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linux-kernel: [patch][smack][2.6.29-rc] fixes for unlabeled host

[patch][smack][2.6.29-rc] fixes for unlabeled host support

From: etienne <etienne.basset_at_nospam>
Date: Wed Mar 04 2009 - 06:33:51 GMT
To: LSM <linux-security-module@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>


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
  5. 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@numericable.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, -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html