Allow to add to the existing environment in process instead of repl…

…acing it (#1763)

* Add env_add to the process module

* Don't mutate passed `env` parameter dictionary

Co-authored-by: Arusekk <arek_koz@o2.pl>

* Update CHANGELOG

* Use a boolean flag instead of env_add

There should be preferably only one obvious way to pass env.

* Update CHANGELOG

---------

Co-authored-by: peace-maker <peace-maker@wcfan.de>
Co-authored-by: peace-maker <peacemakerctf@gmail.com>
Co-authored-by: Arusekk <arek_koz@o2.pl>

CHANGELOG.md

@@ -73,10 +73,12 @@ The table below shows which release corresponds to each branch, and what date th
 - [#2277][2277] elf: Resolve more relocations into GOT entries
 - [#2281][2281] FIX: Getting right amount of data for search fix
 - [#2293][2293] Add x86 CET status to checksec output
+- [#1763][1763] Allow to add to the existing environment in `process` instead of replacing it
 
 [2277]: https://github.com/Gallopsled/pwntools/pull/2277
 [2281]: https://github.com/Gallopsled/pwntools/pull/2281
 [2293]: https://github.com/Gallopsled/pwntools/pull/2293
+[1763]: https://github.com/Gallopsled/pwntools/pull/1763
 
 ## 4.12.0 (`beta`)
 

pwnlib/tubes/process.py

@@ -58,7 +58,9 @@ class process(tube):
         cwd(str):
             Working directory.  Uses the current working directory by default.
         env(dict):
-            Environment variables.  By default, inherits from Python's environment.
+            Environment variables to add to the environment.
+        ignore_environ(bool):
+            Ignore Python's environment.  By default use Python's environment iff env not specified.
         stdin(int):
             File object or file descriptor number to use for ``stdin``.
             By default, a pipe is used.  A pty can be used instead by setting
@@ -224,6 +226,7 @@ def __init__(self, argv = None,
                  executable = None,
                  cwd = None,
                  env = None,
+                 ignore_environ = None,
                  stdin  = PIPE,
                  stdout = PTY,
                  stderr = STDOUT,
@@ -255,7 +258,7 @@ def __init__(self, argv = None,
         original_env = env
 
         if shell:
-            executable_val, argv_val, env_val = executable, argv, env
+            executable_val, argv_val, env_val = executable or '/bin/sh', argv, env
         else:
             executable_val, argv_val, env_val = self._validate(cwd, executable, argv, env)
 
@@ -287,14 +290,14 @@ def __init__(self, argv = None,
         #: Full path to the executable
         self.executable = executable_val
 
+        if ignore_environ is None:
+            ignore_environ = env is not None  # compat
+
         #: Environment passed on envp
-        self.env = os.environ if env is None else env_val
+        self.env = {} if ignore_environ else dict(getattr(os, "environb", os.environ))
 
-        if self.executable is None:
-            if shell:
-                self.executable = '/bin/sh'
-            else:
-                self.executable = which(self.argv[0], path=self.env.get('PATH'))
+        # Add environment variables as needed
+        self.env.update(env_val or {})
 
         self._cwd = os.path.realpath(cwd or os.path.curdir)