As part of preparing SELinux for submission to mainline 2.5, the SELinux API is being reworked based on earlier discussions (starting when sys_security was removed from 2.5). As a preliminary step toward submitting SELinux, I'd like to request comments on a new process attribute API for security modules that is implemented via nodes in a /proc/PID/attr directory (credit for that idea goes to Al Viro). This message includes a patch against 2.5.67 (also available from http://www.nsa.gov/lk/A01proc.patch.gz) that implements the changes to the base kernel and the LSM framework to support such a process attribute API. You can obtain a full SELinux patch against 2.5.67 that includes these changes along with the SELinux code that uses them from http://www.nsa.gov/selinux/lk/2.5.67-selinux1.patch.gz, and some relevant userland components from http://www.nsa.gov/selinux/lk/selinux-2.5.tgz. Note that the full SELinux patch also contains some other changes to the base kernel and LSM framework that will be submitted as separate RFCs. The patch below implements a /proc/PID/attr directory with three nodes that can be read and written to get and set the corresponding attribute values. The get and set operations are implemented by the security module using the getprocattr and setprocattr hook functions. The intended meaning of the three nodes is described below, along with an explanation of the SELinux semantics as an example of how they are used: 1) /proc/PID/attr/current represents the current attributes of the process. In SELinux, this node is used to get the security context of a process, but not to set the security context (a write is always denied), since SELinux limits process security transitions to execve (see below). Other security modules may choose to support set operations via writes to this node, and the patch allows for such usage. 2) /proc/PID/attr/exec represents the attributes to assign to the process upon a subsequent execve call. A write to this node followed by an execve replaces the execve_secure call of the original SELinux API. This is needed to support role/domain transitions in SELinux, and execve is the preferred point to make such transitions because it offers better control over the initialization of the process in the new security label and the inheritance of state. In SELinux, this attribute is reset on execve after use so that the new program reverts to the default behavior for any exec calls that it may make. In SELinux, a process can only set its own /proc/PID/attr/exec attribute. 3) /proc/PID/attr/fscreate represents the attributes to assign to files created by subsequent calls to open, mkdir, symlink, and mknod. A write to this node followed by a file creation call replaces the extended file creation calls of the original SELinux API. This call is necessary to support creation of a file in a secure state, so that there is no risk of inappropriate access being obtained between the time of creation and the time that attributes are set. Using a single default based on the parent directory is inadequate, e.g. /etc/shadow and /etc/passwd require different security protections, but are re-created in the same parent directory on each transaction. In SELinux, this attribute is also reset on execve so that the new program reverts to the default behavior for any file creation calls it may make, but the attribute will persist across multiple file creation calls within a program unless it is explicitly reset. In SELinux, a process can only set its own /proc/PID/attr/fscreate attribute. fs/proc/base.c | 250 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/security.h | 23 ++++ security/dummy.c | 12 ++ 3 files changed, 285 insertions(+) Index: linux-2.5/fs/proc/base.c diff -u linux-2.5/fs/proc/base.c:1.1.1.2 linux-2.5/fs/proc/base.c:1.5 --- linux-2.5/fs/proc/base.c:1.1.1.2 Tue Apr 8 09:47:57 2003 +++ linux-2.5/fs/proc/base.c Tue Apr 8 10:15:57 2003 @@ -58,6 +58,10 @@ PROC_PID_MAPS, PROC_PID_MOUNTS, PROC_PID_WCHAN, + PROC_PID_ATTR, + PROC_PID_ATTR_CURRENT, + PROC_PID_ATTR_EXEC, + PROC_PID_ATTR_FSCREATE, PROC_PID_FD_DIR = 0x8000, /* 0x8000-0xffff */ }; @@ -82,11 +86,18 @@ E(PROC_PID_ROOT, "root", S_IFLNK|S_IRWXUGO), E(PROC_PID_EXE, "exe", S_IFLNK|S_IRWXUGO), E(PROC_PID_MOUNTS, "mounts", S_IFREG|S_IRUGO), + E(PROC_PID_ATTR, "attr", S_IFDIR|S_IRUGO|S_IXUGO), #ifdef CONFIG_KALLSYMS E(PROC_PID_WCHAN, "wchan", S_IFREG|S_IRUGO), #endif {0,0,NULL,0} }; +static struct pid_entry attr_stuff[] = { + E(PROC_PID_ATTR_CURRENT, "current", S_IFREG|S_IRUGO|S_IWUSR), + E(PROC_PID_ATTR_EXEC, "exec", S_IFREG|S_IRUGO|S_IWUSR), + E(PROC_PID_ATTR_FSCREATE, "fscreate", S_IFREG|S_IRUGO|S_IWUSR), + {0,0,NULL,0} +}; #undef E static inline struct task_struct *proc_task(struct inode *inode) @@ -961,6 +972,240 @@ .permission = proc_permission, }; +static int proc_attr_readdir(struct file * filp, + void * dirent, filldir_t filldir) +{ + int i; + int pid, ino; + struct inode *inode = filp->f_dentry->d_inode; + struct pid_entry *p; + int ret = 0; + + lock_kernel(); + + pid = proc_task(inode)->pid; + if (!pid) { + ret = -ENOENT; + goto out; + } + i = filp->f_pos; + switch (i) { + case 0: + if (filldir(dirent, ".", 1, i, inode->i_ino, DT_DIR) < 0) + goto out; + i++; + filp->f_pos++; + /* fall through */ + case 1: + ino = fake_ino(pid, PROC_PID_INO); + if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0) + goto out; + i++; + filp->f_pos++; + /* fall through */ + default: + i -= 2; + if (i>=sizeof(attr_stuff)/sizeof(attr_stuff[0])) { + ret = 1; + goto out; + } + p = attr_stuff + i; + while (p->name) { + if (filldir(dirent, p->name, p->len, filp->f_pos, + fake_ino(pid, p->type), p->mode >> 12) < 0) + goto out; + filp->f_pos++; + p++; + } + } + + ret = 1; +out: + unlock_kernel(); + return ret; +} + +#define ATTRGET(name) \ +static ssize_t proc_pid_attr_get##name(struct task_struct *task, char *buffer, size_t count) \ +{ \ + return security_getprocattr(task, #name , buffer, count); \ +} +ATTRGET(current) +ATTRGET(exec) +ATTRGET(fscreate) +#undef ATTRGET + +static ssize_t proc_pid_attr_read(struct file * file, char * buf, + size_t count, loff_t *ppos, + int (*attr_read)(struct task_struct *task, char *page, size_t count)) +{ + struct inode * inode = file->f_dentry->d_inode; + unsigned long page; + ssize_t length; + ssize_t end; + struct task_struct *task = proc_task(inode); + + if (count > PAGE_SIZE) + count = PAGE_SIZE; + if (!(page = __get_free_page(GFP_KERNEL))) + return -ENOMEM; + + length = attr_read(task, (char*)page, count); + if (length < 0) { + free_page(page); + return length; + } + /* Static 4kB (or whatever) block capacity */ + if (*ppos >= length) { + free_page(page); + return 0; + } + if (count + *ppos > length) + count = length - *ppos; + end = count + *ppos; + copy_to_user(buf, (char *) page + *ppos, count); + *ppos = end; + free_page(page); + return count; +} + +#define ATTRREAD(name) \ +static ssize_t proc_pid_attr_read##name(struct file * file, \ + char * buf, \ + size_t count, loff_t *ppos) \ +{ \ + return proc_pid_attr_read(file, buf, count, ppos, proc_pid_attr_get##name); \ +} +ATTRREAD(current); +ATTRREAD(exec); +ATTRREAD(fscreate); +#undef ATTRREAD + +#define ATTRSET(name) \ +static ssize_t proc_pid_attr_set##name(struct task_struct *task, char *buffer, size_t count) \ +{ \ + return security_setprocattr(task, #name , buffer, count); \ +} +ATTRSET(current) +ATTRSET(exec) +ATTRSET(fscreate) +#undef ATTRSET + +static ssize_t proc_pid_attr_write(struct file * file, const char * buf, + size_t count, loff_t *ppos, + int (*attr_write)(struct task_struct *task, char *page, size_t count)) +{ + struct inode * inode = file->f_dentry->d_inode; + char *page; + ssize_t length; + struct task_struct *task = proc_task(inode); + + if (count > PAGE_SIZE) + count = PAGE_SIZE; + if (*ppos != 0) { + /* No partial writes. */ + return -EINVAL; + } + page = (char*)__get_free_page(GFP_USER); + if (!page) + return -ENOMEM; + length = -EFAULT; + if (copy_from_user(page, buf, count)) + goto out; + + length = attr_write(task, page, count); +out: + free_page((unsigned long) page); + return length; +} + +#define ATTRWRITE(name) \ +static ssize_t proc_pid_attr_write##name(struct file * file, \ + const char * buf, \ + size_t count, loff_t *ppos) \ +{ \ + return proc_pid_attr_write(file, buf, count, ppos, proc_pid_attr_set##name); \ +} +ATTRWRITE(current); +ATTRWRITE(exec); +ATTRWRITE(fscreate); +#undef ATTRWRITE + +#define ATTROPS(name) \ +static struct file_operations proc_pid_attr_##name##_operations = { \ + .read = proc_pid_attr_read##name, \ + .write = proc_pid_attr_write##name, \ +}; +ATTROPS(current); +ATTROPS(exec); +ATTROPS(fscreate); +#undef ATTROPS + +static struct dentry *proc_attr_lookup(struct inode *dir, struct dentry *dentry) +{ + struct inode *inode; + int error; + struct task_struct *task = proc_task(dir); + struct pid_entry *p; + struct proc_inode *ei; + + error = -ENOENT; + inode = NULL; + + for (p = attr_stuff; p->name; p++) { + if (p->len != dentry->d_name.len) + continue; + if (!memcmp(dentry->d_name.name, p->name, p->len)) + break; + } + if (!p->name) + goto out; + + error = -EINVAL; + inode = proc_pid_make_inode(dir->i_sb, task, p->type); + if (!inode) + goto out; + + ei = PROC_I(inode); + inode->i_mode = p->mode; + /* + * Yes, it does not scale. And it should not. Don't add + * new entries into /proc/<pid>/attr without very good reasons. + */ + switch(p->type) { + case PROC_PID_ATTR_CURRENT: + inode->i_fop = &proc_pid_attr_current_operations; + break; + case PROC_PID_ATTR_EXEC: + inode->i_fop = &proc_pid_attr_exec_operations; + break; + case PROC_PID_ATTR_FSCREATE: + inode->i_fop = &proc_pid_attr_fscreate_operations; + break; + default: + printk("procfs: impossible type (%d)",p->type); + iput(inode); + return ERR_PTR(-EINVAL); + } + dentry->d_op = &pid_dentry_operations; + d_add(dentry, inode); + if (!proc_task(dentry->d_inode)->pid) + d_drop(dentry); + return NULL; + +out: + return ERR_PTR(error); +} + +static struct file_operations proc_attr_operations = { + .read = generic_read_dir, + .readdir = proc_attr_readdir, +}; + +static struct inode_operations proc_attr_inode_operations = { + .lookup = proc_attr_lookup, +}; + /* SMP-safe */ static struct dentry *proc_base_lookup(struct inode *dir, struct dentry *dentry) { @@ -1040,6 +1285,11 @@ break; case PROC_PID_MOUNTS: inode->i_fop = &proc_mounts_operations; + break; + case PROC_PID_ATTR: + inode->i_nlink = 2; + inode->i_op = &proc_attr_inode_operations; + inode->i_fop = &proc_attr_operations; break; #ifdef CONFIG_KALLSYMS case PROC_PID_WCHAN: Index: linux-2.5/include/linux/security.h diff -u linux-2.5/include/linux/security.h:1.1.1.2 linux-2.5/include/linux/security.h:1.13 --- linux-2.5/include/linux/security.h:1.1.1.2 Wed Mar 19 09:54:58 2003 +++ linux-2.5/include/linux/security.h Tue Apr 1 15:27:53 2003 @@ -1123,6 +1128,9 @@ void (*d_instantiate) (struct dentry *dentry, struct inode *inode); + int (*getprocattr)(struct task_struct *p, char *name, void *value, size_t size); + int (*setprocattr)(struct task_struct *p, char *name, void *value, size_t size); + #ifdef CONFIG_SECURITY_NETWORK int (*unix_stream_connect) (struct socket * sock, struct socket * other, struct sock * newsk); @@ -1755,6 +1769,16 @@ security_ops->d_instantiate (dentry, inode); } +static inline int security_getprocattr(struct task_struct *p, char *name, void *value, size_t size) +{ + return security_ops->getprocattr(p, name, value, size); +} + +static inline int security_setprocattr(struct task_struct *p, char *name, void *value, size_t size) +{ + return security_ops->setprocattr(p, name, value, size); +} + static inline int security_netlink_send(struct sk_buff * skb) { return security_ops->netlink_send(skb); @@ -2339,6 +2367,16 @@ static inline void security_d_instantiate (struct dentry *dentry, struct inode *inode) { } + +static inline int security_getprocattr(struct task_struct *p, char *name, void *value, size_t size) +{ + return -ENOSYS; +} + +static inline int security_setprocattr(struct task_struct *p, char *name, void *value, size_t size) +{ + return -ENOSYS; +} /* * The netlink capability defaults need to be used inline by default Index: linux-2.5/security/dummy.c diff -u linux-2.5/security/dummy.c:1.1.1.2 linux-2.5/security/dummy.c:1.11 --- linux-2.5/security/dummy.c:1.1.1.2 Wed Mar 19 09:59:17 2003 +++ linux-2.5/security/dummy.c Mon Mar 31 16:37:37 2003 @@ -736,6 +741,16 @@ return; } +static inline int dummy_getprocattr(struct task_struct *p, char *name, void *value, size_t size) +{ + return -ENOSYS; +} + +static inline int dummy_setprocattr(struct task_struct *p, char *name, void *value, size_t size) +{ + return -ENOSYS; +} + struct security_operations dummy_security_ops; @@ -860,6 +876,8 @@ set_to_dummy_if_null(ops, register_security); set_to_dummy_if_null(ops, unregister_security); set_to_dummy_if_null(ops, d_instantiate); + set_to_dummy_if_null(ops, getprocattr); + set_to_dummy_if_null(ops, setprocattr); #ifdef CONFIG_SECURITY_NETWORK set_to_dummy_if_null(ops, unix_stream_connect); set_to_dummy_if_null(ops, unix_may_send); _______________________________________________ linux-security-module mailing list linux-security-moduleat_private http://mail.wirex.com/mailman/listinfo/linux-security-module
This archive was generated by hypermail 2b30 : Tue Apr 08 2003 - 13:19:33 PDT