[PATCH v24 07/25] LSM: Use lsmblob in security_secctx_to_secid
Casey Schaufler
casey at schaufler-ca.com
Tue Jan 26 16:40:50 UTC 2021
Change the security_secctx_to_secid interface to use a lsmblob
structure in place of the single u32 secid in support of
module stacking. Change its callers to do the same.
The security module hook is unchanged, still passing back a secid.
The infrastructure passes the correct entry from the lsmblob.
Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
Cc: netdev at vger.kernel.org
Cc: netfilter-devel at vger.kernel.org
To: Pablo Neira Ayuso <pablo at netfilter.org>
---
include/linux/security.h | 26 ++++++++++++++++++--
kernel/cred.c | 4 +---
net/netfilter/nft_meta.c | 10 ++++----
net/netfilter/xt_SECMARK.c | 7 +++++-
net/netlabel/netlabel_unlabeled.c | 23 +++++++++++-------
security/security.c | 40 ++++++++++++++++++++++++++-----
6 files changed, 85 insertions(+), 25 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index 5d8dbfb1dabb..af1d69b41f1c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -196,6 +196,27 @@ static inline bool lsmblob_equal(struct lsmblob *bloba, struct lsmblob *blobb)
extern int lsm_name_to_slot(char *name);
extern const char *lsm_slot_to_name(int slot);
+/**
+ * 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);
@@ -513,7 +534,8 @@ 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);
@@ -1340,7 +1362,7 @@ 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;
}
diff --git a/kernel/cred.c b/kernel/cred.c
index 22e0e7cbefde..848306c7d823 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -757,14 +757,12 @@ 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/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
index bf4b3ad5314c..58a994db0069 100644
--- a/net/netfilter/nft_meta.c
+++ b/net/netfilter/nft_meta.c
@@ -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(lsmblob_value(&blob));
if (err)
return err;
- priv->secid = tmp_secid;
+ priv->secid = lsmblob_value(&blob);
return 0;
}
diff --git a/net/netfilter/xt_SECMARK.c b/net/netfilter/xt_SECMARK.c
index 75625d13e976..9845d98e6b77 100644
--- a/net/netfilter/xt_SECMARK.c
+++ b/net/netfilter/xt_SECMARK.c
@@ -43,13 +43,14 @@ 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",
@@ -57,6 +58,10 @@ 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);
diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
index ccb491642811..df9448af23dd 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 a3e162c4c0d3..1039f8a8ed09 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2127,10 +2127,22 @@ 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);
@@ -2281,10 +2293,26 @@ 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,
+ u32 *secid)
{
- return call_int_hook(socket_getpeersec_dgram, -ENOPROTOOPT, sock,
- skb, secid);
+ struct security_hook_list *hp;
+ int rc = -ENOPROTOOPT;
+
+ /*
+ * Only one security module should provide a real hook for
+ * this. A stub or bypass like is used in BPF should either
+ * (somehow) leave rc unaltered or return -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, secid);
+ if (rc != -ENOPROTOOPT)
+ break;
+ }
+ return rc;
}
EXPORT_SYMBOL(security_socket_getpeersec_dgram);
--
2.25.4
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