On Mon, Apr 06, 2020 at 05:01:41PM -0700, Casey Schaufler wrote:
> Change the data used in UDS SO_PEERSEC processing from a
> secid to a more general struct lsmblob. Update the
> security_socket_getpeersec_dgram() interface to use the
> lsmblob. There is a small amount of scaffolding code
> that will come out when the security_secid_to_secctx()
> code is brought in line with the lsmblob.
>
> The secid field of the unix_skb_parms structure has been
> replaced with a pointer to an lsmblob structure, and the
> lsmblob is allocated as needed. This is similar to how the
> list of passed files is managed. While an lsmblob structure
> will fit in the available space today, there is no guarantee
> that the addition of other data to the unix_skb_parms or
> support for additional security modules wouldn't exceed what
> is available.
>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
-Kees
> cc: netdev@xxxxxxxxxxxxxxx
> ---
> include/linux/security.h | 7 +++++--
> include/net/af_unix.h | 2 +-
> include/net/scm.h | 8 +++++---
> net/ipv4/ip_sockglue.c | 8 +++++---
> net/unix/af_unix.c | 7 ++++---
> net/unix/scm.c | 6 ++++++
> security/security.c | 18 +++++++++++++++---
> 7 files changed, 41 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 1bfaf9ece13e..2ad58e2900e7 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1358,7 +1358,8 @@ int security_socket_shutdown(struct socket *sock, int how);
> int security_sock_rcv_skb(struct sock *sk, struct sk_buff *skb);
> int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
> int __user *optlen, unsigned len);
> -int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid);
> +int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb,
> + struct lsmblob *blob);
> int security_sk_alloc(struct sock *sk, int family, gfp_t priority);
> void security_sk_free(struct sock *sk);
> void security_sk_clone(const struct sock *sk, struct sock *newsk);
> @@ -1496,7 +1497,9 @@ static inline int security_socket_getpeersec_stream(struct socket *sock, char __
> return -ENOPROTOOPT;
> }
>
> -static inline int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
> +static inline int security_socket_getpeersec_dgram(struct socket *sock,
> + struct sk_buff *skb,
> + struct lsmblob *blob)
> {
> return -ENOPROTOOPT;
> }
> diff --git a/include/net/af_unix.h b/include/net/af_unix.h
> index 17e10fba2152..83c3b3034030 100644
> --- a/include/net/af_unix.h
> +++ b/include/net/af_unix.h
> @@ -36,7 +36,7 @@ struct unix_skb_parms {
> kgid_t gid;
> struct scm_fp_list *fp; /* Passed files */
> #ifdef CONFIG_SECURITY_NETWORK
> - u32 secid; /* Security ID */
> + struct lsmblob *lsmdata; /* Security LSM data */
> #endif
> u32 consumed;
> } __randomize_layout;
> diff --git a/include/net/scm.h b/include/net/scm.h
> index 1ce365f4c256..e2e71c4bf9d0 100644
> --- a/include/net/scm.h
> +++ b/include/net/scm.h
> @@ -33,7 +33,7 @@ struct scm_cookie {
> struct scm_fp_list *fp; /* Passed files */
> struct scm_creds creds; /* Skb credentials */
> #ifdef CONFIG_SECURITY_NETWORK
> - u32 secid; /* Passed security ID */
> + struct lsmblob lsmblob; /* Passed LSM data */
> #endif
> };
>
> @@ -46,7 +46,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl);
> #ifdef CONFIG_SECURITY_NETWORK
> static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
> {
> - security_socket_getpeersec_dgram(sock, NULL, &scm->secid);
> + security_socket_getpeersec_dgram(sock, NULL, &scm->lsmblob);
> }
> #else
> static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
> @@ -97,7 +97,9 @@ static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc
> int err;
>
> if (test_bit(SOCK_PASSSEC, &sock->flags)) {
> - err = security_secid_to_secctx(scm->secid, &secdata, &seclen);
> + /* Scaffolding - it has to be element 0 for now */
> + err = security_secid_to_secctx(scm->lsmblob.secid[0],
> + &secdata, &seclen);
>
> if (!err) {
> put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, seclen, secdata);
> diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> index aa3fd61818c4..6cf57d5ac899 100644
> --- a/net/ipv4/ip_sockglue.c
> +++ b/net/ipv4/ip_sockglue.c
> @@ -130,15 +130,17 @@ static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,
>
> static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
> {
> + struct lsmblob lb;
> char *secdata;
> - u32 seclen, secid;
> + u32 seclen;
> int err;
>
> - err = security_socket_getpeersec_dgram(NULL, skb, &secid);
> + err = security_socket_getpeersec_dgram(NULL, skb, &lb);
> if (err)
> return;
>
> - err = security_secid_to_secctx(secid, &secdata, &seclen);
> + /* Scaffolding - it has to be element 0 */
> + err = security_secid_to_secctx(lb.secid[0], &secdata, &seclen);
> if (err)
> return;
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 68debcb28fa4..179876573d6d 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -138,17 +138,18 @@ static struct hlist_head *unix_sockets_unbound(void *addr)
> #ifdef CONFIG_SECURITY_NETWORK
> static void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
> {
> - UNIXCB(skb).secid = scm->secid;
> + UNIXCB(skb).lsmdata = kmemdup(&scm->lsmblob, sizeof(scm->lsmblob),
> + GFP_KERNEL);
> }
>
> static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb)
> {
> - scm->secid = UNIXCB(skb).secid;
> + scm->lsmblob = *(UNIXCB(skb).lsmdata);
> }
>
> static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb)
> {
> - return (scm->secid == UNIXCB(skb).secid);
> + return lsmblob_equal(&scm->lsmblob, UNIXCB(skb).lsmdata);
> }
> #else
> static inline void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
> diff --git a/net/unix/scm.c b/net/unix/scm.c
> index 8c40f2b32392..3094323935a4 100644
> --- a/net/unix/scm.c
> +++ b/net/unix/scm.c
> @@ -142,6 +142,12 @@ void unix_destruct_scm(struct sk_buff *skb)
> scm.pid = UNIXCB(skb).pid;
> if (UNIXCB(skb).fp)
> unix_detach_fds(&scm, skb);
> +#ifdef CONFIG_SECURITY_NETWORK
> + if (UNIXCB(skb).lsmdata) {
> + kfree(UNIXCB(skb).lsmdata);
> + UNIXCB(skb).lsmdata = NULL;
> + }
> +#endif
>
> /* Alas, it calls VFS */
> /* So fscking what? fput() had been SMP-safe since the last Summer */
> diff --git a/security/security.c b/security/security.c
> index 914aecd89822..2fa826000889 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2140,10 +2140,22 @@ int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
> optval, optlen, len);
> }
>
> -int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
> +int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb,
> + struct lsmblob *blob)
> {
> - return call_int_hook(socket_getpeersec_dgram, -ENOPROTOOPT, sock,
> - skb, secid);
> + struct security_hook_list *hp;
> + int rc = -ENOPROTOOPT;
> +
> + hlist_for_each_entry(hp, &security_hook_heads.socket_getpeersec_dgram,
> + list) {
> + if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
> + continue;
> + rc = hp->hook.socket_getpeersec_dgram(sock, skb,
> + &blob->secid[hp->lsmid->slot]);
> + if (rc != 0)
> + break;
> + }
> + return rc;
> }
> EXPORT_SYMBOL(security_socket_getpeersec_dgram);
>
> --
> 2.24.1
>
--
Kees Cook
