From 7412301b76bd53ee53b860f611fc3b5b1c2245b5 Mon Sep 17 00:00:00 2001 From: Marcin Lis Date: Thu, 22 Jan 2015 15:40:33 +0100 Subject: [PATCH 1/5] Smack: Assign smack_known_web as default smk_in label for kernel thread's socket This change fixes the bug associated with sockets owned by kernel threads. These sockets, created usually by network devices' drivers tasks, received smk_in label from the task that created them - the "floor" label in the most cases. The result was that they were not able to receive data packets because of missing smack rules. The main reason of the access deny is that the socket smk_in label is placed as the object during smk check, kernel thread's capabilities are omitted. Signed-off-by: Marcin Lis --- security/smack/smack_lsm.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index c934311812f1..a097dc7d4669 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -2452,7 +2452,21 @@ static int smack_inode_setsecurity(struct inode *inode, const char *name, static int smack_socket_post_create(struct socket *sock, int family, int type, int protocol, int kern) { - if (family != PF_INET || sock->sk == NULL) + struct socket_smack *ssp; + + if (sock->sk == NULL) + return 0; + + /* + * Sockets created by kernel threads receive web label. + */ + if (unlikely(current->flags & PF_KTHREAD)) { + ssp = sock->sk->sk_security; + ssp->smk_in = &smack_known_web; + ssp->smk_out = &smack_known_web; + } + + if (family != PF_INET) return 0; /* * Set the outbound netlbl. From 7fc5f36e980a8f4830efdae3858f6e64eee538b7 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Jos=C3=A9=20Bollo?= Date: Tue, 17 Feb 2015 15:41:22 +0100 Subject: [PATCH 2/5] Smack: getting the Smack security context of keys MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit With this commit, the LSM Smack implements the LSM side part of the system call keyctl with the action code KEYCTL_GET_SECURITY. It is now possible to get the context of, for example, the user session key using the command "keyctl security @s". The original patch has been modified for merge. Signed-off-by: José Bollo Signed-off-by: Casey Schaufler --- security/smack/smack_lsm.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index a097dc7d4669..e2d1a7b073c0 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4000,6 +4000,36 @@ static int smack_key_permission(key_ref_t key_ref, rc = smk_bu_note("key access", tkp, keyp->security, request, rc); return rc; } + +/* + * smack_key_getsecurity - Smack label tagging the key + * @key points to the key to be queried + * @_buffer points to a pointer that should be set to point to the + * resulting string (if no label or an error occurs). + * Return the length of the string (including terminating NUL) or -ve if + * an error. + * May also return 0 (and a NULL buffer pointer) if there is no label. + */ +static int smack_key_getsecurity(struct key *key, char **_buffer) +{ + struct smack_known *skp = key->security; + size_t length; + char *copy; + + if (key->security == NULL) { + *_buffer = NULL; + return 0; + } + + copy = kstrdup(skp->smk_known, GFP_KERNEL); + if (copy == NULL) + return -ENOMEM; + length = strlen(copy) + 1; + + *_buffer = copy; + return length; +} + #endif /* CONFIG_KEYS */ /* @@ -4324,6 +4354,7 @@ struct security_operations smack_ops = { .key_alloc = smack_key_alloc, .key_free = smack_key_free, .key_permission = smack_key_permission, + .key_getsecurity = smack_key_getsecurity, #endif /* CONFIG_KEYS */ /* Audit hooks */ From bf4b2fee99799780ea3dbb6d79d1909b3e32be13 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Sat, 21 Mar 2015 18:26:40 -0700 Subject: [PATCH 3/5] Smack: Allow an unconfined label in bringup mode I have vehemently opposed adding a "permissive" mode to Smack for the simple reasons that it would be subject to massive abuse and that developers refuse to turn it off come product release. I still believe that this is true, and still refuse to add a general "permissive mode". So don't ask again. Bumjin Im suggested an approach that addresses most of the concerns, and I have implemented it here. I still believe that we'd be better off without this sort of thing, but it looks like this minimizes the abuse potential. Firstly, you have to configure Smack Bringup Mode. That allows for "release" software to be ammune from abuse. Second, only one label gets to be "permissive" at a time. You can use it for debugging, but that's about it. A label written to smackfs/unconfined is treated specially. If either the subject or object label of an access check matches the "unconfined" label, and the access would not have been allowed otherwise an audit record and a console message are generated. The audit record "request" string is marked with either "(US)" or "(UO)", to indicate that the request was granted because of an unconfined label. The fact that an inode was accessed by an unconfined label is remembered, and subsequent accesses to that "impure" object are noted in the log. The impurity is not stored in the filesystem, so a file mislabled as a side effect of using an unconfined label may still cause concern after a reboot. So, it's there, it's dangerous, but so many application developers seem incapable of living without it I have given in. I've tried to make it as safe as I can, but in the end it's still a chain saw. Signed-off-by: Casey Schaufler --- security/smack/smack.h | 8 +++ security/smack/smack_access.c | 43 ++++++++++++---- security/smack/smack_lsm.c | 52 ++++++++++++++++--- security/smack/smackfs.c | 96 +++++++++++++++++++++++++++++++++++ 4 files changed, 182 insertions(+), 17 deletions(-) diff --git a/security/smack/smack.h b/security/smack/smack.h index 67ccb7b2b89b..49eada6266ec 100644 --- a/security/smack/smack.h +++ b/security/smack/smack.h @@ -105,6 +105,7 @@ struct task_smack { #define SMK_INODE_INSTANT 0x01 /* inode is instantiated */ #define SMK_INODE_TRANSMUTE 0x02 /* directory is transmuting */ #define SMK_INODE_CHANGED 0x04 /* smack was transmuted */ +#define SMK_INODE_IMPURE 0x08 /* involved in an impure transaction */ /* * A label access rule. @@ -193,6 +194,10 @@ struct smk_port_label { #define MAY_LOCK 0x00002000 /* Locks should be writes, but ... */ #define MAY_BRINGUP 0x00004000 /* Report use of this rule */ +#define SMACK_BRINGUP_ALLOW 1 /* Allow bringup mode */ +#define SMACK_UNCONFINED_SUBJECT 2 /* Allow unconfined label */ +#define SMACK_UNCONFINED_OBJECT 3 /* Allow unconfined label */ + /* * Just to make the common cases easier to deal with */ @@ -254,6 +259,9 @@ extern int smack_cipso_mapped; extern struct smack_known *smack_net_ambient; extern struct smack_known *smack_onlycap; extern struct smack_known *smack_syslog_label; +#ifdef CONFIG_SECURITY_SMACK_BRINGUP +extern struct smack_known *smack_unconfined; +#endif extern struct smack_known smack_cipso_option; extern int smack_ptrace_rule; diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c index 1158430f5bb9..0f410fc56e33 100644 --- a/security/smack/smack_access.c +++ b/security/smack/smack_access.c @@ -130,7 +130,8 @@ int smk_access(struct smack_known *subject, struct smack_known *object, /* * Hardcoded comparisons. - * + */ + /* * A star subject can't access any object. */ if (subject == &smack_known_star) { @@ -189,10 +190,20 @@ int smk_access(struct smack_known *subject, struct smack_known *object, * succeed because of "b" rules. */ if (may & MAY_BRINGUP) - rc = MAY_BRINGUP; + rc = SMACK_BRINGUP_ALLOW; #endif out_audit: + +#ifdef CONFIG_SECURITY_SMACK_BRINGUP + if (rc < 0) { + if (object == smack_unconfined) + rc = SMACK_UNCONFINED_OBJECT; + if (subject == smack_unconfined) + rc = SMACK_UNCONFINED_SUBJECT; + } +#endif + #ifdef CONFIG_AUDIT if (a) smack_log(subject->smk_known, object->smk_known, @@ -338,19 +349,16 @@ static void smack_log_callback(struct audit_buffer *ab, void *a) void smack_log(char *subject_label, char *object_label, int request, int result, struct smk_audit_info *ad) { +#ifdef CONFIG_SECURITY_SMACK_BRINGUP + char request_buffer[SMK_NUM_ACCESS_TYPE + 5]; +#else char request_buffer[SMK_NUM_ACCESS_TYPE + 1]; +#endif struct smack_audit_data *sad; struct common_audit_data *a = &ad->a; -#ifdef CONFIG_SECURITY_SMACK_BRINGUP - /* - * The result may be positive in bringup mode. - */ - if (result > 0) - result = 0; -#endif /* check if we have to log the current event */ - if (result != 0 && (log_policy & SMACK_AUDIT_DENIED) == 0) + if (result < 0 && (log_policy & SMACK_AUDIT_DENIED) == 0) return; if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0) return; @@ -364,6 +372,21 @@ void smack_log(char *subject_label, char *object_label, int request, smack_str_from_perm(request_buffer, request); sad->subject = subject_label; sad->object = object_label; +#ifdef CONFIG_SECURITY_SMACK_BRINGUP + /* + * The result may be positive in bringup mode. + * A positive result is an allow, but not for normal reasons. + * Mark it as successful, but don't filter it out even if + * the logging policy says to do so. + */ + if (result == SMACK_UNCONFINED_SUBJECT) + strcat(request_buffer, "(US)"); + else if (result == SMACK_UNCONFINED_OBJECT) + strcat(request_buffer, "(UO)"); + + if (result > 0) + result = 0; +#endif sad->request = request_buffer; sad->result = result; diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index e2d1a7b073c0..6f3c7d866d04 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -57,6 +57,13 @@ static struct kmem_cache *smack_inode_cache; int smack_enabled; #ifdef CONFIG_SECURITY_SMACK_BRINGUP +static char *smk_bu_mess[] = { + "Bringup Error", /* Unused */ + "Bringup", /* SMACK_BRINGUP_ALLOW */ + "Unconfined Subject", /* SMACK_UNCONFINED_SUBJECT */ + "Unconfined Object", /* SMACK_UNCONFINED_OBJECT */ +}; + static void smk_bu_mode(int mode, char *s) { int i = 0; @@ -87,9 +94,11 @@ static int smk_bu_note(char *note, struct smack_known *sskp, if (rc <= 0) return rc; + if (rc > SMACK_UNCONFINED_OBJECT) + rc = 0; smk_bu_mode(mode, acc); - pr_info("Smack Bringup: (%s %s %s) %s\n", + pr_info("Smack %s: (%s %s %s) %s\n", smk_bu_mess[rc], sskp->smk_known, oskp->smk_known, acc, note); return 0; } @@ -106,9 +115,11 @@ static int smk_bu_current(char *note, struct smack_known *oskp, if (rc <= 0) return rc; + if (rc > SMACK_UNCONFINED_OBJECT) + rc = 0; smk_bu_mode(mode, acc); - pr_info("Smack Bringup: (%s %s %s) %s %s\n", + pr_info("Smack %s: (%s %s %s) %s %s\n", smk_bu_mess[rc], tsp->smk_task->smk_known, oskp->smk_known, acc, current->comm, note); return 0; @@ -126,9 +137,11 @@ static int smk_bu_task(struct task_struct *otp, int mode, int rc) if (rc <= 0) return rc; + if (rc > SMACK_UNCONFINED_OBJECT) + rc = 0; smk_bu_mode(mode, acc); - pr_info("Smack Bringup: (%s %s %s) %s to %s\n", + pr_info("Smack %s: (%s %s %s) %s to %s\n", smk_bu_mess[rc], tsp->smk_task->smk_known, smk_task->smk_known, acc, current->comm, otp->comm); return 0; @@ -141,14 +154,25 @@ static int smk_bu_task(struct task_struct *otp, int mode, int rc) static int smk_bu_inode(struct inode *inode, int mode, int rc) { struct task_smack *tsp = current_security(); + struct inode_smack *isp = inode->i_security; char acc[SMK_NUM_ACCESS_TYPE + 1]; + if (isp->smk_flags & SMK_INODE_IMPURE) + pr_info("Smack Unconfined Corruption: inode=(%s %ld) %s\n", + inode->i_sb->s_id, inode->i_ino, current->comm); + if (rc <= 0) return rc; + if (rc > SMACK_UNCONFINED_OBJECT) + rc = 0; + if (rc == SMACK_UNCONFINED_SUBJECT && + (mode & (MAY_WRITE | MAY_APPEND))) + isp->smk_flags |= SMK_INODE_IMPURE; smk_bu_mode(mode, acc); - pr_info("Smack Bringup: (%s %s %s) inode=(%s %ld) %s\n", - tsp->smk_task->smk_known, smk_of_inode(inode)->smk_known, acc, + + pr_info("Smack %s: (%s %s %s) inode=(%s %ld) %s\n", smk_bu_mess[rc], + tsp->smk_task->smk_known, isp->smk_inode->smk_known, acc, inode->i_sb->s_id, inode->i_ino, current->comm); return 0; } @@ -162,13 +186,20 @@ static int smk_bu_file(struct file *file, int mode, int rc) struct task_smack *tsp = current_security(); struct smack_known *sskp = tsp->smk_task; struct inode *inode = file_inode(file); + struct inode_smack *isp = inode->i_security; char acc[SMK_NUM_ACCESS_TYPE + 1]; + if (isp->smk_flags & SMK_INODE_IMPURE) + pr_info("Smack Unconfined Corruption: inode=(%s %ld) %s\n", + inode->i_sb->s_id, inode->i_ino, current->comm); + if (rc <= 0) return rc; + if (rc > SMACK_UNCONFINED_OBJECT) + rc = 0; smk_bu_mode(mode, acc); - pr_info("Smack Bringup: (%s %s %s) file=(%s %ld %pD) %s\n", + pr_info("Smack %s: (%s %s %s) file=(%s %ld %pD) %s\n", smk_bu_mess[rc], sskp->smk_known, smk_of_inode(inode)->smk_known, acc, inode->i_sb->s_id, inode->i_ino, file, current->comm); @@ -185,13 +216,20 @@ static int smk_bu_credfile(const struct cred *cred, struct file *file, struct task_smack *tsp = cred->security; struct smack_known *sskp = tsp->smk_task; struct inode *inode = file->f_inode; + struct inode_smack *isp = inode->i_security; char acc[SMK_NUM_ACCESS_TYPE + 1]; + if (isp->smk_flags & SMK_INODE_IMPURE) + pr_info("Smack Unconfined Corruption: inode=(%s %ld) %s\n", + inode->i_sb->s_id, inode->i_ino, current->comm); + if (rc <= 0) return rc; + if (rc > SMACK_UNCONFINED_OBJECT) + rc = 0; smk_bu_mode(mode, acc); - pr_info("Smack Bringup: (%s %s %s) file=(%s %ld %pD) %s\n", + pr_info("Smack %s: (%s %s %s) file=(%s %ld %pD) %s\n", smk_bu_mess[rc], sskp->smk_known, smk_of_inode(inode)->smk_known, acc, inode->i_sb->s_id, inode->i_ino, file, current->comm); diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c index bce4e8f1b267..deb3d3bfbbf3 100644 --- a/security/smack/smackfs.c +++ b/security/smack/smackfs.c @@ -54,6 +54,9 @@ enum smk_inos { SMK_CHANGE_RULE = 19, /* change or add rules (long labels) */ SMK_SYSLOG = 20, /* change syslog label) */ SMK_PTRACE = 21, /* set ptrace rule */ +#ifdef CONFIG_SECURITY_SMACK_BRINGUP + SMK_UNCONFINED = 22, /* define an unconfined label */ +#endif }; /* @@ -95,6 +98,16 @@ int smack_cipso_mapped = SMACK_CIPSO_MAPPED_DEFAULT; */ struct smack_known *smack_onlycap; +#ifdef CONFIG_SECURITY_SMACK_BRINGUP +/* + * Allow one label to be unconfined. This is for + * debugging and application bring-up purposes only. + * It is bad and wrong, but everyone seems to expect + * to have it. + */ +struct smack_known *smack_unconfined; +#endif + /* * If this value is set restrict syslog use to the label specified. * It can be reset via smackfs/syslog @@ -1717,6 +1730,85 @@ static const struct file_operations smk_onlycap_ops = { .llseek = default_llseek, }; +#ifdef CONFIG_SECURITY_SMACK_BRINGUP +/** + * smk_read_unconfined - read() for smackfs/unconfined + * @filp: file pointer, not actually used + * @buf: where to put the result + * @cn: maximum to send along + * @ppos: where to start + * + * Returns number of bytes read or error code, as appropriate + */ +static ssize_t smk_read_unconfined(struct file *filp, char __user *buf, + size_t cn, loff_t *ppos) +{ + char *smack = ""; + ssize_t rc = -EINVAL; + int asize; + + if (*ppos != 0) + return 0; + + if (smack_unconfined != NULL) + smack = smack_unconfined->smk_known; + + asize = strlen(smack) + 1; + + if (cn >= asize) + rc = simple_read_from_buffer(buf, cn, ppos, smack, asize); + + return rc; +} + +/** + * smk_write_unconfined - write() for smackfs/unconfined + * @file: file pointer, not actually used + * @buf: where to get the data from + * @count: bytes sent + * @ppos: where to start + * + * Returns number of bytes written or error code, as appropriate + */ +static ssize_t smk_write_unconfined(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + char *data; + int rc = count; + + if (!smack_privileged(CAP_MAC_ADMIN)) + return -EPERM; + + data = kzalloc(count + 1, GFP_KERNEL); + if (data == NULL) + return -ENOMEM; + + /* + * Should the null string be passed in unset the unconfined value. + * This seems like something to be careful with as usually + * smk_import only expects to return NULL for errors. It + * is usually the case that a nullstring or "\n" would be + * bad to pass to smk_import but in fact this is useful here. + * + * smk_import will also reject a label beginning with '-', + * so "-confine" will also work. + */ + if (copy_from_user(data, buf, count) != 0) + rc = -EFAULT; + else + smack_unconfined = smk_import_entry(data, count); + + kfree(data); + return rc; +} + +static const struct file_operations smk_unconfined_ops = { + .read = smk_read_unconfined, + .write = smk_write_unconfined, + .llseek = default_llseek, +}; +#endif /* CONFIG_SECURITY_SMACK_BRINGUP */ + /** * smk_read_logging - read() for /smack/logging * @filp: file pointer, not actually used @@ -2384,6 +2476,10 @@ static int smk_fill_super(struct super_block *sb, void *data, int silent) "syslog", &smk_syslog_ops, S_IRUGO|S_IWUSR}, [SMK_PTRACE] = { "ptrace", &smk_ptrace_ops, S_IRUGO|S_IWUSR}, +#ifdef CONFIG_SECURITY_SMACK_BRINGUP + [SMK_UNCONFINED] = { + "unconfined", &smk_unconfined_ops, S_IRUGO|S_IWUSR}, +#endif /* last one */ {""} }; From f43b65bad6d54df7562c522a13d30efddae91234 Mon Sep 17 00:00:00 2001 From: Paul Gortmaker Date: Mon, 23 Mar 2015 14:03:17 -0400 Subject: [PATCH 4/5] smack: Fix gcc warning from unused smack_syslog_lock mutex in smackfs.c MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In commit 00f84f3f2e9d088f06722f4351d67f5f577abe22 ("Smack: Make the syslog control configurable") this mutex was added, but the rest of the final commit never actually made use of it, resulting in: In file included from include/linux/mutex.h:29:0, from include/linux/notifier.h:13, from include/linux/memory_hotplug.h:6, from include/linux/mmzone.h:821, from include/linux/gfp.h:5, from include/linux/slab.h:14, from include/linux/security.h:27, from security/smack/smackfs.c:21: security/smack/smackfs.c:63:21: warning: ‘smack_syslog_lock’ defined but not used [-Wunused-variable] static DEFINE_MUTEX(smack_syslog_lock); ^ A git grep shows no other instances/references to smack_syslog_lock. Delete it, assuming that the mutex addition was just a leftover from an earlier work in progress version of the change. Signed-off-by: Paul Gortmaker --- security/smack/smackfs.c | 1 - 1 file changed, 1 deletion(-) diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c index deb3d3bfbbf3..06f719ed63c9 100644 --- a/security/smack/smackfs.c +++ b/security/smack/smackfs.c @@ -64,7 +64,6 @@ enum smk_inos { */ static DEFINE_MUTEX(smack_cipso_lock); static DEFINE_MUTEX(smack_ambient_lock); -static DEFINE_MUTEX(smack_syslog_lock); static DEFINE_MUTEX(smk_netlbladdr_lock); /* From 18779b75e90e75bf7f1aee8e71307b69fa5f7631 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Tue, 31 Mar 2015 09:49:40 -0700 Subject: [PATCH 5/5] Smack: Updates for Smack documentation Document the Smack bringup features. Update the proper location for mounting smackfs from /smack to /sys/fs/smackfs. Fix some spelling errors. Suggest the use of the load2 interface instead of the load interface. Signed-off-by: Casey Schaufler --- Documentation/security/Smack.txt | 129 +++++++++++++++++++------------ 1 file changed, 79 insertions(+), 50 deletions(-) diff --git a/Documentation/security/Smack.txt b/Documentation/security/Smack.txt index b6ef7e9dba30..abc82f85215b 100644 --- a/Documentation/security/Smack.txt +++ b/Documentation/security/Smack.txt @@ -33,11 +33,18 @@ The current git repository for Smack user space is: git://github.com/smack-team/smack.git This should make and install on most modern distributions. -There are three commands included in smackutil: +There are five commands included in smackutil: -smackload - properly formats data for writing to /smack/load -smackcipso - properly formats data for writing to /smack/cipso chsmack - display or set Smack extended attribute values +smackctl - load the Smack access rules +smackaccess - report if a process with one label has access + to an object with another + +These two commands are obsolete with the introduction of +the smackfs/load2 and smackfs/cipso2 interfaces. + +smackload - properly formats data for writing to smackfs/load +smackcipso - properly formats data for writing to smackfs/cipso In keeping with the intent of Smack, configuration data is minimal and not strictly required. The most important @@ -47,9 +54,9 @@ of this, but it can be manually as well. Add this line to /etc/fstab: - smackfs /smack smackfs smackfsdef=* 0 0 + smackfs /sys/fs/smackfs smackfs defaults 0 0 -and create the /smack directory for mounting. +The /sys/fs/smackfs directory is created by the kernel. Smack uses extended attributes (xattrs) to store labels on filesystem objects. The attributes are stored in the extended attribute security @@ -92,13 +99,13 @@ There are multiple ways to set a Smack label on a file: # attr -S -s SMACK64 -V "value" path # chsmack -a value path -A process can see the smack label it is running with by +A process can see the Smack label it is running with by reading /proc/self/attr/current. A process with CAP_MAC_ADMIN -can set the process smack by writing there. +can set the process Smack by writing there. Most Smack configuration is accomplished by writing to files -in the smackfs filesystem. This pseudo-filesystem is usually -mounted on /smack. +in the smackfs filesystem. This pseudo-filesystem is mounted +on /sys/fs/smackfs. access This interface reports whether a subject with the specified @@ -206,23 +213,30 @@ onlycap file or cleared by writing "-" to the file. ptrace This is used to define the current ptrace policy - 0 - default: this is the policy that relies on smack access rules. + 0 - default: this is the policy that relies on Smack access rules. For the PTRACE_READ a subject needs to have a read access on object. For the PTRACE_ATTACH a read-write access is required. 1 - exact: this is the policy that limits PTRACE_ATTACH. Attach is only allowed when subject's and object's labels are equal. - PTRACE_READ is not affected. Can be overriden with CAP_SYS_PTRACE. + PTRACE_READ is not affected. Can be overridden with CAP_SYS_PTRACE. 2 - draconian: this policy behaves like the 'exact' above with an - exception that it can't be overriden with CAP_SYS_PTRACE. + exception that it can't be overridden with CAP_SYS_PTRACE. revoke-subject Writing a Smack label here sets the access to '-' for all access rules with that subject label. +unconfined + If the kernel is configured with CONFIG_SECURITY_SMACK_BRINGUP + a process with CAP_MAC_ADMIN can write a label into this interface. + Thereafter, accesses that involve that label will be logged and + the access permitted if it wouldn't be otherwise. Note that this + is dangerous and can ruin the proper labeling of your system. + It should never be used in production. You can add access rules in /etc/smack/accesses. They take the form: subjectlabel objectlabel access -access is a combination of the letters rwxa which specify the +access is a combination of the letters rwxatb which specify the kind of access permitted a subject with subjectlabel on an object with objectlabel. If there is no rule no access is allowed. @@ -318,8 +332,9 @@ each of the subject and the object. Labels -Smack labels are ASCII character strings, one to twenty-three characters in -length. Single character labels using special characters, that being anything +Smack labels are ASCII character strings. They can be up to 255 characters +long, but keeping them to twenty-three characters is recommended. +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 @@ -335,10 +350,9 @@ There are some predefined labels: ? Pronounced "huh", a single question mark character. @ Pronounced "web", 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 -are assigned labels according to the specification found in the -/etc/smack/user configuration file. +Every task on a Smack system is assigned a label. The Smack label +of a process will usually be assigned by the system initialization +mechanism. Access Rules @@ -393,6 +407,7 @@ describe access modes: w: indicates that write access should be granted. x: indicates that execute access should be granted. t: indicates that the rule requests transmutation. + b: indicates that the rule should be reported for bring-up. Uppercase values for the specification letters are allowed as well. Access mode specifications can be in any order. Examples of acceptable rules @@ -402,6 +417,7 @@ are: Secret Unclass R Manager Game x User HR w + Snap Crackle rwxatb New Old rRrRr Closed Off - @@ -413,7 +429,7 @@ Examples of unacceptable rules are: Spaces are not allowed in labels. Since a subject always has access to files with the same label specifying a rule for that case is pointless. Only -valid letters (rwxatRWXAT) and the dash ('-') character are allowed in +valid letters (rwxatbRWXATB) and the dash ('-') character are allowed in access specifications. The dash is a placeholder, so "a-r" is the same as "ar". A lone dash is used to specify that no access should be allowed. @@ -462,16 +478,11 @@ receiver. The receiver is not required to have read access to the sender. Setting Access Rules The configuration file /etc/smack/accesses contains the rules to be set at -system startup. The contents are written to the special file /smack/load. -Rules can be written to /smack/load at any time and take effect immediately. -For any pair of subject and object labels there can be only one rule, with the -most recently specified overriding any earlier specification. - -The program smackload is provided to ensure data is formatted -properly when written to /smack/load. This program reads lines -of the form - - subjectlabel objectlabel mode. +system startup. The contents are written to the special file +/sys/fs/smackfs/load2. Rules can be added at any time and take effect +immediately. For any pair of subject and object labels there can be only +one rule, with the most recently specified overriding any earlier +specification. Task Attribute @@ -488,7 +499,10 @@ only be changed by a process with privilege. Privilege -A process with CAP_MAC_OVERRIDE is privileged. +A process with CAP_MAC_OVERRIDE or CAP_MAC_ADMIN is privileged. +CAP_MAC_OVERRIDE allows the process access to objects it would +be denied otherwise. CAP_MAC_ADMIN allows a process to change +Smack data, including rules and attributes. Smack Networking @@ -510,14 +524,14 @@ intervention. Unlabeled packets that come into the system will be given the ambient label. Smack requires configuration in the case where packets from a system that is -not smack that speaks CIPSO may be encountered. Usually this will be a Trusted +not Smack that speaks CIPSO may be encountered. Usually this will be a Trusted Solaris system, but there are other, less widely deployed systems out there. CIPSO provides 3 important values, a Domain Of Interpretation (DOI), a level, and a category set with each packet. The DOI is intended to identify a group of systems that use compatible labeling schemes, and the DOI specified on the -smack system must match that of the remote system or packets will be -discarded. The DOI is 3 by default. The value can be read from /smack/doi and -can be changed by writing to /smack/doi. +Smack system must match that of the remote system or packets will be +discarded. The DOI is 3 by default. The value can be read from +/sys/fs/smackfs/doi and can be changed by writing to /sys/fs/smackfs/doi. The label and category set are mapped to a Smack label as defined in /etc/smack/cipso. @@ -539,15 +553,13 @@ The ":" and "," characters are permitted in a Smack label but have no special meaning. The mapping of Smack labels to CIPSO values is defined by writing to -/smack/cipso. Again, the format of data written to this special file -is highly restrictive, so the program smackcipso is provided to -ensure the writes are done properly. This program takes mappings -on the standard input and sends them to /smack/cipso properly. +/sys/fs/smackfs/cipso2. In addition to explicit mappings Smack supports direct CIPSO mappings. One CIPSO level is used to indicate that the category set passed in the packet is in fact an encoding of the Smack label. The level used is 250 by default. The -value can be read from /smack/direct and changed by writing to /smack/direct. +value can be read from /sys/fs/smackfs/direct and changed by writing to +/sys/fs/smackfs/direct. Socket Attributes @@ -565,8 +577,8 @@ sockets. 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 : +unlabeled world. To do this there's a special file /sys/fs/smackfs/netlabel +where you can add some exceptions in the form of : @IP1 LABEL1 or @IP2/MASK LABEL2 @@ -574,22 +586,22 @@ 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. +Entries in the /sys/fs/smackfs/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 +echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel +echo 0.0.0.0/0 @ > /sys/fs/smackfs/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 +echo 127.0.0.1 -CIPSO > /sys/fs/smackfs/netlabel +echo 192.168.0.0/16 -CIPSO > /sys/fs/smackfs/netlabel +echo 0.0.0.0/0 @ > /sys/fs/smackfs/netlabel Writing Applications for Smack @@ -676,7 +688,7 @@ Smack auditing If you want Smack auditing of security events, you need to set CONFIG_AUDIT in your kernel configuration. By default, all denied events will be audited. You can change this behavior by -writing a single character to the /smack/logging file : +writing a single character to the /sys/fs/smackfs/logging file : 0 : no logging 1 : log denied (default) 2 : log accepted @@ -686,3 +698,20 @@ Events are logged as 'key=value' pairs, for each event you at least will get the subject, the object, the rights requested, the action, the kernel function that triggered the event, plus other pairs depending on the type of event audited. + +Bringup Mode + +Bringup mode provides logging features that can make application +configuration and system bringup easier. Configure the kernel with +CONFIG_SECURITY_SMACK_BRINGUP to enable these features. When bringup +mode is enabled accesses that succeed due to rules marked with the "b" +access mode will logged. When a new label is introduced for processes +rules can be added aggressively, marked with the "b". The logging allows +tracking of which rules actual get used for that label. + +Another feature of bringup mode is the "unconfined" option. Writing +a label to /sys/fs/smackfs/unconfined makes subjects with that label +able to access any object, and objects with that label accessible to +all subjects. Any access that is granted because a label is unconfined +is logged. This feature is dangerous, as files and directories may +be created in places they couldn't if the policy were being enforced.