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Date: Fri, 27 Mar 2009 20:05:38 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Paul Moore <paul.moore@...com>
CC: linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
netdev@...r.kernel.org, etienne.basset@...ericable.fr,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH 6/6] smack: Add a new '-CIPSO' option to the network address
label configuration
Paul Moore wrote:
> From: Etienne Basset <etienne.basset@...ericable.fr>
>
> This patch adds a new special option '-CIPSO' to the Smack subsystem. When used
> in the netlabel list, it means "use CIPSO networking". A use case is when your
> local network speaks CIPSO and you want also to connect to the unlabeled
> Internet. This patch also add some documentation describing that. The patch
> also corrects an oops when setting a '' SMACK64 xattr to a file.
>
> Signed-off-by: Etienne Basset <etienne.basset@...ericable.fr>
> Signed-off-by: Paul Moore <paul.moore@...com>
>
Acked-by: Casey Schaufler <casey@...aufler-ca.com>
> ---
>
> Documentation/Smack.txt | 42 ++++++++++++++++++++++++++++++++++++-----
> security/smack/smack.h | 3 +++
> security/smack/smack_access.c | 3 +++
> security/smack/smack_lsm.c | 11 +++++++++--
> security/smack/smackfs.c | 38 +++++++++++++++++++++++++++++--------
> 5 files changed, 82 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/Smack.txt b/Documentation/Smack.txt
> index 989c2fc..629c92e 100644
> --- a/Documentation/Smack.txt
> +++ b/Documentation/Smack.txt
> @@ -184,14 +184,16 @@ length. Single character labels using special characters, that being anything
> other than a letter or digit, are reserved for use by the Smack development
> team. Smack labels are unstructured, case sensitive, and the only operation
> ever performed on them is comparison for equality. Smack labels cannot
> -contain unprintable characters or the "/" (slash) character.
> +contain unprintable characters or the "/" (slash) character. Smack labels
> +cannot begin with a '-', which is reserved for special options.
>
> There are some predefined labels:
>
> - _ Pronounced "floor", a single underscore character.
> - ^ Pronounced "hat", a single circumflex character.
> - * Pronounced "star", a single asterisk character.
> - ? Pronounced "huh", a single question mark character.
> + _ Pronounced "floor", a single underscore character.
> + ^ Pronounced "hat", a single circumflex character.
> + * Pronounced "star", a single asterisk character.
> + ? Pronounced "huh", a single question mark character.
> + @ Pronounced "Internet", a single at sign character.
>
> Every task on a Smack system is assigned a label. System tasks, such as
> init(8) and systems daemons, are run with the floor ("_") label. User tasks
> @@ -412,6 +414,36 @@ sockets.
> A privileged program may set this to match the label of another
> task with which it hopes to communicate.
>
> +Smack Netlabel Exceptions
> +
> +You will often find that your labeled application has to talk to the outside,
> +unlabeled world. To do this there's a special file /smack/netlabel where you can
> +add some exceptions in the form of :
> +@IP1 LABEL1 or
> +@.../MASK LABEL2
> +
> +It means that your application will have unlabeled access to @IP1 if it has
> +write access on LABEL1, and access to the subnet @IP2/MASK if it has write
> +access on LABEL2.
> +
> +Entries in the /smack/netlabel file are matched by longest mask first, like in
> +classless IPv4 routing.
> +
> +A special label '@' and an option '-CIPSO' can be used there :
> +@ means Internet, any application with any label has access to it
> +-CIPSO means standard CIPSO networking
> +
> +If you don't know what CIPSO is and don't plan to use it, you can just do :
> +echo 127.0.0.1 -CIPSO > /smack/netlabel
> +echo 0.0.0.0/0 @ > /smack/netlabel
> +
> +If you use CIPSO on your 192.168.0.0/16 local network and need also unlabeled
> +Internet access, you can have :
> +echo 127.0.0.1 -CIPSO > /smack/netlabel
> +echo 192.168.0.0/16 -CIPSO > /smack/netlabel
> +echo 0.0.0.0/0 @ > /smack/netlabel
> +
> +
> Writing Applications for Smack
>
> There are three sorts of applications that will run on a Smack system. How an
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index 5e5a3bc..42ef313 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -132,6 +132,8 @@ struct smack_known {
> #define XATTR_NAME_SMACKIPIN XATTR_SECURITY_PREFIX XATTR_SMACK_IPIN
> #define XATTR_NAME_SMACKIPOUT XATTR_SECURITY_PREFIX XATTR_SMACK_IPOUT
>
> +#define SMACK_CIPSO_OPTION "-CIPSO"
> +
> /*
> * How communications on this socket are treated.
> * Usually it's determined by the underlying netlabel code
> @@ -199,6 +201,7 @@ u32 smack_to_secid(const char *);
> extern int smack_cipso_direct;
> extern char *smack_net_ambient;
> extern char *smack_onlycap;
> +extern const char *smack_cipso_option;
>
> extern struct smack_known smack_known_floor;
> extern struct smack_known smack_known_hat;
> diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
> index 5856419..ac0a270 100644
> --- a/security/smack/smack_access.c
> +++ b/security/smack/smack_access.c
> @@ -261,6 +261,9 @@ char *smk_import(const char *string, int len)
> {
> struct smack_known *skp;
>
> + /* labels cannot begin with a '-' */
> + if (string[0] == '-')
> + return NULL;
> skp = smk_import_entry(string, len);
> if (skp == NULL)
> return NULL;
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 8ed502c..9215149 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -609,6 +609,9 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
> strcmp(name, XATTR_NAME_SMACKIPOUT) == 0) {
> if (!capable(CAP_MAC_ADMIN))
> rc = -EPERM;
> + /* a label cannot be void and cannot begin with '-' */
> + if (size == 0 || (size > 0 && ((char *)value)[0] == '-'))
> + rc = -EINVAL;
> } else
> rc = cap_inode_setxattr(dentry, name, value, size, flags);
>
> @@ -1323,8 +1326,12 @@ static char *smack_host_label(struct sockaddr_in *sip)
> * so we have found the most specific match
> */
> if ((&snp->smk_host.sin_addr)->s_addr ==
> - (siap->s_addr & (&snp->smk_mask)->s_addr))
> + (siap->s_addr & (&snp->smk_mask)->s_addr)) {
> + /* we have found the special CIPSO option */
> + if (snp->smk_label == smack_cipso_option)
> + return NULL;
> return snp->smk_label;
> + }
>
> return NULL;
> }
> @@ -1486,7 +1493,7 @@ static int smack_inode_setsecurity(struct inode *inode, const char *name,
> struct socket *sock;
> int rc = 0;
>
> - if (value == NULL || size > SMK_LABELLEN)
> + if (value == NULL || size > SMK_LABELLEN || size == 0)
> return -EACCES;
>
> sp = smk_import(value, size);
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index 856c8a2..e03a7e1 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -86,6 +86,9 @@ LIST_HEAD(smack_rule_list);
>
> static int smk_cipso_doi_value = SMACK_CIPSO_DOI_DEFAULT;
>
> +const char *smack_cipso_option = SMACK_CIPSO_OPTION;
> +
> +
> #define SEQ_READ_FINISHED 1
>
> /*
> @@ -565,6 +568,11 @@ static ssize_t smk_write_cipso(struct file *file, const char __user *buf,
> goto unlockedout;
> }
>
> + /* labels cannot begin with a '-' */
> + if (data[0] == '-') {
> + rc = -EINVAL;
> + goto unlockedout;
> + }
> data[count] = '\0';
> rule = data;
> /*
> @@ -808,9 +816,18 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
> if (m > BEBITS)
> return -EINVAL;
>
> - sp = smk_import(smack, 0);
> - if (sp == NULL)
> - return -EINVAL;
> + /* if smack begins with '-', its an option, don't import it */
> + if (smack[0] != '-') {
> + sp = smk_import(smack, 0);
> + if (sp == NULL)
> + return -EINVAL;
> + } else {
> + /* check known options */
> + if (strcmp(smack, smack_cipso_option) == 0)
> + sp = (char *)smack_cipso_option;
> + else
> + return -EINVAL;
> + }
>
> for (temp_mask = 0; m > 0; m--) {
> temp_mask |= mask_bits;
> @@ -849,18 +866,23 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
> smk_netlbladdr_insert(skp);
> }
> } else {
> - rc = netlbl_cfg_unlbl_static_del(&init_net, NULL,
> - &skp->smk_host.sin_addr, &skp->smk_mask,
> - PF_INET, &audit_info);
> + /* we delete the unlabeled entry, only if the previous label
> + * wasnt the special CIPSO option */
> + if (skp->smk_label != smack_cipso_option)
> + rc = netlbl_cfg_unlbl_static_del(&init_net, NULL,
> + &skp->smk_host.sin_addr, &skp->smk_mask,
> + PF_INET, &audit_info);
> + else
> + rc = 0;
> skp->smk_label = sp;
> }
>
> /*
> * Now tell netlabel about the single label nature of
> * this host so that incoming packets get labeled.
> + * but only if we didn't get the special CIPSO option
> */
> -
> - if (rc == 0)
> + if (rc == 0 && sp != smack_cipso_option)
> rc = netlbl_cfg_unlbl_static_add(&init_net, NULL,
> &skp->smk_host.sin_addr, &skp->smk_mask, PF_INET,
> smack_to_secid(skp->smk_label), &audit_info);
>
>
>
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