Adds a new open permission inside SELinux when 'opening' a file. The
idea is that opening a file and reading/writing to that file are not the
same thing. Its different if a program had its stdout redirected
to /tmp/output than if the program tried to directly open /tmp/output.
This should allow policy writers to more liberally give read/write
permissions across the policy while still blocking many design and
programing flaws SELinux is so good at catching today.
Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
---
As an example, process1 in httpd_t opened a bunch of files of type
user_tmp_t. It then called process2 running as ntpd_t which did nothing
but accept those open fd's and terminate. Notice proc1 needed open
perms and proc2 only needed read and write.
#============= httpd_t ==============
allow httpd_t tmp_t:dir open;
allow httpd_t user_tmp_t:blk_file { read write open };
allow httpd_t user_tmp_t:chr_file { read write open };
allow httpd_t user_tmp_t:dir { read open };
allow httpd_t user_tmp_t:fifo_file { read write open };
allow httpd_t user_tmp_t:file { read write execute entrypoint open };
allow httpd_t user_tmp_t:lnk_file read;
#============= ntpd_t ==============
allow ntpd_t user_tmp_t:blk_file { read write };
allow ntpd_t user_tmp_t:chr_file { read write };
allow ntpd_t user_tmp_t:dir read;
allow ntpd_t user_tmp_t:fifo_file { read write };
allow ntpd_t user_tmp_t:file { read write entrypoint };
security/selinux/hooks.c | 31 +++++++++++++++++++++++++-
security/selinux/include/av_perm_to_string.h | 5 ++++
security/selinux/include/av_permissions.h | 5 ++++
security/selinux/include/security.h | 2 +
security/selinux/selinuxfs.c | 1 +
security/selinux/ss/services.c | 3 ++
6 files changed, 46 insertions(+), 1 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 75c2e99..a4cf5ff 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1599,6 +1599,35 @@ static inline u32 file_mask_to_av(int mode, int mask)
return av;
}
+/*
+ * Convert a file mask to an access vector and include the correct open
+ * open permission.
+ */
+static inline u32 open_file_mask_to_av(int mode, int mask)
+{
+ u32 av = file_mask_to_av(mode, mask);
+
+ if (selinux_policycap_openperm) {
+ /*
+ * lnk files and socks do not really have an 'open'
+ */
+ if (S_ISREG(mode))
+ av |= FILE__OPEN;
+ else if (S_ISCHR(mode))
+ av |= CHR_FILE__OPEN;
+ else if (S_ISBLK(mode))
+ av |= BLK_FILE__OPEN;
+ else if (S_ISFIFO(mode))
+ av |= FIFO_FILE__OPEN;
+ else if (S_ISDIR(mode))
+ av |= DIR__OPEN;
+ else
+ printk(KERN_ERR "SELinux: WARNING: inside open_file_to_av "
+ "with unknown mode:%x\n", mode);
+ }
+ return av;
+}
+
/* Convert a Linux file to an access vector. */
static inline u32 file_to_av(struct file *file)
{
@@ -2517,7 +2546,7 @@ static int selinux_inode_permission(struct inode *inode, int mask,
}
return inode_has_perm(current, inode,
- file_mask_to_av(inode->i_mode, mask), NULL);
+ open_file_mask_to_av(inode->i_mode, mask), NULL);
}
static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
diff --git a/security/selinux/include/av_perm_to_string.h b/security/selinux/include/av_perm_to_string.h
index d569669..1223b4f 100644
--- a/security/selinux/include/av_perm_to_string.h
+++ b/security/selinux/include/av_perm_to_string.h
@@ -14,12 +14,17 @@
S_(SECCLASS_DIR, DIR__REPARENT, "reparent")
S_(SECCLASS_DIR, DIR__SEARCH, "search")
S_(SECCLASS_DIR, DIR__RMDIR, "rmdir")
+ S_(SECCLASS_DIR, DIR__OPEN, "open")
S_(SECCLASS_FILE, FILE__EXECUTE_NO_TRANS, "execute_no_trans")
S_(SECCLASS_FILE, FILE__ENTRYPOINT, "entrypoint")
S_(SECCLASS_FILE, FILE__EXECMOD, "execmod")
+ S_(SECCLASS_FILE, FILE__OPEN, "open")
S_(SECCLASS_CHR_FILE, CHR_FILE__EXECUTE_NO_TRANS, "execute_no_trans")
S_(SECCLASS_CHR_FILE, CHR_FILE__ENTRYPOINT, "entrypoint")
S_(SECCLASS_CHR_FILE, CHR_FILE__EXECMOD, "execmod")
+ S_(SECCLASS_CHR_FILE, CHR_FILE__OPEN, "open")
+ S_(SECCLASS_BLK_FILE, BLK_FILE__OPEN, "open")
+ S_(SECCLASS_FIFO_FILE, FIFO_FILE__OPEN, "open")
S_(SECCLASS_FD, FD__USE, "use")
S_(SECCLASS_TCP_SOCKET, TCP_SOCKET__CONNECTTO, "connectto")
S_(SECCLASS_TCP_SOCKET, TCP_SOCKET__NEWCONN, "newconn")
diff --git a/security/selinux/include/av_permissions.h b/security/selinux/include/av_permissions.h
index 75b4131..c4c5116 100644
--- a/security/selinux/include/av_permissions.h
+++ b/security/selinux/include/av_permissions.h
@@ -79,6 +79,7 @@
#define DIR__REPARENT 0x00080000UL
#define DIR__SEARCH 0x00100000UL
#define DIR__RMDIR 0x00200000UL
+#define DIR__OPEN 0x00400000UL
#define FILE__IOCTL 0x00000001UL
#define FILE__READ 0x00000002UL
#define FILE__WRITE 0x00000004UL
@@ -99,6 +100,7 @@
#define FILE__EXECUTE_NO_TRANS 0x00020000UL
#define FILE__ENTRYPOINT 0x00040000UL
#define FILE__EXECMOD 0x00080000UL
+#define FILE__OPEN 0x00100000UL
#define LNK_FILE__IOCTL 0x00000001UL
#define LNK_FILE__READ 0x00000002UL
#define LNK_FILE__WRITE 0x00000004UL
@@ -136,6 +138,7 @@
#define CHR_FILE__EXECUTE_NO_TRANS 0x00020000UL
#define CHR_FILE__ENTRYPOINT 0x00040000UL
#define CHR_FILE__EXECMOD 0x00080000UL
+#define CHR_FILE__OPEN 0x00100000UL
#define BLK_FILE__IOCTL 0x00000001UL
#define BLK_FILE__READ 0x00000002UL
#define BLK_FILE__WRITE 0x00000004UL
@@ -153,6 +156,7 @@
#define BLK_FILE__SWAPON 0x00004000UL
#define BLK_FILE__QUOTAON 0x00008000UL
#define BLK_FILE__MOUNTON 0x00010000UL
+#define BLK_FILE__OPEN 0x00020000UL
#define SOCK_FILE__IOCTL 0x00000001UL
#define SOCK_FILE__READ 0x00000002UL
#define SOCK_FILE__WRITE 0x00000004UL
@@ -187,6 +191,7 @@
#define FIFO_FILE__SWAPON 0x00004000UL
#define FIFO_FILE__QUOTAON 0x00008000UL
#define FIFO_FILE__MOUNTON 0x00010000UL
+#define FIFO_FILE__OPEN 0x00020000UL
#define FD__USE 0x00000001UL
#define SOCKET__IOCTL 0x00000001UL
#define SOCKET__READ 0x00000002UL
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index 837ce42..fa30f53 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -43,11 +43,13 @@ extern int selinux_mls_enabled;
/* Policy capabilities */
enum {
POLICYDB_CAPABILITY_NETPEER,
+ POLICYDB_CAPABILITY_OPENPERM,
__POLICYDB_CAPABILITY_MAX
};
#define POLICYDB_CAPABILITY_MAX (__POLICYDB_CAPABILITY_MAX - 1)
extern int selinux_policycap_netpeer;
+extern int selinux_policycap_openperm;
int security_load_policy(void * data, size_t len);
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 0341567..6e31ce6 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -43,6 +43,7 @@
/* Policy capability filenames */
static char *policycap_names[] = {
"network_peer_controls"
+ "open_perms"
};
unsigned int selinux_checkreqprot = CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index f374186..23a61f1 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -61,6 +61,7 @@ extern void selnl_notify_policyload(u32 seqno);
unsigned int policydb_loaded_version;
int selinux_policycap_netpeer;
+int selinux_policycap_openperm;
/*
* This is declared in avc.c
@@ -1306,6 +1307,8 @@ static void security_load_policycaps(void)
{
selinux_policycap_netpeer = ebitmap_get_bit(&policydb.policycaps,
POLICYDB_CAPABILITY_NETPEER);
+ selinux_policycap_openperm = ebitmap_get_bit(&policydb.policycaps,
+ POLICYDB_CAPABILITY_OPENPERM);
}
extern void selinux_complete_init(void);
--
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