Add some warnings about AcceptEnv to env var setting bits.

Re #398

3 files changed, 17 insertions, 1 deletions

diff --git a/paramiko/channel.py b/paramiko/channel.py
index 7689b266..3b6a59df 100644
--- a/paramiko/channel.py
+++ b/paramiko/channel.py
@@ -292,6 +292,10 @@ class Channel (ClosingContextManager):
             This operation is additive - i.e. the current environment is not
             reset before the given environment variables are set.
 
+        .. warning::
+            Servers may silently reject some environment variables; see the
+            warning in `set_environment_variable` for details.
+
         :param dict environment:
             a dictionary containing the name and respective values to set
         :raises SSHException:
@@ -310,6 +314,12 @@ class Channel (ClosingContextManager):
         """
         Set the value of an environment variable.
 
+        .. warning::
+            The server may reject this request depending on its ``AcceptEnv``
+            setting; such rejections will fail silently (which is common client
+            practice for this particular request type). Make sure you
+            understand your server's configuration before using!
+
         :param str name: name of the environment variable
         :param str value: value of the environment variable
 
diff --git a/paramiko/client.py b/paramiko/client.py
index 978bde51..40cd5cf2 100644
--- a/paramiko/client.py
+++ b/paramiko/client.py
@@ -421,6 +421,11 @@ class SSHClient (ClosingContextManager):
         :param dict environment:
             a dict of shell environment variables, to be merged into the
             default environment that the remote command executes within.
+
+            .. warning::
+                Servers may silently reject some environment variables; see the
+                warning in `.Channel.set_environment_variable` for details.
+
         :return:
             the stdin, stdout, and stderr of the executing command, as a
             3-tuple
diff --git a/sites/www/changelog.rst b/sites/www/changelog.rst
index 12fecdc5..3207d8f2 100644
--- a/sites/www/changelog.rst
+++ b/sites/www/changelog.rst
@@ -8,7 +8,8 @@ Changelog
   and `Channel.set_environment_variable
   <paramiko.channel.Channel.set_environment_variable>` methods) which
   implements the ``env`` SSH message type. This means the remote shell
-  environment can be set without the use of ``VARNAME=value`` shell tricks.
+  environment can be set without the use of ``VARNAME=value`` shell tricks,
+  provided the server's ``AcceptEnv`` lists the variables you need to set.
   Thanks to Philip Lorenz for the pull request.
 * :support:`819 backported (>=1.15,<2.0)` Document how lacking ``gmp`` headers
   at install time can cause a significant performance hit if you build PyCrypto