Update third_party/nss to NSS 3.15.4.

nss/lib/freebl/unix_rand.c

Index: nss/lib/freebl/unix_rand.c
===================================================================
--- nss/lib/freebl/unix_rand.c	(revision 239365)
+++ nss/lib/freebl/unix_rand.c	(working copy)
@@ -970,7 +970,8 @@
 size_t RNG_FileUpdate(const char *fileName, size_t limit)
 {
     FILE *        file;
-    size_t        bytes;
+    int           fd;
+    int           bytes;
     size_t        fileBytes = 0;
     struct stat   stat_buf;
     unsigned char buffer[BUFSIZ];
@@ -983,12 +984,22 @@
 	return fileBytes;
     RNG_RandomUpdate(&stat_buf, sizeof(stat_buf));
     
-    file = fopen((char *)fileName, "r");
+    file = fopen(fileName, "r");
     if (file != NULL) {
+	/* Read from the underlying file descriptor directly to bypass stdio
+	 * buffering and avoid reading more bytes than we need from
+	 * /dev/urandom. NOTE: we can't use fread with unbuffered I/O because
+	 * fread may return EOF in unbuffered I/O mode on Android.
+	 *
+	 * Moreover, we read into a buffer of size BUFSIZ, so buffered I/O
+	 * has no performance advantage. */
+	fd = fileno(file);
+	/* 'file' was just opened, so this should not fail. */
+	PORT_Assert(fd != -1);
 	while (limit > fileBytes) {
 	    bytes = PR_MIN(sizeof buffer, limit - fileBytes);
-	    bytes = fread(buffer, 1, bytes, file);
-	    if (bytes == 0) 
+	    bytes = read(fd, buffer, bytes);
+	    if (bytes <= 0)
 		break;
 	    RNG_RandomUpdate(buffer, bytes);
 	    fileBytes      += bytes;
@@ -1020,7 +1031,7 @@
     FILE *        file;
     unsigned char buffer[BUFSIZ];
     
-    file = fopen((char *)fileName, "rb");
+    file = fopen(fileName, "rb");
     if (file != NULL) {
 	while (fread(buffer, 1, sizeof(buffer), file) > 0)
 	    ;
@@ -1142,7 +1153,8 @@
 size_t RNG_SystemRNG(void *dest, size_t maxLen)
 {
     FILE *file;
-    size_t bytes;
+    int fd;
+    int bytes;
     size_t fileBytes = 0;
     unsigned char *buffer = dest;
 
@@ -1153,10 +1165,18 @@
 	fflush(stderr);
 	abort();
     }
+    /* Read from the underlying file descriptor directly to bypass stdio
+     * buffering and avoid reading more bytes than we need from /dev/urandom.
+     * NOTE: we can't use fread with unbuffered I/O because fread may return
+     * EOF in unbuffered I/O mode on Android.
+     */
+    fd = fileno(file);
+    /* 'file' was just opened, so this should not fail. */
+    PORT_Assert(fd != -1);
     while (maxLen > fileBytes) {
 	bytes = maxLen - fileBytes;
-	bytes = fread(buffer, 1, bytes, file);
-	if (bytes == 0) 
+	bytes = read(fd, buffer, bytes);
+	if (bytes <= 0)
 	    break;
 	fileBytes += bytes;
 	buffer += bytes;