git: 62dab3d016ab - main - getentropy: Remove fallback code

The branch main has been updated by emaste:

URL: https://cgit.FreeBSD.org/src/commit/?id=62dab3d016abca717e396119ff33fdf22ed604f3

commit 62dab3d016abca717e396119ff33fdf22ed604f3
Author:     Ed Maste <emaste@FreeBSD.org>
AuthorDate: 2024-11-16 15:25:44 +0000
Commit:     Ed Maste <emaste@FreeBSD.org>
CommitDate: 2024-11-20 02:29:46 +0000

    getentropy: Remove fallback code
    
    We don't in general support running newer libc on an older kernel, but
    have occasionally added support for specific functionality on a case-by-
    case basis.  When we do this it is usually done as an aid for developers
    to get across a change that introduced new functionality, as for 64-bit
    inodes and the introduction of the getrandom syscall.
    
    The getrandom syscall was added in commit e9ac27430c0c ("Implement
    getrandom(2) and getentropy(3)") in 2018, and exists in all supported
    FreeBSD versions.  The ECAPMODE special case applied to a few months
    worth of kernel versions also in 2018 -- fixed as of commit ed1fa01ac45a
    ("Regen after r337998.").
    
    The backwards-compatibility support is no longer needed, so remove it.
    
    Relnotes:       Yes
    Reviewed by:    brooks, cem, delphij
    Sponsored by:   The FreeBSD Foundation
    Differential Revision: https://reviews.freebsd.org/D47636
---
 lib/libc/gen/getentropy.c | 99 +++++------------------------------------------
 1 file changed, 9 insertions(+), 90 deletions(-)

diff --git a/lib/libc/gen/getentropy.c b/lib/libc/gen/getentropy.c
index 40debe4ab662..e87796ace58c 100644
--- a/lib/libc/gen/getentropy.c
+++ b/lib/libc/gen/getentropy.c
@@ -28,121 +28,40 @@
 
 #include <sys/param.h>
 #include <sys/random.h>
-#include <sys/sysctl.h>
 
 #include <errno.h>
 #include <signal.h>
-#include <stdbool.h>
-#include <stdlib.h>
-#include <unistd.h>
 #include <ssp/ssp.h>
 
 #include "libc_private.h"
 
-/* First __FreeBSD_version bump after introduction of getrandom(2) (r331279) */
-#define GETRANDOM_FIRST 1200061
-
-extern int __sysctl(int *, u_int, void *, size_t *, void *, size_t);
-
 static inline void
 _getentropy_fail(void)
 {
 	raise(SIGKILL);
 }
 
-static size_t
-arnd_sysctl(u_char *buf, size_t size)
-{
-	int mib[2];
-	size_t len, done;
-
-	mib[0] = CTL_KERN;
-	mib[1] = KERN_ARND;
-	done = 0;
-
-	do {
-		len = size;
-		if (__sysctl(mib, 2, buf, &len, NULL, 0) == -1)
-			return (done);
-		done += len;
-		buf += len;
-		size -= len;
-	} while (size > 0);
-
-	return (done);
-}
-
-/*
- * If a newer libc is accidentally installed on an older kernel, provide high
- * quality random data anyway.  The sysctl interface is not as fast and does
- * not block by itself, but is provided by even very old kernels.
- */
-static int
-getentropy_fallback(void *buf, size_t buflen)
-{
-	/*
-	 * oldp (buf) == NULL has a special meaning for sysctl that results in
-	 * no EFAULT.  For compatibility with the kernel getrandom(2), detect
-	 * this case and return the appropriate error.
-	 */
-	if (buf == NULL && buflen > 0) {
-		errno = EFAULT;
-		return (-1);
-	}
-	if (arnd_sysctl(buf, buflen) != buflen) {
-		if (errno == EFAULT)
-			return (-1);
-		/*
-		 * This cannot happen.  arnd_sysctl() spins until the random
-		 * device is seeded and then repeatedly reads until the full
-		 * request is satisfied.  The only way for this to return a zero
-		 * byte or short read is if sysctl(2) on the kern.arandom MIB
-		 * fails.  In this case, excepting the user-provided-a-bogus-
-		 * buffer EFAULT, give up (like for arc4random(3)'s arc4_stir).
-		 */
-		_getentropy_fail();
-	}
-	return (0);
-}
-
 int
 __ssp_real(getentropy)(void *buf, size_t buflen)
 {
 	ssize_t rd;
-	bool have_getrandom;
 
 	if (buflen > 256) {
 		errno = EIO;
 		return (-1);
 	}
 
-	have_getrandom = (__getosreldate() >= GETRANDOM_FIRST);
-
 	while (buflen > 0) {
-		if (have_getrandom) {
-			rd = getrandom(buf, buflen, 0);
-			if (rd == -1) {
-				switch (errno) {
-				case ECAPMODE:
-					/*
-					 * Kernel >= r331280 (4948f7bf1153)
-					 * and < r337999 (ed1fa01ac45a) will
-					 * return ECAPMODE when the caller is
-					 * already in capability mode; fallback
-					 * to traditional method in this case.
-					 */
-					have_getrandom = false;
-					continue;
-				case EINTR:
-					continue;
-				case EFAULT:
-					return (-1);
-				default:
-					_getentropy_fail();
-				}
+		rd = getrandom(buf, buflen, 0);
+		if (rd == -1) {
+			switch (errno) {
+			case EINTR:
+				continue;
+			case EFAULT:
+				return (-1);
+			default:
+				_getentropy_fail();
 			}
-		} else {
-			return (getentropy_fallback(buf, buflen));
 		}
 
 		/* This cannot happen. */