wiki:soc2007/epimenov

Sorry for my English.

Idea

Port isolation :). When MacPorts build port it can deny to see files that port should not see.

Current status

It almost work :)

SVN commits: r26682 r28091 r28147 r29367 r29369 r29641
Sources: darwintrace.c porttrace.tcl portutil.tcl tracelib.c tracelib.h

How it works

tracelib

port command opens unix socket in /tmp/macports/{pid of port command} and injects tracelib into process' address space. Tracelib hooks close, execve, lstat, mkdir, open, readlink, rename, rmdir, stat, unlink.

When some activity is occurred, it looks at filemap. There are 4 cases:

  1. path marked as 0 — grant access
  2. path marked as 1 — do redirect
  3. path marked as 2 — ask port command for advise
  4. path not listed in filemap — deny and report incident to port command

When fourth case is occurred you'll see something like “Warning: A creation/deletion/modification was attempted outside sandbox: /etc/group”. It a little bit incorrect, because it can happen on read/stat actions too. But it is old Paul's warning, and I don't know why I didn't change it :)

When third case is occurred tracelib asks port command about permit to interact with file. If it says no you'll see “trace: access denied to /opt/local/bin/perl (perl5.8)”. If it says yes we allow access to file. Unlike fourth case dirs are ignored.

Filemap

Filemap is piece of memory in form:

path\0action[redirect_path]\0path\0\action...path\0action[redirect_path]\0\0

path is path prefix (for example, / matches all paths, /opt matches /optblah/blah and /opt/blah etc)
action is actions listed before
redirect_path is path for !SDK redirection, present only with 1 action.
\0 — is byte with code zero

Filemap's building performed here. And it can be influenced by tcl code here.

SDK redirection

There are SDKs in /Developer/SDKs/. Tracelib can map / to SDK dir.

Example: We building port with SDK MacOSX10.2.8.sdk. gcc wants to use /usr/include/stdio.h and calls open(/usr/include/stdio.h), but tracelib returns open(/Developer/SDKs/MacOSX10.2.8.sdk/usr/include/stdio.h).

But there are some problems.

  1. I don't have any version of Mac OS X but 10.4, and can test, but I think there will be issues with ABI, and version of gcc.
  2. Some files missed in SDK directory (for example CPAN).

User's part

User can use SDK redirection by specify --with-trace-sdk=SDK

Port trace can be enabled by specifying option -t for port command. For example:

sudo port -t install ghc

Problems

Some ports can reject to build in port trace mode because of sandbox. For example before r29641 you could not build gtk (it use files dir in $portdir, which wasn't allowed for read).

There are common programs (like gawk or perl) which dirt output.

SDK redirection is untested in real world.

How it can be used

Maintainers can test dependencies with it.

MacPorts can provide binary packages (SDK redirection is for it) :)

Last modified 10 years ago Last modified on Oct 5, 2007, 5:51:25 PM