Allow enabling FIPS mode from an environment variable

[gibfahn]

Problem

As of cae9eb35f0, it is no longer possible to enable FIPS mode with an environment variable. This change was to prevent security issues caused by the misuse of the $OPENSSL_CONF variable. However this means it is no longer possible to test that the FIPS binary actually fails as expected in CitGM.

We can expect (for example) citgm ws to fail with:

error: | 4) WebSocketServer hixie mode connection establishing handles messages passed along with the upg
error: | Uncaught Error: error:060A80A3:digital envelope routines:FIPS_DIGESTINIT:disabled for fips      
error: | at Error (native)                                                                               
error: | at new Hash (crypto.js:56:18)                                                                   
error: | at Object.Hash (crypto.js:55:12)                                                                
error: | at WebSocketServer.completeHandshake (lib/WebSocketServer.js:411:24)                            
error: | at onClientVerified (lib/WebSocketServer.js:471:25)                                             
error: | at WebSocketServer.handleHixieUpgrade (lib/WebSocketServer.js:526:3)                            
error: | at WebSocketServer.handleUpgrade (lib/WebSocketServer.js:172:61)                                
error: | at Server.WebSocketServer._onServerUpgrade (lib/WebSocketServer.js:89:12)                       
error: | at onParserExecuteCommon (_http_server.js:409:14)                                               
error: | at HTTPParser.onParserExecute (_http_server.js:377:5)                         

Node Version	How to enable FIPS	Command to test
v4	On by default	citgm ws
v6.0.0..v6.8.1	Requires env var	OPENSSL_CONF=/path/to/openssl_fips_enabled.cnf citgm ws
v6.9.0..	Command line flag only	mkdir bin; printf '#!/bin/sh'"\n/path/to/node --force-fips "'$*'>bin/node; export PATH=$PWD/bin:$PATH; citgm ws (doesn't work as child processes are spawned).

Possible solution

Allow OPENSSL_FIPS=enable to enable FIPS mode, but don't provide an equivalent to disable it, I don't think this causes any security issues.

Refs:

Turn off FIPS by default: #5181
Discussion of OPENSSL_FIPS: #3820
PR to ignore OPENSSL_CONF: https://github.com/nodejs/node-private/pull/82

cc/ @rvagg @bnoordhuis @shigeki @mhdawson @gdams @sxa555

[gdams]

I am personally slightly confused as to what security difference there would be between using an environment variable to set the config file rather than passing it as a flag. Looking at the PR it seems to be implying that the issue was with attackers being able to swap out the default config file from a known location. So my question is what is the difference between the two commands below?

node --force-fips /path/to/openssl_fips_enabled.cnf
export OPENSSL_CONF=/path/to/openssl_fips_enabled.cnf

We are still using the same path so surely an attacker could still modify/change the config file?
@rvagg perhaps you can explain this to me?

[bnoordhuis]

The security issue was that node unconditionally loaded a config file. The OPENSSL_CONF variable only influenced where it looked, not if. On Windows, it was in a location that is usually writable by other users.

Support for OPENSSL_CONF could be brought back. I'm not a huge fan of the side channel nature of environment variables, though.

[gdams]

Ahh okay, thanks for clearing that up, The only issue with using a flag is that we are seriously reducing the usability of fips. Not only are we unable to spawn child processes of node (such as in citgm) but I would also imagine that this prevents us from using clusters too?

[sam-github]

Setting OPENSSL_CONF=/dev/null would cause node to not use a conf file.

Command line flags are difficult to control compared to env vars, the node invocation is often hidden (such as inside a batch or shell script).

Since it it was windows in particular that doesn't store OpenSSL's conf file in a secure location by default, how about we bring back the default loading of the conf file on non-Windows, and the env var that controls the location?

[bnoordhuis]

The environment variable might be acceptable but I don't like the idea of a default config file, it's very implicit and un-node-y.

Meta: I don't understand why FIPS is configurable at runtime in the first place. In order to tick those government contract checkboxes, crypto needs to be locked down with no way to disable or override it. I would have expected separate FIPS-only binaries.

[gibfahn]

@bnoordhuis Separate FIPS-only binaries is how it worked in v4, it was changed for v6 as a result of #3819. It might be a discussion we should reconsider, but I guess people want to use their FIPS node binaries to npm install things.

So are you saying that you're fine with loading an OpenSSL config file if OPENSSL_CONF=/path/to/file is set, but not ok with having a default location that always gets loaded if it exists (like /usr/local/ssl/openssl.cnf).

[bnoordhuis]

@gibfahn Correct.

@mhdawson @stefanmb See #10938 (comment) - I have no love for FIPS and it's not my department but doesn't a runtime knob weaken its security guarantees? Perhaps something to reconsider if you agree.

[mhdawson]

@bnoordhuis I started at the same point thinking that you'd just want to know it was on. However, there was strong push from community members who wanted/needed the runtime switch for their use cases and so it was added in 6.x.

[mhdawson]

From the discussion sounds like we have consensus that adding back the option to set the config file with OPENSSL_CONF without any fallback default (ie unless you specify it through env or command line no default file will be opened) . Seems like the next step is to submit a PR for that.

[sam-github]

I'll do that tomorrow.

[sam-github]

#11006