security/ccsecurity/domain.c

/*
 * security/ccsecurity/domain.c
 *
 * Copyright (C) 2005-2010  NTT DATA CORPORATION
 *
 * Version: 1.8.0-pre   2010/10/05
 *
 * 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"

/* Variables definitions.*/

/* The global domain. */
struct ccs_domain_info ccs_acl_group[CCS_MAX_ACL_GROUPS];

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

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

struct list_head ccs_policy_list[CCS_MAX_POLICY];
struct list_head ccs_group_list[CCS_MAX_GROUP];
struct list_head ccs_shared_list[CCS_MAX_LIST];

/**
 * ccs_update_policy - Update an entry for exception policy.
 *
 * @new_entry:       Pointer to "struct ccs_acl_info".
 * @size:            Size of @new_entry in bytes.
 * @is_delete:       True if it is a delete request.
 * @list:            Pointer to "struct list_head".
 * @check_duplicate: Callback function to find duplicated entry.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds ccs_read_lock().
 */
int ccs_update_policy(struct ccs_acl_head *new_entry, const int size,
                      bool is_delete, struct list_head *list,
                      bool (*check_duplicate) (const struct ccs_acl_head *,
                                               const struct ccs_acl_head *))
{
        int error = is_delete ? -ENOENT : -ENOMEM;
        struct ccs_acl_head *entry;
        if (mutex_lock_interruptible(&ccs_policy_lock))
                return -ENOMEM;
        list_for_each_entry_srcu(entry, list, list, &ccs_ss) {
                if (!check_duplicate(entry, new_entry))
                        continue;
                entry->is_deleted = is_delete;
                error = 0;
                break;
        }
        if (error && !is_delete) {
                entry = ccs_commit_ok(new_entry, size);
                if (entry) {
                        list_add_tail_rcu(&entry->list, list);
                        error = 0;
                }
        }
        mutex_unlock(&ccs_policy_lock);
        return error;
}

static inline bool ccs_same_acl_head(const struct ccs_acl_info *p1,
                                     const struct ccs_acl_info *p2)
{
        return p1->type == p2->type && p1->cond == p2->cond;
}

/**
 * ccs_update_domain - Update an entry for domain policy.
 *
 * @new_entry:       Pointer to "struct ccs_acl_info".
 * @size:            Size of @new_entry in bytes.
 * @param:           Pointer to "struct ccs_acl_param".
 * @check_duplicate: Callback function to find duplicated entry.
 * @merge_duplicate: Callback function to merge duplicated entry. Maybe NULL.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds ccs_read_lock().
 */
int ccs_update_domain(struct ccs_acl_info *new_entry, const int size,
                      struct ccs_acl_param *param,
                      bool (*check_duplicate) (const struct ccs_acl_info *,
                                               const struct ccs_acl_info *),
                      bool (*merge_duplicate) (struct ccs_acl_info *,
                                               struct ccs_acl_info *,
                                               const bool))
{
        int error = param->is_delete ? -ENOENT : -ENOMEM;
        struct ccs_acl_info *entry;
        const u8 type = new_entry->type;
        const u8 i = type == CCS_TYPE_AUTO_EXECUTE_HANDLER ||
                type == CCS_TYPE_DENIED_EXECUTE_HANDLER ||
                type == CCS_TYPE_AUTO_TASK_ACL;
        const bool is_delete = param->is_delete;
        struct ccs_domain_info * const domain = param->domain;
        if (param->data[0]) {
                new_entry->cond = ccs_get_condition(param->data);
                if (!new_entry->cond)
                        return -EINVAL;
        }
        if (mutex_lock_interruptible(&ccs_policy_lock))
                goto out;
        list_for_each_entry_srcu(entry, &domain->acl_info_list[i], list,
                                 &ccs_ss) {
                if (!ccs_same_acl_head(entry, new_entry) ||
                    !check_duplicate(entry, new_entry))
                        continue;
                if (merge_duplicate)
                        entry->is_deleted = merge_duplicate(entry, new_entry,
                                                            is_delete);
                else
                        entry->is_deleted = is_delete;
                error = 0;
                break;
        }
        if (error && !is_delete) {
                entry = ccs_commit_ok(new_entry, size);
                if (entry) {
                        list_add_tail_rcu(&entry->list,
                                          &domain->acl_info_list[i]);
                        error = 0;
                }
        }
        mutex_unlock(&ccs_policy_lock);
out:
        ccs_put_condition(new_entry->cond);
        return error;
}

void ccs_check_acl(struct ccs_request_info *r,
                   bool (*check_entry) (struct ccs_request_info *,
                                        const struct ccs_acl_info *))
{
        const struct ccs_domain_info *domain = ccs_current_domain();
        struct ccs_acl_info *ptr;
        bool retried = false;
        const u8 i = !check_entry;
retry:
        list_for_each_entry_srcu(ptr, &domain->acl_info_list[i], list,
                                 &ccs_ss) {
                if (ptr->is_deleted)
                        continue;
                if (ptr->type != r->param_type)
                        continue;
                if (check_entry && !check_entry(r, ptr))
                        continue;
                if (!ccs_condition(r, ptr->cond))
                        continue;
                r->matched_acl = ptr;
                r->granted = true;
                return;
        }
        if (!retried) {
                retried = true;
                domain = &ccs_acl_group[domain->group];
                goto retry;
        }
        r->granted = false;
}

static bool ccs_same_transition_control(const struct ccs_acl_head *a,
                                        const struct ccs_acl_head *b)
{
        const struct ccs_transition_control *p1 = container_of(a, typeof(*p1),
                                                               head);
        const struct ccs_transition_control *p2 = container_of(b, typeof(*p2),
                                                               head);
        return p1->type == p2->type && p1->is_last_name == p2->is_last_name
                && p1->domainname == p2->domainname
                && p1->program == p2->program;
}

/**
 * ccs_update_transition_control_entry - Update "struct ccs_transition_control" list.
 *
 * @domainname: The name of domain. Maybe NULL.
 * @program:    The name of program. Maybe NULL.
 * @type:       Type of transition.
 * @is_delete:  True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_update_transition_control_entry(const char *domainname,
                                               const char *program,
                                               const u8 type,
                                               const bool is_delete)
{
        struct ccs_transition_control e = { .type = type };
        int error = is_delete ? -ENOENT : -ENOMEM;
        if (program && strcmp(program, "any")) {
                if (!ccs_correct_path(program))
                        return -EINVAL;
                e.program = ccs_get_name(program);
                if (!e.program)
                        goto out;
        }
        if (domainname && strcmp(domainname, "any")) {
                if (!ccs_correct_domain(domainname)) {
                        if (!ccs_correct_path(domainname))
                                goto out;
                        e.is_last_name = true;
                }
                e.domainname = ccs_get_name(domainname);
                if (!e.domainname)
                        goto out;
        }
        error = ccs_update_policy(&e.head, sizeof(e), is_delete,
                                  &ccs_policy_list[CCS_ID_TRANSITION_CONTROL],
                                  ccs_same_transition_control);
out:
        ccs_put_name(e.domainname);
        ccs_put_name(e.program);
        return error;
}

/**
 * ccs_write_transition_control - Write "struct ccs_transition_control" list.
 *
 * @data:      String to parse.
 * @is_delete: True if it is a delete request.
 * @type:      Type of this entry.
 *
 * Returns 0 on success, negative value otherwise.
 */
int ccs_write_transition_control(char *data, const bool is_delete,
                                 const u8 type)
{
        char *domainname = strstr(data, " from ");
        if (domainname) {
                *domainname = '\0';
                domainname += 6;
        } else if (type == CCS_TRANSITION_CONTROL_NO_KEEP ||
                   type == CCS_TRANSITION_CONTROL_KEEP) {
                domainname = data;
                data = NULL;
        }
        return ccs_update_transition_control_entry(domainname, data, type,
                                                   is_delete);
}

/**
 * ccs_last_word - Get last component of a domainname.
 *
 * @name: Domainname to check.
 *
 * Returns the last word of @name.
 */
static const char *ccs_last_word(const char *name)
{
        const char *cp = strrchr(name, ' ');
        if (cp)
                return cp + 1;
        return name;
}

/**
 * ccs_transition_type - Get domain transition type.
 *
 * @domainname: The name of domain.
 * @program:    The name of program.
 *
 * Returns CCS_TRANSITION_CONTROL_INITIALIZE if executing @program
 * reinitializes domain transition, CCS_TRANSITION_CONTROL_KEEP if executing
 * @program suppresses domain transition, others otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static u8 ccs_transition_type(const struct ccs_path_info *domainname,
                              const struct ccs_path_info *program)
{
        const struct ccs_transition_control *ptr;
        const char *last_name = ccs_last_word(domainname->name);
        u8 type;
        for (type = 0; type < CCS_MAX_TRANSITION_TYPE; type++) {
next:
                list_for_each_entry_srcu(ptr, &ccs_policy_list
                                         [CCS_ID_TRANSITION_CONTROL],
                                         head.list, &ccs_ss) {
                        if (ptr->head.is_deleted || ptr->type != type)
                                continue;
                        if (ptr->domainname) {
                                if (!ptr->is_last_name) {
                                        if (ptr->domainname != domainname)
                                                continue;
                                } else {
                                        /*
                                         * Use direct strcmp() since this is
                                         * unlikely used.
                                         */
                                        if (strcmp(ptr->domainname->name,
                                                   last_name))
                                                continue;
                                }
                        }
                        if (ptr->program && ccs_pathcmp(ptr->program, program))
                                continue;
                        if (type == CCS_TRANSITION_CONTROL_NO_INITIALIZE) {
                                /*
                                 * Do not check for initialize_domain if
                                 * no_initialize_domain matched.
                                 */
                                type = CCS_TRANSITION_CONTROL_NO_KEEP;
                                goto next;
                        }
                        goto done;
                }
        }
done:
        return type;
}

static bool ccs_same_aggregator(const struct ccs_acl_head *a,
                                const struct ccs_acl_head *b)
{
        const struct ccs_aggregator *p1 = container_of(a, typeof(*p1), head);
        const struct ccs_aggregator *p2 = container_of(b, typeof(*p2), head);
        return p1->original_name == p2->original_name &&
                p1->aggregated_name == p2->aggregated_name;
}

/**
 * ccs_update_aggregator_entry - Update "struct ccs_aggregator" 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 e = { };
        int error = is_delete ? -ENOENT : -ENOMEM;
        if (!ccs_correct_word(original_name) ||
            !ccs_correct_path(aggregated_name))
                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 ||
            e.aggregated_name->is_patterned) /* No patterns allowed. */
                goto out;
        error = ccs_update_policy(&e.head, sizeof(e), is_delete,
                                  &ccs_policy_list[CCS_ID_AGGREGATOR],
                                  ccs_same_aggregator);
out:
        ccs_put_name(e.original_name);
        ccs_put_name(e.aggregated_name);
        return error;
}

/**
 * ccs_write_aggregator - Write "struct ccs_aggregator" 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(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);
        if (mutex_lock_interruptible(&ccs_policy_lock))
                return 0;
        /* Is there an active domain? */
        list_for_each_entry_srcu(domain, &ccs_domain_list, list, &ccs_ss) {
                /* 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_assign_domain - Create a domain.
 *
 * @domainname: The name of domain.
 * @profile:    Profile number to assign if the domain was newly created.
 * @group:      Group number to assign if the domain was newly created.
 * @transit:    True if transit to domain found or created.
 *
 * Returns pointer to "struct ccs_domain_info" on success, NULL otherwise.
 *
 * Caller holds ccs_read_lock().
 */
struct ccs_domain_info *ccs_assign_domain(const char *domainname,
                                          const u8 profile, const u8 group,
                                          const bool transit)
{
        struct ccs_domain_info e = { };
        struct ccs_domain_info *entry = ccs_find_domain(domainname);
        bool created = false;
        if (entry)
                goto out;
        if (strlen(domainname) >= CCS_EXEC_TMPSIZE - 10 ||
            !ccs_correct_domain(domainname))
                return NULL;
        e.profile = profile;
        e.group = group;
        e.domainname = ccs_get_name(domainname);
        if (!e.domainname)
                return NULL;
        if (mutex_lock_interruptible(&ccs_policy_lock))
                goto out;
        entry = ccs_find_domain(domainname);
        if (!entry) {
                entry = ccs_commit_ok(&e, sizeof(e));
                if (entry) {
                        INIT_LIST_HEAD(&entry->acl_info_list[0]);
                        INIT_LIST_HEAD(&entry->acl_info_list[1]);
                        list_add_tail_rcu(&entry->list, &ccs_domain_list);
                        created = true;
                }
        }
        mutex_unlock(&ccs_policy_lock);
out:
        ccs_put_name(e.domainname);
        if (entry && transit) {
                ccs_current_security()->ccs_domain_info = entry;
                if (created) {
                        struct ccs_request_info r;
                        ccs_init_request_info(&r, CCS_MAC_FILE_EXECUTE);
                        r.granted = false;
                        ccs_write_log(&r, "use_profile %u\n", profile);
                        ccs_write_log(&r, "use_group %u\n", group);
                        ccs_update_stat(CCS_STAT_POLICY_UPDATES);
                }
        }
        return entry;
}

/**
 * ccs_find_next_domain - Find a domain.
 *
 * @ee: Pointer to "struct ccs_execve".
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_find_next_domain(struct ccs_execve *ee)
{
        struct ccs_request_info *r = &ee->r;
        const struct ccs_path_info *handler = ee->handler;
        struct ccs_domain_info *domain = NULL;
        struct ccs_domain_info * const old_domain = ccs_current_domain();
        struct linux_binprm *bprm = ee->bprm;
        struct ccs_security *task = ccs_current_security();
        struct ccs_path_info rn = { }; /* real name */
        int retval;
        bool need_kfree = false;
retry:
        r->matched_acl = NULL;
        if (need_kfree) {
                kfree(rn.name);
                need_kfree = false;
        }

        /* Get symlink's pathname of program. */
        retval = ccs_symlink_path(bprm->filename, &rn);
        if (retval < 0)
                goto out;
        need_kfree = true;

        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;
                }
        } else {
                struct ccs_aggregator *ptr;
                /* Check 'aggregator' directive. */
                list_for_each_entry_srcu(ptr,
                                         &ccs_policy_list[CCS_ID_AGGREGATOR],
                                         head.list, &ccs_ss) {
                        if (ptr->head.is_deleted ||
                            !ccs_path_matches_pattern(&rn, ptr->original_name))
                                continue;
                        kfree(rn.name);
                        need_kfree = false;
                        /* This is OK because it is read only. */
                        rn = *ptr->aggregated_name;
                        break;
                }

                /* Check execute permission. */
                retval = ccs_path_permission(r, CCS_TYPE_EXECUTE, &rn);
                if (retval == CCS_RETRY_REQUEST)
                        goto retry;
                if (retval < 0)
                        goto out;
                /*
                 * To be able to specify domainnames with wildcards, use the
                 * pathname specified in the policy (which may contain
                 * wildcard) rather than the pathname passed to execve()
                 * (which never contains wildcard).
                 */
                if (r->param.path.matched_path) {
                        if (need_kfree)
                                kfree(rn.name);
                        need_kfree = false;
                        /* This is OK because it is read only. */
                        rn = *r->param.path.matched_path;
                }
        }

        /* Calculate domain to transit to. */
        switch (ccs_transition_type(old_domain->domainname, &rn)) {
        case CCS_TRANSITION_CONTROL_INITIALIZE:
                /* Transit to the child of ccs_kernel_domain domain. */
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, CCS_ROOT_NAME " " "%s",
                         rn.name);
                break;
        case CCS_TRANSITION_CONTROL_KEEP:
                /* Keep current domain. */
                domain = old_domain;
                break;
        default:
                if (old_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 = old_domain;
                } else {
                        /* Normal domain transition. */
                        snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "%s %s",
                                 old_domain->domainname->name, rn.name);
                }
                break;
        }
        /*
         * Tell GC that I started execve().
         * Also, tell open_exec() to check read permission.
         */
        task->ccs_flags |= CCS_TASK_IS_IN_EXECVE;
        /*
         * Make task->ccs_flags visible to GC before changing
         * task->ccs_domain_info .
         */
        smp_mb();
        /*
         * Proceed to the next domain in order to allow reaching via PID.
         * It will be reverted if execve() failed. Reverting is not good.
         * But it is better than being unable to reach via PID in interactive
         * enforcing mode.
         */
        if (!domain)
                domain = ccs_assign_domain(ee->tmp, r->profile,
                                           old_domain->group, true);
        if (domain)
                retval = 0;
        else if (r->mode == CCS_CONFIG_ENFORCING)
                retval = -ENOMEM;
        else {
                retval = 0;
                if (!old_domain->flags[CCS_DIF_TRANSITION_FAILED]) {
                        old_domain->flags[CCS_DIF_TRANSITION_FAILED] = true;
                        r->granted = false;
                        ccs_write_log(r, "%s",
                                      ccs_dif[CCS_DIF_TRANSITION_FAILED]);
                        printk(KERN_WARNING
                               "ERROR: Domain '%s' not defined.\n", ee->tmp);
                }
        }
out:
        if (need_kfree)
                kfree(rn.name);
        return retval;
}

/**
 * ccs_environ - Check permission for environment variable names.
 *
 * @ee: Pointer to "struct ccs_execve".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_environ(struct ccs_execve *ee)
{
        struct ccs_request_info *r = &ee->r;
        struct linux_binprm *bprm = ee->bprm;
        /* env_page->data is allocated by ccs_dump_page(). */
        struct ccs_page_dump env_page = { };
        char *arg_ptr; /* Size is CCS_EXEC_TMPSIZE bytes */
        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;
        ee->r.type = CCS_MAC_ENVIRON;
        ee->r.mode = ccs_get_mode(ccs_current_domain()->profile,
                                  CCS_MAC_ENVIRON);
        if (!r->mode || !envp_count)
                return 0;
        arg_ptr = kzalloc(CCS_EXEC_TMPSIZE, CCS_GFP_FLAGS);
        if (!arg_ptr)
                goto out;
        while (error == -ENOMEM) {
                if (!ccs_dump_page(bprm, pos, &env_page))
                        goto out;
                pos += PAGE_SIZE - offset;
                /* Read. */
                while (argv_count && offset < PAGE_SIZE) {
                        if (!env_page.data[offset++])
                                argv_count--;
                }
                if (argv_count) {
                        offset = 0;
                        continue;
                }
                while (offset < PAGE_SIZE) {
                        const unsigned char c = env_page.data[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;
        kfree(env_page.data);
        kfree(arg_ptr);
        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';
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 36)
static int ccs_copy_argv(const char *arg, struct linux_binprm *bprm)
{
        const int ret = copy_strings_kernel(1, &arg, bprm);
        if (ret >= 0)
                bprm->argc++;
        return ret;
}
#else
static int ccs_copy_argv(char *arg, struct linux_binprm *bprm)
{
        const int ret = copy_strings_kernel(1, &arg, bprm);
        if (ret >= 0)
                bprm->argc++;
        return ret;
}
#endif

/**
 * ccs_try_alt_exec - Try to start execute handler.
 *
 * @ee: Pointer to "struct ccs_execve".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_try_alt_exec(struct ccs_execve *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 ccs_security *task = ccs_current_security();

        /* Close the requested program's dentry. */
        ee->obj.path1.dentry = NULL;
        ee->obj.path1.mnt = NULL;
        ee->obj.validate_done = false;
        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] */
        {
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "%d", original_envc);
                retval = ccs_copy_argv(ee->tmp, bprm);
                if (retval < 0)
                        goto out;
        }

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

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

        /* Set argv[3] */
        {
                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", ccs_sys_getpid(),
                         current_uid(), current_gid(), current_euid(),
                         current_egid(), current_suid(), current_sgid(),
                         current_fsuid(), current_fsgid());
                retval = ccs_copy_argv(ee->tmp, bprm);
                if (retval < 0)
                        goto out;
        }

        /* Set argv[2] */
        {
                char *exe = (char *) ccs_get_exe();
                if (exe) {
                        retval = ccs_copy_argv(exe, bprm);
                        kfree(exe);
                } else {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 36)
                        retval = ccs_copy_argv("<unknown>", bprm);
#else
                        snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "<unknown>");
                        retval = ccs_copy_argv(ee->tmp, bprm);
#endif
                }
                if (retval < 0)
                        goto out;
        }

        /* Set argv[1] */
        {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 36)
                retval = ccs_copy_argv(ccs_current_domain()->domainname->name,
                                       bprm);
#else
                snprintf(ee->tmp, CCS_EXEC_TMPSIZE - 1, "%s",
                         ccs_current_domain()->domainname->name);
                retval = ccs_copy_argv(ee->tmp, bprm);
#endif
                if (retval < 0)
                        goto out;
        }

        /* Set argv[0] */
        {
                struct path root;
                char *cp;
                int root_len;
                int handler_len;
                get_fs_root(current->fs, &root);
                cp = ccs_realpath_from_path(&root);
                path_put(&root);
                if (!cp) {
                        retval = -ENOMEM;
                        goto out;
                }
                root_len = strlen(cp);
                retval = strncmp(ee->handler->name, cp, root_len);
                root_len--;
                kfree(cp);
                if (retval) {
                        retval = -ENOENT;
                        goto out;
                }
                handler_len = ee->handler->total_len + 1;
                cp = kmalloc(handler_len, CCS_GFP_FLAGS);
                if (!cp) {
                        retval = -ENOMEM;
                        goto out;
                }
                /* ee->handler_path is released by ccs_finish_execve(). */
                ee->handler_path = cp;
                /* Adjust root directory for open_exec(). */
                memmove(cp, ee->handler->name + root_len,
                        handler_len - root_len);
                ccs_unescape(cp);
                retval = -ENOENT;
                if (!*cp || *cp != '/')
                        goto out;
                retval = ccs_copy_argv(cp, bprm);
                if (retval < 0)
                        goto out;
        }
#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;
        }
        ee->obj.path1.dentry = filp->f_dentry;
        ee->obj.path1.mnt = filp->f_vfsmnt;
        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".
 * @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 *ee, const u8 type)
{
        struct ccs_request_info *r = &ee->r;
        /*
         * To avoid infinite execute handler loop, don't use execute handler
         * if the current process is marked as execute handler .
         */
        if (ccs_current_flags() & CCS_TASK_IS_EXECUTE_HANDLER)
                return false;
        r->param_type = type;
        ccs_check_acl(r, NULL);
        if (!r->granted)
                return false;
        ee->handler = container_of(r->matched_acl, struct ccs_handler_acl,
                                   head)->handler;
        return true;
}

#ifdef CONFIG_MMU
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 23)
#define CCS_BPRM_MMU
#elif defined(RHEL_MAJOR) && RHEL_MAJOR == 5 && defined(RHEL_MINOR) && RHEL_MINOR >= 3
#define CCS_BPRM_MMU
#elif defined(AX_MAJOR) && AX_MAJOR == 3 && defined(AX_MINOR) && AX_MINOR >= 2
#define CCS_BPRM_MMU
#endif
#endif

/**
 * 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_finish_execve(). */
        if (!dump->data) {
                dump->data = kzalloc(PAGE_SIZE, CCS_GFP_FLAGS);
                if (!dump->data)
                        return false;
        }
        /* Same with get_arg_page(bprm, pos, 0) in fs/exec.c */
#ifdef CCS_BPRM_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 */
#ifdef CCS_BPRM_MMU
        put_page(page);
#endif
        return true;
}

/**
 * ccs_start_execve - Prepare for execve() operation.
 *
 * @bprm: Pointer to "struct linux_binprm".
 * @eep:  Pointer to "struct ccs_execve *".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_start_execve(struct linux_binprm *bprm,
                            struct ccs_execve **eep)
{
        int retval;
        struct ccs_security *task = ccs_current_security();
        struct ccs_execve *ee;
        *eep = NULL;
        ee = kzalloc(sizeof(*ee), CCS_GFP_FLAGS);
        if (!ee)
                return -ENOMEM;
        ee->tmp = kzalloc(CCS_EXEC_TMPSIZE, CCS_GFP_FLAGS);
        if (!ee->tmp) {
                kfree(ee);
                return -ENOMEM;
        }
        ee->reader_idx = ccs_read_lock();
        /* ee->dump->data is allocated by ccs_dump_page(). */
        ee->previous_domain = task->ccs_domain_info;
        /* Clear manager flag. */
        task->ccs_flags &= ~CCS_TASK_IS_MANAGER;
        *eep = ee;
        ccs_init_request_info(&ee->r, CCS_MAC_FILE_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;
        /*
         * No need to call ccs_environ() for execute handler because envp[] is
         * moved to argv[].
         */
        if (ccs_find_execute_handler(ee, CCS_TYPE_AUTO_EXECUTE_HANDLER))
                return ccs_try_alt_exec(ee);
        retval = ccs_find_next_domain(ee);
        if (retval == -EPERM) {
                if (ccs_find_execute_handler(ee,
                                             CCS_TYPE_DENIED_EXECUTE_HANDLER))
                        return ccs_try_alt_exec(ee);
        }
        if (!retval)
                retval = ccs_environ(ee);
        return retval;
}

/**
 * ccs_finish_execve - Clean up execve() operation.
 *
 * @retval: Return code of an execve() operation.
 * @ee:     Pointer to "struct ccs_execve".
 *
 * Caller holds ccs_read_lock().
 */
static void ccs_finish_execve(int retval, struct ccs_execve *ee)
{
        struct ccs_security *task = ccs_current_security();
        if (!ee)
                return;
        if (retval < 0) {
                task->ccs_domain_info = ee->previous_domain;
                /*
                 * Make task->ccs_domain_info visible to GC before changing
                 * task->ccs_flags .
                 */
                smp_mb();
        } else {
                /* 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;
        }
        /* Tell GC that I finished execve(). */
        task->ccs_flags &= ~CCS_TASK_IS_IN_EXECVE;
        ccs_read_unlock(ee->reader_idx);
        kfree(ee->handler_path);
        kfree(ee->tmp);
        kfree(ee->dump.data);
        kfree(ee);
}

static int __ccs_search_binary_handler(struct linux_binprm *bprm,
                                       struct pt_regs *regs)
{
        struct ccs_execve *ee;
        int retval;
        if (!ccs_policy_loaded)
                ccsecurity_exports.load_policy(bprm->filename);
        retval = ccs_start_execve(bprm, &ee);
        if (!retval)
                retval = search_binary_handler(bprm, regs);
        ccs_finish_execve(retval, ee);
        return retval;
}

void __init ccs_domain_init(void)
{
        ccsecurity_ops.search_binary_handler = __ccs_search_binary_handler;
}