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net: sctp: fix memory leak in auth key management

PATCH In review Daniel Borkmann 3 participants 3 messages Nov 10, 2014 – Nov 11, 2014

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Networking Network drivers SCTP protocol
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Daniel Borkmann

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#0 lore raw

PATCH 1/1 net: sctp: fix memory leak in auth key management

A very minimal and simple user space application allocating an SCTP socket, setting SCTP_AUTH_KEY setsockopt(2) on it and then closing the socket again will leak the memory containing the authentication key from user space:

unreferenced object 0xffff8800837047c0 (size 16):
comm "a.out", pid 2789, jiffies 4296954322 (age 192.258s) hex dump (first 16 bytes):

    01 00 00 00 04 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff816d7e8e>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff811c88d8>] __kmalloc+0xe8/0x270
    [<ffffffffa0870c23>] sctp_auth_create_key+0x23/0x50 [sctp]
    [<ffffffffa08718b1>] sctp_auth_set_key+0xa1/0x140 [sctp]
    [<ffffffffa086b383>] sctp_setsockopt+0xd03/0x1180 [sctp]
    [<ffffffff815bfd94>] sock_common_setsockopt+0x14/0x20
    [<ffffffff815beb61>] SyS_setsockopt+0x71/0xd0
    [<ffffffff816e58a9>] system_call_fastpath+0x12/0x17
    [<ffffffffffffffff>] 0xffffffffffffffff

This is bad because of two things, we can bring down a machine from user space when auth_enable=1, but also we would leave security sensitive keying material in memory without clearing it after use. The issue is that sctp_auth_create_key() already sets the refcount to 1, but after allocation sctp_auth_set_key() does an additional refcount on it, and thus leaving it around when we free the socket.

Fixes 65b07e5d0d0 ("[SCTP]: API updates to suport SCTP-AUTH extensions.")
Signed-off-by Daniel Borkmann <[email protected]>
Cc Vlad Yasevich <[email protected]>
---
 net/sctp/auth.c | 2 --
 1 file changed, 2 deletions(-)
net/sctp/auth.c +0 -2
index 0e85291..fb7976a 100644
@@ -862,8 +862,6 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
 		list_add(&cur_key->key_list, sh_keys);
 
 	cur_key->key = key;
-	sctp_auth_key_hold(key);
-
 	return 0;
 nomem:
 	if (!replace)
Signature · 1 line
1.7.11.7
Acked-by on v1 1/1
#1 lore raw
Quoted 55 lines · Daniel Borkmann

A very minimal and simple user space application allocating an SCTP socket, setting SCTP_AUTH_KEY setsockopt(2) on it and then closing the socket again will leak the memory containing the authentication key from user space:

unreferenced object 0xffff8800837047c0 (size 16):
comm "a.out", pid 2789, jiffies 4296954322 (age 192.258s) hex dump (first 16 bytes):

    01 00 00 00 04 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff816d7e8e>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff811c88d8>] __kmalloc+0xe8/0x270
    [<ffffffffa0870c23>] sctp_auth_create_key+0x23/0x50 [sctp]
    [<ffffffffa08718b1>] sctp_auth_set_key+0xa1/0x140 [sctp]
    [<ffffffffa086b383>] sctp_setsockopt+0xd03/0x1180 [sctp]
    [<ffffffff815bfd94>] sock_common_setsockopt+0x14/0x20
    [<ffffffff815beb61>] SyS_setsockopt+0x71/0xd0
    [<ffffffff816e58a9>] system_call_fastpath+0x12/0x17
    [<ffffffffffffffff>] 0xffffffffffffffff

This is bad because of two things, we can bring down a machine from user space when auth_enable=1, but also we would leave security sensitive keying material in memory without clearing it after use. The issue is that sctp_auth_create_key() already sets the refcount to 1, but after allocation sctp_auth_set_key() does an additional refcount on it, and thus leaving it around when we free the socket.

Fixes 65b07e5d0d0 ("[SCTP]: API updates to suport SCTP-AUTH extensions.")
Signed-off-by Daniel Borkmann <[email protected]>
Cc Vlad Yasevich <[email protected]>
---
 net/sctp/auth.c | 2 --
 1 file changed, 2 deletions(-)
net/sctp/auth.c +0 -2
index 0e85291..fb7976a 100644
@@ -862,8 +862,6 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
 		list_add(&cur_key->key_list, sh_keys);
 
 	cur_key->key = key;
-	sctp_auth_key_hold(key);
-
 	return 0;
 nomem:
 	if (!replace)
Signature · 6 lines
1.7.11.7

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Acked-by Neil Horman <[email protected]>
maintainer
#2 lore raw
In reply to Daniel Borkmann

From: Daniel Borkmann <[email protected]>
Date: Mon, 10 Nov 2014 18:00:09 +0100

Quoted 4 lines

A very minimal and simple user space application allocating an SCTP socket, setting SCTP_AUTH_KEY setsockopt(2) on it and then closing the socket again will leak the memory containing the authentication key from user space:

...

Quoted 10 lines

This is bad because of two things, we can bring down a machine from user space when auth_enable=1, but also we would leave security sensitive keying material in memory without clearing it after use. The issue is that sctp_auth_create_key() already sets the refcount to 1, but after allocation sctp_auth_set_key() does an additional refcount on it, and thus leaving it around when we free the socket.

Fixes 65b07e5d0d0 ("[SCTP]: API updates to suport SCTP-AUTH extensions.")
Signed-off-by Daniel Borkmann <[email protected]>
Cc Vlad Yasevich <[email protected]>

Also applied and queued up for -stable, thanks again.