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Message-ID: <49AE20CF.1030601@numericable.fr>
Date: Wed, 04 Mar 2009 07:33:51 +0100
From: etienne <etienne.basset@...ericable.fr>
To: LSM <linux-security-module@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
CC: Casey Schaufler <casey@...aufler-ca.com>,
Paul Moore <paul.moore@...com>
Subject: [patch][smack][2.6.29-rc] fixes for unlabeled host support
Hello,
The following patch (against 2.6.29rc5) fixes a few issues in the smack/netlabel
"unlabeled host support" functionnality that was added in 2.6.29rc.
It should go in before -final.
1) smack_host_label disregard a "0.0.0.0/0 @" rule (or other label), preventing 'tagged' tasks to access Internet (many systems drop packets with IP options)
2) netmasks were not handled correctly, they were stored in a way _not equivalent_ to conversion to be32 (it was equivalent for /0, /8, /16, /24, /32 masks but not other masks)
3) smack_netlbladdr prefixes (IP/mask) were not consistent (mask&IP was not done), so there could have been different list entries for the same IP prefix; if those entries had different labels, well ...
4) they were not sorted
1) 2) 3) are bugs, 4) is a more cosmetic issue.
The patch :
-creates a new helper smk_netlbladdr_insert to insert a smk_netlbladdr, sorted by netmask length
-use the new sorted nature of smack_netlbladdrs list to simplify smack_host_label :
the first match _will_ be the more specific
-corrects endianness issues in smk_write_netlbladdr & netlbladdr_seq_show
regards,
Etienne Basset
Signed-off-by: <etienne.basset@...ericable.fr>
---
security/smack/smack_lsm.c | 43 +++++------------------------
security/smack/smackfs.c | 64 +++++++++++++++++++++++++++++++++----------
2 files changed, 57 insertions(+), 50 deletions(-)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 0278bc0..e7ded13 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1498,58 +1498,31 @@ static int smack_socket_post_create(struct socket *sock, int family,
* looks for host based access restrictions
*
* This version will only be appropriate for really small
- * sets of single label hosts. Because of the masking
- * it cannot shortcut out on the first match. There are
- * numerious ways to address the problem, but none of them
- * have been applied here.
+ * sets of single label hosts.
*
* Returns the label of the far end or NULL if it's not special.
*/
static char *smack_host_label(struct sockaddr_in *sip)
{
struct smk_netlbladdr *snp;
- char *bestlabel = NULL;
struct in_addr *siap = &sip->sin_addr;
- struct in_addr *liap;
- struct in_addr *miap;
- struct in_addr bestmask;
if (siap->s_addr == 0)
return NULL;
- bestmask.s_addr = 0;
-
for (snp = smack_netlbladdrs; snp != NULL; snp = snp->smk_next) {
- liap = &snp->smk_host.sin_addr;
- miap = &snp->smk_mask;
- /*
- * If the addresses match after applying the list entry mask
- * the entry matches the address. If it doesn't move along to
- * the next entry.
- */
- if ((liap->s_addr & miap->s_addr) !=
- (siap->s_addr & miap->s_addr))
- continue;
/*
- * If the list entry mask identifies a single address
- * it can't get any more specific.
+ * we break after finding the first match because
+ * the list is sorted from longest to shortest mask
+ * so we have found the most specific match
*/
- if (miap->s_addr == 0xffffffff)
+ if ((&snp->smk_host.sin_addr)->s_addr ==
+ (siap->s_addr & (&snp->smk_mask)->s_addr)) {
return snp->smk_label;
- /*
- * If the list entry mask is less specific than the best
- * already found this entry is uninteresting.
- */
- if ((miap->s_addr | bestmask.s_addr) == bestmask.s_addr)
- continue;
- /*
- * This is better than any entry found so far.
- */
- bestmask.s_addr = miap->s_addr;
- bestlabel = snp->smk_label;
+ }
}
- return bestlabel;
+ return NULL;
}
/**
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 8e42800..51f0efc 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -650,10 +650,6 @@ static void *netlbladdr_seq_next(struct seq_file *s, void *v, loff_t *pos)
return skp;
}
-/*
-#define BEMASK 0x80000000
-*/
-#define BEMASK 0x00000001
#define BEBITS (sizeof(__be32) * 8)
/*
@@ -663,12 +659,10 @@ static int netlbladdr_seq_show(struct seq_file *s, void *v)
{
struct smk_netlbladdr *skp = (struct smk_netlbladdr *) v;
unsigned char *hp = (char *) &skp->smk_host.sin_addr.s_addr;
- __be32 bebits;
- int maskn = 0;
+ int maskn;
+ u32 temp_mask = be32_to_cpu(skp->smk_mask.s_addr);
- for (bebits = BEMASK; bebits != 0; maskn++, bebits <<= 1)
- if ((skp->smk_mask.s_addr & bebits) == 0)
- break;
+ for (maskn = 0; temp_mask; temp_mask <<= 1, maskn++);
seq_printf(s, "%u.%u.%u.%u/%d %s\n",
hp[0], hp[1], hp[2], hp[3], maskn, skp->smk_label);
@@ -702,6 +696,42 @@ static int smk_open_netlbladdr(struct inode *inode, struct file *file)
}
/**
+ * smk_netlbladdr_insert
+ * @new : netlabel to insert
+ *
+ * This helper insert netlabel in the smack_netlbladdrs list
+ * sorted by netmask length (longest to smallest)
+ */
+static void smk_netlbladdr_insert(struct smk_netlbladdr *new)
+{
+ struct smk_netlbladdr *m;
+
+ if (smack_netlbladdrs == NULL) {
+ smack_netlbladdrs = new;
+ return;
+ }
+
+ /* the comparison '>' is a bit hacky, but works */
+ if (new->smk_mask.s_addr > smack_netlbladdrs->smk_mask.s_addr) {
+ new->smk_next = smack_netlbladdrs;
+ smack_netlbladdrs = new;
+ return;
+ }
+ for (m = smack_netlbladdrs; m != NULL; m = m->smk_next) {
+ if (m->smk_next == NULL) {
+ m->smk_next = new;
+ return;
+ }
+ if (new->smk_mask.s_addr > m->smk_next->smk_mask.s_addr) {
+ new->smk_next = m->smk_next;
+ m->smk_next = new;
+ return;
+ }
+ }
+}
+
+
+/**
* smk_write_netlbladdr - write() for /smack/netlabel
* @filp: file pointer, not actually used
* @buf: where to get the data from
@@ -724,8 +754,9 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
struct netlbl_audit audit_info;
struct in_addr mask;
unsigned int m;
- __be32 bebits = BEMASK;
+ u32 mask_bits = (1<<31);
__be32 nsa;
+ u32 temp_mask;
/*
* Must have privilege.
@@ -761,10 +792,13 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
if (sp == NULL)
return -EINVAL;
- for (mask.s_addr = 0; m > 0; m--) {
- mask.s_addr |= bebits;
- bebits <<= 1;
+ for (temp_mask = 0; m > 0; m--) {
+ temp_mask |= mask_bits;
+ mask_bits >>= 1;
}
+ mask.s_addr = cpu_to_be32(temp_mask);
+
+ newname.sin_addr.s_addr &= mask.s_addr;
/*
* Only allow one writer at a time. Writes should be
* quite rare and small in any case.
@@ -772,6 +806,7 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
mutex_lock(&smk_netlbladdr_lock);
nsa = newname.sin_addr.s_addr;
+ /* try to find if the prefix is already in the list */
for (skp = smack_netlbladdrs; skp != NULL; skp = skp->smk_next)
if (skp->smk_host.sin_addr.s_addr == nsa &&
skp->smk_mask.s_addr == mask.s_addr)
@@ -787,9 +822,8 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
rc = 0;
skp->smk_host.sin_addr.s_addr = newname.sin_addr.s_addr;
skp->smk_mask.s_addr = mask.s_addr;
- skp->smk_next = smack_netlbladdrs;
skp->smk_label = sp;
- smack_netlbladdrs = skp;
+ smk_netlbladdr_insert(skp);
}
} else {
rc = netlbl_cfg_unlbl_static_del(&init_net, NULL,
--
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