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Date: Tue, 11 Mar 2014 17:07:06 +0100
From: Lukasz Pawelczyk <l.pawelczyk@...tner.samsung.com>
To: Casey Schaufler <casey@...aufler-ca.com>,
James Morris <james.l.morris@...cle.com>,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: r.krypa@...sung.com, t.swierczek@...sung.com,
Lukasz Pawelczyk <l.pawelczyk@...tner.samsung.com>
Subject: [PATCH 3/3] Smack: adds smackfs/ptrace interface
This allows to limit ptrace beyond the regular smack access rules.
It adds a smackfs/ptrace interface that allows smack to be configured
to require equal smack labels for PTRACE_MODE_ATTACH access.
See the changes in Documentation/security/Smack.txt below for details.
Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@...tner.samsung.com>
Signed-off-by: Rafal Krypa <r.krypa@...sung.com>
---
Documentation/security/Smack.txt | 10 ++++++
security/smack/smack.h | 9 +++++
security/smack/smack_access.c | 5 ++-
security/smack/smack_lsm.c | 22 +++++++++++-
security/smack/smackfs.c | 74 ++++++++++++++++++++++++++++++++++++++++
5 files changed, 118 insertions(+), 2 deletions(-)
diff --git a/Documentation/security/Smack.txt b/Documentation/security/Smack.txt
index 7a2d30c..5597917 100644
--- a/Documentation/security/Smack.txt
+++ b/Documentation/security/Smack.txt
@@ -204,6 +204,16 @@ onlycap
these capabilities are effective at for processes with any
label. The value is set by writing the desired label to the
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.
+ 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.
+ 2 - draconian: this policy behaves like the 'exact' above with an
+ exception that it can't be overriden with CAP_SYS_PTRACE.
revoke-subject
Writing a Smack label here sets the access to '-' for all access
rules with that subject label.
diff --git a/security/smack/smack.h b/security/smack/smack.h
index b9dfc4e..fade085 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -177,6 +177,14 @@ struct smk_port_label {
#define SMACK_CIPSO_MAXCATNUM 184 /* 23 * 8 */
/*
+ * Ptrace rules
+ */
+#define SMACK_PTRACE_DEFAULT 0
+#define SMACK_PTRACE_EXACT 1
+#define SMACK_PTRACE_DRACONIAN 2
+#define SMACK_PTRACE_MAX SMACK_PTRACE_DRACONIAN
+
+/*
* Flags for untraditional access modes.
* It shouldn't be necessary to avoid conflicts with definitions
* in fs.h, but do so anyway.
@@ -245,6 +253,7 @@ extern struct smack_known *smack_net_ambient;
extern struct smack_known *smack_onlycap;
extern struct smack_known *smack_syslog_label;
extern const char *smack_cipso_option;
+extern int smack_ptrace_rule;
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 f161deb..c062e94 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -304,7 +304,10 @@ static void smack_log_callback(struct audit_buffer *ab, void *a)
audit_log_untrustedstring(ab, sad->subject);
audit_log_format(ab, " object=");
audit_log_untrustedstring(ab, sad->object);
- audit_log_format(ab, " requested=%s", sad->request);
+ if (sad->request[0] == '\0')
+ audit_log_format(ab, " labels_differ");
+ else
+ audit_log_format(ab, " requested=%s", sad->request);
}
/**
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 3da13fd..1876bfc 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -178,7 +178,8 @@ static inline unsigned int smk_ptrace_mode(unsigned int mode)
/**
* smk_ptrace_rule_check - helper for ptrace access
* @tracer: tracer process
- * @tracee_label: label of the process that's about to be traced
+ * @tracee_label: label of the process that's about to be traced,
+ * the pointer must originate from smack structures
* @mode: ptrace attachment mode (PTRACE_MODE_*)
* @func: name of the function that called us, used for audit
*
@@ -201,6 +202,25 @@ static int smk_ptrace_rule_check(struct task_struct *tracer, char *tracee_label,
tsp = task_security(tracer);
skp = smk_of_task(tsp);
+ if ((mode & PTRACE_MODE_ATTACH) &&
+ (smack_ptrace_rule == SMACK_PTRACE_EXACT ||
+ smack_ptrace_rule == SMACK_PTRACE_DRACONIAN)) {
+ if (skp->smk_known == tracee_label)
+ rc = 0;
+ else if (smack_ptrace_rule == SMACK_PTRACE_DRACONIAN)
+ rc = -EACCES;
+ else if (capable(CAP_SYS_PTRACE))
+ rc = 0;
+ else
+ rc = -EACCES;
+
+ if (saip)
+ smack_log(skp->smk_known, tracee_label, 0, rc, saip);
+
+ return rc;
+ }
+
+ /* In case of rule==SMACK_PTRACE_DEFAULT or mode==PTRACE_MODE_READ */
rc = smk_tskacc(tsp, tracee_label, smk_ptrace_mode(mode), saip);
return rc;
}
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 3198cfe..177d878 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -53,6 +53,7 @@ enum smk_inos {
SMK_REVOKE_SUBJ = 18, /* set rules with subject label to '-' */
SMK_CHANGE_RULE = 19, /* change or add rules (long labels) */
SMK_SYSLOG = 20, /* change syslog label) */
+ SMK_PTRACE = 21, /* set ptrace rule */
};
/*
@@ -101,6 +102,15 @@ struct smack_known *smack_onlycap;
struct smack_known *smack_syslog_label;
/*
+ * Ptrace current rule
+ * SMACK_PTRACE_DEFAULT regular smack ptrace rules (/proc based)
+ * SMACK_PTRACE_EXACT labels must match, but can be overriden with
+ * CAP_SYS_PTRACE
+ * SMACK_PTRACE_DRACONIAN lables must match, CAP_SYS_PTRACE has no effect
+ */
+int smack_ptrace_rule = SMACK_PTRACE_DEFAULT;
+
+/*
* Certain IP addresses may be designated as single label hosts.
* Packets are sent there unlabeled, but only from tasks that
* can write to the specified label.
@@ -2244,6 +2254,68 @@ static const struct file_operations smk_syslog_ops = {
/**
+ * smk_read_ptrace - read() for /smack/ptrace
+ * @filp: file pointer, not actually used
+ * @buf: where to put the result
+ * @count: maximum to send along
+ * @ppos: where to start
+ *
+ * Returns number of bytes read or error code, as appropriate
+ */
+static ssize_t smk_read_ptrace(struct file *filp, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ char temp[32];
+ ssize_t rc;
+
+ if (*ppos != 0)
+ return 0;
+
+ sprintf(temp, "%d\n", smack_ptrace_rule);
+ rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
+ return rc;
+}
+
+/**
+ * smk_write_ptrace - write() for /smack/ptrace
+ * @file: file pointer
+ * @buf: data from user space
+ * @count: bytes sent
+ * @ppos: where to start - must be 0
+ */
+static ssize_t smk_write_ptrace(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ char temp[32];
+ int i;
+
+ if (!smack_privileged(CAP_MAC_ADMIN))
+ return -EPERM;
+
+ if (*ppos != 0 || count >= sizeof(temp) || count == 0)
+ return -EINVAL;
+
+ if (copy_from_user(temp, buf, count) != 0)
+ return -EFAULT;
+
+ temp[count] = '\0';
+
+ if (sscanf(temp, "%d", &i) != 1)
+ return -EINVAL;
+ if (i < SMACK_PTRACE_DEFAULT || i > SMACK_PTRACE_MAX)
+ return -EINVAL;
+ smack_ptrace_rule = i;
+
+ return count;
+}
+
+static const struct file_operations smk_ptrace_ops = {
+ .write = smk_write_ptrace,
+ .read = smk_read_ptrace,
+ .llseek = default_llseek,
+};
+
+/**
* smk_fill_super - fill the smackfs superblock
* @sb: the empty superblock
* @data: unused
@@ -2296,6 +2368,8 @@ static int smk_fill_super(struct super_block *sb, void *data, int silent)
"change-rule", &smk_change_rule_ops, S_IRUGO|S_IWUSR},
[SMK_SYSLOG] = {
"syslog", &smk_syslog_ops, S_IRUGO|S_IWUSR},
+ [SMK_PTRACE] = {
+ "ptrace", &smk_ptrace_ops, S_IRUGO|S_IWUSR},
/* last one */
{""}
};
--
1.8.5.3
--
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