Messages in this thread | | | Date | Wed, 30 Mar 2022 09:39:25 -0700 | From | Jakub Kicinski <> | Subject | Re: [PATCH net] net/tls: fix slab-out-of-bounds bug in decrypt_internal |
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On Wed, 30 Mar 2022 16:50:09 +0800 Ziyang Xuan wrote: > 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
Interesting, are you running on non-x86 platform or with some crypto accelerator? I wonder why we're not hitting it with KASAN and the selftest we have.
> 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@huawei.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;
This change is not strictly required for the patch, right? Can we drop it, and perhaps send as an optimization separately later?
> /* 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);
If the IV really is 16B then we're passing 4 bytes of uninitialized data at the end of the buffer, right?
> xor_iv_with_seq(prot, iv + iv_offset, tls_ctx->rx.rec_seq); >
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