Subject: Re: [PATCH] (02/15/08 Linus git) Smack unlabeled outgoing ambient packets - v4

From: Paul Moore <[email-masked]>
Date: Fri, 15 Feb 2008 22:13:11 -0500

On Friday 15 February 2008 6:24:25 pm Casey Schaufler wrote:
> From: Casey Schaufler <[email-masked]>
>
> Smack uses CIPSO labeling, but allows for unlabeled packets
> by specifying an "ambient" label that is applied to incoming
> unlabeled packets. Because the other end of the connection
> may dislike IP options, and ssh is one know application that
> behaves thus, it is prudent to respond in kind. This patch
> changes the network labeling behavior such that an outgoing
> packet that would be given a CIPSO label that matches the
> ambient label is left unlabeled. An "unlbl" domain is added
> and the netlabel defaulting mechanism invoked rather than
> assuming that everything is CIPSO. Locking has been added
> around changes to the ambient label as the mechanisms used
> to do so are more involved.
>
> Cleaned up some issues noted in review.
> Make smk_cipso_doi() static.
> Create a hook for the new security_secctx_to_secid()
> using existing underlying code.
> Fill in audit data for netlbl domain calls.
> Collapse unnecessary multiple assignments.
>
> Signed-off-by: Casey Schaufler <[email-masked]>

Looks good to me, thanks for making those changes.

Acked-by: Paul Moore <[email-masked]>

> ---
>
>  security/smack/smack_lsm.c |   36 ++++++++++++++++----
>  security/smack/smackfs.c   |   61 ++++++++++++++++++++++++++---------
>  2 files changed, 74 insertions(+), 23 deletions(-)
>
> diff -uprN -X linux-2.6.25-g0215-base//Documentation/dontdiff
> linux-2.6.25-g0215-base/security/smack/smackfs.c
> linux-2.6.25-g0215/security/smack/smackfs.c ---
> linux-2.6.25-g0215-base/security/smack/smackfs.c	2008-02-15
> 14:25:37.000000000 -0800 +++
> linux-2.6.25-g0215/security/smack/smackfs.c	2008-02-15 14:30:36.000000000
> -0800 @@ -24,6 +24,7 @@
>  #include <net/cipso_ipv4.h>
>  #include <linux/seq_file.h>
>  #include <linux/ctype.h>
> +#include <linux/audit.h>
>  #include "smack.h"
>
>  /*
> @@ -45,6 +46,7 @@ enum smk_inos {
>   */
>  static DEFINE_MUTEX(smack_list_lock);
>  static DEFINE_MUTEX(smack_cipso_lock);
> +static DEFINE_MUTEX(smack_ambient_lock);
>
>  /*
>   * This is the "ambient" label for network traffic.
> @@ -342,6 +344,9 @@ void smk_cipso_doi(void)
>  	struct cipso_v4_doi *doip;
>  	struct netlbl_audit audit_info;
>
> +	audit_info.loginuid = audit_get_loginuid(current);
> +	audit_info.secid = smack_to_secid(current->security);
> +
>  	rc = netlbl_cfg_map_del(NULL, &audit_info);
>  	if (rc != 0)
>  		printk(KERN_WARNING "%s:%d remove rc = %d\n",
> @@ -363,6 +368,30 @@ void smk_cipso_doi(void)
>  		       __func__, __LINE__, rc);
>  }
>
> +/**
> + * smk_unlbl_ambient - initialize the unlabeled domain
> + */
> +void smk_unlbl_ambient(char *oldambient)
> +{
> +	int rc;
> +	struct netlbl_audit audit_info;
> +
> +	audit_info.loginuid = audit_get_loginuid(current);
> +	audit_info.secid = smack_to_secid(current->security);
> +
> +	if (oldambient != NULL) {
> +		rc = netlbl_cfg_map_del(oldambient, &audit_info);
> +		if (rc != 0)
> +			printk(KERN_WARNING "%s:%d remove rc = %d\n",
> +			       __func__, __LINE__, rc);
> +	}
> +
> +	rc = netlbl_cfg_unlbl_add_map(smack_net_ambient, &audit_info);
> +	if (rc != 0)
> +		printk(KERN_WARNING "%s:%d add rc = %d\n",
> +		       __func__, __LINE__, rc);
> +}
> +
>  /*
>   * Seq_file read operations for /smack/cipso
>   */
> @@ -709,7 +738,6 @@ static ssize_t smk_read_ambient(struct f
>  				size_t cn, loff_t *ppos)
>  {
>  	ssize_t rc;
> -	char out[SMK_LABELLEN];
>  	int asize;
>
>  	if (*ppos != 0)
> @@ -717,23 +745,18 @@ static ssize_t smk_read_ambient(struct f
>  	/*
>  	 * Being careful to avoid a problem in the case where
>  	 * smack_net_ambient gets changed in midstream.
> -	 * Since smack_net_ambient is always set with a value
> -	 * from the label list, including initially, and those
> -	 * never get freed, the worst case is that the pointer
> -	 * gets changed just after this strncpy, in which case
> -	 * the value passed up is incorrect. Locking around
> -	 * smack_net_ambient wouldn't be any better than this
> -	 * copy scheme as by the time the caller got to look
> -	 * at the ambient value it would have cleared the lock
> -	 * and been changed.
>  	 */
> -	strncpy(out, smack_net_ambient, SMK_LABELLEN);
> -	asize = strlen(out) + 1;
> +	mutex_lock(&smack_ambient_lock);
>
> -	if (cn < asize)
> -		return -EINVAL;
> +	asize = strlen(smack_net_ambient) + 1;
> +
> +	if (cn >= asize)
> +		rc = simple_read_from_buffer(buf, cn, ppos,
> +					     smack_net_ambient, asize);
> +	else
> +		rc = -EINVAL;
>
> -	rc = simple_read_from_buffer(buf, cn, ppos, out, asize);
> +	mutex_unlock(&smack_ambient_lock);
>
>  	return rc;
>  }
> @@ -751,6 +774,7 @@ static ssize_t smk_write_ambient(struct
>  				 size_t count, loff_t *ppos)
>  {
>  	char in[SMK_LABELLEN];
> +	char *oldambient;
>  	char *smack;
>
>  	if (!capable(CAP_MAC_ADMIN))
> @@ -766,7 +790,13 @@ static ssize_t smk_write_ambient(struct
>  	if (smack == NULL)
>  		return -EINVAL;
>
> +	mutex_lock(&smack_ambient_lock);
> +
> +	oldambient = smack_net_ambient;
>  	smack_net_ambient = smack;
> +	smk_unlbl_ambient(oldambient);
> +
> +	mutex_unlock(&smack_ambient_lock);
>
>  	return count;
>  }
> @@ -974,6 +1004,7 @@ static int __init init_smk_fs(void)
>
>  	sema_init(&smack_write_sem, 1);
>  	smk_cipso_doi();
> +	smk_unlbl_ambient(NULL);
>
>  	return err;
>  }
> diff -uprN -X linux-2.6.25-g0215-base//Documentation/dontdiff
> linux-2.6.25-g0215-base/security/smack/smack_lsm.c
> linux-2.6.25-g0215/security/smack/smack_lsm.c ---
> linux-2.6.25-g0215-base/security/smack/smack_lsm.c	2008-02-15
> 14:25:37.000000000 -0800 +++
> linux-2.6.25-g0215/security/smack/smack_lsm.c	2008-02-15 14:31:21.000000000
> -0800 @@ -1251,9 +1251,8 @@ static void smack_to_secattr(char *smack
>
>  	switch (smack_net_nltype) {
>  	case NETLBL_NLTYPE_CIPSOV4:
> -		nlsp->domain = NULL;
> -		nlsp->flags = NETLBL_SECATTR_DOMAIN;
> -		nlsp->flags |= NETLBL_SECATTR_MLS_LVL;
> +		nlsp->domain = kstrdup(smack, GFP_ATOMIC);
> +		nlsp->flags = NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL;
>
>  		rc = smack_to_cipso(smack, &cipso);
>  		if (rc == 0) {
> @@ -1282,15 +1281,14 @@ static int smack_netlabel(struct sock *s
>  {
>  	struct socket_smack *ssp;
>  	struct netlbl_lsm_secattr secattr;
> -	int rc = 0;
> +	int rc;
>
>  	ssp = sk->sk_security;
>  	netlbl_secattr_init(&secattr);
>  	smack_to_secattr(ssp->smk_out, &secattr);
> -	if (secattr.flags != NETLBL_SECATTR_NONE)
> -		rc = netlbl_sock_setattr(sk, &secattr);
> -
> +	rc = netlbl_sock_setattr(sk, &secattr);
>  	netlbl_secattr_destroy(&secattr);
> +
>  	return rc;
>  }
>
> @@ -1313,6 +1311,7 @@ static int smack_inode_setsecurity(struc
>  	struct inode_smack *nsp = inode->i_security;
>  	struct socket_smack *ssp;
>  	struct socket *sock;
> +	int rc = 0;
>
>  	if (value == NULL || size > SMK_LABELLEN)
>  		return -EACCES;
> @@ -1341,7 +1340,10 @@ static int smack_inode_setsecurity(struc
>  		ssp->smk_in = sp;
>  	else if (strcmp(name, XATTR_SMACK_IPOUT) == 0) {
>  		ssp->smk_out = sp;
> -		return smack_netlabel(sock->sk);
> +		rc = smack_netlabel(sock->sk);
> +		if (rc != 0)
> +			printk(KERN_WARNING "Smack: \"%s\" netlbl error %d.\n",
> +			       __func__, -rc);
>  	} else
>  		return -EOPNOTSUPP;
>
> @@ -2214,6 +2216,9 @@ static void smack_sock_graft(struct sock
>  	ssp->smk_packet[0] = '\0';
>
>  	rc = smack_netlabel(sk);
> +	if (rc != 0)
> +		printk(KERN_WARNING "Smack: \"%s\" netlbl error %d.\n",
> +		       __func__, -rc);
>  }
>
>  /**
> @@ -2346,6 +2351,20 @@ static int smack_secid_to_secctx(u32 sec
>  }
>
>  /*
> + * smack_secctx_to_secid - return the secid for a smack label
> + * @secdata: smack label
> + * @seclen: how long result is
> + * @secid: outgoing integer
> + *
> + * Exists for audit and networking code.
> + */
> +static int smack_secctx_to_secid(char *secdata, u32 seclen, u32 *secid)
> +{
> +	*secid = smack_to_secid(secdata);
> +	return 0;
> +}
> +
> +/*
>   * smack_release_secctx - don't do anything.
>   * @key_ref: unused
>   * @context: unused
> @@ -2475,6 +2494,7 @@ static struct security_operations smack_
>  	.key_permission = 		smack_key_permission,
>  #endif /* CONFIG_KEYS */
>  	.secid_to_secctx = 		smack_secid_to_secctx,
> +	.secctx_to_secid = 		smack_secctx_to_secid,
>  	.release_secctx = 		smack_release_secctx,
>  };

-- 
paul moore
linux security @ hp