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add cli integration for masked and readonly paths #1347

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jessfraz
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@jessfraz jessfraz commented Sep 6, 2018

I wanted to make sure this design was okay before going any further.

This adds flags --masked-paths and --readonly-paths to the cli as a follow up from moby/moby#36644 cc @AkihiroSuda

Happy to change the design in any way you want then will add docs and tests.

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>
@@ -183,6 +187,8 @@ func addFlags(flags *pflag.FlagSet) *containerOptions {
flags.StringVarP(&copts.user, "user", "u", "", "Username or UID (format: <name|uid>[:<group|gid>])")
flags.StringVarP(&copts.workingDir, "workdir", "w", "", "Working directory inside the container")
flags.BoolVar(&copts.autoRemove, "rm", false, "Automatically remove the container when it exits")
flags.Var(&copts.maskedPaths, "masked-paths", "Denote the paths to be masked for the container, empty implies none")
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empty implies default, not "none"?

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It implies none, of "paths to be masked for the containers"

@@ -50,6 +50,19 @@ func TestRunWithContentTrust(t *testing.T) {
})
}

func TestRunMaskedPaths(t *testing.T) {
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WIP?

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Especially we need to make sure nil and []string{} are treated differently

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yeah was about to add tests but waited also im confused as to if the tests from docker/docker will be moved here too?

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@jessfraz new tests from docker/docker should only test the API — or be unit tests 😝). Any tests using the cli should indeed be there.

for _, p := range paths {
if p == "none" {
if len(paths) > 1 {
return nil, errors.New("Passing 'none' and other paths is not allowed")
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nit: error string should not be capitalized

@rroller
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rroller commented Oct 1, 2018

Any update on this and if it'll get merged?

@AkihiroSuda
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Can we also have --unmask-proc for simplicity?

@tiborvass
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@jessfraz @AkihiroSuda @vdemeester So I know this may be controversial but what do you think of putting these behind --security-opt like so --security-opt readonly-paths=... and --security-opt masked-paths=... ?

I know it's ugly because in the API it's not a security opt, but the rationale for this suggestion is that it's not necessarily obvious for users that this may have a security implication as defaults are overridden.

If we agree on this, we could have the API accept either security opts or regular run options.

Let me know what you think!

@AkihiroSuda
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AkihiroSuda commented Oct 12, 2018

FYI: it turned out that unshare -rmn mount -t sysfs none /sys (for /sys/class/net) requires rw/unmasked sysfs

rootless-containers/rootlesskit#23

@AkihiroSuda
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Maybe:

  • --security-opt readonly-paths (low-level, rarely used)
  • --security-opt masked-paths (ditto)
  • --security-opt unconfined-paths (frequently used as --security-opt unconfined-paths=/proc,/sys)

@thaJeztah
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If we agree on this, we could have the API accept either security opts or regular run options.

Wondering if the API must reflect the UX, I don't think that's strictly required.

--security-opt unconfined-paths (frequently used as --security-opt unconfined-paths=/proc,/sys)

@AkihiroSuda wondering how that option would work in conjunction with the other options; should we error (conflicting options)?

I recall the original discussion on the API side of things that we preferred explicit over implicit, so providing your own set of "masked" and/or "read only" paths. That was of course from the API perspective, so UX can differentiate from that.

If we use unconfined-paths; how would the CLI determine the default set of masked paths? (I don't think there's currently an endpoint that would allow querying the default set from the daemon, other than inspecting an already created container)

@jessfraz
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I'm okay with any of the options listed above :)

@tonistiigi
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--security-opt unconfined-paths (frequently used as --security-opt unconfined-paths=/proc,/sys)

I don't think you can actually do --security-opt unconfined-paths=/proc,/sys because the API only supports whitelist and modifications to the default set are not allowed. Not sure if there is any usecase for actually specifying a special path from CLI though as it is quite an effort required from the user to remember to whole list of possibly insecure paths. Usually you just want to either allow all or make an excpetion to the default. How about just --security-opt systempaths=unconfined. (or protectedpaths, securitypaths, ...)

@tiborvass
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@tonistiigi If it's systempaths=unconfined then what's the other value for systempaths= ? confined ?

@tonistiigi
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@tiborvass There is no other value. If we want then confined would mean the daemon default and if there is a good usecase we could add more names. I'm fine with a constant value. I noticed that --security-opt no-new-privileges=false uses a bool so we could use that as well.

@scher200
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@tonistiigi how is this going? I am exited to see this working

@tonistiigi
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How about just --security-opt systempaths=unconfined. (or protectedpaths, securitypaths, ...)
or --security-opt unmaskedsystempaths=true --security-opt rawsystempaths=true

Does anyone have objections to this? I'm good with any of them.

@thaJeztah Might be good to add this to maintainer session today.

@thaJeztah
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Does anyone have objections to this? I'm good with any of them.

UX-wise, I like that option, so (name to be discussed);

--security-opt systempaths=unconfined

Would send the equivalent of --masked-paths=[]

Concern:

  • systempaths=unconfined would disable all masked paths
  • because of the above, doing the wrong thing ("just unmask the whole shebang) is easier than doing the right thing ("specify which paths you want to unmask")

I think it's important when dealing with security configuration to make "doing the right thing" easier than "doing the wrong thing".

So; do we also want to provide a more fine-grained approach on the CLI; an option to manually provide exactly which paths to mask/mark readonly?

If yes: that would raise the question #1347 (comment)

how would the CLI determine the default set of masked paths? (I don't think there's currently an endpoint that would allow querying the default set from the daemon, other than inspecting an already created container)

Approach could then be;

Implement a defaults endpoint for containers (I think that's useful for other purposes as well, such as showing defaults for flags/options; especially if those defaults are configurable on the daemon), for example;

  • GET /v1.40/containers/-/defaults (- indenting as "no id" ? idk)
  • GET /v1.40/containers/-/json (ugh .. the trailing /json sucks haha)

When creating a container;

  1. Fetch the defaults
  2. Patch the defaults with changes from the CLI (?) (---security-opt unconfined-paths=/proc,/sys)
  3. Send the resulting masked-paths and readonly-paths over the API

@justincormack @jessfraz I know you're better at security than I am, so wondering what you think, or what suggestions you have 😅

Adding this to next week's maintainers meeting as well (this week didn't happen, due to many people travelling or at KubeCon)

@justincormack
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I don't think setting the defaults makes sense, it is too confusing for different people to have different defaults. A security option to remove them all seems ok, and an API option to set them, and maybe a security option eg systempaths=/path1,/path2,... although its going to be hard to drive. Unconfined seems the most likely case and most consistent eg with seccomp.

@imbolo
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imbolo commented Dec 29, 2018

Any update ?

@scher200
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when in this expected to be released?

@tiborvass
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Let's roll with --security-opt systempaths=unconfined and call it a day. We can add more things later. If no one answers in disagreement, I'll consider it an agreement. Ping @thaJeztah @justincormack

@biblix
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biblix commented Mar 26, 2019

Hi @jessfraz, https://github.com/genuinetools/img#running-with-docker led me here. While this PR is still pending, is there a way to take your fix here and test img build in a unprivileged container in Kubernetes?

@thaJeztah
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Let's roll with --security-opt systempaths=unconfined and call it a day. We can add more things later. If no one answers in disagreement, I'll consider it an agreement.

OK, so;

  • --security-opt systempaths=unconfined would set masked-paths=[] and readonly-paths=[]
  • no option yet to set them individually
  • no option yet to set an individual list of paths to (un)mask, make read-only/writable

Correct?

@tiborvass
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@thaJeztah yes. cc @justincormack

@vdemeester
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Needs a rebase 😅

@thaJeztah
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Needs a rebase 😅

Also needs an actual implementation of the proposed changes #1347 (comment)

@tiborvass were you planning on making those?

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let me "request changes" pending the proposed changes 😅

@jessfraz
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jessfraz commented Apr 4, 2019

ah okay is this on me? I can do that

@tiborvass
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@jessfraz I was about to do it but feel free!

@thaJeztah
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@tiborvass @jessfraz I see @martencassel started working on the implementation; see #1808

@jessfraz
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jessfraz commented Apr 6, 2019 via email

@elgalu
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elgalu commented May 30, 2019

#1808 is merged

@tiborvass
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Thank you @jessfraz and @martencassel !

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