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Subject[PATCH 2/2] af_key: Always verify length of provided sadb_key
Key extensions (struct sadb_key) include a user-specified number of key
bits. The kernel uses that number to determine how much key data to copy
out of the message in pfkey_msg2xfrm_state().

The length of the sadb_key message must be verified to be long enough,
even in the case of SADB_X_AALG_NULL. Furthermore, the sadb_key_len value
must be long enough to include both the key data and the struct sadb_key
itself.

Introduce a helper function verify_key_len(), and call it from
parse_exthdrs() where other exthdr types are similarly checked for
correctness.

Signed-off-by: Kevin Easton <kevin@guarana.org>
Reported-by: syzbot+5022a34ca5a3d49b84223653fab632dfb7b4cf37@syzkaller.appspotmail.com
---
net/key/af_key.c | 45 +++++++++++++++++++++++++++++++++++----------
1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/net/key/af_key.c b/net/key/af_key.c
index 911b68d..f3ebb84 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -437,6 +437,24 @@ static int verify_address_len(const void *p)
return 0;
}

+static inline int sadb_key_len(const struct sadb_key *key)
+{
+ int key_bytes = DIV_ROUND_UP(key->sadb_key_bits, 8);
+
+ return DIV_ROUND_UP(sizeof(struct sadb_key) + key_bytes,
+ sizeof(uint64_t));
+}
+
+static int verify_key_len(const void *p)
+{
+ const struct sadb_key *key = p;
+
+ if (sadb_key_len(key) > key->sadb_key_len)
+ return -EINVAL;
+
+ return 0;
+}
+
static inline int pfkey_sec_ctx_len(const struct sadb_x_sec_ctx *sec_ctx)
{
return DIV_ROUND_UP(sizeof(struct sadb_x_sec_ctx) +
@@ -533,16 +551,25 @@ static int parse_exthdrs(struct sk_buff *skb, const struct sadb_msg *hdr, void *
return -EINVAL;
if (ext_hdrs[ext_type-1] != NULL)
return -EINVAL;
- if (ext_type == SADB_EXT_ADDRESS_SRC ||
- ext_type == SADB_EXT_ADDRESS_DST ||
- ext_type == SADB_EXT_ADDRESS_PROXY ||
- ext_type == SADB_X_EXT_NAT_T_OA) {
+ switch (ext_type) {
+ case SADB_EXT_ADDRESS_SRC:
+ case SADB_EXT_ADDRESS_DST:
+ case SADB_EXT_ADDRESS_PROXY:
+ case SADB_X_EXT_NAT_T_OA:
if (verify_address_len(p))
return -EINVAL;
- }
- if (ext_type == SADB_X_EXT_SEC_CTX) {
+ break;
+ case SADB_X_EXT_SEC_CTX:
if (verify_sec_ctx_len(p))
return -EINVAL;
+ break;
+ case SADB_EXT_KEY_AUTH:
+ case SADB_EXT_KEY_ENCRYPT:
+ if (verify_key_len(p))
+ return -EINVAL;
+ break;
+ default:
+ break;
}
ext_hdrs[ext_type-1] = (void *) p;
}
@@ -1105,14 +1132,12 @@ static struct xfrm_state * pfkey_msg2xfrm_state(struct net *net,
key = ext_hdrs[SADB_EXT_KEY_AUTH - 1];
if (key != NULL &&
sa->sadb_sa_auth != SADB_X_AALG_NULL &&
- (DIV_ROUND_UP(key->sadb_key_bits, 8) == 0 ||
- DIV_ROUND_UP(key->sadb_key_bits, 8) > key->sadb_key_len * sizeof(uint64_t)))
+ key->sadb_key_bits == 0)
return ERR_PTR(-EINVAL);
key = ext_hdrs[SADB_EXT_KEY_ENCRYPT-1];
if (key != NULL &&
sa->sadb_sa_encrypt != SADB_EALG_NULL &&
- (DIV_ROUND_UP(key->sadb_key_bits, 8) == 0 ||
- DIV_ROUND_UP(key->sadb_key_bits, 8) > key->sadb_key_len * sizeof(uint64_t)))
+ key->sadb_key_bits == 0)
return ERR_PTR(-EINVAL);

x = xfrm_state_alloc(net);
--
2.8.1
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