Add 64-bit capability support to the kernel

The patch supports legacy (32-bit) capability userspace, and where possible
translates 32-bit capabilities to/from userspace and the VFS to 64-bit
kernel space capabilities.  If a capability set cannot be compressed into
32-bits for consumption by user space, the system call fails, with -ERANGE.

FWIW libcap-2.00 supports this change (and earlier capability formats)

 http://www.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.6/

[akpm@linux-foundation.org: coding-syle fixes]
[akpm@linux-foundation.org: use get_task_comm()]
[ezk@cs.sunysb.edu: build fix]
[akpm@linux-foundation.org: do not initialise statics to 0 or NULL]
[akpm@linux-foundation.org: unused var]
[serue@us.ibm.com: export __cap_ symbols]
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: James Morris <jmorris@namei.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 155 insertions, 66 deletions

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 7a8d7ad..a934dac 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -23,13 +23,20 @@ struct task_struct;
    kernel might be somewhat backwards compatible, but don't bet on
    it. */
 
-/* XXX - Note, cap_t, is defined by POSIX to be an "opaque" pointer to
+/* Note, cap_t, is defined by POSIX (draft) to be an "opaque" pointer to
    a set of three capability sets.  The transposition of 3*the
    following structure to such a composite is better handled in a user
    library since the draft standard requires the use of malloc/free
    etc.. */
 
-#define _LINUX_CAPABILITY_VERSION  0x19980330
+#define _LINUX_CAPABILITY_VERSION_1  0x19980330
+#define _LINUX_CAPABILITY_U32S_1     1
+
+#define _LINUX_CAPABILITY_VERSION_2  0x20071026
+#define _LINUX_CAPABILITY_U32S_2     2
+
+#define _LINUX_CAPABILITY_VERSION    _LINUX_CAPABILITY_VERSION_2
+#define _LINUX_CAPABILITY_U32S       _LINUX_CAPABILITY_U32S_2
 
 typedef struct __user_cap_header_struct {
 	__u32 version;
@@ -42,43 +49,42 @@ typedef struct __user_cap_data_struct {
         __u32 inheritable;
 } __user *cap_user_data_t;
 
+
 #define XATTR_CAPS_SUFFIX "capability"
 #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX
 
-#define XATTR_CAPS_SZ (3*sizeof(__le32))
 #define VFS_CAP_REVISION_MASK	0xFF000000
+#define VFS_CAP_FLAGS_MASK	~VFS_CAP_REVISION_MASK
+#define VFS_CAP_FLAGS_EFFECTIVE	0x000001
+
 #define VFS_CAP_REVISION_1	0x01000000
+#define VFS_CAP_U32_1           1
+#define XATTR_CAPS_SZ_1         (sizeof(__le32)*(1 + 2*VFS_CAP_U32_1))
 
-#define VFS_CAP_REVISION	VFS_CAP_REVISION_1
+#define VFS_CAP_REVISION_2	0x02000000
+#define VFS_CAP_U32_2           2
+#define XATTR_CAPS_SZ_2         (sizeof(__le32)*(1 + 2*VFS_CAP_U32_2))
+
+#define XATTR_CAPS_SZ           XATTR_CAPS_SZ_2
+#define VFS_CAP_U32             VFS_CAP_U32_2
+#define VFS_CAP_REVISION	VFS_CAP_REVISION_2
 
-#define VFS_CAP_FLAGS_MASK	~VFS_CAP_REVISION_MASK
-#define VFS_CAP_FLAGS_EFFECTIVE	0x000001
 
 struct vfs_cap_data {
-	__u32 magic_etc;  /* Little endian */
+	__le32 magic_etc;            /* Little endian */
 	struct {
-		__u32 permitted;    /* Little endian */
-		__u32 inheritable;  /* Little endian */
-	} data[1];
+		__le32 permitted;    /* Little endian */
+		__le32 inheritable;  /* Little endian */
+	} data[VFS_CAP_U32];
 };
 
 #ifdef __KERNEL__
 
-/* #define STRICT_CAP_T_TYPECHECKS */
-
-#ifdef STRICT_CAP_T_TYPECHECKS
-
 typedef struct kernel_cap_struct {
-	__u32 cap;
+	__u32 cap[_LINUX_CAPABILITY_U32S];
 } kernel_cap_t;
 
-#else
-
-typedef __u32 kernel_cap_t;
-
-#endif
-
-#define _USER_CAP_HEADER_SIZE  (2*sizeof(__u32))
+#define _USER_CAP_HEADER_SIZE  (sizeof(struct __user_cap_header_struct))
 #define _KERNEL_CAP_T_SIZE     (sizeof(kernel_cap_t))
 
 #endif
@@ -121,10 +127,6 @@ typedef __u32 kernel_cap_t;
 
 #define CAP_FSETID           4
 
-/* Used to decide between falling back on the old suser() or fsuser(). */
-
-#define CAP_FS_MASK          0x1f
-
 /* Overrides the restriction that the real or effective user ID of a
    process sending a signal must match the real or effective user ID
    of the process receiving the signal. */
@@ -147,8 +149,12 @@ typedef __u32 kernel_cap_t;
  ** Linux-specific capabilities
  **/
 
-/* Transfer any capability in your permitted set to any pid,
-   remove any capability in your permitted set from any pid */
+/* Without VFS support for capabilities:
+ *   Transfer any capability in your permitted set to any pid,
+ *   remove any capability in your permitted set from any pid
+ * With VFS support for capabilities (neither of above, but)
+ *   Add any capability to the current process' inheritable set
+ */
 
 #define CAP_SETPCAP          8
 
@@ -309,70 +315,153 @@ typedef __u32 kernel_cap_t;
 
 #define CAP_SETFCAP	     31
 
+/*
+ * Bit location of each capability (used by user-space library and kernel)
+ */
+
+#define CAP_TO_INDEX(x)     ((x) >> 5)        /* 1 << 5 == bits in __u32 */
+#define CAP_TO_MASK(x)      (1 << ((x) & 31)) /* mask for indexed __u32 */
+
 #ifdef __KERNEL__
 
 /*
  * Internal kernel functions only
  */
 
-#ifdef STRICT_CAP_T_TYPECHECKS
+#define CAP_FOR_EACH_U32(__capi)  \
+	for (__capi = 0; __capi < _LINUX_CAPABILITY_U32S; ++__capi)
+
+# define CAP_FS_MASK_B0     (CAP_TO_MASK(CAP_CHOWN)		\
+			    | CAP_TO_MASK(CAP_DAC_OVERRIDE)	\
+			    | CAP_TO_MASK(CAP_DAC_READ_SEARCH)	\
+			    | CAP_TO_MASK(CAP_FOWNER)		\
+			    | CAP_TO_MASK(CAP_FSETID))
+
+#if _LINUX_CAPABILITY_U32S != 2
+# error Fix up hand-coded capability macro initializers
+#else /* HAND-CODED capability initializers */
+
+# define CAP_EMPTY_SET    {{ 0, 0 }}
+# define CAP_FULL_SET     {{ ~0, ~0 }}
+# define CAP_INIT_EFF_SET {{ ~CAP_TO_MASK(CAP_SETPCAP), ~0 }}
+# define CAP_FS_SET       {{ CAP_FS_MASK_B0, 0 }}
+# define CAP_NFSD_SET     {{ CAP_FS_MASK_B0|CAP_TO_MASK(CAP_SYS_RESOURCE), 0 }}
+
+#endif /* _LINUX_CAPABILITY_U32S != 2 */
+
+#define CAP_INIT_INH_SET    CAP_EMPTY_SET
+
+# define cap_clear(c)         do { (c) = __cap_empty_set; } while (0)
+# define cap_set_full(c)      do { (c) = __cap_full_set; } while (0)
+# define cap_set_init_eff(c)  do { (c) = __cap_init_eff_set; } while (0)
+
+#define cap_raise(c, flag)  ((c).cap[CAP_TO_INDEX(flag)] |= CAP_TO_MASK(flag))
+#define cap_lower(c, flag)  ((c).cap[CAP_TO_INDEX(flag)] &= ~CAP_TO_MASK(flag))
+#define cap_raised(c, flag) ((c).cap[CAP_TO_INDEX(flag)] & CAP_TO_MASK(flag))
+
+#define CAP_BOP_ALL(c, a, b, OP)                                    \
+do {                                                                \
+	unsigned __capi;                                            \
+	CAP_FOR_EACH_U32(__capi) {                                  \
+		c.cap[__capi] = a.cap[__capi] OP b.cap[__capi];     \
+	}                                                           \
+} while (0)
+
+#define CAP_UOP_ALL(c, a, OP)                                       \
+do {                                                                \
+	unsigned __capi;                                            \
+	CAP_FOR_EACH_U32(__capi) {                                  \
+		c.cap[__capi] = OP a.cap[__capi];                   \
+	}                                                           \
+} while (0)
+
+static inline kernel_cap_t cap_combine(const kernel_cap_t a,
+				       const kernel_cap_t b)
+{
+	kernel_cap_t dest;
+	CAP_BOP_ALL(dest, a, b, |);
+	return dest;
+}
 
-#define to_cap_t(x) { x }
-#define cap_t(x) (x).cap
+static inline kernel_cap_t cap_intersect(const kernel_cap_t a,
+					 const kernel_cap_t b)
+{
+	kernel_cap_t dest;
+	CAP_BOP_ALL(dest, a, b, &);
+	return dest;
+}
 
-#else
+static inline kernel_cap_t cap_drop(const kernel_cap_t a,
+				    const kernel_cap_t drop)
+{
+	kernel_cap_t dest;
+	CAP_BOP_ALL(dest, a, drop, &~);
+	return dest;
+}
 
-#define to_cap_t(x) (x)
-#define cap_t(x) (x)
+static inline kernel_cap_t cap_invert(const kernel_cap_t c)
+{
+	kernel_cap_t dest;
+	CAP_UOP_ALL(dest, c, ~);
+	return dest;
+}
 
-#endif
+static inline int cap_isclear(const kernel_cap_t a)
+{
+	unsigned __capi;
+	CAP_FOR_EACH_U32(__capi) {
+		if (a.cap[__capi] != 0)
+			return 0;
+	}
+	return 1;
+}
 
-#define CAP_EMPTY_SET       to_cap_t(0)
-#define CAP_FULL_SET        to_cap_t(~0)
-#define CAP_INIT_EFF_SET    to_cap_t(~0 & ~CAP_TO_MASK(CAP_SETPCAP))
-#define CAP_INIT_INH_SET    to_cap_t(0)
+static inline int cap_issubset(const kernel_cap_t a, const kernel_cap_t set)
+{
+	kernel_cap_t dest;
+	dest = cap_drop(a, set);
+	return cap_isclear(dest);
+}
 
-#define CAP_TO_MASK(x) (1 << (x))
-#define cap_raise(c, flag)   (cap_t(c) |=  CAP_TO_MASK(flag))
-#define cap_lower(c, flag)   (cap_t(c) &= ~CAP_TO_MASK(flag))
-#define cap_raised(c, flag)  (cap_t(c) & CAP_TO_MASK(flag))
+/* Used to decide between falling back on the old suser() or fsuser(). */
 
-static inline kernel_cap_t cap_combine(kernel_cap_t a, kernel_cap_t b)
+static inline int cap_is_fs_cap(int cap)
 {
-     kernel_cap_t dest;
-     cap_t(dest) = cap_t(a) | cap_t(b);
-     return dest;
+	const kernel_cap_t __cap_fs_set = CAP_FS_SET;
+	return !!(CAP_TO_MASK(cap) & __cap_fs_set.cap[CAP_TO_INDEX(cap)]);
 }
 
-static inline kernel_cap_t cap_intersect(kernel_cap_t a, kernel_cap_t b)
+static inline kernel_cap_t cap_drop_fs_set(const kernel_cap_t a)
 {
-     kernel_cap_t dest;
-     cap_t(dest) = cap_t(a) & cap_t(b);
-     return dest;
+	const kernel_cap_t __cap_fs_set = CAP_FS_SET;
+	return cap_drop(a, __cap_fs_set);
 }
 
-static inline kernel_cap_t cap_drop(kernel_cap_t a, kernel_cap_t drop)
+static inline kernel_cap_t cap_raise_fs_set(const kernel_cap_t a,
+					    const kernel_cap_t permitted)
 {
-     kernel_cap_t dest;
-     cap_t(dest) = cap_t(a) & ~cap_t(drop);
-     return dest;
+	const kernel_cap_t __cap_fs_set = CAP_FS_SET;
+	return cap_combine(a,
+			   cap_intersect(permitted, __cap_fs_set));
 }
 
-static inline kernel_cap_t cap_invert(kernel_cap_t c)
+static inline kernel_cap_t cap_drop_nfsd_set(const kernel_cap_t a)
 {
-     kernel_cap_t dest;
-     cap_t(dest) = ~cap_t(c);
-     return dest;
+	const kernel_cap_t __cap_fs_set = CAP_NFSD_SET;
+	return cap_drop(a, __cap_fs_set);
 }
 
-#define cap_isclear(c)       (!cap_t(c))
-#define cap_issubset(a,set)  (!(cap_t(a) & ~cap_t(set)))
-
-#define cap_clear(c)         do { cap_t(c) =  0; } while(0)
-#define cap_set_full(c)      do { cap_t(c) = ~0; } while(0)
-#define cap_mask(c,mask)     do { cap_t(c) &= cap_t(mask); } while(0)
+static inline kernel_cap_t cap_raise_nfsd_set(const kernel_cap_t a,
+					      const kernel_cap_t permitted)
+{
+	const kernel_cap_t __cap_nfsd_set = CAP_NFSD_SET;
+	return cap_combine(a,
+			   cap_intersect(permitted, __cap_nfsd_set));
+}
 
-#define cap_is_fs_cap(c)     (CAP_TO_MASK(c) & CAP_FS_MASK)
+extern const kernel_cap_t __cap_empty_set;
+extern const kernel_cap_t __cap_full_set;
+extern const kernel_cap_t __cap_init_eff_set;
 
 int capable(int cap);
 int __capable(struct task_struct *t, int cap);