netdev - [PATCH net] net/tls: fix slab-out-of-bounds bug in decrypt

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Date:   Wed, 30 Mar 2022 16:50:09 +0800
From:   Ziyang Xuan <william.xuanziyang@...wei.com>
To:     <borisp@...dia.com>, <john.fastabend@...il.com>,
        <daniel@...earbox.net>, <kuba@...nel.org>, <davem@...emloft.net>,
        <pabeni@...hat.com>, <netdev@...r.kernel.org>
CC:     <vakul.garg@....com>, <davejwatson@...com>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH net] net/tls: fix slab-out-of-bounds bug in decrypt_internal

The memory size of tls_ctx->rx.iv for AES128-CCM is 12 setting in
tls_set_sw_offload(). The return value of crypto_aead_ivsize()
for "ccm(aes)" is 16. So memcpy() require 16 bytes from 12 bytes
memory space will trigger slab-out-of-bounds bug as following:

==================================================================
BUG: KASAN: slab-out-of-bounds in decrypt_internal+0x385/0xc40 [tls]
Read of size 16 at addr ffff888114e84e60 by task tls/10911

Call Trace:
 <TASK>
 dump_stack_lvl+0x34/0x44
 print_report.cold+0x5e/0x5db
 ? decrypt_internal+0x385/0xc40 [tls]
 kasan_report+0xab/0x120
 ? decrypt_internal+0x385/0xc40 [tls]
 kasan_check_range+0xf9/0x1e0
 memcpy+0x20/0x60
 decrypt_internal+0x385/0xc40 [tls]
 ? tls_get_rec+0x2e0/0x2e0 [tls]
 ? process_rx_list+0x1a5/0x420 [tls]
 ? tls_setup_from_iter.constprop.0+0x2e0/0x2e0 [tls]
 decrypt_skb_update+0x9d/0x400 [tls]
 tls_sw_recvmsg+0x3c8/0xb50 [tls]

Allocated by task 10911:
 kasan_save_stack+0x1e/0x40
 __kasan_kmalloc+0x81/0xa0
 tls_set_sw_offload+0x2eb/0xa20 [tls]
 tls_setsockopt+0x68c/0x700 [tls]
 __sys_setsockopt+0xfe/0x1b0

Reserve MAX_IV_SIZE memory space for iv to be compatible with all
ciphers. And do iv and salt copy like done in tls_do_encryption().

Fixes: f295b3ae9f59 ("net/tls: Add support of AES128-CCM based ciphers")
Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.com>
---
 net/tls/tls_sw.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 0024a692f0f8..6b858f995b23 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1456,7 +1456,7 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 	aead_size = sizeof(*aead_req) + crypto_aead_reqsize(ctx->aead_recv);
 	mem_size = aead_size + (nsg * sizeof(struct scatterlist));
 	mem_size = mem_size + prot->aad_size;
-	mem_size = mem_size + crypto_aead_ivsize(ctx->aead_recv);
+	mem_size = mem_size + MAX_IV_SIZE;
 
 	/* Allocate a single block of memory which contains
 	 * aead_req || sgin[] || sgout[] || aad || iv.
@@ -1493,12 +1493,8 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
 		kfree(mem);
 		return err;
 	}
-	if (prot->version == TLS_1_3_VERSION ||
-	    prot->cipher_type == TLS_CIPHER_CHACHA20_POLY1305)
-		memcpy(iv + iv_offset, tls_ctx->rx.iv,
-		       crypto_aead_ivsize(ctx->aead_recv));
-	else
-		memcpy(iv + iv_offset, tls_ctx->rx.iv, prot->salt_size);
+	memcpy(iv + iv_offset, tls_ctx->rx.iv,
+	       prot->iv_size + prot->salt_size);
 
 	xor_iv_with_seq(prot, iv + iv_offset, tls_ctx->rx.rec_seq);
 
-- 
2.25.1