| Message ID | 20200214234203.7086-6-casey@schaufler-ca.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | LSM: Module stacking for AppArmor | expand |
On Fri, Feb 14, 2020 at 6:42 PM Casey Schaufler <casey@schaufler-ca.com> 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. > > Reviewed-by: Kees Cook <keescook@chromium.org> > Reviewed-by: John Johansen <john.johansen@canonical.com> > Acked-by: Stephen Smalley <sds@tycho.nsa.gov> > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> > cc: netdev@vger.kernel.org > --- > 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 | 6 +++--- > security/security.c | 18 +++++++++++++++--- > 6 files changed, 34 insertions(+), 15 deletions(-) ... > diff --git a/include/net/af_unix.h b/include/net/af_unix.h > index 17e10fba2152..59af08ca802f 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 lsmblob; /* Security LSM data */ > #endif > u32 consumed; > } __randomize_layout; This might be a problem. As it currently stands, the sk_buff.cb field is 48 bytes; with CONFIG_SECURITY_NETWORK=n unix_skb_parms is 28 bytes on a 64-bit system. That leaves 20 bytes (room for 5 LSMs) assuming a tight packing *and* that netdev doesn't swoop in and drop another few fields in unix_skb_parms. This may work now, and you might manage to sneak this by the netdev crowd, but I predict problems in the future.
On 3/6/2020 2:14 PM, Paul Moore wrote: > On Fri, Feb 14, 2020 at 6:42 PM Casey Schaufler <casey@schaufler-ca.com> 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. >> >> Reviewed-by: Kees Cook <keescook@chromium.org> >> Reviewed-by: John Johansen <john.johansen@canonical.com> >> Acked-by: Stephen Smalley <sds@tycho.nsa.gov> >> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> >> cc: netdev@vger.kernel.org >> --- >> 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 | 6 +++--- >> security/security.c | 18 +++++++++++++++--- >> 6 files changed, 34 insertions(+), 15 deletions(-) > ... > >> diff --git a/include/net/af_unix.h b/include/net/af_unix.h >> index 17e10fba2152..59af08ca802f 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 lsmblob; /* Security LSM data */ >> #endif >> u32 consumed; >> } __randomize_layout; > This might be a problem. As it currently stands, the sk_buff.cb field > is 48 bytes; with CONFIG_SECURITY_NETWORK=n unix_skb_parms is 28 bytes > on a 64-bit system. That leaves 20 bytes (room for 5 LSMs) assuming a > tight packing *and* that netdev doesn't swoop in and drop another few > fields in unix_skb_parms. > > This may work now, and you might manage to sneak this by the netdev > crowd, but I predict problems in the future. Do you think that making this a struct lsmblob * instead would make the change more likely to be accepted? It would complicate the code but remove the issue.
On Mon, Mar 9, 2020 at 8:13 PM Casey Schaufler <casey@schaufler-ca.com> wrote: > On 3/6/2020 2:14 PM, Paul Moore wrote: > > On Fri, Feb 14, 2020 at 6:42 PM Casey Schaufler <casey@schaufler-ca.com> 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. > >> > >> Reviewed-by: Kees Cook <keescook@chromium.org> > >> Reviewed-by: John Johansen <john.johansen@canonical.com> > >> Acked-by: Stephen Smalley <sds@tycho.nsa.gov> > >> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> > >> cc: netdev@vger.kernel.org > >> --- > >> 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 | 6 +++--- > >> security/security.c | 18 +++++++++++++++--- > >> 6 files changed, 34 insertions(+), 15 deletions(-) > > ... > > > >> diff --git a/include/net/af_unix.h b/include/net/af_unix.h > >> index 17e10fba2152..59af08ca802f 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 lsmblob; /* Security LSM data */ > >> #endif > >> u32 consumed; > >> } __randomize_layout; > > This might be a problem. As it currently stands, the sk_buff.cb field > > is 48 bytes; with CONFIG_SECURITY_NETWORK=n unix_skb_parms is 28 bytes > > on a 64-bit system. That leaves 20 bytes (room for 5 LSMs) assuming a > > tight packing *and* that netdev doesn't swoop in and drop another few > > fields in unix_skb_parms. > > > > This may work now, and you might manage to sneak this by the netdev > > crowd, but I predict problems in the future. > > Do you think that making this a struct lsmblob * instead would make > the change more likely to be accepted? It would complicate the code > but remove the issue. I honestly have no idea anymore when it comes to the netdev crowd. I can toss out a few examples, but you've been in this space long enough to have seen the same things I have wrt to LSMs and the networking folks. Regardless of the implementation, I don't think you can embed the lsmblob struct in the skb.cb; room for five LSMs is likely going to be a limiting factor. Once you settle on that, no matter what you do for a reference, pointer/index/etc., the problems are all roughly the same. The trick is to find out what netdev will begrudgingly accept, and for that I'm afraid you'll need to ask them directly.
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..59af08ca802f 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 lsmblob; /* 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 62c12cb5763e..5bed7361ec4c 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -138,17 +138,17 @@ 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).lsmblob = scm->lsmblob; } static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb) { - scm->secid = UNIXCB(skb).secid; + scm->lsmblob = UNIXCB(skb).lsmblob; } 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).lsmblob)); } #else static inline void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb) 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);