ echo "move me" > move
  $ for i in 1 2 3 4 5 6 7 8 9; do
  >     echo "merge ok $i" >> zzz1_merge_ok
  > done
  $ echo "merge bad" > zzz2_merge_bad
  $ hg ci -Am "revision 0"
  adding copy
  adding move
  adding remove
  adding unchanged
  adding zzz1_merge_ok
  adding zzz2_merge_bad

Revision 1:

  $ hg rm remove
  $ hg mv move moved
  $ hg cp copy copied
  $ echo "added" > added
  $ hg add added
  $ echo "new first line" > zzz1_merge_ok
  $ hg cat zzz1_merge_ok >> zzz1_merge_ok
  $ echo "new last line" >> zzz2_merge_bad
  $ hg ci -m "revision 1"

Local changes to revision 0:

  $ hg co 0
  4 files updated, 0 files merged, 3 files removed, 0 files unresolved
  $ echo "new last line" >> zzz1_merge_ok
  $ echo "another last line" >> zzz2_merge_bad

  $ hg diff --nodates | grep "^[+-][^<>]"
  --- a/zzz1_merge_ok
  +++ b/zzz1_merge_ok
  +new last line
  --- a/zzz2_merge_bad
  +++ b/zzz2_merge_bad
  +another last line

  $ hg st
  M zzz1_merge_ok
  M zzz2_merge_bad

Local merge with bad merge tool:

  $ HGMERGE=false hg co
  merging zzz1_merge_ok
  merging zzz2_merge_bad
  merging zzz2_merge_bad failed!
  3 files updated, 1 files merged, 2 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]

  $ hg resolve -m
  (no more unresolved files)

  $ hg co 0
  merging zzz1_merge_ok
  merging zzz2_merge_bad
  warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
  2 files updated, 1 files merged, 3 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]

  $ hg diff --nodates | grep "^[+-][^<>]"
  --- a/zzz1_merge_ok
  +++ b/zzz1_merge_ok
  +new last line
  --- a/zzz2_merge_bad
  +++ b/zzz2_merge_bad
  +another last line
  +=======

  $ hg st
  M zzz1_merge_ok
  M zzz2_merge_bad
  ? zzz2_merge_bad.orig

Local merge with conflicts:

  $ hg resolve -m
  (no more unresolved files)

  $ hg co
  merging zzz1_merge_ok
  merging zzz2_merge_bad
  warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
  3 files updated, 1 files merged, 2 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]

  $ hg resolve -m
  (no more unresolved files)

  $ hg co 0 --config 'ui.origbackuppath=.hg/origbackups'
  merging zzz1_merge_ok
  merging zzz2_merge_bad
  warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
  2 files updated, 1 files merged, 3 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]

Are orig files from the last commit where we want them?
  $ ls .hg/origbackups
  zzz2_merge_bad

  $ hg diff --nodates | grep "^[+-][^<>]"
  --- a/zzz1_merge_ok
  +++ b/zzz1_merge_ok
  +new last line
  --- a/zzz2_merge_bad
  +++ b/zzz2_merge_bad
  +another last line
  +=======
  +=======
  +new last line
  +=======

  $ hg st
  M zzz1_merge_ok
  M zzz2_merge_bad
  ? zzz2_merge_bad.orig

Local merge without conflicts:

  $ hg revert zzz2_merge_bad

  $ hg resolve -m
  (no more unresolved files)

  $ hg co
  merging zzz1_merge_ok
  4 files updated, 1 files merged, 2 files removed, 0 files unresolved

  $ hg diff --nodates | grep "^[+-][^<>]"
  --- a/zzz1_merge_ok
  +++ b/zzz1_merge_ok
  +new last line

  $ hg st
  M zzz1_merge_ok
  ? zzz2_merge_bad.orig