util/uuid: replace with util/token, remove libuuid #2833

r-c-f · 2021-04-07T18:21:59Z

Uses getentropy() when available, otherwise /dev/urandom. Closes #2830

meson.build

util/meson.build

emersion · 2021-04-07T20:08:48Z

util/uuid.c

+
+#ifndef HAS_GETENTROPY
+static int getentropy(void *buffer, size_t len)
+{


Nit: { should be on the previous line

util/uuid.c

jbeich · 2021-04-08T01:43:35Z

Note, DragonFly and NetBSD lack getentropy but have getrandom. OpenBSD has getentropy but lacks getrandom. FreeBSD has both. All BSDs (and Android) have arc4random_buf.

r-c-f · 2021-04-08T13:05:40Z

The main benefit to getentropy is the avoidance of file IO, with the possible future benefit of being considered for acceptance into POSIX; if that doesn't matter, static /dev/urandom for everything would be the simpler (if slightly leakier) approach, given that a Wayland compositor is already opening up too many file descriptors to worry about constraints.

kennylevinsen · 2021-04-08T18:29:53Z

From the proposed POSIX spec:

NAME

    getentropy -- fill a buffer with random bytes

<< SNIP >>

APPLICATION USAGE

    The intended use of this function is to create a seed for other pseudo-random number generators.


RATIONALE

    The getentropy() function is not a cancellation point. (See [xref to 2.9.5.2 Cancellation Points].)

Even though they use the same source, /dev/urandom appears more portable for now and is in line with what libuuid was doing.

util/uuid.c

emersion · 2021-04-09T15:28:03Z

util/uuid.c

+
+	if (!urandom) {
+		if (!(urandom = fopen("/dev/urandom", "r"))) {
+			return false;


It would be nice to call wlr_log_errno here to make it clear something wrong happened.

util/uuid.c

emersion · 2021-04-09T15:30:00Z

Marking as a breaking change since this removes WLR_HAS_XDG_FOREIGN.

emersion · 2021-04-09T15:31:16Z

Hm, actually, it removes xdg-foreign for features but leaves WLR_HAS_XDG_FOREIGN. We should either keep both or get rid of both.

emersion · 2021-04-09T15:31:52Z

We can also get rid of libuuid in CI.

emersion

Code LGTM! Can you squash all commits into a single one, and remove the CI dependencies introduced in bf4e2e0 (in .builds/*.yml)?

util/token.c

emersion · 2021-04-11T07:55:46Z

Ah, also please remove libuuid from the README.

Use 128-bit hexadecimal string tokens generated with /dev/urandom instead of UUIDs for xdg-foreign handles, removing the libuuid dependency. Update readme and CI. Closes swaywm#2830. build: remove xdg-foreign feature With no external dependencies required, there's no reason not to always build it. Remove WLR_HAS_XDG_FOREIGN as well.

emersion

LGTM, thanks!

References: swaywm/wlroots#2833

References: swaywm/wlroots#2833 (cherry picked from commit 1a72049)

r-c-f force-pushed the builtin_uuid branch from 7f80e8f to e392e5b Compare April 7, 2021 18:59