security/ccsecurity/domain.c

/*
 * security/ccsecurity/domain.c
 *
 * Copyright (C) 2005-2009  NTT DATA CORPORATION
 *
 * Version: 1.7.0-pre   2009/08/08
 *
 * This file is applicable to both 2.4.30 and 2.6.11 and later.
 * See README.ccs for ChangeLog.
 *
 */

#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/version.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 0)
#include <linux/namei.h>
#include <linux/mount.h>
#endif
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 30)
#include <linux/fs_struct.h>
#endif
#include "internal.h"

/* For compatibility with older kernels. */
#ifndef for_each_process
#define for_each_process for_each_task
#endif

/* Variables definitions.*/

/* The initial domain. */
struct ccs_domain_info ccs_kernel_domain;

/* The list for "struct ccs_domain_info". */
LIST_HEAD(ccs_domain_list);

/**
 * ccs_get_last_name - Get last component of a domainname.
 *
 * @domain: Pointer to "struct ccs_domain_info".
 *
 * Returns the last component of the domainname.
 */
const char *ccs_get_last_name(const struct ccs_domain_info *domain)
{
        const char *cp0 = domain->domainname->name;
        const char *cp1 = strrchr(cp0, ' ');
        if (cp1)
                return cp1 + 1;
        return cp0;
}

/**
 * ccs_audit_execute_handler_log - Audit execute_handler log.
 *
 * @ee:         Pointer to "struct ccs_execve_entry".
 * @is_default: True if it is "execute_handler" log.
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_audit_execute_handler_log(struct ccs_execve_entry *ee,
                                         const bool is_default)
{
        struct ccs_request_info *r = &ee->r;
        const char *handler = ee->handler->name;
        r->mode = ccs_flags(r->domain, CCS_MAC_EXECUTE);
        return ccs_write_audit_log(true, r, "%s %s\n",
                                   is_default ? CCS_KEYWORD_EXECUTE_HANDLER :
                                   CCS_KEYWORD_DENIED_EXECUTE_HANDLER, handler);
}

/**
 * ccs_audit_domain_creation_log - Audit domain creation log.
 *
 * @domain:  Pointer to "struct ccs_domain_info".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_audit_domain_creation_log(struct ccs_domain_info *domain)
{
        int error;
        struct ccs_request_info r;
        ccs_init_request_info(&r, domain, CCS_MAC_EXECUTE);
        error = ccs_write_audit_log(false, &r, "use_profile %u\n", r.profile);
        return error;
}

/* The list for "struct ccs_domain_initializer_entry". */
LIST_HEAD(ccs_domain_initializer_list);

/**
 * ccs_update_domain_initializer_entry - Update "struct ccs_domain_initializer_entry" list.
 *
 * @domainname: The name of domain. May be NULL.
 * @program:    The name of program.
 * @is_not:     True if it is "no_initialize_domain" entry.
 * @is_delete:  True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_update_domain_initializer_entry(const char *domainname,
                                               const char *program,
                                               const bool is_not,
                                               const bool is_delete)
{
        struct ccs_domain_initializer_entry *entry = NULL;
        struct ccs_domain_initializer_entry *ptr;
        struct ccs_domain_initializer_entry e = { .is_not = is_not };
        int error = is_delete ? -ENOENT : -ENOMEM;
        if (!ccs_is_correct_path(program, 1, -1, -1))
                return -EINVAL; /* No patterns allowed. */
        if (domainname) {
                if (!ccs_is_domain_def(domainname) &&
                    ccs_is_correct_path(domainname, 1, -1, -1))
                        e.is_last_name = true;
                else if (!ccs_is_correct_domain(domainname))
                        return -EINVAL;
                e.domainname = ccs_get_name(domainname);
                if (!e.domainname)
                        goto out;
        }
        e.program = ccs_get_name(program);
        if (!e.program)
                goto out;
        if (!is_delete)
                entry = kmalloc(sizeof(e), GFP_KERNEL);
        mutex_lock(&ccs_policy_lock);
        list_for_each_entry_rcu(ptr, &ccs_domain_initializer_list, list) {
                if (ccs_memcmp(ptr, &e, offsetof(typeof(e), is_not),
                               sizeof(e)))
                        continue;
                ptr->is_deleted = is_delete;
                error = 0;
                break;
        }
        if (!is_delete && error && ccs_commit_ok(entry, &e, sizeof(e))) {
                list_add_tail_rcu(&entry->list, &ccs_domain_initializer_list);
                entry = NULL;
                error = 0;
        }
        mutex_unlock(&ccs_policy_lock);
 out:
        ccs_put_name(e.domainname);
        ccs_put_name(e.program);
        kfree(entry);
        return error;
}

/**
 * ccs_read_domain_initializer_policy - Read "struct ccs_domain_initializer_entry" list.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns true on success, false otherwise.
 *
 * Caller holds ccs_read_lock().
 */
bool ccs_read_domain_initializer_policy(struct ccs_io_buffer *head)
{
        struct list_head *pos;
        bool done = true;
        ccs_assert_read_lock();
        list_for_each_cookie(pos, head->read_var2,
                             &ccs_domain_initializer_list) {
                const char *no;
                const char *from = "";
                const char *domain = "";
                struct ccs_domain_initializer_entry *ptr;
                ptr = list_entry(pos, struct ccs_domain_initializer_entry,
                                  list);
                if (ptr->is_deleted)
                        continue;
                no = ptr->is_not ? "no_" : "";
                if (ptr->domainname) {
                        from = " from ";
                        domain = ptr->domainname->name;
                }
                done = ccs_io_printf(head,
                                     "%s" CCS_KEYWORD_INITIALIZE_DOMAIN "%s%s%s\n",
                                     no, ptr->program->name, from, domain);
                if (!done)
                        break;
        }
        return done;
}

/**
 * ccs_write_domain_initializer_policy - Write "struct ccs_domain_initializer_entry" list.
 *
 * @data:      String to parse.
 * @is_not:    True if it is "no_initialize_domain" entry.
 * @is_delete: True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 */
int ccs_write_domain_initializer_policy(char *data, const bool is_not,
                                        const bool is_delete)
{
        char *cp = strstr(data, " from ");
        if (cp) {
                *cp = '\0';
                return ccs_update_domain_initializer_entry(cp + 6, data,
                                                           is_not, is_delete);
        }
        return ccs_update_domain_initializer_entry(NULL, data, is_not,
                                                   is_delete);
}

/**
 * ccs_is_domain_initializer - Check whether the given program causes domainname reinitialization.
 *
 * @domainname: The name of domain.
 * @program:    The name of program.
 * @last_name:  The last component of @domainname.
 *
 * Returns true if executing @program reinitializes domain transition,
 * false otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static bool ccs_is_domain_initializer(const struct ccs_path_info *domainname,
                                      const struct ccs_path_info *program,
                                      const struct ccs_path_info *last_name)
{
        struct ccs_domain_initializer_entry *ptr;
        bool flag = false;
        ccs_assert_read_lock();
        list_for_each_entry_rcu(ptr, &ccs_domain_initializer_list, list) {
                if (ptr->is_deleted)
                        continue;
                if (ptr->domainname) {
                        if (!ptr->is_last_name) {
                                if (ptr->domainname != domainname)
                                        continue;
                        } else {
                                if (ccs_pathcmp(ptr->domainname, last_name))
                                        continue;
                        }
                }
                if (ccs_pathcmp(ptr->program, program))
                        continue;
                if (ptr->is_not) {
                        flag = false;
                        break;
                }
                flag = true;
        }
        return flag;
}

/* The list for "struct ccs_domain_keeper_entry". */
LIST_HEAD(ccs_domain_keeper_list);

/**
 * ccs_update_domain_keeper_entry - Update "struct ccs_domain_keeper_entry" list.
 *
 * @domainname: The name of domain.
 * @program:    The name of program. May be NULL.
 * @is_not:     True if it is "no_keep_domain" entry.
 * @is_delete:  True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_update_domain_keeper_entry(const char *domainname,
                                          const char *program,
                                          const bool is_not,
                                          const bool is_delete)
{
        struct ccs_domain_keeper_entry *entry = NULL;
        struct ccs_domain_keeper_entry *ptr;
        struct ccs_domain_keeper_entry e = { .is_not = is_not };
        int error = is_delete ? -ENOENT : -ENOMEM;
        if (!ccs_is_domain_def(domainname) &&
            ccs_is_correct_path(domainname, 1, -1, -1))
                e.is_last_name = true;
        else if (!ccs_is_correct_domain(domainname))
                return -EINVAL;
        if (program) {
                if (!ccs_is_correct_path(program, 1, -1, -1))
                        return -EINVAL;
                e.program = ccs_get_name(program);
                if (!e.program)
                        goto out;
        }
        e.domainname = ccs_get_name(domainname);
        if (!e.domainname)
                goto out;
        if (!is_delete)
                entry = kmalloc(sizeof(e), GFP_KERNEL);
        mutex_lock(&ccs_policy_lock);
        list_for_each_entry_rcu(ptr, &ccs_domain_keeper_list, list) {
                if (ccs_memcmp(ptr, &e, offsetof(typeof(e), is_not),
                               sizeof(e)))
                        continue;
                ptr->is_deleted = is_delete;
                error = 0;
                break;
        }
        if (!is_delete && error && ccs_commit_ok(entry, &e, sizeof(e))) {
                list_add_tail_rcu(&entry->list, &ccs_domain_keeper_list);
                entry = NULL;
                error = 0;
        }
        mutex_unlock(&ccs_policy_lock);
 out:
        ccs_put_name(e.domainname);
        ccs_put_name(e.program);
        kfree(entry);
        return error;
}

/**
 * ccs_write_domain_keeper_policy - Write "struct ccs_domain_keeper_entry" list.
 *
 * @data:      String to parse.
 * @is_not:    True if it is "no_keep_domain" entry.
 * @is_delete: True if it is a delete request.
 *
 */
int ccs_write_domain_keeper_policy(char *data, const bool is_not,
                                   const bool is_delete)
{
        char *cp = strstr(data, " from ");
        if (cp) {
                *cp = '\0';
                return ccs_update_domain_keeper_entry(cp + 6, data,
                                                      is_not, is_delete);
        }
        return ccs_update_domain_keeper_entry(data, NULL, is_not, is_delete);
}

/**
 * ccs_read_domain_keeper_policy - Read "struct ccs_domain_keeper_entry" list.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns true on success, false otherwise.
 *
 * Caller holds ccs_read_lock().
 */
bool ccs_read_domain_keeper_policy(struct ccs_io_buffer *head)
{
        struct list_head *pos;
        bool done = true;
        ccs_assert_read_lock();
        list_for_each_cookie(pos, head->read_var2,
                             &ccs_domain_keeper_list) {
                struct ccs_domain_keeper_entry *ptr;
                const char *no;
                const char *from = "";
                const char *program = "";
                ptr = list_entry(pos, struct ccs_domain_keeper_entry, list);
                if (ptr->is_deleted)
                        continue;
                no = ptr->is_not ? "no_" : "";
                if (ptr->program) {
                        from = " from ";
                        program = ptr->program->name;
                }
                done = ccs_io_printf(head, "%s" CCS_KEYWORD_KEEP_DOMAIN
                                     "%s%s%s\n", no, program, from,
                                     ptr->domainname->name);
                if (!done)
                        break;
        }
        return done;
}

/**
 * ccs_is_domain_keeper - Check whether the given program causes domain transition suppression.
 *
 * @domainname: The name of domain.
 * @program:    The name of program.
 * @last_name:  The last component of @domainname.
 *
 * Returns true if executing @program supresses domain transition,
 * false otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static bool ccs_is_domain_keeper(const struct ccs_path_info *domainname,
                                 const struct ccs_path_info *program,
                                 const struct ccs_path_info *last_name)
{
        struct ccs_domain_keeper_entry *ptr;
        bool flag = false;
        ccs_assert_read_lock();
        list_for_each_entry_rcu(ptr, &ccs_domain_keeper_list, list) {
                if (ptr->is_deleted)
                        continue;
                if (!ptr->is_last_name) {
                        if (ptr->domainname != domainname)
                                continue;
                } else {
                        if (ccs_pathcmp(ptr->domainname, last_name))
                                continue;
                }
                if (ptr->program && ccs_pathcmp(ptr->program, program))
                        continue;
                if (ptr->is_not) {
                        flag = false;
                        break;
                }
                flag = true;
        }
        return flag;
}

/* The list for "struct ccs_aggregator_entry". */
LIST_HEAD(ccs_aggregator_list);

/**
 * ccs_update_aggregator_entry - Update "struct ccs_aggregator_entry" list.
 *
 * @original_name:   The original program's name.
 * @aggregated_name: The aggregated program's name.
 * @is_delete:       True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_update_aggregator_entry(const char *original_name,
                                       const char *aggregated_name,
                                       const bool is_delete)
{
        struct ccs_aggregator_entry *entry = NULL;
        struct ccs_aggregator_entry *ptr;
        struct ccs_aggregator_entry e = { };
        int error = is_delete ? -ENOENT : -ENOMEM;
        if (!ccs_is_correct_path(original_name, 1, 0, -1) ||
            !ccs_is_correct_path(aggregated_name, 1, -1, -1))
                return -EINVAL;
        e.original_name = ccs_get_name(original_name);
        e.aggregated_name = ccs_get_name(aggregated_name);
        if (!e.original_name || !e.aggregated_name)
                goto out;
        if (!is_delete)
                entry = kmalloc(sizeof(e), GFP_KERNEL);
        mutex_lock(&ccs_policy_lock);
        list_for_each_entry_rcu(ptr, &ccs_aggregator_list, list) {
                if (ccs_memcmp(ptr, &e, offsetof(typeof(e), original_name),
                               sizeof(e)))
                        continue;
                ptr->is_deleted = is_delete;
                error = 0;
                break;
        }
        if (!is_delete && error && ccs_commit_ok(entry, &e, sizeof(e))) {
                list_add_tail_rcu(&entry->list, &ccs_aggregator_list);
                entry = NULL;
                error = 0;
        }
        mutex_unlock(&ccs_policy_lock);
 out:
        ccs_put_name(e.original_name);
        ccs_put_name(e.aggregated_name);
        kfree(entry);
        return error;
}

/**
 * ccs_read_aggregator_policy - Read "struct ccs_aggregator_entry" list.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns true on success, false otherwise.
 *
 * Caller holds ccs_read_lock().
 */
bool ccs_read_aggregator_policy(struct ccs_io_buffer *head)
{
        struct list_head *pos;
        bool done = true;
        ccs_assert_read_lock();
        list_for_each_cookie(pos, head->read_var2, &ccs_aggregator_list) {
                struct ccs_aggregator_entry *ptr;
                ptr = list_entry(pos, struct ccs_aggregator_entry, list);
                if (ptr->is_deleted)
                        continue;
                done = ccs_io_printf(head, CCS_KEYWORD_AGGREGATOR "%s %s\n",
                                     ptr->original_name->name,
                                     ptr->aggregated_name->name);
                if (!done)
                        break;
        }
        return done;
}

/**
 * ccs_write_aggregator_policy - Write "struct ccs_aggregator_entry" list.
 *
 * @data:      String to parse.
 * @is_delete: True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 */
int ccs_write_aggregator_policy(char *data, const bool is_delete)
{
        char *w[2];
        if (!ccs_tokenize(data, w, sizeof(w)) || !w[1][0])
                return -EINVAL;
        return ccs_update_aggregator_entry(w[0], w[1], is_delete);
}

/* Domain create/delete handler. */

/**
 * ccs_delete_domain - Delete a domain.
 *
 * @domainname: The name of domain.
 *
 * Returns 0.
 */
int ccs_delete_domain(char *domainname)
{
        struct ccs_domain_info *domain;
        struct ccs_path_info name;
        name.name = domainname;
        ccs_fill_path_info(&name);
        mutex_lock(&ccs_policy_lock);
        /* Is there an active domain? */
        list_for_each_entry_rcu(domain, &ccs_domain_list, list) {
                /* Never delete ccs_kernel_domain */
                if (domain == &ccs_kernel_domain)
                        continue;
                if (domain->is_deleted ||
                    ccs_pathcmp(domain->domainname, &name))
                        continue;
                domain->is_deleted = true;
                break;
        }
        mutex_unlock(&ccs_policy_lock);
        return 0;
}

/**
 * ccs_find_or_assign_new_domain - Create a domain.
 *
 * @domainname: The name of domain.
 * @profile:    Profile number to assign if the domain was newly created.
 *
 * Returns pointer to "struct ccs_domain_info" on success, NULL otherwise.
 */
struct ccs_domain_info *ccs_find_or_assign_new_domain(const char *domainname,
                                                      const u8 profile)
{
        struct ccs_domain_info *entry;
        struct ccs_domain_info *domain;
        const struct ccs_path_info *saved_domainname;
        bool found = false;

        if (!ccs_is_correct_domain(domainname))
                return NULL;
        saved_domainname = ccs_get_name(domainname);
        if (!saved_domainname)
                return NULL;
        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        mutex_lock(&ccs_policy_lock);
        list_for_each_entry_rcu(domain, &ccs_domain_list, list) {
                if (domain->is_deleted ||
                    ccs_pathcmp(saved_domainname, domain->domainname))
                        continue;
                found = true;
                break;
        }
        if (!found && ccs_memory_ok(entry, sizeof(*entry))) {
                INIT_LIST_HEAD(&entry->acl_info_list);
                entry->domainname = saved_domainname;
                saved_domainname = NULL;
                entry->profile = profile;
                list_add_tail_rcu(&entry->list, &ccs_domain_list);
                domain = entry;
                entry = NULL;
                found = true;
        }
        mutex_unlock(&ccs_policy_lock);
        ccs_put_name(saved_domainname);
        kfree(entry);
        return found ? domain : NULL;
}

/**
 * ccs_find_next_domain - Find a domain.
 *
 * @ee: Pointer to "struct ccs_execve_entry".
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_find_next_domain(struct ccs_execve_entry *ee)
{
        struct ccs_request_info *r = &ee->r;
        const struct ccs_path_info *handler = ee->handler;
        struct ccs_domain_info *domain = NULL;
        const char *old_domain_name = r->domain->domainname->name;
        struct linux_binprm *bprm = ee->bprm;
        const u8 mode = r->mode;
        const bool is_enforce = (mode == 3);
        const u32 ccs_flags = current->ccs_flags;
        struct ccs_path_info rn = { }; /* real name */
        struct ccs_path_info ln; /* last name */
        int retval;
        bool need_kfree = false;
        ccs_assert_read_lock();
 retry:
        current->ccs_flags = ccs_flags;
        r->cond = NULL;
        /* Get symlink's pathname of program. */
        retval = ccs_symlink_path(bprm->filename, &rn);
        if (retval < 0)
                goto out;
        need_kfree = true;

        ln.name = ccs_get_last_name(r->domain);
        ccs_fill_path_info(&ln);

        if (handler) {
                if (ccs_pathcmp(&rn, handler)) {
                        /* Failed to verify execute handler. */
                        static u8 counter = 20;
                        if (counter) {
                                counter--;
                                printk(KERN_WARNING "Failed to verify: %s\n",
                                       handler->name);
                        }
                        goto out;
                }
                goto calculate_domain;
        }

        /* Check 'aggregator' directive. */
        {
                struct ccs_aggregator_entry *ptr;
                /* Is this program allowed to be aggregated? */
                list_for_each_entry_rcu(ptr, &ccs_aggregator_list, list) {
                        if (ptr->is_deleted ||
                            !ccs_path_matches_pattern(&rn, ptr->original_name))
                                continue;
                        kfree(rn.name);
                        need_kfree = false;
                        rn = *ptr->aggregated_name;
                        break;
                }
        }

        /* Check execute permission. */
        r->mode = mode;
        retval = ccs_exec_perm(r, &rn);
        if (retval == 1)
                goto retry;
        if (retval < 0)
                goto out;

 calculate_domain:
        if (ccs_is_domain_initializer(r->domain->domainname, &rn, &ln)) {
                /* Transit to the child of ccs_kernel_domain domain. */
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, ROOT_NAME " " "%s",
                         rn.name);
        } else if (r->domain == &ccs_kernel_domain && !ccs_policy_loaded) {
                /*
                 * Needn't to transit from kernel domain before starting
                 * /sbin/init. But transit from kernel domain if executing
                 * initializers because they might start before /sbin/init.
                 */
                domain = r->domain;
        } else if (ccs_is_domain_keeper(r->domain->domainname, &rn, &ln)) {
                /* Keep current domain. */
                domain = r->domain;
        } else {
                /* Normal domain transition. */
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "%s %s",
                         old_domain_name, rn.name);
        }
        if (domain || strlen(ee->tmp) >= CCS_EXEC_TMPSIZE - 10)
                goto done;
        domain = ccs_find_domain(ee->tmp);
        if (domain)
                goto done;
        if (is_enforce) {
                int error = ccs_supervisor(r, "# wants to create domain\n"
                                           "%s\n", ee->tmp);
                if (error == 1)
                        goto retry;
                if (error < 0)
                        goto done;
        }
        domain = ccs_find_or_assign_new_domain(ee->tmp, r->profile);
        if (domain)
                ccs_audit_domain_creation_log(r->domain);
 done:
        if (!domain) {
                printk(KERN_WARNING "ERROR: Domain '%s' not defined.\n",
                       ee->tmp);
                if (is_enforce)
                        retval = -EPERM;
                else {
                        retval = 0;
                        r->domain->domain_transition_failed = true;
                }
        } else {
                retval = 0;
        }
 out:
        if (domain)
                r->domain = domain;
        if (need_kfree)
                kfree(rn.name);
        return retval;
}

/**
 * ccs_environ - Check permission for environment variable names.
 *
 * @ee: Pointer to "struct ccs_execve_entry".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_environ(struct ccs_execve_entry *ee)
{
        struct ccs_request_info *r = &ee->r;
        struct linux_binprm *bprm = ee->bprm;
        char *arg_ptr = ee->tmp;
        int arg_len = 0;
        unsigned long pos = bprm->p;
        int offset = pos % PAGE_SIZE;
        int argv_count = bprm->argc;
        int envp_count = bprm->envc;
        /* printk(KERN_DEBUG "start %d %d\n", argv_count, envp_count); */
        int error = -ENOMEM;
        if (!r->mode || !envp_count)
                return 0;
        while (error == -ENOMEM) {
                if (!ccs_dump_page(bprm, pos, &ee->dump))
                        goto out;
                pos += PAGE_SIZE - offset;
                /* Read. */
                while (argv_count && offset < PAGE_SIZE) {
                        const char *kaddr = ee->dump.data;
                        if (!kaddr[offset++])
                                argv_count--;
                }
                if (argv_count) {
                        offset = 0;
                        continue;
                }
                while (offset < PAGE_SIZE) {
                        const char *kaddr = ee->dump.data;
                        const unsigned char c = kaddr[offset++];
                        if (c && arg_len < CCS_EXEC_TMPSIZE - 10) {
                                if (c == '=') {
                                        arg_ptr[arg_len++] = '\0';
                                } else if (c == '\\') {
                                        arg_ptr[arg_len++] = '\\';
                                        arg_ptr[arg_len++] = '\\';
                                } else if (c > ' ' && c < 127) {
                                        arg_ptr[arg_len++] = c;
                                } else {
                                        arg_ptr[arg_len++] = '\\';
                                        arg_ptr[arg_len++] = (c >> 6) + '0';
                                        arg_ptr[arg_len++]
                                                = ((c >> 3) & 7) + '0';
                                        arg_ptr[arg_len++] = (c & 7) + '0';
                                }
                        } else {
                                arg_ptr[arg_len] = '\0';
                        }
                        if (c)
                                continue;
                        if (ccs_env_perm(r, arg_ptr)) {
                                error = -EPERM;
                                break;
                        }
                        if (!--envp_count) {
                                error = 0;
                                break;
                        }
                        arg_len = 0;
                }
                offset = 0;
        }
 out:
        if (r->mode != 3)
                error = 0;
        return error;
}

/**
 * ccs_unescape - Unescape escaped string.
 *
 * @dest: String to unescape.
 *
 * Returns nothing.
 */
static void ccs_unescape(unsigned char *dest)
{
        unsigned char *src = dest;
        unsigned char c;
        unsigned char d;
        unsigned char e;
        while (1) {
                c = *src++;
                if (!c)
                        break;
                if (c != '\\') {
                        *dest++ = c;
                        continue;
                }
                c = *src++;
                if (c == '\\') {
                        *dest++ = c;
                        continue;
                }
                if (c < '0' || c > '3')
                        break;
                d = *src++;
                if (d < '0' || d > '7')
                        break;
                e = *src++;
                if (e < '0' || e > '7')
                        break;
                *dest++ = ((c - '0') << 6) + ((d - '0') << 3) + (e - '0');
        }
        *dest = '\0';
}

/**
 * ccs_root_depth - Get number of directories to strip.
 *
 * @dentry: Pointer to "struct dentry".
 * @vfsmnt: Pointer to "struct vfsmount".
 *
 * Returns number of directories to strip.
 */
static inline int ccs_root_depth(struct dentry *dentry, struct vfsmount *vfsmnt)
{
        int depth = 0;
        ccs_realpath_lock();
        for (;;) {
                if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
                        /* Global root? */
                        if (vfsmnt->mnt_parent == vfsmnt)
                                break;
                        dentry = vfsmnt->mnt_mountpoint;
                        vfsmnt = vfsmnt->mnt_parent;
                        continue;
                }
                dentry = dentry->d_parent;
                depth++;
        }
        ccs_realpath_unlock();
        return depth;
}

/**
 * ccs_get_root_depth - return the depth of root directory.
 *
 * Returns number of directories to strip.
 */
static int ccs_get_root_depth(void)
{
        int depth;
        struct dentry *dentry;
        struct vfsmount *vfsmnt;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
        struct path root;
#endif
        read_lock(&current->fs->lock);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
        root = current->fs->root;
        path_get(&current->fs->root);
        dentry = root.dentry;
        vfsmnt = root.mnt;
#else
        dentry = dget(current->fs->root);
        vfsmnt = mntget(current->fs->rootmnt);
#endif
        read_unlock(&current->fs->lock);
        depth = ccs_root_depth(dentry, vfsmnt);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
        path_put(&root);
#else
        dput(dentry);
        mntput(vfsmnt);
#endif
        return depth;
}

static LIST_HEAD(ccs_execve_list);
static DEFINE_SPINLOCK(ccs_execve_list_lock);

/**
 * ccs_allocate_execve_entry - Allocate memory for execve().
 *
 * Returns pointer to "struct ccs_execve_entry" on success, NULL otherwise.
 */
static struct ccs_execve_entry *ccs_allocate_execve_entry(void)
{
        struct ccs_execve_entry *ee = kzalloc(sizeof(*ee), GFP_KERNEL);
        if (!ee)
                return NULL;
        ee->tmp = kzalloc(CCS_EXEC_TMPSIZE, GFP_KERNEL);
        if (!ee->tmp) {
                kfree(ee);
                return NULL;
        }
        ee->reader_idx = ccs_read_lock();
        /* ee->dump->data is allocated by ccs_dump_page(). */
        ee->task = current;
        spin_lock(&ccs_execve_list_lock);
        list_add(&ee->list, &ccs_execve_list);
        spin_unlock(&ccs_execve_list_lock);
        return ee;
}

/**
 * ccs_find_execve_entry - Find ccs_execve_entry of current process.
 *
 * Returns pointer to "struct ccs_execve_entry" on success, NULL otherwise.
 */
static struct ccs_execve_entry *ccs_find_execve_entry(void)
{
        struct task_struct *task = current;
        struct ccs_execve_entry *ee = NULL;
        struct ccs_execve_entry *p;
        spin_lock(&ccs_execve_list_lock);
        list_for_each_entry(p, &ccs_execve_list, list) {
                if (p->task != task)
                        continue;
                ee = p;
                break;
        }
        spin_unlock(&ccs_execve_list_lock);
        return ee;
}

/**
 * ccs_free_execve_entry - Free memory for execve().
 *
 * @ee: Pointer to "struct ccs_execve_entry".
 */
static void ccs_free_execve_entry(struct ccs_execve_entry *ee)
{
        if (!ee)
                return;
        spin_lock(&ccs_execve_list_lock);
        list_del(&ee->list);
        spin_unlock(&ccs_execve_list_lock);
        kfree(ee->handler_path);
        kfree(ee->tmp);
        kfree(ee->dump.data);
        ccs_read_unlock(ee->reader_idx);
        kfree(ee);
}

/**
 * ccs_try_alt_exec - Try to start execute handler.
 *
 * @ee: Pointer to "struct ccs_execve_entry".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_try_alt_exec(struct ccs_execve_entry *ee)
{
        /*
         * Contents of modified bprm.
         * The envp[] in original bprm is moved to argv[] so that
         * the alternatively executed program won't be affected by
         * some dangerous environment variables like LD_PRELOAD.
         *
         * modified bprm->argc
         *    = original bprm->argc + original bprm->envc + 7
         * modified bprm->envc
         *    = 0
         *
         * modified bprm->argv[0]
         *    = the program's name specified by execute_handler
         * modified bprm->argv[1]
         *    = ccs_current_domain()->domainname->name
         * modified bprm->argv[2]
         *    = the current process's name
         * modified bprm->argv[3]
         *    = the current process's information (e.g. uid/gid).
         * modified bprm->argv[4]
         *    = original bprm->filename
         * modified bprm->argv[5]
         *    = original bprm->argc in string expression
         * modified bprm->argv[6]
         *    = original bprm->envc in string expression
         * modified bprm->argv[7]
         *    = original bprm->argv[0]
         *  ...
         * modified bprm->argv[bprm->argc + 6]
         *     = original bprm->argv[bprm->argc - 1]
         * modified bprm->argv[bprm->argc + 7]
         *     = original bprm->envp[0]
         *  ...
         * modified bprm->argv[bprm->envc + bprm->argc + 6]
         *     = original bprm->envp[bprm->envc - 1]
         */
        struct linux_binprm *bprm = ee->bprm;
        struct file *filp;
        int retval;
        const int original_argc = bprm->argc;
        const int original_envc = bprm->envc;
        struct task_struct *task = current;

        /* Close the requested program's dentry. */
        allow_write_access(bprm->file);
        fput(bprm->file);
        bprm->file = NULL;

        /* Invalidate page dump cache. */
        ee->dump.page = NULL;

        /* Move envp[] to argv[] */
        bprm->argc += bprm->envc;
        bprm->envc = 0;

        /* Set argv[6] */
        {
                char *cp = ee->tmp;
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "%d", original_envc);
                retval = copy_strings_kernel(1, &cp, bprm);
                if (retval < 0)
                        goto out;
                bprm->argc++;
        }

        /* Set argv[5] */
        {
                char *cp = ee->tmp;
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "%d", original_argc);
                retval = copy_strings_kernel(1, &cp, bprm);
                if (retval < 0)
                        goto out;
                bprm->argc++;
        }

        /* Set argv[4] */
        {
                retval = copy_strings_kernel(1, &bprm->filename, bprm);
                if (retval < 0)
                        goto out;
                bprm->argc++;
        }

        /* Set argv[3] */
        {
                char *cp = ee->tmp;
                const u32 ccs_flags = task->ccs_flags;
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1,
                         "pid=%d uid=%d gid=%d euid=%d egid=%d suid=%d "
                         "sgid=%d fsuid=%d fsgid=%d state[0]=%u "
                         "state[1]=%u state[2]=%u",
                         (pid_t) sys_getpid(), current_uid(), current_gid(),
                         current_euid(), current_egid(), current_suid(),
                         current_sgid(), current_fsuid(), current_fsgid(),
                         (u8) (ccs_flags >> 24), (u8) (ccs_flags >> 16),
                         (u8) (ccs_flags >> 8));
                retval = copy_strings_kernel(1, &cp, bprm);
                if (retval < 0)
                        goto out;
                bprm->argc++;
        }

        /* Set argv[2] */
        {
                char *exe = (char *) ccs_get_exe();
                if (exe) {
                        retval = copy_strings_kernel(1, &exe, bprm);
                        kfree(exe);
                } else {
                        exe = ee->tmp;
                        snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "<unknown>");
                        retval = copy_strings_kernel(1, &exe, bprm);
                }
                if (retval < 0)
                        goto out;
                bprm->argc++;
        }

        /* Set argv[1] */
        {
                char *cp = ee->tmp;
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "%s",
                         ccs_current_domain()->domainname->name);
                retval = copy_strings_kernel(1, &cp, bprm);
                if (retval < 0)
                        goto out;
                bprm->argc++;
        }

        /* Set argv[0] */
        {
                int depth = ccs_get_root_depth();
                int len = ee->handler->total_len + 1;
                char *cp = kmalloc(len, GFP_KERNEL);
                if (!cp) {
                        retval = ENOMEM;
                        goto out;
                }
                ee->handler_path = cp;
                memmove(cp, ee->handler->name, len);
                ccs_unescape(cp);
                retval = -ENOENT;
                if (!*cp || *cp != '/')
                        goto out;
                /* Adjust root directory for open_exec(). */
                while (depth) {
                        cp = strchr(cp + 1, '/');
                        if (!cp)
                                goto out;
                        depth--;
                }
                memmove(ee->handler_path, cp, strlen(cp) + 1);
                cp = ee->handler_path;
                retval = copy_strings_kernel(1, &cp, bprm);
                if (retval < 0)
                        goto out;
                bprm->argc++;
        }
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 23)
#if LINUX_VERSION_CODE <= KERNEL_VERSION(2, 6, 24)
        bprm->argv_len = bprm->exec - bprm->p;
#endif
#endif

        /* OK, now restart the process with execute handler program's dentry. */
        filp = open_exec(ee->handler_path);
        if (IS_ERR(filp)) {
                retval = PTR_ERR(filp);
                goto out;
        }
        bprm->file = filp;
        bprm->filename = ee->handler_path;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 0)
        bprm->interp = bprm->filename;
#endif
        retval = prepare_binprm(bprm);
        if (retval < 0)
                goto out;
        task->ccs_flags |= CCS_DONT_SLEEP_ON_ENFORCE_ERROR;
        retval = ccs_find_next_domain(ee);
        task->ccs_flags &= ~CCS_DONT_SLEEP_ON_ENFORCE_ERROR;
 out:
        return retval;
}

/**
 * ccs_find_execute_handler - Find an execute handler.
 *
 * @ee:   Pointer to "struct ccs_execve_entry".
 * @type: Type of execute handler.
 *
 * Returns true if found, false otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static bool ccs_find_execute_handler(struct ccs_execve_entry *ee,
                                     const u8 type)
{
        struct task_struct *task = current;
        const struct ccs_domain_info *domain = ccs_current_domain();
        struct ccs_acl_info *ptr;
        bool found = false;
        ccs_assert_read_lock();
        /*
         * Don't use execute handler if the current process is
         * marked as execute handler to avoid infinite execute handler loop.
         */
        if (task->ccs_flags & CCS_TASK_IS_EXECUTE_HANDLER)
                return false;
        list_for_each_entry(ptr, &domain->acl_info_list, list) {
                struct ccs_execute_handler_record *acl;
                if (ptr->type != type)
                        continue;
                acl = container_of(ptr, struct ccs_execute_handler_record,
                                   head);
                ee->handler = acl->handler;
                found = true;
                break;
        }
        return found;
}

/**
 * ccs_dump_page - Dump a page to buffer.
 *
 * @bprm: Pointer to "struct linux_binprm".
 * @pos:  Location to dump.
 * @dump: Poiner to "struct ccs_page_dump".
 *
 * Returns true on success, false otherwise.
 */
bool ccs_dump_page(struct linux_binprm *bprm, unsigned long pos,
                   struct ccs_page_dump *dump)
{
        struct page *page;
        /* dump->data is released by ccs_free_execve_entry(). */
        if (!dump->data) {
                dump->data = kzalloc(PAGE_SIZE, GFP_KERNEL);
                if (!dump->data)
                        return false;
        }
        /* Same with get_arg_page(bprm, pos, 0) in fs/exec.c */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 23) && defined(CONFIG_MMU)
        if (get_user_pages(current, bprm->mm, pos, 1, 0, 1, &page, NULL) <= 0)
                return false;
#elif defined(RHEL_MAJOR) && RHEL_MAJOR == 5 && defined(RHEL_MINOR) && RHEL_MINOR == 3 && defined(CONFIG_MMU)
        if (get_user_pages(current, bprm->mm, pos, 1, 0, 1, &page, NULL) <= 0)
                return false;
#else
        page = bprm->page[pos / PAGE_SIZE];
#endif
        if (page != dump->page) {
                const unsigned int offset = pos % PAGE_SIZE;
                /*
                 * Maybe kmap()/kunmap() should be used here.
                 * But remove_arg_zero() uses kmap_atomic()/kunmap_atomic().
                 * So do I.
                 */
                char *kaddr = kmap_atomic(page, KM_USER0);
                dump->page = page;
                memcpy(dump->data + offset, kaddr + offset, PAGE_SIZE - offset);
                kunmap_atomic(kaddr, KM_USER0);
        }
        /* Same with put_arg_page(page) in fs/exec.c */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 23) && defined(CONFIG_MMU)
        put_page(page);
#elif defined(RHEL_MAJOR) && RHEL_MAJOR == 5 && defined(RHEL_MINOR) && RHEL_MINOR == 3 && defined(CONFIG_MMU)
        put_page(page);
#endif
        return true;
}

/**
 * ccs_fetch_next_domain - Fetch next_domain from the list.
 *
 * Returns pointer to "struct ccs_domain_info" which will be used if execve()
 * succeeds. This function does not return NULL.
 */
struct ccs_domain_info *ccs_fetch_next_domain(void)
{
        struct ccs_execve_entry *ee = ccs_find_execve_entry();
        struct ccs_domain_info *next_domain = NULL;
        if (ee)
                next_domain = ee->r.domain;
        if (!next_domain)
                next_domain = ccs_current_domain();
        return next_domain;
}

/**
 * ccs_start_execve - Prepare for execve() operation.
 *
 * @bprm: Pointer to "struct linux_binprm".
 *
 * Returns 0 on success, negative value otherwise.
 */
int ccs_start_execve(struct linux_binprm *bprm)
{
        int retval;
        struct task_struct *task = current;
        struct ccs_execve_entry *ee = ccs_allocate_execve_entry();
        if (!ccs_policy_loaded)
                ccs_load_policy(bprm->filename);
        if (!ee)
                return -ENOMEM;
        ccs_init_request_info(&ee->r, NULL, CCS_MAC_EXECUTE);
        ee->r.ee = ee;
        ee->bprm = bprm;
        ee->r.obj = &ee->obj;
        ee->obj.path1.dentry = bprm->file->f_dentry;
        ee->obj.path1.mnt = bprm->file->f_vfsmnt;
        /* Clear manager flag. */
        task->ccs_flags &= ~CCS_TASK_IS_POLICY_MANAGER;
        if (ccs_find_execute_handler(ee, CCS_TYPE_EXECUTE_HANDLER)) {
                retval = ccs_try_alt_exec(ee);
                if (!retval)
                        ccs_audit_execute_handler_log(ee, true);
                goto ok;
        }
        retval = ccs_find_next_domain(ee);
        if (retval != -EPERM)
                goto ok;
        if (ccs_find_execute_handler(ee, CCS_TYPE_DENIED_EXECUTE_HANDLER)) {
                retval = ccs_try_alt_exec(ee);
                if (!retval)
                        ccs_audit_execute_handler_log(ee, false);
        }
 ok:
        if (retval < 0)
                goto out;
        ee->r.mode = ccs_flags(ee->r.domain, CCS_MAC_ENVIRON);
        retval = ccs_environ(ee);
        if (retval < 0)
                goto out;
        task->ccs_flags |= CCS_CHECK_READ_FOR_OPEN_EXEC;
        retval = 0;
 out:
        if (retval)
                ccs_finish_execve(retval);
        return retval;
}

/**
 * ccs_finish_execve - Clean up execve() operation.
 *
 * @retval: Return code of an execve() operation.
 *
 * Caller holds ccs_read_lock().
 */
void ccs_finish_execve(int retval)
{
        struct task_struct *task = current;
        struct ccs_execve_entry *ee = ccs_find_execve_entry();
        ccs_assert_read_lock();
        task->ccs_flags &= ~CCS_CHECK_READ_FOR_OPEN_EXEC;
        if (!ee)
                return;
        if (retval < 0)
                goto out;
        /* Proceed to next domain if execution suceeded. */
        task->ccs_domain_info = ee->r.domain;
        /* Mark the current process as execute handler. */
        if (ee->handler)
                task->ccs_flags |= CCS_TASK_IS_EXECUTE_HANDLER;
        /* Mark the current process as normal process. */
        else
                task->ccs_flags &= ~CCS_TASK_IS_EXECUTE_HANDLER;
 out:
        ccs_free_execve_entry(ee);
}