interfaces: add random interface #3045

renatgalimov · 2017-03-17T06:06:31Z

Allow access to the /dev/hwrng device (used in the Raspberry Pi).

niemeyer

We can probably name this as simply "random", and include in this interface any random-number generation infrastructure available in the system.

Otherwise, just a few notes:

niemeyer · 2017-03-17T10:10:39Z

interfaces/builtin/hw_random.go

+# Description: Allow access to the hardware random number generator device - /dev/hwrng
+
+/dev/hwrng rw,
+/devices/virtual/misc/hw_random rw,


Missing a /sys prefix.

niemeyer · 2017-03-17T10:21:44Z

interfaces/builtin/basedeclaration.go

+    allow-installation:
+      slot-snap-type:
+        - core
+    deny-auto-connection: true


Why? This looks like something we should hand off by default.

renatgalimov · 2017-03-17T15:21:56Z

@niemeyer , I fixed the code after your comments.

For the some reason tests fail because of timeout.

niemeyer · 2017-03-20T18:09:11Z

@femdom Thanks. We had some issues last week with test machine contention (too many tests, not enough machines), which resulted in them waiting too much for a machine to be available. Situation is normalized now and I've restarted the test.

@jdstrand can you please have a look at this one when you have a moment?

niemeyer · 2017-03-20T18:41:42Z

Travis tests passing.

stolowski · 2017-03-27T09:52:08Z

@femdom FYI, I've updated this PR for the latest API changes.

renatgalimov · 2017-03-27T12:55:49Z

Thanks, @stolowski! Checks passed!

jdstrand

Several open questions in addition to requested changes.

@niemeyer - you should weigh in on 'hardware-random' vs 'hardware-random-control' and 'hardware-random-observe'.

jdstrand · 2017-03-27T18:13:45Z

interfaces/builtin/basedeclaration.go

+    allow-installation:
+      slot-snap-type:
+        - core
+    allow-auto-connection: true


I think this should be renamed to hardware-random or even hardware-random-control since random implies /dev/random and /dev/urandom and we already allow access to those by default.

I also think this should be: deny-auto-connection: true since direct access to /dev/hwrng is not normally needed and typically only used by applications such as rng-tools to mix /dev/hwrng into kernel entropy. More importantly, a hardware-specific kernel driver for /dev/hwrng could be implemented in any number of ways including with weak (or non-existent) entropy (the kernel does not perform any fitness tests). Since this interface allows changing the hwrng via sysfs, it is possible to switch out a stronger rng for a weaker one and this is something that should not be auto-connected.

Perhaps this could be broken out into two interfaces:

hardware-random-observe - read access to relevant files from this PR, manually connected

hardware-random-control - all of hardware-random-observe plugs write access to /sys/class/misc/hw_random/rng_current for changing the hwrng, manually connected

I would argue that hardware-random-observe would still be a manual connection because the access is not typically needed, the device may not be provided by the kernel and there is no guarantee that the fitness of the device is good (ie, the gadget developer or device owner should decide whether a snap should use /dev/hwrng).

All recommendations, including naming, feel sound. 👍

I'm doing this change now.

jdstrand · 2017-03-27T18:19:36Z

interfaces/builtin/random.go

+const randomConnectedPlugAppArmor = `
+# Description: Allow access to the hardware random number generator device - /dev/hwrng
+
+/dev/hwrng rw,


This should just be 'r'.

Done though have a look, I'm not sure if the control-vs-observe split applies here

jdstrand · 2017-03-27T18:32:50Z

interfaces/builtin/random.go

+)
+
+const randomConnectedPlugAppArmor = `
+# Description: Allow access to the hardware random number generator device - /dev/hwrng


Please change this to:

# Description: allow direct access to the hardware random number generator device. Usually, # the default access to /dev/random is sufficient, but this allows applications such as rng-tools # to use /dev/hwrng directly or change the hwrng via sysfs. For details, see # https://www.kernel.org/doc/Documentation/hw_random.txt

jdstrand · 2017-03-27T18:51:13Z

interfaces/builtin/random.go

+# Description: Allow access to the hardware random number generator device - /dev/hwrng
+
+/dev/hwrng rw,
+/sys/devices/virtual/misc/hw_random rw,


This is a directory, not a file. This rule should be:

/sys/devices/virtual/misc/ r, /sys/devices/virtual/misc/hw_random/rng_{available,current} r, # Allow changing the hwrng /sys/devices/virtual/misc/hw_random/rng_current w,

The above assumes you actually need write access to /sys/devices/virtual/misc/hw_random/rng_current. Do you?

You should also add this rule:

/run/udev/data/c10:183 r,

renatgalimov · 2017-03-28T12:57:57Z

Understood, thanks.

jdstrand · 2017-03-28T13:56:57Z

@femdom - just to be clear, please don't make any changes just yet until these open questions are answered.

renatgalimov · 2017-04-25T09:15:49Z

Just updating the ticket. Let me know if I can fix addressed issues.

niemeyer · 2017-04-26T02:02:56Z

@femdom This is good to move on following @jdstrand's advices.

This patch splits the "random" interface into a hardware-random-observe and -control interface pair. In addition the plugs no longer auto-connect and there are some extra permission for the -control plug. There are several smaller changes as requested by jdstrand. Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

…erface

zyga · 2017-05-08T17:17:59Z

I just updated this according to @jdstrand specification. Let me know if there's anything more needed, I can quickly iterate and hopefully land this interface.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

jdstrand

Approving since my feedback is all nitpicks, but please update before committing.

BTW - thanks for the alphabetizing! :)

jdstrand · 2017-05-08T21:15:53Z

interfaces/builtin/hardware_random_control.go

+# Description: allow direct access to the hardware random number generator device. Usually,
+# the default access to /dev/random is sufficient, but this allows applications such as rng-tools
+# to use /dev/hwrng directly or change the hwrng via sysfs. For details, see
+# https://www.kernel.org/doc/Documentation/hw_random.txt


Nit: can you wrap these to 80 chars?

jdstrand · 2017-05-08T21:17:22Z

interfaces/builtin/hardware_random_control.go

+/sys/devices/virtual/misc/hw_random/rng_{available,current} r,
+# Allow changing the hwrng
+/sys/devices/virtual/misc/hw_random/rng_current w,
+/run/udev/data/c10:183 r,


Can you move this to below /dev/hwrng? It corresponds to that device and this access isn't needed for changing the hwrng. I also like to have blcnks lines before comments in policy, for readability. Eg:

+/dev/hwrng rw, +/run/udev/data/c10:183 r, +/sys/devices/virtual/misc/ r, +/sys/devices/virtual/misc/hw_random/rng_{available,current} r, + +# Allow changing the hwrng +/sys/devices/virtual/misc/hw_random/rng_current w,

jdstrand · 2017-05-08T21:19:05Z

interfaces/builtin/hardware_random_control.go

+}
+
+func (iface *HardwareRandomControlInterface) AutoConnect(*interfaces.Plug, *interfaces.Slot) bool {
+	return true


Can you add above this 'return' (for consistency with other interfaces):

// Allow what is allowed in the declarations

jdstrand · 2017-05-08T21:20:00Z

interfaces/builtin/hardware_random_observe.go

+/dev/hwrng r,
+/sys/devices/virtual/misc/ r,
+/sys/devices/virtual/misc/hw_random/rng_{available,current} r,
+/run/udev/data/c10:183 r,


Can you move this under /dev/hwrng, like above?

jdstrand · 2017-05-08T21:20:39Z

interfaces/builtin/hardware_random_observe.go

+}
+
+func (iface *HardwareRandomObserveInterface) AutoConnect(*interfaces.Plug, *interfaces.Slot) bool {
+	return true


and add above this 'return':

// Allow what is allowed in the declarations

Also done :-)

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

renatgalimov added 5 commits March 17, 2017 09:05

Adds hw-random interface

747fe68

Fixes base declaration test

45233b8

Removed gadget snap from the basedeclaration entry

9fea7e0

Deny auto-connection

8b964ee

Changing auto-connection to true

be38c2b

niemeyer requested changes Mar 17, 2017

View reviewed changes

niemeyer changed the title ~~Adds hw-random interface~~ interfaces: add random interface Mar 17, 2017

renatgalimov added 2 commits March 17, 2017 14:31

Updated after the review

ef09f63

Added missing /sys directory prefix

6e4f7ac

niemeyer requested a review from jdstrand March 20, 2017 18:07

niemeyer approved these changes Mar 20, 2017

View reviewed changes

stolowski added 2 commits March 27, 2017 11:16

Merge branch 'master' into hw-random-interface-new-api

2f5cd22

Updated for new API.

0326d3c

jdstrand suggested changes Mar 27, 2017

View reviewed changes

zyga added 2 commits May 8, 2017 19:13

Merge branch 'master' of github.com:snapcore/snapd into hw-random-int…

8f1f3e3

…erface

zyga added 2 commits May 8, 2017 19:19

interfaces/builtin: add extra checks for hardware-random-*

d0caae2

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

interfaces/builtin: tweak description for hardware-random-observe

b126df3

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

jdstrand approved these changes May 8, 2017

View reviewed changes

interfaces/builtin: wrap description to 80 columns

767cda6

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

zyga added 3 commits May 9, 2017 00:03

interfaces/builtin: reorder apparmor rules for association

999426d

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

interfaces/builtin: add newlines for visual spacing

c9fe5c4

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

interfaces/builtin: add comments for consistency

ffb36da

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@canonical.com>

zyga merged commit a98da33 into snapcore:master May 8, 2017

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interfaces: add random interface #3045

interfaces: add random interface #3045

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interfaces: add random interface #3045

interfaces: add random interface #3045

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renatgalimov commented Mar 28, 2017

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jdstrand Mar 27, 2017 •

edited