kernel/git/stable/linux.git/security/smack, branch linux-6.13.y

smack: ipv4/ipv6: tcp/dccp/sctp: fix incorrect child socket label

2025-04-10T12:41:31+00:00

[ Upstream commit 6cce0cc3861337b3ad8d4ac131d6e47efa0954ec ] Since inception [1], SMACK initializes ipv* child socket security for connection-oriented communications (tcp/sctp/dccp) during accept() syscall, in the security_sock_graft() hook: | void smack_sock_graft(struct sock *sk, ...) | { | // only ipv4 and ipv6 are eligible here | // ... | ssp = sk->sk_security; // socket security | ssp->smk_in = skp; // process label: smk_of_current() | ssp->smk_out = skp; // process label: smk_of_current() | } This approach is incorrect for two reasons: A) initialization occurs too late for child socket security: The child socket is created by the kernel once the handshake completes (e.g., for tcp: after receiving ack for syn+ack). Data can legitimately start arriving to the child socket immediately, long before the application calls accept() on the socket. Those data are (currently — were) processed by SMACK using incorrect child socket security attributes. B) Incoming connection requests are handled using the listening socket's security, hence, the child socket must inherit the listening socket's security attributes. smack_sock_graft() initilizes the child socket's security with a process label, as is done for a new socket() But ... the process label is not necessarily the same as the listening socket label. A privileged application may legitimately set other in/out labels for a listening socket. When this happens, SMACK processes incoming packets using incorrect socket security attributes. In [2] Michael Lontke noticed (A) and fixed it in [3] by adding socket initialization into security_sk_clone_security() hook like | void smack_sk_clone_security(struct sock *oldsk, struct sock *newsk) | { | *(struct socket_smack *)newsk->sk_security = | *(struct socket_smack *)oldsk->sk_security; | } This initializes the child socket security with the parent (listening) socket security at the appropriate time. I was forced to revisit this old story because smack_sock_graft() was left in place by [3] and continues overwriting the child socket's labels with the process label, and there might be a reason for this, so I undertook a study. If the process label differs from the listening socket's labels, the following occurs for ipv4: assigning the smk_out is not accompanied by netlbl_sock_setattr, so the outgoing packet's cipso label does not change. So, the only effect of this assignment for interhost communications is a divergence between the program-visible “out” socket label and the cipso network label. For intrahost communications this label, however, becomes visible via secmark netfilter marking, and is checked for access rights by the client, receiving side. Assigning the smk_in affects both interhost and intrahost communications: the server begins to check access rights against an wrong label. Access check against wrong label (smk_in or smk_out), unsurprisingly fails, breaking the connection. The above affects protocols that calls security_sock_graft() during accept(), namely: {tcp,dccp,sctp}/{ipv4,ipv6} One extra security_sock_graft() caller, crypto/af_alg.c`af_alg_accept is not affected, because smack_sock_graft() does nothing for PF_ALG. To reproduce, assign non-default in/out labels to a listening socket, setup rules between these labels and client label, attempt to connect and send some data. Ipv6 specific: ipv6 packets do not convey SMACK labels. To reproduce the issue in interhost communications set opposite labels in /smack/ipv6host on both hosts. Ipv6 intrahost communications do not require tricking, because SMACK labels are conveyed via secmark netfilter marking. So, currently smack_sock_graft() is not useful, but harmful, therefore, I have removed it. This fixes the issue for {tcp,dccp}/{ipv4,ipv6}, but not sctp/{ipv4,ipv6}. Although this change is necessary for sctp+smack to function correctly, it is not sufficient because: sctp/ipv4 does not call security_sk_clone() and sctp/ipv6 ignores SMACK completely. These are separate issues, belong to other subsystem, and should be addressed separately. [1] 2008-02-04, Fixes: e114e473771c ("Smack: Simplified Mandatory Access Control Kernel") [2] Michael Lontke, 2022-08-31, SMACK LSM checks wrong object label during ingress network traffic Link: https://lore.kernel.org/linux-security-module/6324997ce4fc092c5020a4add075257f9c5f6442.camel@elektrobit.com/ [3] 2022-08-31, michael.lontke, commit 4ca165fc6c49 ("SMACK: Add sk_clone_security LSM hook") Signed-off-by: Konstantin Andreev Signed-off-by: Casey Schaufler Signed-off-by: Sasha Levin

smack: dont compile ipv6 code unless ipv6 is configured

2025-04-10T12:41:31+00:00

[ Upstream commit bfcf4004bcbce2cb674b4e8dbd31ce0891766bac ] I want to be sure that ipv6-specific code is not compiled in kernel binaries if ipv6 is not configured. [1] was getting rid of "unused variable" warning, but, with that, it also mandated compilation of a handful ipv6- specific functions in ipv4-only kernel configurations: smk_ipv6_localhost, smack_ipv6host_label, smk_ipv6_check. Their compiled bodies are likely to be removed by compiler from the resulting binary, but, to be on the safe side, I remove them from the compiler view. [1] Fixes: 00720f0e7f28 ("smack: avoid unused 'sip' variable warning") Signed-off-by: Konstantin Andreev Signed-off-by: Casey Schaufler Signed-off-by: Sasha Levin

lsm: remove lsm_prop scaffolding

2024-10-11T18:34:16+00:00

Remove the scaffold member from the lsm_prop. Remove the remaining places it is being set. Signed-off-by: Casey Schaufler [PM: subj line tweak] Signed-off-by: Paul Moore

netlabel,smack: use lsm_prop for audit data

2024-10-11T18:34:16+00:00

Replace the secid in the netlbl_audit structure with an lsm_prop. Remove scaffolding that was required when the value was a secid. Signed-off-by: Casey Schaufler [PM: fix the subject line] Signed-off-by: Paul Moore

lsm: create new security_cred_getlsmprop LSM hook

2024-10-11T18:34:15+00:00

Create a new LSM hook security_cred_getlsmprop() which, like security_cred_getsecid(), fetches LSM specific attributes from the cred structure. The associated data elements in the audit sub-system are changed from a secid to a lsm_prop to accommodate multiple possible LSM audit users. Cc: linux-integrity@vger.kernel.org Cc: audit@vger.kernel.org Cc: selinux@vger.kernel.org Signed-off-by: Casey Schaufler [PM: subj line tweak] Signed-off-by: Paul Moore

lsm: use lsm_prop in security_inode_getsecid

2024-10-11T18:34:14+00:00

Change the security_inode_getsecid() interface to fill in a lsm_prop structure instead of a u32 secid. This allows for its callers to gather data from all registered LSMs. Data is provided for IMA and audit. Change the name to security_inode_getlsmprop(). Cc: linux-integrity@vger.kernel.org Cc: selinux@vger.kernel.org Signed-off-by: Casey Schaufler [PM: subj line tweak] Signed-off-by: Paul Moore

lsm: use lsm_prop in security_current_getsecid

2024-10-11T18:34:14+00:00

Change the security_current_getsecid_subj() and security_task_getsecid_obj() interfaces to fill in a lsm_prop structure instead of a u32 secid. Audit interfaces will need to collect all possible security data for possible reporting. Cc: linux-integrity@vger.kernel.org Cc: audit@vger.kernel.org Cc: selinux@vger.kernel.org Signed-off-by: Casey Schaufler [PM: subject line tweak] Signed-off-by: Paul Moore

lsm: use lsm_prop in security_ipc_getsecid

2024-10-11T18:34:13+00:00

There may be more than one LSM that provides IPC data for auditing. Change security_ipc_getsecid() to fill in a lsm_prop structure instead of the u32 secid. Change the name to security_ipc_getlsmprop() to reflect the change. Cc: audit@vger.kernel.org Cc: linux-security-module@vger.kernel.org Cc: selinux@vger.kernel.org Signed-off-by: Casey Schaufler [PM: subject line tweak] Signed-off-by: Paul Moore

lsm: add lsmprop_to_secctx hook

2024-10-11T18:34:12+00:00

Add a new hook security_lsmprop_to_secctx() and its LSM specific implementations. The LSM specific code will use the lsm_prop element allocated for that module. This allows for the possibility that more than one module may be called upon to translate a secid to a string, as can occur in the audit code. Signed-off-by: Casey Schaufler [PM: subject line tweak] Signed-off-by: Paul Moore

lsm: use lsm_prop in security_audit_rule_match

2024-10-11T18:34:12+00:00

Change the secid parameter of security_audit_rule_match to a lsm_prop structure pointer. Pass the entry from the lsm_prop structure for the approprite slot to the LSM hook. Change the users of security_audit_rule_match to use the lsm_prop instead of a u32. The scaffolding function lsmprop_init() fills the structure with the value of the old secid, ensuring that it is available to the appropriate module hook. The sources of the secid, security_task_getsecid() and security_inode_getsecid(), will be converted to use the lsm_prop structure later in the series. At that point the use of lsmprop_init() is dropped. Signed-off-by: Casey Schaufler [PM: subject line tweak] Signed-off-by: Paul Moore