hgweb: map Abort to 403 error to report inaccessible path for example

Abort is so common in our codebase. We could instead introduce a dedicated
type for path auditing errors, but we'll probably have to catch error.Abort
anyway.

As you can see, an abort message may include a full path to the repository,
which might be considered information leak. If that matters, we should hide
the message and send it to the server log instead.

mercurial/hgweb/hgweb_mod.py

@@ -439,6 +439,10 b' class hgweb(object):'
             res.status = '500 Internal Server Error'
             res.headers['Content-Type'] = ctype
             return rctx.sendtemplate('error', error=pycompat.bytestr(e))
+        except error.Abort as e:
+            res.status = '403 Forbidden'
+            res.headers['Content-Type'] = ctype
+            return rctx.sendtemplate('error', error=pycompat.bytestr(e))
         except ErrorResponse as e:
             for k, v in e.headers:
                 res.headers[k] = v

tests/test-hgwebdir.t

@@ -66,6 +66,20 b' create a subdirectory containing reposit'
   > EOF
   $ cd ..
 
+add file under the directory which could be shadowed by another repository
+
+  $ mkdir notrepo/f/f3
+  $ echo f3/file > notrepo/f/f3/file
+  $ hg -R notrepo/f ci -Am 'f3/file'
+  adding f3/file
+  $ hg -R notrepo/f update null
+  0 files updated, 0 files merged, 4 files removed, 0 files unresolved
+  $ hg init notrepo/f/f3
+  $ cat <<'EOF' > notrepo/f/f3/.hg/hgrc
+  > [web]
+  > hidden = true
+  > EOF
+
 create repository without .hg/store
 
   $ hg init nostore
@@ -1217,6 +1231,38 b' Test subrepositories inside intermediate'
   
   f2
 
+Test accessing file that is shadowed by another repository
+
+  $ get-with-headers.py localhost:$HGPORT1 'rcoll/notrepo/f/file/tip/f3/file?style=raw'
+  403 Forbidden
+  
+  
+  error: path 'f3/file' is inside nested repo 'f3'
+  [1]
+
+  $ get-with-headers.py localhost:$HGPORT1 'rcoll/notrepo/f/file/ffffffffffff/f3/file?style=raw'
+  403 Forbidden
+  
+  
+  error: path 'f3/file' is inside nested repo 'f3'
+  [1]
+
+Test accessing invalid paths:
+
+  $ get-with-headers.py localhost:$HGPORT1 'rcoll/notrepo/f/file/tip/..?style=raw'
+  403 Forbidden
+  
+  
+  error: .. not under root '$TESTTMP/dir/webdir/notrepo/f'
+  [1]
+
+  $ get-with-headers.py localhost:$HGPORT1 'rcoll/notrepo/f/file/tip/.hg/hgrc?style=raw'
+  403 Forbidden
+  
+  
+  error: path contains illegal component: .hg/hgrc
+  [1]
+
 Test descend = False
 
   $ killdaemons.py