From 73e81dc78ddb6f1bc0d8750c1a9e19e6cc123d48 Mon Sep 17 00:00:00 2001
From: Vladis Dronov <vdronov@redhat.com>
Date: Sat, 12 Jun 2021 09:16:25 +0200
Subject: Fix logic in ossl_aes_random_key()
- Using sizeof is correct for arr[], but is not correct for *ptr. read() here
makes a 8-bytes read (on 64-bit arch). It should read AES_BLOCK bytes instead,
as callers of ossl_aes_random_key() imply.
Covscan emits the following warning:
Error: SIZEOF_MISMATCH (CWE-398): [#def1]
rng-tools-6.12/ossl_helpers.c:51: suspicious_sizeof: Passing argument "key" of
type "unsigned char *" and argument "8UL /* sizeof (key) */" to function "read"
is suspicious.
51|-> int r = read(fd, key, sizeof key);
- According to the following warning, mark r as not used explicitly:
Error: CLANG_WARNING: [#def2]
rng-tools-6.12/ossl_helpers.c:51:7: warning[deadcode.DeadStores]: Value stored
to 'r' during its initialization is never read
51|-> int r = read(fd, key, sizeof key);
- Add volatile to stack_junk to avoid possible compiler optimization. This does
not silence "Uninitialized variable: stack_junk" covscan warning.
- Remove a check for pepper == NULL where it is not needed.
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
---
ossl_helpers.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/ossl_helpers.c b/ossl_helpers.c
index c3c1fbb..9569b74 100644
--- a/ossl_helpers.c
+++ b/ossl_helpers.c
@@ -42,22 +42,23 @@ void ossl_aes_random_key(unsigned char *key, const unsigned char *pepper)
0x00,0x10,0x20,0x30,0x40,0x50,0x60,0x70,
0x80,0x90,0xa0,0xb0,0xc0,0xd0,0xe0,0xf0
}; /* AES data reduction key */
- unsigned char stack_junk[AES_BLOCK];
+ volatile unsigned char stack_junk[AES_BLOCK];
int fd, i;
/* Try getting some randomness from the kernel */
fd = open("/dev/urandom", O_RDONLY);
if (fd >= 0) {
- int r = read(fd, key, sizeof key);
+ int r __attribute__((unused));
+ r = read(fd, key, AES_BLOCK);
close(fd);
}
/* Mix in our default key */
- for (i = 0; i < AES_BLOCK && pepper; i++)
+ for (i = 0; i < AES_BLOCK; i++)
key[i] ^= default_key[i];
/* Mix in stack junk */
- for (i = 0; i < AES_BLOCK && pepper; i++)
+ for (i = 0; i < AES_BLOCK; i++)
key[i] ^= stack_junk[i];
/* Spice it up if we can */
--
2.26.3