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Date:      Mon, 13 Jul 2015 08:38:21 +0000 (UTC)
From:      Mark Murray <markm@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r285439 - head/sys/dev/random
Message-ID:  <201507130838.t6D8cLEZ076018@repo.freebsd.org>
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Author: markm
Date: Mon Jul 13 08:38:21 2015
New Revision: 285439
URL: https://svnweb.freebsd.org/changeset/base/285439

Log:
  Rework the read routines to keep the PRNG sources happy. These work
  in units of crypto blocks, so must have adequate space to write.
  This means needing to be careful about buffers and keeping track
  of external read request length.
  
  Approved by:	so (/dev/random blanket)

Modified:
  head/sys/dev/random/randomdev.c

Modified: head/sys/dev/random/randomdev.c
==============================================================================
--- head/sys/dev/random/randomdev.c	Mon Jul 13 05:59:41 2015	(r285438)
+++ head/sys/dev/random/randomdev.c	Mon Jul 13 08:38:21 2015	(r285439)
@@ -153,8 +153,8 @@ static int
 randomdev_read(struct cdev *dev __unused, struct uio *uio, int flags)
 {
 	uint8_t *random_buf;
-	int c, error;
-	ssize_t nbytes;
+	int error;
+	ssize_t read_len, total_read, c;
 
 	random_buf = malloc(PAGE_SIZE, M_ENTROPY, M_WAITOK);
 	random_alg_context.ra_pre_read();
@@ -175,14 +175,24 @@ randomdev_read(struct cdev *dev __unused
 		/* XXX: FIX!! Next line as an atomic operation? */
 		read_rate += (uio->uio_resid + sizeof(uint32_t))/sizeof(uint32_t);
 #endif
-		nbytes = uio->uio_resid;
+		total_read = 0;
 		while (uio->uio_resid && !error) {
-			c = MIN(uio->uio_resid, PAGE_SIZE);
-			/* See the random_buf size requirements in the Yarrow/Fortuna code */
-			random_alg_context.ra_read(random_buf, c);
+			read_len = uio->uio_resid;
+			/*
+			 * Belt-and-braces.
+			 * Round up the read length to a crypto block size multiple,
+			 * which is what the underlying generator is expecting.
+			 * See the random_buf size requirements in the Yarrow/Fortuna code.
+			 */
+			read_len += RANDOM_BLOCKSIZE;
+			read_len -= read_len % RANDOM_BLOCKSIZE;
+			read_len = MIN(read_len, PAGE_SIZE);
+			random_alg_context.ra_read(random_buf, read_len);
+			c = MIN(uio->uio_resid, read_len);
 			error = uiomove(random_buf, c, uio);
+			total_read += c;
 		}
-		if (nbytes != uio->uio_resid && (error == ERESTART || error == EINTR) )
+		if (total_read != uio->uio_resid && (error == ERESTART || error == EINTR) )
 			/* Return partial read, not error. */
 			error = 0;
 	}
@@ -212,6 +222,13 @@ read_random(void *random_buf, u_int len)
 		read_rate += (len + sizeof(uint32_t))/sizeof(uint32_t);
 #endif
 		read_len = len;
+		/*
+		 * Belt-and-braces.
+		 * Round up the read length to a crypto block size multiple,
+		 * which is what the underlying generator is expecting.
+		 */
+		read_len += RANDOM_BLOCKSIZE;
+		read_len -= read_len % RANDOM_BLOCKSIZE;
 		total_read = 0;
 		while (read_len) {
 			c = MIN(read_len, PAGE_SIZE);

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