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util/nvmutil: Do not allow /dev/urandom on OBSD

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There, we use arc4random_buf which does not directly
access /dev/urandom on BSD; it uses a userspace method
instead, which bypasses this.

This is therefore much more restrictive, which is
exactly the point of unveil(2) and pledge(2); restrict
your program's operation while ensuring that it has what
it needs, to help with debugging and prevent common bugs.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-08 02:45:20 +00:00
parent b1866312bd
commit 63fcc0891f
1 changed files with 8 additions and 10 deletions
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util/nvmutil/nvmutil.c
+8 -10
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@@ -212,18 +212,16 @@ main(int argc, char *argv[])
/*
* For restricted filesystem access on early error.
*
* Unveiling the random device early, regardless of
* whether we will use it, prevents operations on any
* GbE files until we permit it, while performing the
* prerequisite error checks.
* This prevents access to /dev/urandom, which we
* should never use in OpenBSD (we use arc4random),
* thus guarding against any future bugs there.
*
* We don't actually use the random device on platforms
* that have arc4random, which includes OpenBSD.
* This also prevents early reads to the GbE file,
* while performing other checks; we will later
* unveil the GbE file, to allow access.
*/
if (unveil("/dev/urandom", "r") == -1)
err(ECANCELED, "unveil '/dev/urandom'");
if (unveil("/dev/random", "r") == -1)
err(ECANCELED, "unveil '/dev/random'");
if (unveil("/dev/null", "r") == -1)
err(ECANCELED, "unveil '/dev/null'");
#endif
set_cmd(argc, argv);