This patch add a generic cpu endian caps structure and enternally available functions which retrieve fcaps information from disk. This information is necessary so fcaps information can be collected and recorded by the audit system. Signed-off-by: Eric Paris <eparis(a)redhat.com&gt; --- include/linux/capability.h | 7 ++ security/commoncap.c | 128 +++++++++++++++++++++++++------------------- 2 files changed, 79 insertions(+), 56 deletions(-) diff --git a/include/linux/capability.h b/include/linux/capability.h index 9d1fe30..9d64a9c 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -96,6 +96,13 @@ typedef struct kernel_cap_struct { __u32 cap[_KERNEL_CAPABILITY_U32S]; } kernel_cap_t; +/* exact same as vfs_cap_data but in cpu endian and always filled completely */ +struct cpu_vfs_cap_data { + __u32 magic_etc; + kernel_cap_t permitted; + kernel_cap_t inheritable; +}; + #define _USER_CAP_HEADER_SIZE (sizeof(struct __user_cap_header_struct)) #define _KERNEL_CAP_T_SIZE (sizeof(kernel_cap_t)) diff --git a/security/commoncap.c b/security/commoncap.c index 399bfdb..888b292 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -202,17 +202,70 @@ int cap_inode_killpriv(struct dentry *dentry) return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); } -static inline int cap_from_disk(struct vfs_cap_data *caps, - struct linux_binprm *bprm, unsigned size) +static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, + struct linux_binprm *bprm) { + unsigned i; + int ret = 0; + + if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) + bprm->cap_effective = true; + else + bprm->cap_effective = false; + + CAP_FOR_EACH_U32(i) { + __u32 permitted = caps->permitted.cap[i]; + __u32 inheritable = caps->inheritable.cap[i]; + + /* + * pP' = (X & fP) | (pI & fI) + */ + bprm->cap_post_exec_permitted.cap[i] = + (current->cap_bset.cap[i] & permitted) | + (current->cap_inheritable.cap[i] & inheritable); + + if (permitted & ~bprm->cap_post_exec_permitted.cap[i]) { + /* + * insufficient to execute correctly + */ + ret = -EPERM; + } + } + + /* + * For legacy apps, with no internal support for recognizing they + * do not have enough capabilities, we return an error if they are + * missing some "forced" (aka file-permitted) capabilities. + */ + return bprm->cap_effective ? ret : 0; +} + +int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) +{ + struct inode *inode = dentry->d_inode; __u32 magic_etc; unsigned tocopy, i; - int ret; + int size; + struct vfs_cap_data caps; + + memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); + + if (!inode || !inode->i_op || !inode->i_op->getxattr) + return -ENODATA; + + size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, + XATTR_CAPS_SZ); + if (size == -ENODATA || size == -EOPNOTSUPP) { + /* no data, that's ok */ + return -ENODATA; + } + if (size < 0) + return size; if (size < sizeof(magic_etc)) return -EINVAL; - magic_etc = le32_to_cpu(caps->magic_etc); + cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); switch ((magic_etc & VFS_CAP_REVISION_MASK)) { case VFS_CAP_REVISION_1: @@ -229,46 +282,16 @@ static inline int cap_from_disk(struct vfs_cap_data *caps, return -EINVAL; } - if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE) { - bprm->cap_effective = true; - } else { - bprm->cap_effective = false; - } - - ret = 0; - CAP_FOR_EACH_U32(i) { - __u32 value_cpu; - - if (i >= tocopy) { - /* - * Legacy capability sets have no upper bits - */ - bprm->cap_post_exec_permitted.cap[i] = 0; + if (i > tocopy) { + cpu_caps->permitted.cap[i] = 0; + cpu_caps->inheritable.cap[i] = 0; continue; } - /* - * pP' = (X & fP) | (pI & fI) - */ - value_cpu = le32_to_cpu(caps->data[i].permitted); - bprm->cap_post_exec_permitted.cap[i] = - (current->cap_bset.cap[i] & value_cpu) | - (current->cap_inheritable.cap[i] & - le32_to_cpu(caps->data[i].inheritable)); - if (value_cpu & ~bprm->cap_post_exec_permitted.cap[i]) { - /* - * insufficient to execute correctly - */ - ret = -EPERM; - } + cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); + cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); } - - /* - * For legacy apps, with no internal support for recognizing they - * do not have enough capabilities, we return an error if they are - * missing some "forced" (aka file-permitted) capabilities. - */ - return bprm->cap_effective ? ret : 0; + return 0; } /* Locate any VFS capabilities: */ @@ -276,8 +299,7 @@ static int get_file_caps(struct linux_binprm *bprm) { struct dentry *dentry; int rc = 0; - struct vfs_cap_data vcaps; - struct inode *inode; + struct cpu_vfs_cap_data vcaps; if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) { bprm_clear_caps(bprm); @@ -285,24 +307,18 @@ static int get_file_caps(struct linux_binprm *bprm) } dentry = dget(bprm->file->f_dentry); - inode = dentry->d_inode; - if (!inode->i_op || !inode->i_op->getxattr) - goto out; - rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, &vcaps, - XATTR_CAPS_SZ); - if (rc == -ENODATA || rc == -EOPNOTSUPP) { - /* no data, that's ok */ - rc = 0; + rc = get_vfs_caps_from_disk(dentry, &vcaps); + if (rc < 0) { + if (rc == -EINVAL) + printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", + __func__, rc, bprm->filename); + else if (rc == -ENODATA) + rc = 0; goto out; } - if (rc < 0) - goto out; - rc = cap_from_disk(&vcaps, bprm, rc); - if (rc == -EINVAL) - printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", - __func__, rc, bprm->filename); + rc = bprm_caps_from_vfs_caps(&vcaps, bprm); out: dput(dentry);

Any time fcaps are used to increase a processes pP or pE we will crate a new audit record which contains the entire set of known information about the executable in question, fP, fI, fE, version and includes the parent processes pE, pI, pP. This record type will only be emitted from execve syscalls. an example of making ping use fcaps instead of setuid: setcap "cat_net_raw+pe" /bin/ping type=SYSCALL msg=audit(1224539237.785:55): arch=c000003e syscall=59 success=yes exit=0 a0=1b511c0 a1=1b50aa0 a2=1b5f140 a3=3445170a70 items=2 ppid=2328 pid=2358 auid=0 uid=500 gid=500 euid=500 suid=500 fsuid=500 egid=500 sgid=500 fsgid=500 tty=pts0 ses=1 comm="ping" exe="/bin/ping" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=EXECVE msg=audit(1224539237.785:55): argc=2 a0="ping" a1="127.0.0.1" type=UNKNOWN[1321] msg=audit(1224539237.785:55): cap_fVer=2 cap_fP=0000000000002000 cap_fI=0000000000000000 cap_fE=1 cap_pP=0000000000001000 cap_pI=0000000000000000 cap_pE=0000000000001000 cap_bprmEff=0000000000002000 type=CWD msg=audit(1224539237.785:55): cwd="/home/test" type=PATH msg=audit(1224539237.785:55): item=0 name="/bin/ping" inode=49227 dev=fd:00 mode=0100755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:ping_exec_t:s0 cap_fP=0000000000002000 cap_fE=1 cap_fVer=2 type=PATH msg=audit(1224539237.785:55): item=1 name=(null) inode=507963 dev=fd:00 mode=0100755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:ld_so_t:s0 Signed-off-by: Eric Paris <eparis(a)redhat.com&gt; --- include/linux/audit.h | 12 ++++++++ kernel/auditsc.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++++ security/commoncap.c | 3 ++ 3 files changed, 86 insertions(+), 0 deletions(-) diff --git a/include/linux/audit.h b/include/linux/audit.h index 6272a39..88a0f04 100644 --- a/include/linux/audit.h +++ b/include/linux/audit.h @@ -99,6 +99,7 @@ #define AUDIT_OBJ_PID 1318 /* ptrace target */ #define AUDIT_TTY 1319 /* Input on an administrative TTY */ #define AUDIT_EOE 1320 /* End of multi-record event */ +#define AUDIT_BPRM_FCAPS 1321 /* Information about fcaps increasing perms */ #define AUDIT_AVC 1400 /* SE Linux avc denial or grant */ #define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */ @@ -452,6 +453,8 @@ extern int __audit_mq_timedsend(mqd_t mqdes, size_t msg_len, unsigned int msg_pr extern int __audit_mq_timedreceive(mqd_t mqdes, size_t msg_len, unsigned int __user *u_msg_prio, const struct timespec __user *u_abs_timeout); extern int __audit_mq_notify(mqd_t mqdes, const struct sigevent __user *u_notification); extern int __audit_mq_getsetattr(mqd_t mqdes, struct mq_attr *mqstat); +extern int __audit_log_bprm_fcaps(struct linux_binprm *bprm, struct cpu_vfs_cap_data *caps); + static inline int audit_ipc_obj(struct kern_ipc_perm *ipcp) { @@ -501,6 +504,14 @@ static inline int audit_mq_getsetattr(mqd_t mqdes, struct mq_attr *mqstat) return __audit_mq_getsetattr(mqdes, mqstat); return 0; } + +static inline int audit_log_bprm_fcaps(struct linux_binprm *bprm, struct cpu_vfs_cap_data *caps) +{ + if (unlikely(!audit_dummy_context())) + return __audit_log_bprm_fcaps(bprm, caps); + return 0; +} + extern int audit_n_rules; extern int audit_signals; #else @@ -532,6 +543,7 @@ extern int audit_signals; #define audit_mq_timedreceive(d,l,p,t) ({ 0; }) #define audit_mq_notify(d,n) ({ 0; }) #define audit_mq_getsetattr(d,s) ({ 0; }) +#define audit_log_bprm_fcaps(b, c) 0 #define audit_ptrace(t) ((void)0) #define audit_n_rules 0 #define audit_signals 0 diff --git a/kernel/auditsc.c b/kernel/auditsc.c index bf1f11a..6d2487c 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -196,6 +196,14 @@ struct audit_aux_data_pids { int pid_count; }; +struct audit_aux_data_bprm_fcaps { + struct audit_aux_data d; + struct audit_cap_data fcap; + unsigned int fcap_ver; + struct audit_cap_data pcap; + kernel_cap_t bprm_effective; +}; + struct audit_tree_refs { struct audit_tree_refs *next; struct audit_chunk *c[31]; @@ -1375,6 +1383,18 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts audit_log_format(ab, "fd0=%d fd1=%d", axs->fd[0], axs->fd[1]); break; } + case AUDIT_BPRM_FCAPS: { + struct audit_aux_data_bprm_fcaps *axs = (void *)aux; + audit_log_format(ab, "cap_fVer=%x", axs->fcap_ver); + audit_log_cap(ab, "cap_fP", &axs->fcap.permitted); + audit_log_cap(ab, "cap_fI", &axs->fcap.inheritable); + audit_log_format(ab, " cap_fE=%d", axs->fcap.fE); + audit_log_cap(ab, "cap_pP", &axs->pcap.permitted); + audit_log_cap(ab, "cap_pI", &axs->pcap.inheritable); + audit_log_cap(ab, "cap_pE", &axs->pcap.effective); + audit_log_cap(ab, "cap_bprmEff", &axs->bprm_effective); + break; } + } audit_log_end(ab); } @@ -2502,6 +2522,57 @@ int __audit_signal_info(int sig, struct task_struct *t) } /** + * __audit_log_bprm_fcaps - store information about a loading bprm and relevant fcaps + * @bprm pointer to the bprm being processed + * @caps the caps read from the disk + * + * Simply check if the proc already has the caps given by the file and if not + * store the priv escalation info for later auditing at the end of the syscall + */ +int __audit_log_bprm_fcaps(struct linux_binprm *bprm, struct cpu_vfs_cap_data *caps) +{ + struct audit_aux_data_bprm_fcaps *ax; + struct audit_context *context = current->audit_context; + struct task_struct *tsk = current; + + if (likely(!audit_enabled || !context || context->dummy)) + return 0; + + /* + * bprm is in pP interset pI && + * we will change pE && + * bprm is in pE intersect pI + * + * fcaps make no different so don't record this + */ + if (cap_issubset(bprm->cap_post_exec_permitted, cap_intersect(tsk->cap_permitted, tsk->cap_inheritable)) && + bprm->cap_effective && + cap_issubset(bprm->cap_post_exec_permitted, cap_intersect(tsk->cap_effective, tsk->cap_inheritable))) + return 0; + + ax = kmalloc(sizeof(*ax), GFP_KERNEL); + if (!ax) + return -ENOMEM; + + ax->d.type = AUDIT_BPRM_FCAPS; + ax->d.next = context->aux; + context->aux = (void *)ax; + + ax->fcap.permitted = caps->permitted; + ax->fcap.inheritable = caps->inheritable; + ax->fcap.fE = !!(caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE); + ax->fcap_ver = (caps->magic_etc & VFS_CAP_REVISION_MASK) >> VFS_CAP_REVISION_SHIFT; + + ax->pcap.permitted = tsk->cap_permitted; + ax->pcap.inheritable = tsk->cap_inheritable; + ax->pcap.effective = tsk->cap_effective; + + ax->bprm_effective = bprm->cap_post_exec_permitted; + + return 0; +} + +/** * audit_core_dumps - record information about processes that end abnormally * @signr: signal value * diff --git a/security/commoncap.c b/security/commoncap.c index 888b292..9bb285d 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -8,6 +8,7 @@ */ #include <linux/capability.h> +#include <linux/audit.h> #include <linux/module.h> #include <linux/init.h> #include <linux/kernel.h> @@ -320,6 +321,8 @@ static int get_file_caps(struct linux_binprm *bprm) rc = bprm_caps_from_vfs_caps(&vcaps, bprm); + audit_log_bprm_fcaps(bprm, &vcaps); + out: dput(dentry); if (rc)

Quoting Andrew G. Morgan (morgan(a)kernel.org): True. ... except if (!issecure(SECURE_NOROOT) && uid==0) I guess? And then it also might be interesting in the case where (!issecure(SECURE_NOROOT) && uid==0) and pP is not full. It might fail because fP contains bits not in pP', right? That's probably interesting to auditors. -serge

When the capset syscall is used it is not possible for audit to record the actual capbilities being added/removed. This patch adds a new record type which emits the target pid and the eff, inh, and perm cap sets. example output if you audit capset syscalls would be: type=SYSCALL msg=audit(1224539227.691:49): arch=c000003e syscall=126 success=yes exit=0 a0=11e8014 a1=11e801c a2=80000000 a3=7fffe3dc90d0 items=0 ppid=2262 pid=2323 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=1 comm="setcap" exe="/usr/sbin/setcap" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=UNKNOWN[1322] msg=audit(1224539227.691:49): pid=0 CapEff=ffffffffffffffff CapInh=ffffffffffffffff CapPrm=ffffffffffffffff Signed-off-by: Eric Paris <eparis(a)redhat.com&gt; --- include/linux/audit.h | 10 ++++++++++ kernel/auditsc.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ kernel/capability.c | 3 +++ 3 files changed, 61 insertions(+), 0 deletions(-) diff --git a/include/linux/audit.h b/include/linux/audit.h index 88a0f04..b5c7c3f 100644 --- a/include/linux/audit.h +++ b/include/linux/audit.h @@ -100,6 +100,7 @@ #define AUDIT_TTY 1319 /* Input on an administrative TTY */ #define AUDIT_EOE 1320 /* End of multi-record event */ #define AUDIT_BPRM_FCAPS 1321 /* Information about fcaps increasing perms */ +#define AUDIT_CAPSET 1322 /* Record showing argument to sys_capset */ #define AUDIT_AVC 1400 /* SE Linux avc denial or grant */ #define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */ @@ -454,6 +455,7 @@ extern int __audit_mq_timedreceive(mqd_t mqdes, size_t msg_len, unsigned int __u extern int __audit_mq_notify(mqd_t mqdes, const struct sigevent __user *u_notification); extern int __audit_mq_getsetattr(mqd_t mqdes, struct mq_attr *mqstat); extern int __audit_log_bprm_fcaps(struct linux_binprm *bprm, struct cpu_vfs_cap_data *caps); +extern int __audit_log_capset(pid_t pid, kernel_cap_t *eff, kernel_cap_t *inh, kernel_cap_t *perm); static inline int audit_ipc_obj(struct kern_ipc_perm *ipcp) @@ -512,6 +514,13 @@ static inline int audit_log_bprm_fcaps(struct linux_binprm *bprm, struct cpu_vfs return 0; } +static inline int audit_log_capset(pid_t pid, kernel_cap_t *eff, kernel_cap_t *inh, kernel_cap_t *perm) +{ + if (unlikely(!audit_dummy_context())) + return __audit_log_capset(pid, eff, inh, perm); + return 0; +} + extern int audit_n_rules; extern int audit_signals; #else @@ -544,6 +553,7 @@ extern int audit_signals; #define audit_mq_notify(d,n) ({ 0; }) #define audit_mq_getsetattr(d,s) ({ 0; }) #define audit_log_bprm_fcaps(b, c) 0 +#define audit_log_capset(pid, e, i, p) do { ; } while (0) #define audit_ptrace(t) ((void)0) #define audit_n_rules 0 #define audit_signals 0 diff --git a/kernel/auditsc.c b/kernel/auditsc.c index 6d2487c..0db824f 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -204,6 +204,12 @@ struct audit_aux_data_bprm_fcaps { kernel_cap_t bprm_effective; }; +struct audit_aux_data_capset { + struct audit_aux_data d; + pid_t pid; + struct audit_cap_data cap; +}; + struct audit_tree_refs { struct audit_tree_refs *next; struct audit_chunk *c[31]; @@ -1395,6 +1401,14 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts audit_log_cap(ab, "cap_bprmEff", &axs->bprm_effective); break; } + case AUDIT_CAPSET: { + struct audit_aux_data_capset *axs = (void *)aux; + audit_log_format(ab, "pid=%d", axs->pid); + audit_log_cap(ab, "CapEff", &axs->cap.effective); + audit_log_cap(ab, "CapInh", &axs->cap.inheritable); + audit_log_cap(ab, "CapPrm", &axs->cap.permitted); + break; } + } audit_log_end(ab); } @@ -2573,6 +2587,40 @@ int __audit_log_bprm_fcaps(struct linux_binprm *bprm, struct cpu_vfs_cap_data *c } /** + * __audit_log_capset - store information about the arguments to the capset syscall + * @pid target pid of the capset call + * @eff effective cap set + * @inh inheritible cap set + * @perm permited cap set + * + * Record the aguments userspace sent to sys_capset for later printing by the + * audit system if applicable + */ +int __audit_log_capset(pid_t pid, kernel_cap_t *eff, kernel_cap_t *inh, kernel_cap_t *perm) +{ + struct audit_aux_data_capset *ax; + struct audit_context *context = current->audit_context; + + if (likely(!audit_enabled || !context || context->dummy)) + return 0; + + ax = kmalloc(sizeof(*ax), GFP_KERNEL); + if (!ax) + return -ENOMEM; + + ax->d.type = AUDIT_CAPSET; + ax->d.next = context->aux; + context->aux = (void *)ax; + + ax->pid = pid; + ax->cap.effective = *eff; + ax->cap.inheritable = *eff; + ax->cap.permitted = *perm; + + return 0; +} + +/** * audit_core_dumps - record information about processes that end abnormally * @signr: signal value * diff --git a/kernel/capability.c b/kernel/capability.c index 33e51e7..3d7fc70 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -7,6 +7,7 @@ * 30 May 2002: Cleanup, Robert M. Love <rml(a)tech9.net&gt; */ +#include <linux/audit.h> #include <linux/capability.h> #include <linux/mm.h> #include <linux/module.h> @@ -457,6 +458,8 @@ asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data) i++; } + audit_log_capset(pid, &effective, &inheritable, &permitted); + if (pid && (pid != task_pid_vnr(current))) ret = do_sys_capset_other_tasks(pid, &effective, &inheritable, &permitted);