[PATCH v16 06/23] Use lsmblob in security_secctx_to_secid
Kees Cook
keescook at chromium.org
Tue Apr 7 18:36:30 UTC 2020
On Mon, Apr 06, 2020 at 05:01:42PM -0700, Casey Schaufler wrote:
> Change security_secctx_to_secid() to fill in a lsmblob instead
> of a u32 secid. Multiple LSMs may be able to interpret the
> string, and this allows for setting whichever secid is
> appropriate. Change security_secmark_relabel_packet() to use a
> lsmblob instead of a u32 secid. In some other cases there is
> scaffolding where interfaces have yet to be converted.
>
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
Reviewed-by: Kees Cook <keescook at chromium.org>
-Kees
> ---
> include/linux/security.h | 30 +++++++++++++++++++++++----
> include/net/scm.h | 7 +++++--
> kernel/cred.c | 4 +---
> net/ipv4/ip_sockglue.c | 6 ++++--
> net/netfilter/nft_meta.c | 18 +++++++++-------
> net/netfilter/xt_SECMARK.c | 9 ++++++--
> net/netlabel/netlabel_unlabeled.c | 23 +++++++++++++--------
> security/security.c | 34 ++++++++++++++++++++++++++-----
> 8 files changed, 98 insertions(+), 33 deletions(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 2ad58e2900e7..554fe4cbbf48 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -188,6 +188,27 @@ static inline bool lsmblob_equal(struct lsmblob *bloba, struct lsmblob *blobb)
> return !memcmp(bloba, blobb, sizeof(*bloba));
> }
>
> +/**
> + * lsmblob_value - find the first non-zero value in an lsmblob structure.
> + * @blob: Pointer to the data
> + *
> + * This needs to be used with extreme caution, as the cases where
> + * it is appropriate are rare.
> + *
> + * Return the first secid value set in the lsmblob.
> + * There should only be one.
> + */
> +static inline u32 lsmblob_value(const struct lsmblob *blob)
> +{
> + int i;
> +
> + for (i = 0; i < LSMBLOB_ENTRIES; i++)
> + if (blob->secid[i])
> + return blob->secid[i];
> +
> + return 0;
> +}
> +
> /* These functions are in security/commoncap.c */
> extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
> int cap, unsigned int opts);
> @@ -498,7 +519,8 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
> int security_netlink_send(struct sock *sk, struct sk_buff *skb);
> int security_ismaclabel(const char *name);
> int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
> -int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
> +int security_secctx_to_secid(const char *secdata, u32 seclen,
> + struct lsmblob *blob);
> void security_release_secctx(char *secdata, u32 seclen);
> void security_inode_invalidate_secctx(struct inode *inode);
> int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
> @@ -1304,7 +1326,7 @@ static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *secle
>
> static inline int security_secctx_to_secid(const char *secdata,
> u32 seclen,
> - u32 *secid)
> + struct lsmblob *blob)
> {
> return -EOPNOTSUPP;
> }
> @@ -1372,7 +1394,7 @@ void security_inet_csk_clone(struct sock *newsk,
> const struct request_sock *req);
> void security_inet_conn_established(struct sock *sk,
> struct sk_buff *skb);
> -int security_secmark_relabel_packet(u32 secid);
> +int security_secmark_relabel_packet(struct lsmblob *blob);
> void security_secmark_refcount_inc(void);
> void security_secmark_refcount_dec(void);
> int security_tun_dev_alloc_security(void **security);
> @@ -1545,7 +1567,7 @@ static inline void security_inet_conn_established(struct sock *sk,
> {
> }
>
> -static inline int security_secmark_relabel_packet(u32 secid)
> +static inline int security_secmark_relabel_packet(struct lsmblob *blob)
> {
> return 0;
> }
> diff --git a/include/net/scm.h b/include/net/scm.h
> index e2e71c4bf9d0..c09f2dfeec88 100644
> --- a/include/net/scm.h
> +++ b/include/net/scm.h
> @@ -97,8 +97,11 @@ static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc
> int err;
>
> if (test_bit(SOCK_PASSSEC, &sock->flags)) {
> - /* Scaffolding - it has to be element 0 for now */
> - err = security_secid_to_secctx(scm->lsmblob.secid[0],
> + /* There can currently be only one value in the lsmblob,
> + * so getting it from lsmblob_value is appropriate until
> + * security_secid_to_secctx() is converted to taking a
> + * lsmblob directly. */
> + err = security_secid_to_secctx(lsmblob_value(&scm->lsmblob),
> &secdata, &seclen);
>
> if (!err) {
> diff --git a/kernel/cred.c b/kernel/cred.c
> index fae63c0a1b36..e654a5a84408 100644
> --- a/kernel/cred.c
> +++ b/kernel/cred.c
> @@ -756,14 +756,12 @@ EXPORT_SYMBOL(set_security_override);
> int set_security_override_from_ctx(struct cred *new, const char *secctx)
> {
> struct lsmblob blob;
> - u32 secid;
> int ret;
>
> - ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
> + ret = security_secctx_to_secid(secctx, strlen(secctx), &blob);
> if (ret < 0)
> return ret;
>
> - lsmblob_init(&blob, secid);
> return set_security_override(new, &blob);
> }
> EXPORT_SYMBOL(set_security_override_from_ctx);
> diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> index 6cf57d5ac899..7207f90eba44 100644
> --- a/net/ipv4/ip_sockglue.c
> +++ b/net/ipv4/ip_sockglue.c
> @@ -139,8 +139,10 @@ static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
> if (err)
> return;
>
> - /* Scaffolding - it has to be element 0 */
> - err = security_secid_to_secctx(lb.secid[0], &secdata, &seclen);
> + /* There can only be one secid in the lsmblob at this point,
> + * so getting it using lsmblob_value() is sufficient until
> + * security_secid_to_secctx() is changed to use a lsmblob */
> + err = security_secid_to_secctx(lsmblob_value(&lb), &secdata, &seclen);
> if (err)
> return;
>
> diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
> index 951b6e87ed5d..5875222aeac5 100644
> --- a/net/netfilter/nft_meta.c
> +++ b/net/netfilter/nft_meta.c
> @@ -801,7 +801,7 @@ struct nft_expr_type nft_meta_type __read_mostly = {
>
> #ifdef CONFIG_NETWORK_SECMARK
> struct nft_secmark {
> - u32 secid;
> + struct lsmblob lsmdata;
> char *ctx;
> };
>
> @@ -811,21 +811,21 @@ static const struct nla_policy nft_secmark_policy[NFTA_SECMARK_MAX + 1] = {
>
> static int nft_secmark_compute_secid(struct nft_secmark *priv)
> {
> - u32 tmp_secid = 0;
> + struct lsmblob blob;
> int err;
>
> - err = security_secctx_to_secid(priv->ctx, strlen(priv->ctx), &tmp_secid);
> + err = security_secctx_to_secid(priv->ctx, strlen(priv->ctx), &blob);
> if (err)
> return err;
>
> - if (!tmp_secid)
> + if (!lsmblob_is_set(&blob))
> return -ENOENT;
>
> - err = security_secmark_relabel_packet(tmp_secid);
> + err = security_secmark_relabel_packet(&blob);
> if (err)
> return err;
>
> - priv->secid = tmp_secid;
> + priv->lsmdata = blob;
> return 0;
> }
>
> @@ -835,7 +835,11 @@ static void nft_secmark_obj_eval(struct nft_object *obj, struct nft_regs *regs,
> const struct nft_secmark *priv = nft_obj_data(obj);
> struct sk_buff *skb = pkt->skb;
>
> - skb->secmark = priv->secid;
> + /* It is not possible for more than one secid to be set in
> + * the lsmblob structure because it is set using
> + * security_secctx_to_secid(). Any secid that is set must therefore
> + * be the one that should go in the secmark. */
> + skb->secmark = lsmblob_value(&priv->lsmdata);
> }
>
> static int nft_secmark_obj_init(const struct nft_ctx *ctx,
> diff --git a/net/netfilter/xt_SECMARK.c b/net/netfilter/xt_SECMARK.c
> index 2317721f3ecb..8a004d018871 100644
> --- a/net/netfilter/xt_SECMARK.c
> +++ b/net/netfilter/xt_SECMARK.c
> @@ -45,13 +45,14 @@ secmark_tg(struct sk_buff *skb, const struct xt_action_param *par)
>
> static int checkentry_lsm(struct xt_secmark_target_info *info)
> {
> + struct lsmblob blob;
> int err;
>
> info->secctx[SECMARK_SECCTX_MAX - 1] = '\0';
> info->secid = 0;
>
> err = security_secctx_to_secid(info->secctx, strlen(info->secctx),
> - &info->secid);
> + &blob);
> if (err) {
> if (err == -EINVAL)
> pr_info_ratelimited("invalid security context \'%s\'\n",
> @@ -59,13 +60,17 @@ static int checkentry_lsm(struct xt_secmark_target_info *info)
> return err;
> }
>
> + /* xt_secmark_target_info can't be changed to use lsmblobs because
> + * it is exposed as an API. Use lsmblob_value() to get the one
> + * value that got set by security_secctx_to_secid(). */
> + info->secid = lsmblob_value(&blob);
> if (!info->secid) {
> pr_info_ratelimited("unable to map security context \'%s\'\n",
> info->secctx);
> return -ENOENT;
> }
>
> - err = security_secmark_relabel_packet(info->secid);
> + err = security_secmark_relabel_packet(&blob);
> if (err) {
> pr_info_ratelimited("unable to obtain relabeling permission\n");
> return err;
> diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
> index 77bb1bb22c3b..8948557eaebb 100644
> --- a/net/netlabel/netlabel_unlabeled.c
> +++ b/net/netlabel/netlabel_unlabeled.c
> @@ -882,7 +882,7 @@ static int netlbl_unlabel_staticadd(struct sk_buff *skb,
> void *addr;
> void *mask;
> u32 addr_len;
> - u32 secid;
> + struct lsmblob blob;
> struct netlbl_audit audit_info;
>
> /* Don't allow users to add both IPv4 and IPv6 addresses for a
> @@ -906,13 +906,18 @@ static int netlbl_unlabel_staticadd(struct sk_buff *skb,
> ret_val = security_secctx_to_secid(
> nla_data(info->attrs[NLBL_UNLABEL_A_SECCTX]),
> nla_len(info->attrs[NLBL_UNLABEL_A_SECCTX]),
> - &secid);
> + &blob);
> if (ret_val != 0)
> return ret_val;
>
> + /* netlbl_unlhsh_add will be changed to pass a struct lsmblob *
> + * instead of a u32 later in this patch set. security_secctx_to_secid()
> + * will only be setting one entry in the lsmblob struct, so it is
> + * safe to use lsmblob_value() to get that one value. */
> +
> return netlbl_unlhsh_add(&init_net,
> - dev_name, addr, mask, addr_len, secid,
> - &audit_info);
> + dev_name, addr, mask, addr_len,
> + lsmblob_value(&blob), &audit_info);
> }
>
> /**
> @@ -933,7 +938,7 @@ static int netlbl_unlabel_staticadddef(struct sk_buff *skb,
> void *addr;
> void *mask;
> u32 addr_len;
> - u32 secid;
> + struct lsmblob blob;
> struct netlbl_audit audit_info;
>
> /* Don't allow users to add both IPv4 and IPv6 addresses for a
> @@ -955,13 +960,15 @@ static int netlbl_unlabel_staticadddef(struct sk_buff *skb,
> ret_val = security_secctx_to_secid(
> nla_data(info->attrs[NLBL_UNLABEL_A_SECCTX]),
> nla_len(info->attrs[NLBL_UNLABEL_A_SECCTX]),
> - &secid);
> + &blob);
> if (ret_val != 0)
> return ret_val;
>
> + /* security_secctx_to_secid() will only put one secid into the lsmblob
> + * so it's safe to use lsmblob_value() to get the secid. */
> return netlbl_unlhsh_add(&init_net,
> - NULL, addr, mask, addr_len, secid,
> - &audit_info);
> + NULL, addr, mask, addr_len,
> + lsmblob_value(&blob), &audit_info);
> }
>
> /**
> diff --git a/security/security.c b/security/security.c
> index 2fa826000889..6edbcb4c655e 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2002,10 +2002,22 @@ int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
> }
> EXPORT_SYMBOL(security_secid_to_secctx);
>
> -int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid)
> +int security_secctx_to_secid(const char *secdata, u32 seclen,
> + struct lsmblob *blob)
> {
> - *secid = 0;
> - return call_int_hook(secctx_to_secid, 0, secdata, seclen, secid);
> + struct security_hook_list *hp;
> + int rc;
> +
> + lsmblob_init(blob, 0);
> + hlist_for_each_entry(hp, &security_hook_heads.secctx_to_secid, list) {
> + if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
> + continue;
> + rc = hp->hook.secctx_to_secid(secdata, seclen,
> + &blob->secid[hp->lsmid->slot]);
> + if (rc != 0)
> + return rc;
> + }
> + return 0;
> }
> EXPORT_SYMBOL(security_secctx_to_secid);
>
> @@ -2222,9 +2234,21 @@ void security_inet_conn_established(struct sock *sk,
> }
> EXPORT_SYMBOL(security_inet_conn_established);
>
> -int security_secmark_relabel_packet(u32 secid)
> +int security_secmark_relabel_packet(struct lsmblob *blob)
> {
> - return call_int_hook(secmark_relabel_packet, 0, secid);
> + struct security_hook_list *hp;
> + int rc = 0;
> +
> + hlist_for_each_entry(hp, &security_hook_heads.secmark_relabel_packet,
> + list) {
> + if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
> + continue;
> + rc = hp->hook.secmark_relabel_packet(
> + blob->secid[hp->lsmid->slot]);
> + if (rc != 0)
> + break;
> + }
> + return rc;
> }
> EXPORT_SYMBOL(security_secmark_relabel_packet);
>
> --
> 2.24.1
>
--
Kees Cook
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