authsrv: handle short reads in initkeyseed()

1 files changed, 12 insertions, 6 deletions

diff --git a/sys/src/cmd/auth/authsrv.c b/sys/src/cmd/auth/authsrv.c
index 051c08ff1..23a6a38a2 100644
--- a/sys/src/cmd/auth/authsrv.c
+++ b/sys/src/cmd/auth/authsrv.c
@@ -1008,14 +1008,20 @@ initkeyseed(void)
 	int fd;
 
 	genrandom(keyseed, sizeof(keyseed));
-	if((fd = create("/adm/keyseed", OWRITE|OEXCL, 0600)) >= 0){
-		write(fd, keyseed, sizeof(keyseed));
-	} else if((fd = open("/adm/keyseed", OREAD)) >= 0){
-		read(fd, keyseed, sizeof(keyseed));
-	} else{
-		syslog(0, AUTHLOG, "initkeyseed: no seed file: %r");
+	if((fd = open("/adm/keyseed", OREAD)) >= 0){
+		werrstr("file truncated");
+		if(read(fd, keyseed, sizeof(keyseed)) == sizeof(keyseed)){
+			close(fd);
+			return;
+		}
+		close(fd);
+	}
+	syslog(0, AUTHLOG, "initkeyseed: no keyseed: %r");
+	if((fd = create("/adm/keyseed", OWRITE, 0600)) < 0){
+		syslog(0, AUTHLOG, "initkeyseed: can't create: %r");
 		return;
 	}
+	write(fd, keyseed, sizeof(keyseed));
 	close(fd);
 }