unique debugger pin in Docker containers

Author: davidism

CHANGES.rst

@@ -20,6 +20,8 @@ Unreleased
  (:issue:`1510`)
 - The debugger detects cycles in chained exceptions and does not time
  out in that case. (:issue:`1536`)
+- When running the development server in Docker, the debugger security
+ pin is now unique per container.
 
 
 Version 0.15.2

src/werkzeug/debug/__init__.py

@@ -67,6 +67,19 @@ def get_machine_id():
  return rv
 
  def _generate():
+ # docker containers share the same machine id, get the
+ # container id instead
+ try:
+ with open("/proc/self/cgroup") as f:
+ value = f.readline()
+ except IOError:
+ pass
+ else:
+ value = value.strip().partition("/docker/")[2]
+
+ if value:
+ return value
+
  # Potential sources of secret information on linux. The machine-id
  # is stable across boots, the boot id is not
  for filename in "/etc/machine-id", "/proc/sys/kernel/random/boot_id":