![Casey Schaufler](/assets/img/avatar_default.png)
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 <casey@schaufler-ca.com>
445 lines
12 KiB
C
445 lines
12 KiB
C
/*
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* Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2.
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*
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* Author:
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* Casey Schaufler <casey@schaufler-ca.com>
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*
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*/
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#ifndef _SECURITY_SMACK_H
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#define _SECURITY_SMACK_H
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#include <linux/capability.h>
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#include <linux/spinlock.h>
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#include <linux/security.h>
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#include <linux/in.h>
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#include <net/netlabel.h>
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#include <linux/list.h>
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#include <linux/rculist.h>
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#include <linux/lsm_audit.h>
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/*
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* Smack labels were limited to 23 characters for a long time.
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*/
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#define SMK_LABELLEN 24
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#define SMK_LONGLABEL 256
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/*
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* This is the repository for labels seen so that it is
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* not necessary to keep allocating tiny chuncks of memory
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* and so that they can be shared.
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*
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* Labels are never modified in place. Anytime a label
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* is imported (e.g. xattrset on a file) the list is checked
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* for it and it is added if it doesn't exist. The address
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* is passed out in either case. Entries are added, but
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* never deleted.
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*
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* Since labels are hanging around anyway it doesn't
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* hurt to maintain a secid for those awkward situations
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* where kernel components that ought to use LSM independent
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* interfaces don't. The secid should go away when all of
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* these components have been repaired.
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*
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* The cipso value associated with the label gets stored here, too.
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*
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* Keep the access rules for this subject label here so that
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* the entire set of rules does not need to be examined every
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* time.
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*/
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struct smack_known {
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struct list_head list;
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struct hlist_node smk_hashed;
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char *smk_known;
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u32 smk_secid;
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struct netlbl_lsm_secattr smk_netlabel; /* on wire labels */
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struct list_head smk_rules; /* access rules */
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struct mutex smk_rules_lock; /* lock for rules */
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};
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/*
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* Maximum number of bytes for the levels in a CIPSO IP option.
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* Why 23? CIPSO is constrained to 30, so a 32 byte buffer is
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* bigger than can be used, and 24 is the next lower multiple
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* of 8, and there are too many issues if there isn't space set
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* aside for the terminating null byte.
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*/
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#define SMK_CIPSOLEN 24
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struct superblock_smack {
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struct smack_known *smk_root;
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struct smack_known *smk_floor;
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struct smack_known *smk_hat;
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struct smack_known *smk_default;
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int smk_initialized;
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};
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struct socket_smack {
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struct smack_known *smk_out; /* outbound label */
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struct smack_known *smk_in; /* inbound label */
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struct smack_known *smk_packet; /* TCP peer label */
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};
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/*
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* Inode smack data
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*/
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struct inode_smack {
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struct smack_known *smk_inode; /* label of the fso */
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struct smack_known *smk_task; /* label of the task */
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struct smack_known *smk_mmap; /* label of the mmap domain */
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struct mutex smk_lock; /* initialization lock */
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int smk_flags; /* smack inode flags */
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};
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struct task_smack {
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struct smack_known *smk_task; /* label for access control */
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struct smack_known *smk_forked; /* label when forked */
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struct list_head smk_rules; /* per task access rules */
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struct mutex smk_rules_lock; /* lock for the rules */
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};
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#define SMK_INODE_INSTANT 0x01 /* inode is instantiated */
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#define SMK_INODE_TRANSMUTE 0x02 /* directory is transmuting */
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#define SMK_INODE_CHANGED 0x04 /* smack was transmuted */
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#define SMK_INODE_IMPURE 0x08 /* involved in an impure transaction */
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/*
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* A label access rule.
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*/
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struct smack_rule {
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struct list_head list;
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struct smack_known *smk_subject;
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struct smack_known *smk_object;
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int smk_access;
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};
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/*
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* An entry in the table identifying hosts.
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*/
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struct smk_netlbladdr {
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struct list_head list;
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struct sockaddr_in smk_host; /* network address */
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struct in_addr smk_mask; /* network mask */
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struct smack_known *smk_label; /* label */
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};
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/*
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* An entry in the table identifying ports.
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*/
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struct smk_port_label {
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struct list_head list;
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struct sock *smk_sock; /* socket initialized on */
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unsigned short smk_port; /* the port number */
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struct smack_known *smk_in; /* inbound label */
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struct smack_known *smk_out; /* outgoing label */
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};
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/*
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* Mount options
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*/
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#define SMK_FSDEFAULT "smackfsdef="
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#define SMK_FSFLOOR "smackfsfloor="
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#define SMK_FSHAT "smackfshat="
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#define SMK_FSROOT "smackfsroot="
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#define SMK_FSTRANS "smackfstransmute="
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#define SMACK_CIPSO_OPTION "-CIPSO"
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/*
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* How communications on this socket are treated.
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* Usually it's determined by the underlying netlabel code
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* but there are certain cases, including single label hosts
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* and potentially single label interfaces for which the
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* treatment can not be known in advance.
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*
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* The possibility of additional labeling schemes being
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* introduced in the future exists as well.
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*/
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#define SMACK_UNLABELED_SOCKET 0
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#define SMACK_CIPSO_SOCKET 1
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/*
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* CIPSO defaults.
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*/
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#define SMACK_CIPSO_DOI_DEFAULT 3 /* Historical */
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#define SMACK_CIPSO_DOI_INVALID -1 /* Not a DOI */
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#define SMACK_CIPSO_DIRECT_DEFAULT 250 /* Arbitrary */
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#define SMACK_CIPSO_MAPPED_DEFAULT 251 /* Also arbitrary */
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#define SMACK_CIPSO_MAXLEVEL 255 /* CIPSO 2.2 standard */
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/*
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* CIPSO 2.2 standard is 239, but Smack wants to use the
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* categories in a structured way that limits the value to
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* the bits in 23 bytes, hence the unusual number.
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*/
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#define SMACK_CIPSO_MAXCATNUM 184 /* 23 * 8 */
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/*
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* Ptrace rules
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*/
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#define SMACK_PTRACE_DEFAULT 0
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#define SMACK_PTRACE_EXACT 1
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#define SMACK_PTRACE_DRACONIAN 2
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#define SMACK_PTRACE_MAX SMACK_PTRACE_DRACONIAN
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/*
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* Flags for untraditional access modes.
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* It shouldn't be necessary to avoid conflicts with definitions
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* in fs.h, but do so anyway.
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*/
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#define MAY_TRANSMUTE 0x00001000 /* Controls directory labeling */
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#define MAY_LOCK 0x00002000 /* Locks should be writes, but ... */
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#define MAY_BRINGUP 0x00004000 /* Report use of this rule */
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#define SMACK_BRINGUP_ALLOW 1 /* Allow bringup mode */
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#define SMACK_UNCONFINED_SUBJECT 2 /* Allow unconfined label */
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#define SMACK_UNCONFINED_OBJECT 3 /* Allow unconfined label */
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/*
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* Just to make the common cases easier to deal with
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*/
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#define MAY_ANYREAD (MAY_READ | MAY_EXEC)
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#define MAY_READWRITE (MAY_READ | MAY_WRITE)
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#define MAY_NOT 0
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/*
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* Number of access types used by Smack (rwxatlb)
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*/
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#define SMK_NUM_ACCESS_TYPE 7
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/* SMACK data */
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struct smack_audit_data {
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const char *function;
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char *subject;
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char *object;
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char *request;
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int result;
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};
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/*
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* Smack audit data; is empty if CONFIG_AUDIT not set
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* to save some stack
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*/
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struct smk_audit_info {
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#ifdef CONFIG_AUDIT
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struct common_audit_data a;
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struct smack_audit_data sad;
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#endif
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};
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/*
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* These functions are in smack_lsm.c
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*/
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struct inode_smack *new_inode_smack(struct smack_known *);
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/*
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* These functions are in smack_access.c
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*/
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int smk_access_entry(char *, char *, struct list_head *);
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int smk_access(struct smack_known *, struct smack_known *,
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int, struct smk_audit_info *);
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int smk_tskacc(struct task_smack *, struct smack_known *,
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u32, struct smk_audit_info *);
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int smk_curacc(struct smack_known *, u32, struct smk_audit_info *);
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struct smack_known *smack_from_secid(const u32);
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char *smk_parse_smack(const char *string, int len);
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int smk_netlbl_mls(int, char *, struct netlbl_lsm_secattr *, int);
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struct smack_known *smk_import_entry(const char *, int);
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void smk_insert_entry(struct smack_known *skp);
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struct smack_known *smk_find_entry(const char *);
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/*
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* Shared data.
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*/
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extern int smack_enabled;
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extern int smack_cipso_direct;
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extern int smack_cipso_mapped;
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extern struct smack_known *smack_net_ambient;
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extern struct smack_known *smack_onlycap;
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extern struct smack_known *smack_syslog_label;
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#ifdef CONFIG_SECURITY_SMACK_BRINGUP
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extern struct smack_known *smack_unconfined;
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#endif
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extern struct smack_known smack_cipso_option;
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extern int smack_ptrace_rule;
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extern struct smack_known smack_known_floor;
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extern struct smack_known smack_known_hat;
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extern struct smack_known smack_known_huh;
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extern struct smack_known smack_known_invalid;
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extern struct smack_known smack_known_star;
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extern struct smack_known smack_known_web;
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extern struct mutex smack_known_lock;
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extern struct list_head smack_known_list;
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extern struct list_head smk_netlbladdr_list;
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extern struct security_operations smack_ops;
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#define SMACK_HASH_SLOTS 16
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extern struct hlist_head smack_known_hash[SMACK_HASH_SLOTS];
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/*
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* Is the directory transmuting?
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*/
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static inline int smk_inode_transmutable(const struct inode *isp)
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{
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struct inode_smack *sip = isp->i_security;
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return (sip->smk_flags & SMK_INODE_TRANSMUTE) != 0;
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}
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/*
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* Present a pointer to the smack label entry in an inode blob.
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*/
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static inline struct smack_known *smk_of_inode(const struct inode *isp)
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{
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struct inode_smack *sip = isp->i_security;
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return sip->smk_inode;
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}
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/*
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* Present a pointer to the smack label entry in an task blob.
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*/
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static inline struct smack_known *smk_of_task(const struct task_smack *tsp)
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{
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return tsp->smk_task;
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}
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static inline struct smack_known *smk_of_task_struct(const struct task_struct *t)
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{
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struct smack_known *skp;
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rcu_read_lock();
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skp = smk_of_task(__task_cred(t)->security);
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rcu_read_unlock();
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return skp;
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}
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/*
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* Present a pointer to the forked smack label entry in an task blob.
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*/
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static inline struct smack_known *smk_of_forked(const struct task_smack *tsp)
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{
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return tsp->smk_forked;
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}
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/*
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* Present a pointer to the smack label in the current task blob.
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*/
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static inline struct smack_known *smk_of_current(void)
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{
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return smk_of_task(current_security());
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}
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/*
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* Is the task privileged and allowed to be privileged
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* by the onlycap rule.
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*/
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static inline int smack_privileged(int cap)
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{
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struct smack_known *skp = smk_of_current();
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if (!capable(cap))
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return 0;
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if (smack_onlycap == NULL || smack_onlycap == skp)
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return 1;
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return 0;
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}
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/*
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* logging functions
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*/
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#define SMACK_AUDIT_DENIED 0x1
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#define SMACK_AUDIT_ACCEPT 0x2
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extern int log_policy;
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void smack_log(char *subject_label, char *object_label,
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int request,
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int result, struct smk_audit_info *auditdata);
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#ifdef CONFIG_AUDIT
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/*
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* some inline functions to set up audit data
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* they do nothing if CONFIG_AUDIT is not set
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*
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*/
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static inline void smk_ad_init(struct smk_audit_info *a, const char *func,
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char type)
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{
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memset(&a->sad, 0, sizeof(a->sad));
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a->a.type = type;
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a->a.smack_audit_data = &a->sad;
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a->a.smack_audit_data->function = func;
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}
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static inline void smk_ad_init_net(struct smk_audit_info *a, const char *func,
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char type, struct lsm_network_audit *net)
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{
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smk_ad_init(a, func, type);
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memset(net, 0, sizeof(*net));
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a->a.u.net = net;
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}
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static inline void smk_ad_setfield_u_tsk(struct smk_audit_info *a,
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struct task_struct *t)
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{
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a->a.u.tsk = t;
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}
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static inline void smk_ad_setfield_u_fs_path_dentry(struct smk_audit_info *a,
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struct dentry *d)
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{
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a->a.u.dentry = d;
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}
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static inline void smk_ad_setfield_u_fs_inode(struct smk_audit_info *a,
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struct inode *i)
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{
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a->a.u.inode = i;
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}
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static inline void smk_ad_setfield_u_fs_path(struct smk_audit_info *a,
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struct path p)
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{
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a->a.u.path = p;
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}
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static inline void smk_ad_setfield_u_net_sk(struct smk_audit_info *a,
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struct sock *sk)
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{
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a->a.u.net->sk = sk;
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}
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#else /* no AUDIT */
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static inline void smk_ad_init(struct smk_audit_info *a, const char *func,
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char type)
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{
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}
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static inline void smk_ad_setfield_u_tsk(struct smk_audit_info *a,
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struct task_struct *t)
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{
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}
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static inline void smk_ad_setfield_u_fs_path_dentry(struct smk_audit_info *a,
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struct dentry *d)
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{
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}
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static inline void smk_ad_setfield_u_fs_path_mnt(struct smk_audit_info *a,
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struct vfsmount *m)
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{
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}
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static inline void smk_ad_setfield_u_fs_inode(struct smk_audit_info *a,
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struct inode *i)
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{
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}
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static inline void smk_ad_setfield_u_fs_path(struct smk_audit_info *a,
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struct path p)
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{
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}
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static inline void smk_ad_setfield_u_net_sk(struct smk_audit_info *a,
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struct sock *sk)
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{
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}
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#endif
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#endif /* _SECURITY_SMACK_H */
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