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ksmbd: throttle session setup failures to avoid dictionary attacks

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To avoid dictionary attacks (repeated session setups rapidly sent) to
connect to server, ksmbd make a delay of a 5 seconds on session setup
failure to make it harder to send enough random connection requests
to break into a server if a user insert the wrong password 10 times
in a row.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Namjae Jeon 2021-10-13 17:28:31 +09:00 committed by Steve French
parent 34061d6b76
commit 621be84a9d
6 changed files with 31 additions and 6 deletions
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2
fs/ksmbd/ksmbd_netlink.h
View file

@ -211,6 +211,7 @@ struct ksmbd_tree_disconnect_request {
*/
struct ksmbd_logout_request {
__s8 account[KSMBD_REQ_MAX_ACCOUNT_NAME_SZ]; /* user account name */
__u32 account_flags;
};
/*
@ -317,6 +318,7 @@ enum KSMBD_TREE_CONN_STATUS {
#define KSMBD_USER_FLAG_BAD_UID BIT(2)
#define KSMBD_USER_FLAG_BAD_USER BIT(3)
#define KSMBD_USER_FLAG_GUEST_ACCOUNT BIT(4)
#define KSMBD_USER_FLAG_DELAY_SESSION BIT(5)
/*
* Share config flags.

2
fs/ksmbd/mgmt/user_config.c
View file

@ -55,7 +55,7 @@ struct ksmbd_user *ksmbd_alloc_user(struct ksmbd_login_response *resp)
void ksmbd_free_user(struct ksmbd_user *user)
{
ksmbd_ipc_logout_request(user->name);
ksmbd_ipc_logout_request(user->name, user->flags);
kfree(user->name);
kfree(user->passkey);
kfree(user);

1
fs/ksmbd/mgmt/user_config.h
View file

@ -18,6 +18,7 @@ struct ksmbd_user {
size_t passkey_sz;
char *passkey;
unsigned int failed_login_count;
};
static inline bool user_guest(struct ksmbd_user *user)

27
fs/ksmbd/smb2pdu.c
View file

@ -1779,9 +1779,30 @@ int smb2_sess_setup(struct ksmbd_work *work)
conn->mechToken = NULL;
}
if (rc < 0 && sess) {
ksmbd_session_destroy(sess);
work->sess = NULL;
if (rc < 0) {
/*
* SecurityBufferOffset should be set to zero
* in session setup error response.
*/
rsp->SecurityBufferOffset = 0;
if (sess) {
bool try_delay = false;
/*
* To avoid dictionary attacks (repeated session setups rapidly sent) to
* connect to server, ksmbd make a delay of a 5 seconds on session setup
* failure to make it harder to send enough random connection requests
* to break into a server.
*/
if (sess->user && sess->user->flags & KSMBD_USER_FLAG_DELAY_SESSION)
try_delay = true;
ksmbd_session_destroy(sess);
work->sess = NULL;
if (try_delay)
ssleep(5);
}
}
return rc;

3
fs/ksmbd/transport_ipc.c
View file

@ -601,7 +601,7 @@ int ksmbd_ipc_tree_disconnect_request(unsigned long long session_id,
return ret;
}
int ksmbd_ipc_logout_request(const char *account)
int ksmbd_ipc_logout_request(const char *account, int flags)
{
struct ksmbd_ipc_msg *msg;
struct ksmbd_logout_request *req;
@ -616,6 +616,7 @@ int ksmbd_ipc_logout_request(const char *account)
msg->type = KSMBD_EVENT_LOGOUT_REQUEST;
req = (struct ksmbd_logout_request *)msg->payload;
req->account_flags = flags;
strscpy(req->account, account, KSMBD_REQ_MAX_ACCOUNT_NAME_SZ);
ret = ipc_msg_send(msg);

2
fs/ksmbd/transport_ipc.h
View file

@ -25,7 +25,7 @@ ksmbd_ipc_tree_connect_request(struct ksmbd_session *sess,
struct sockaddr *peer_addr);
int ksmbd_ipc_tree_disconnect_request(unsigned long long session_id,
unsigned long long connect_id);
int ksmbd_ipc_logout_request(const char *account);
int ksmbd_ipc_logout_request(const char *account, int flags);
struct ksmbd_share_config_response *
ksmbd_ipc_share_config_request(const char *name);
struct ksmbd_spnego_authen_response *