libreboot-utils: tidy up the rand code

Signed-off-by: Leah Rowe <leah@libreboot.org>

2 files changed, 26 insertions, 60 deletions

diff --git a/util/libreboot-utils/lib/mkhtemp.c b/util/libreboot-utils/lib/mkhtemp.c
index 2fb2f01a..191d657c 100644
--- a/util/libreboot-utils/lib/mkhtemp.c
+++ b/util/libreboot-utils/lib/mkhtemp.c
@@ -886,53 +886,30 @@ err:
 int
 mkhtemp_fill_random(char *p, size_t xc)
 {
-	size_t chx = 0;
-	int rand_failures = 0;
-
-	size_t r;
-
-	int saved_rand_error = 0;
 	static char ch[] =
 	    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 
+	size_t chx = 0;
+	size_t r;
+
 	/* clamp rand to prevent modulo bias
-	 * (reduced risk of entropy leak)
 	 */
 	size_t limit = ((size_t)-1) - (((size_t)-1) % (sizeof(ch) - 1));
-
 	int saved_errno = errno;
 
-	if (p == NULL) {
-		errno = EFAULT;
-		goto err_mkhtemp_fill_random;
-	}
+	if (if_err(p == NULL, EFAULT))
+		return -1;
 
 	for (chx = 0; chx < xc; chx++) {
 
-		do {
-			saved_rand_error = errno;
-			rand_failures = 0;
 retry_rand:
-			errno = 0;
-
-			/* on bsd: uses arc4random
-			   on linux: uses getrandom
-			   on OLD linux: /dev/urandom
-			   on old/other unix: /dev/urandom
-			 */
-			r = rlong();
-
-			if (errno > 0) {
-				if (++rand_failures <= 8)
-					goto retry_rand;
-
-				goto err_mkhtemp_fill_random;
-			}
-
-			rand_failures = 0;
-			errno = saved_rand_error;
-
-		} while (r >= limit);
+		/* on bsd: uses arc4random
+		   on linux: uses getrandom
+		   *never returns error*
+		 */
+		r = rlong(); /* always returns successful */
+		if (r >= limit)
+			goto retry_rand;
 
 		p[chx] = ch[r % (sizeof(ch) - 1)];
 	}
@@ -940,12 +917,6 @@ retry_rand:
 	errno = saved_errno;
 	return 0;
 
-err_mkhtemp_fill_random:
-
-	if (errno == saved_errno)
-		errno = ECANCELED;
-
-	return -1;
 }
 
 /* WARNING: **ONCE** per file.
diff --git a/util/libreboot-utils/lib/rand.c b/util/libreboot-utils/lib/rand.c
index 2f88b420..0b156e51 100644
--- a/util/libreboot-utils/lib/rand.c
+++ b/util/libreboot-utils/lib/rand.c
@@ -59,6 +59,7 @@ rlong(void)
 {
 	size_t rval;
 	int saved_errno = errno;
+	errno = 0;
 
 #if (defined(__OpenBSD__) && (OpenBSD) >= 201) || \
     defined(__FreeBSD__) || \
@@ -71,30 +72,23 @@ rlong(void)
 
 	size_t off = 0;
 	size_t len = sizeof(rval);
-
 	ssize_t rc;
 
-	if (!len)
-		goto err;
-
-	while (off < len) {
-
-		rc = (ssize_t)syscall(SYS_getrandom,
-		    (char *)&rval + off, len - off, 0);
-
-		if (rc < 0) {
-			if (errno == EINTR || errno == EAGAIN)
-				continue;
+retry_rand:
+	rc = (ssize_t)syscall(SYS_getrandom,
+	    (char *)&rval + off, len - off, 0);
 
-			goto err; /* possibly unsupported by kernel */
-		}
+	if (rc < 0) {
+		if (errno == EINTR || errno == EAGAIN)
+			goto retry_rand;
 
-		off += (size_t)rc;
+		goto err; /* possibly unsupported by kernel */
 	}
 
-	goto out;
+	if ((off += (size_t)rc) < len)
+		goto retry_rand;
 
-	return rval;
+	goto out;
 err:
 	/*
 	 * getrandom can return with error, butt arc4random
@@ -103,8 +97,9 @@ err:
 	 * BSD. So a rand failure is to be interpreted as
 	 * a major systems failure, and we act accordingly.
 	 */
-	err_no_cleanup(1, ECANCELED, "Randomisation failure");
-	exit(1);
+	err_no_cleanup(1, ECANCELED,
+	    "Randomisation failure, possibly unsupported in your kernel.");
+	exit(EXIT_FAILURE);
 
 #else
 #error Unsupported operating system (possibly unsecure randomisation)