[PATCH 1/4] security: capabilities patch (version 0.4.4), part 1/4: enlarge capability sets

David Madore
2006-09-10T13:38:05Z

Increase the size of capability sets to 64 bits:

* bits 32-47 are "regular", i.e., present by default on non-root
processes;

* maintain compatibility with former kernel interface for capset()
and capget().

See <URL: http://www.madore.org/~david/linux/newcaps/ > for more
detailed explanations.

Signed-off-by: David A. Madore <david.madore@ens.fr>

---
fs/open.c | 3 ++-
fs/proc/array.c | 6 +++---
include/linux/capability.h | 30 ++++++++++++++++++-----------
kernel/capability.c | 46 +++++++++++++++++++++++++++++++++++---------
security/commoncap.c | 16 +++++++++++----
security/dummy.c | 6 +++---
6 files changed, 75 insertions(+), 32 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 303f06d..e58a525 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -515,7 +515,8 @@ asmlinkage long sys_faccessat(int dfd, c
* but we cannot because user_path_walk can sleep.
*/
if (current->uid)
- cap_clear(current->cap_effective);
+ current->cap_effective = cap_intersect(current->cap_effective,
+ CAP_REGULAR_SET);
else
current->cap_effective = current->cap_permitted;

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 0b615d6..6724fc2 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -285,9 +285,9 @@ static inline char * task_sig(struct tas

static inline char *task_cap(struct task_struct *p, char *buffer)
{
- return buffer + sprintf(buffer, "CapInh:\t%016x\n"
- "CapPrm:\t%016x\n"
- "CapEff:\t%016x\n",
+ return buffer + sprintf(buffer, "CapInh:\t%016llx\n"
+ "CapPrm:\t%016llx\n"
+ "CapEff:\t%016llx\n",
cap_t(p->cap_inheritable),
cap_t(p->cap_permitted),
cap_t(p->cap_effective));
diff --git a/include/linux/capability.h b/include/linux/capability.h
index 6548b35..aa00b60 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -27,7 +27,8 @@ #include <linux/compiler.h>
library since the draft standard requires the use of malloc/free
etc.. */

-#define _LINUX_CAPABILITY_VERSION 0x19980330
+#define _LINUX_CAPABILITY_VERSION 0x20060903
+#define _LINUX_CAPABILITY_OLD_VERSION 0x19980330

typedef struct __user_cap_header_struct {
__u32 version;
@@ -35,10 +36,16 @@ typedef struct __user_cap_header_struct
} __user *cap_user_header_t;

typedef struct __user_cap_data_struct {
+ __u64 effective;
+ __u64 permitted;
+ __u64 inheritable;
+} __user *cap_user_data_t;
+
+typedef struct __user_cap_data_old_struct {
__u32 effective;
__u32 permitted;
__u32 inheritable;
-} __user *cap_user_data_t;
+} __user *cap_user_data_old_t;

#ifdef __KERNEL__

@@ -50,12 +57,12 @@ #include <asm/current.h>
#ifdef STRICT_CAP_T_TYPECHECKS

typedef struct kernel_cap_struct {
- __u32 cap;
+ __u64 cap;
} kernel_cap_t;

#else

-typedef __u32 kernel_cap_t;
+typedef __u64 kernel_cap_t;

#endif

@@ -310,12 +317,13 @@ #define cap_t(x) (x)

#endif

-#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)
+#define CAP_EMPTY_SET to_cap_t(0ULL)
+#define CAP_FULL_SET to_cap_t(~0ULL)
+#define CAP_REGULAR_SET to_cap_t(0x0000ffff00000000ULL)
+#define CAP_INIT_EFF_SET to_cap_t(~0ULL)
+#define CAP_INIT_INH_SET to_cap_t(~0ULL)

-#define CAP_TO_MASK(x) (1 << (x))
+#define CAP_TO_MASK(x) (1ULL << (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))
@@ -351,8 +359,8 @@ static inline kernel_cap_t cap_invert(ke
#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_clear(c) do { cap_t(c) = 0ULL; } while(0)
+#define cap_set_full(c) do { cap_t(c) = ~0ULL; } while(0)
#define cap_mask(c,mask) do { cap_t(c) &= cap_t(mask); } while(0)

#define cap_is_fs_cap(c) (CAP_TO_MASK(c) & CAP_FS_MASK)
diff --git a/kernel/capability.c b/kernel/capability.c
index c7685ad..32b2521 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -52,7 +52,8 @@ asmlinkage long sys_capget(cap_user_head
if (get_user(version, &header->version))
return -EFAULT;

- if (version != _LINUX_CAPABILITY_VERSION) {
+ if (version != _LINUX_CAPABILITY_VERSION
+ && version != _LINUX_CAPABILITY_OLD_VERSION) {
if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
return -EFAULT;
return -EINVAL;
@@ -82,8 +83,18 @@ out:
read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);

- if (!ret && copy_to_user(dataptr, &data, sizeof data))
- return -EFAULT;
+ if (!ret) {
+ if (version == _LINUX_CAPABILITY_OLD_VERSION) {
+ struct __user_cap_data_old_struct data_old;
+ data_old.effective = data_old.effective & 0xffffffffULL;
+ data_old.permitted = data_old.permitted & 0xffffffffULL;
+ data_old.inheritable = data_old.inheritable & 0xffffffffULL;
+ if (copy_to_user(dataptr, &data_old, sizeof data_old))
+ return -EFAULT;
+ } else
+ if (copy_to_user(dataptr, &data, sizeof data))
+ return -EFAULT;
+ }

return ret;
}
@@ -179,7 +190,8 @@ asmlinkage long sys_capset(cap_user_head
if (get_user(version, &header->version))
return -EFAULT;

- if (version != _LINUX_CAPABILITY_VERSION) {
+ if (version != _LINUX_CAPABILITY_VERSION
+ && version != _LINUX_CAPABILITY_OLD_VERSION) {
if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
return -EFAULT;
return -EINVAL;
@@ -191,10 +203,25 @@ asmlinkage long sys_capset(cap_user_head
if (pid && pid != current->pid && !capable(CAP_SETPCAP))
return -EPERM;

- if (copy_from_user(&effective, &data->effective, sizeof(effective)) ||
- copy_from_user(&inheritable, &data->inheritable, sizeof(inheritable)) ||
- copy_from_user(&permitted, &data->permitted, sizeof(permitted)))
- return -EFAULT;
+ if (version == _LINUX_CAPABILITY_OLD_VERSION) {
+ const cap_user_data_old_t data2 = (void *)data;
+ __u32 w;
+ /* Assume caller wants to keep all regular caps and clear
+ * all unknown additional caps. Is this right? */
+ if (copy_from_user(&w, &data2->effective, sizeof(w)))
+ return -EFAULT;
+ effective = (__u64)w | CAP_REGULAR_SET;
+ if (copy_from_user(&w, &data2->inheritable, sizeof(w)))
+ return -EFAULT;
+ inheritable = (__u64)w | CAP_REGULAR_SET;
+ if (copy_from_user(&w, &data2->permitted, sizeof(w)))
+ return -EFAULT;
+ permitted = (__u64)w | CAP_REGULAR_SET;
+ } else
+ if (copy_from_user(&effective, &data->effective, sizeof(effective)) ||
+ copy_from_user(&inheritable, &data->inheritable, sizeof(inheritable)) ||
+ copy_from_user(&permitted, &data->permitted, sizeof(permitted)))
+ return -EFAULT;

spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
@@ -237,7 +264,8 @@ out:
int __capable(struct task_struct *t, int cap)
{
if (security_capable(t, cap) == 0) {
- t->flags |= PF_SUPERPRIV;
+ if (!cap_raised(CAP_REGULAR_SET, cap))
+ t->flags |= PF_SUPERPRIV;
return 1;
}
return 0;
diff --git a/security/commoncap.c b/security/commoncap.c
index f50fc29..91dc53d 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -244,13 +244,19 @@ static inline void cap_emulate_setxuid (
int old_suid)
{
if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
- (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
- !current->keep_capabilities) {
- cap_clear (current->cap_permitted);
- cap_clear (current->cap_effective);
+ (current->uid != 0 && current->euid != 0 && current->suid != 0)) {
+ if (!current->keep_capabilities) {
+ current->cap_permitted
+ = cap_intersect (current->cap_permitted,
+ CAP_REGULAR_SET);
+ current->cap_effective
+ = cap_intersect (current->cap_effective,
+ CAP_REGULAR_SET);
+ }
}
if (old_euid == 0 && current->euid != 0) {
- cap_clear (current->cap_effective);
+ current->cap_effective = cap_intersect (current->cap_effective,
+ CAP_REGULAR_SET);
}
if (old_euid != 0 && current->euid == 0) {
current->cap_effective = current->cap_permitted;
diff --git a/security/dummy.c b/security/dummy.c
index 58c6d39..572a15b 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -37,11 +37,11 @@ static int dummy_ptrace (struct task_str
static int dummy_capget (struct task_struct *target, kernel_cap_t * effective,
kernel_cap_t * inheritable, kernel_cap_t * permitted)
{
- *effective = *inheritable = *permitted = 0;
+ *effective = *inheritable = *permitted = CAP_REGULAR_SET;
if (!issecure(SECURE_NOROOT)) {
if (target->euid == 0) {
- *permitted |= (~0 & ~CAP_FS_MASK);
- *effective |= (~0 & ~CAP_TO_MASK(CAP_SETPCAP) & ~CAP_FS_MASK);
+ *permitted |= (CAP_FULL_SET & ~CAP_FS_MASK);
+ *effective |= (CAP_FULL_SET & ~CAP_TO_MASK(CAP_SETPCAP) & ~CAP_FS_MASK);
}
if (target->fsuid == 0) {
*permitted |= CAP_FS_MASK;