src: allow CLI args in env with NODE_OPTIONS #12028

sam-github · 2017-03-24T22:15:58Z

Not all CLI options are supported, those that are problematic from a
security or implementation point of view are disallowed, as are ones
that are inappropriate.

Disallowed because they don't make any sense to inject, they change node behaviour to fundamentally to be useful:

--version/-v
--help/-h
--eval/-e/--print/-pe/-p
--check/-c
--interactive/-i
--v8-options (mapped to v8's --help)
--: NODEOPT only supports options, so doesn't need a seperator between options and script
script.js: the main script and its CLI options can only be specified on the actual command line
--preserve-symlinks

Disallowed because of security concerns:

--tls-cipher-list: This is the kind of thing I personally prefer to see configured by env var than by CLI, but @jasnell has concerns, and I've never seen the CLI option used, so I am prepared to wait until someone presents a use-case before allowing this in the future (if ever).

Disallowed because of implementation difficulties:

--expose-internals: Isn't actually implemented by the options parser, will need some code rearranged to become possible to specify in the env

V8 options:

--help (mentioned above)
I don't see any other V8 options that should be disallowed, they mostly tune or profile the V8 engine run, which is specifically a use-case for NODEOPT

Tests are still missing, and I'm in the process of testing -r, the most important option, but it seems basically workable.

Fix: #11997
Replace: #11888
Reference: #881

NODEOPT=--expose_gc ./node -p 'typeof gc'
NODEOPT=--expose_gc ./node --no-expose_gc -p 'typeof gc'
NODEOPT=hi ./node --no-expose_gc -p 'typeof gc'
NODEOPT=--expose-internals ./node -p "require('internals')"
NODEOPT=--throw-deprecation ./node -p "require('_linklist')"

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
tests and/or benchmarks are included
documentation is changed or added
commit message follows commit guidelines

Affected core subsystem(s)

src

sam-github · 2017-03-24T22:20:30Z

src/node.cc

+    char* cstr = strdup(nodeopt.c_str());
+    // [0] is expected to be the program name, fill it in from the real argv.
+    argv_from_env[argc_from_env++] = argv[0];
+    // XXX(sam) can I use strtok or strtok_r?


@bnoordhuis ----^

Why would you not be able to use strtok_r?

why not use std::string::find and substr?

strtok_r isn't ANSI C, not sure it exists on Windows or even all the unixen.

@sam-github My version of the manpage says it’s part of the recent POSIX standards, so I’d take that as a good sign. If you want to be sure whether it’s okay you could just kick of a CI run that uses it.

(You can also wait for Ben’s answer, of course, but I got the impression that he’s a bit more busy than usual right now…)

I thought the little one wasn't due for a while. :-) Anyhow, Windows is not so POSIX, but I'll just do it and if it works in CI I guess its good for us. Of course, strtok is everywhere, but its not clear to me whether we care about it not being thread safe. Node doesn't here, but it might matter when its used as a library.

addaleax · 2017-03-24T22:29:54Z

src/node.cc

+          const char** argv,
+          int* exec_argc,
+          const char*** exec_argv,
+          bool is_nodeopt = false) {


Can you align the arguments vertically?

addaleax · 2017-03-24T22:31:22Z

src/node.cc

+    char* cstr = strdup(nodeopt.c_str());
+    // [0] is expected to be the program name, fill it in from the real argv.
+    argv_from_env[argc_from_env++] = argv[0];
+    // XXX(sam) can I use strtok or strtok_r?


Why would you not be able to use strtok_r?

addaleax · 2017-03-24T22:33:30Z

src/node.cc

+  if (SafeGetenv("NODEOPT", &nodeopt)) {
+    const char** argv_from_env = new const char*[(nodeopt.length()+1) / 2];
+    int argc_from_env = 0;
+    char* cstr = strdup(nodeopt.c_str());


Why the copy? nodeopt will have its own memory anyway

Suspicion, the c_str() docs aren't amazingly clear about the lifetime of the underlying mem. I'll try without (though I've a mem bug somewhere anyway that I have to find).

@sam-github c_str() is an alias for data() nowadays, it lives as long as the string instance itself

can't non-const methods on the string reallocate the memory invalidating the last pointer?

They can, but you’re not doing that? Indexed accesses seem to be excluded from invalidating the pointer (according to http://en.cppreference.com/w/cpp/string/basic_string/c_str), which makes sense

gibfahn · 2017-03-24T23:30:39Z

src/node.cc

@@ -3661,16 +3665,19 @@ static void ParseArgs(int* argc,
    if (debug_options.ParseOption(arg)) {
      // Done, consumed by DebugOptions::ParseOption().
    } else if (strcmp(arg, "--version") == 0 || strcmp(arg, "-v") == 0) {
+      DisallowInNodeopts(argv[0], is_nodeopt, arg);


Probably worth listing all the options you've excluded in the first comment.

You mean in git commit body, list the options? I can do.

Yeah, I suspect a large amount of the discussion will be around which options we should enable under what conditions etc.

I added the list and reasons to the description of this item for visibility, and will add them back in later.

when you say you will add them back in later. Do you mean add the reasons for the exclusion as comments in the code ? I think a comment in the code as well is good in terms of longer term history when people look and wonder why its not allowed. I do see you have the comments for some of them.

added comments in source, will add to the commit message when the list stabilizes

jasnell · 2017-03-25T19:13:09Z

Couple of discussion points on this:

For the blacklisted options like --tls-cipher-list, should be there an explicit opt in that would allow those to work. For instance NODEOPT="--tls-cipher-list" node --ignore-nodeopt-blacklist foo ... or do we simply always blacklist those items for sake of simplicity?
There needs to be a simple way for embedders like Electron to switch off NODEOPT support (a compile time flag should work fine for this)
I still very much want to see NODEOPT to not be passed down to child_process.fork() processes by default.

sam-github · 2017-03-27T15:44:55Z

@jasnell

There are no other options like --tls-cipher-list, its one of a kind, all the other blacklisted items are pretty clearly not the kind of thing that should be in an env var. Having to specify a CLI option to enable an env var isn't something I've heard a use-case for, I think we should wait until someone asks for it and makes a case.
Good idea, I'll add a compile time flag.
Stripping some env vars is something that needs more discussion, I'll follow up when I get out of this meeting.

jasnell · 2017-03-27T15:53:34Z

For (1) .. good point :-) The only other one that I would definitely rule out, however, is the --security-revert= flag. It's a purposefully undocumented flag that is a very special case. It's use needs to be explicitly opt-in in every situation.

sam-github · 2017-03-27T15:56:49Z

Right, forgot --security-revert (I'd read through the code and it didn't do anything, there aren't any reverts at the moment, so I forgot). See c0836e5

jasnell · 2017-03-27T15:59:11Z

+1 ... yeah, --security-revert is a special snowflake that is reset with every semver-major. We haven't had any CVE's that needed to be included in this since 4.x I think so it's a non-op at the current time. Hopefully it'll be able to remain a non-op forever :-)

sam-github · 2017-03-27T16:34:08Z

On stripping of NODEOPT env var during spawn: I think it takes away from the usefullness of NODEOPT (specifically, it means we can't use NODEOPT="-r node-report" npm install ... to debug install scripts), intrudes confusingly into the child_process API, and goes against the basic philosophy of environment, which is that environment is inherited by children.

However, I'd rather have at least a one-level NODEOPT with this confusing caveat than none at all.

@jasnell, can you make a case for why you want this non-inheritable env var behaviour? And what specifically you propose?

For example:

require('child_process').exec('node -p process.env.NODE_PATH', function(err, out) {
  console.log(err || out);                                                       
});
require('child_process').exec('node -p process.env.NODEOPT', function(err, out) {
  console.log(err || out);                                                       
});

That NODE_PATH=/some/path NODEOPT=--prof node echo.js should print:

/some/path

instead of

/some/path
--prof

I would find confusing, is that what you propose?

And what do you propose that the following code would print?

process.env.NODEOPT = '-r node-report';
require('child_process').exec('node -p process.env.NODEOPT', function(err, out) {
  console.log(err || out);
});

I would expect it to print the value of NODEOPT, do you propose it print something else?

jasnell · 2017-03-27T16:58:55Z

@sam-github ... the concern is largely about backwards compatibility and the possibility of NODEOPT settings altering the behavior of child processes in ways that could break.

For instance, imagine a child process that uses fs.readFileSync() internally to read a file and return it's contents to the parent. The parent is written to scan stdout / stderr to determine whatever status it needs to know. The child process is launched specifically assuming that flags like --trace-sync-io are not passed (because it is not passed in the args). Using NODEOPT=--trace-sync-io, however, causes a number of warnings to be printed to stderr in the child process potentially causing existing code to break.

(Essentially, passing NODEOPT automatically to child processes breaks the existing API contract around args passing to forked child processes.)

My proposal is that NODEOPT would be simply removed from the env passed to the child process unless an option is set, e.g. fork(path, {nodeopt: true}).

richardlau · 2017-03-27T17:30:32Z

But don't we already have that issue with existing environment variables, e.g. NODE_DEBUG?

sam-github · 2017-03-27T17:40:21Z

NODE_TTY_UNSAFE_ASYNC is also inherited, and modifies API contract in ways that would break child processes, there seems to be some precedence for these "use at own risk" env vars.

If there is widespread concern, I'd rather disable V8 options that output to stdio then break the inheritance, it leaves the behaviour much more predictable.

jasnell · 2017-03-27T17:48:43Z

NODE_TTY_UNSAFE_ASYNC is in the process of being removed entirely, however. There is also extremely little evidence that it's actually used by anyone.

sam-github · 2017-03-27T17:53:44Z

NODE_DEBUG isn't getting removed, and has the same characteristics as you describe for NODEOPT=--trace-sync-io: it can be useful, it is inherited, and it will (unsprisingly) break any code that doesn't expect extra output.

bmeck · 2017-03-27T18:26:45Z

I would be much more comfortable if this was a whitelist instead of a blacklist. It would prevent accidentally harmful flags from being exposed.

jasnell · 2017-03-27T19:47:54Z

NODE_DEBUG has been around since v0.1.32 and is well established as an environment variable. It predates the child_process API and it's side effects and inheritance by spawned child processes is well known. It also does not alter arbitrary command line arguments passed into the child process. There is no backwards compatibility concern there and therefore is not directly comparable.

mhdawson · 2017-03-27T20:20:25Z

@jasnell , what about if we have NODEOPT and NODEOPT_INHERIT and let people choose the behavior they want. NODEOPT_INHERIT would be passed to child processes while NODEOPT would not. In that way you can use the environment to set options and chose if they are inherited or not. I think having the ability to pass on options to child processes is important and this would be one way to let the end user make a specific choice.

sam-github · 2017-03-27T20:32:29Z

@jasnell Before I implement this, lets be really clear:

My proposal is that NODEOPT would be simply removed from the env passed to the child process unless an option is set, e.g. fork(path, {nodeopt: true}).

child_process.spawn(process.execPath, {env: {NODEOPT='xxx'}}, function(...

You propose NODEOPT to not be set in the child process's env?

@bmeck, Do you mean for node options, or V8 options? I can switch it around to opt-in for node, I think there is a way I can do that, but there are 417 V8 options as of this moment on master, and they all look like the kinds of things someone might want to set via env to tune performance or diagnose mis-performance, and there don't appear to be anything we'd want to blacklist.

jchip · 2017-03-27T20:57:31Z

src/node.cc

+    ProcessArgv(&argc_from_env, argv_from_env, &exec_argc_, &exec_argv_, true);
+    delete[] exec_argv_;
+    delete[] argv_from_env;
+    free(cstr);


Personally, I'd rather that C++ std lib classes are used to avoid all the manual allocations. And you shouldn't have to worry about if the C++ std lib is available on a certain platform. And you don't need to rely on the non-reentrant legacy c strtok.

std::vector<std::string> env_args; std::string::size_type pos = 0, pos_next = 0; while (pos_next < nodeopt.size()) { pos_next = nodeopt.find(" ", pos); if (pos_next == std::string::npos) { pos_next = nodeopt.size(); } if (pos_next > pos) { env_args.push_back(nodeopt.substr(pos, pos_next - pos)); } pos = pos_next + 1; } std::vector<const char *> argv_from_env; argv_from_env.reserve(args.size() + 2); argv_from_env.push_back(argv[0]); for (size_t i = 0; i < args.size(); i++) { argv_from_env.push_back(env_args[i].c_str()); } argv_from_env.push_back(nullptr);

and now you can call ProcessArgv:

ProcessArgv(&argc_from_env, &argv_from_env[0], &exec_argc_, &exec_argv_, true );

jasnell · 2017-03-27T20:59:52Z

@sam-github ... no, if NODEOPT is explicitly passed in the call to fork like in your example, it would be used. What I'm saying is that env is not explicitly given and the default process.env is used, then it's NODEOPT would not be inherited.

In other words... NODEOPT is used:

child_process.spawn(process.execPath, {env: {NODEOPT:'...'}}, () => {});

process.env.NODEOPT is used:

child_process.spawn(process.execPath, {nodeopt: true}, () => {});

process.env.NODEOPT is not used:

child_process.spawn(process.execPath, () => {});

@mhdawson ... as long as there is an explicit opt-in for the options to be used in child processes I'm fine with however it happens. A second environment variable would not be my first choice tho but I could live with it.

jasnell · 2017-03-27T21:03:06Z

Note: that if we went with the nodeopt:true option to spawn/fork now, we can always choose to switch the default later (making the option a non-op) if it can be shown that inheriting the NODEOPT env does not break anyone in practice.

jchip · 2017-03-27T21:04:10Z

src/node.cc

-      break;
+    char* cstr = strdup(nodeopt.c_str());
+    char* initptr = cstr;
+    while (char* token = strtok(initptr, " ")) {


does this handle multiple spaces? like "-a -b".

addaleax · 2017-03-27T21:07:25Z

@jasnell @mhdawson If the main risk you have in mind is security, it won’t matter whether you pass one or two environment variables.

(But as I’ve said before, using environment variables that are not inherited by child processes seems pointless by definition.)

bmeck · 2017-03-27T21:11:14Z

@sam-github I am definitely thinking about more than just node arguments. Things like --harmony-* would prevent some polyfill detection and use incomplete/broken v8 implementations if they are passed.

jasnell · 2017-03-27T21:45:33Z

Another note: the documentation on this should need to be clear that:

(a) command line arguments passed directly on the command line take precedence over those passed in NODEOPT and
(b) Child processing inheriting NODEOPT would not inherit arguments passed on the command line.

To illustrate the kind of impact this has consider the following example:

$ NODEOPT="--icu-data-dir=a" ./node --icu-data-dir=b
> process.binding('config');
{ hasIntl: true, hasSmallICU: true, icuDataDir: 'b' }
> var m = child_process.spawn('./node', ['-pe', 'console.log(process.binding("config"))'], {stdio:['inherit','inherit', 'inherit']})
undefined
> { hasIntl: true, hasSmallICU: true, icuDataDir: 'a' }

To be certain, this is not a criticism, just something that should be noted. (This is also true when using the NODE_ICU_DATA environment variable)

Note that the current CLI/env documentation (https://nodejs.org/dist/latest-v7.x/docs/api/cli.html) currently does not explain that arguments would take precedence over env vars.

cjihrig · 2017-03-27T21:47:25Z

I agree with @addaleax that environment variables should be passed to child processes by default.

jasnell · 2017-03-27T21:50:05Z

Another test case that will need be looked at:

NODEOPT="--inspect=localhost:1234" ./node
Debugger listening on port 1234.
Warning: This is an experimental feature and could change at any time.
To start debugging, open the following URL in Chrome:
    chrome-devtools://devtools/bundled/inspector.html?experiments=true&v8only=true&ws=localhost:1234/f8884219-6fd2-442e-aa5e-257cb686e3a5
> var m = child_process.spawn('./node', {stdio:['inherit', 'inherit', 'inherit']})
undefined
> Starting inspector on localhost:1234 failed: address already in use

Not all CLI options are supported, those that are problematic from a security or implementation point of view are disallowed, as are ones that are inappropriate (for example, -e, -p, --i), or that only make sense when changed with code changes (such as options that change the javascript syntax or add new APIs). PR-URL: nodejs#12028 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michael Dawson <[email protected]> Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: Gibson Fahnestock <[email protected]> Reviewed-By: Bradley Farias <[email protected]>

Not all CLI options are supported, those that are problematic from a security or implementation point of view are disallowed, as are ones that are inappropriate (for example, -e, -p, --i), or that only make sense when changed with code changes (such as options that change the javascript syntax or add new APIs). Backport-PR-URL: #12677 PR-URL: #12028 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michael Dawson <[email protected]> Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: Gibson Fahnestock <[email protected]> Reviewed-By: Bradley Farias <[email protected]>

Notable Changes: * assert: - assert.fail() can now take one or two arguments (Rich Trott) #12293 * crypto: - add sign/verify support for RSASSA-PSS (Tobias Nießen) #11705 * deps: - upgrade openssl sources to 1.0.2m (Shigeki Ohtsu) #16691 - upgrade libuv to 1.15.0 (cjihrig) #15745 - upgrade libuv to 1.14.1 (cjihrig) #14866 - upgrade libuv to 1.13.1 (cjihrig) #14117 - upgrade libuv to 1.12.0 (cjihrig) #13306 * fs: - Add support for fs.write/fs.writeSync(fd, buffer, cb) and fs.write/fs.writeSync(fd, buffer, offset, cb) as documented (Andreas Lind) #7856 * inspector: - enable --inspect-brk (Refael Ackermann) #12615 * process: - add --redirect-warnings command line argument (James M Snell) #10116 * src: - allow CLI args in env with NODE_OPTIONS (Sam Roberts) #12028) - --abort-on-uncaught-exception in NODE_OPTIONS (Sam Roberts) #13932 - allow --tls-cipher-list in NODE_OPTIONS (Sam Roberts) #13172 - use SafeGetenv() for NODE_REDIRECT_WARNINGS (Sam Roberts) #12677 * test: - remove common.fail() (Rich Trott) #12293 PR-URL: #16263

nodejs-github-bot added the c++ Issues and PRs that require attention from people who are familiar with C++. label Mar 24, 2017

sam-github commented Mar 24, 2017

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addaleax reviewed Mar 24, 2017

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jasnell added the wip Issues and PRs that are still a work in progress. label Mar 24, 2017

gibfahn reviewed Mar 24, 2017

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sam-github force-pushed the cli-env-option branch from c0836e5 to f7e2e40 Compare March 27, 2017 17:16

jchip reviewed Mar 27, 2017

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jasnell mentioned this pull request May 11, 2017

8.0.0 Release Proposal #12220

Closed

vsemozhetbyt mentioned this pull request May 30, 2017

blog: add release post for 8.0.0 nodejs/nodejs.org#1241

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gibfahn added backported-to-v7.x and removed backport-requested-v7.x labels Jun 14, 2017

MylesBorins added backported-to-v6.x and removed backport-requested-v6.x labels Oct 16, 2017

MylesBorins mentioned this pull request Oct 17, 2017

v6.12.0 proposal #16263

Merged

MylesBorins mentioned this pull request Nov 3, 2017

v4.8.6 proposal #16500

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gibfahn mentioned this pull request Nov 13, 2017

v6.12.0: max-old-space-size can no longer be set via NODE_OPTIONS #16999

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gibfahn mentioned this pull request Mar 14, 2018

process: add allowedNodeEnvironmentFlags property #19335

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4 tasks

mhdawson mentioned this pull request Mar 11, 2024

Enable --security-revert to be used in NODE_OPTIONS environment variable #52017

Closed

src: allow CLI args in env with NODE_OPTIONS #12028

src: allow CLI args in env with NODE_OPTIONS #12028

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sam-github commented Mar 24, 2017 • edited Loading

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jasnell commented Mar 25, 2017

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