OpenHarmony-v3.1.7-Release/s

/*
 * Copyright (c) 2022 Huawei Device Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "paraperm_checker.h"
#include <fcntl.h>
#include <fstream>
#include <regex>
#include <securec.h>
#include <selinux_internal.h>
#include <sstream>
#include <string>
#include <sys/socket.h>
#include <unistd.h>
#include "callbacks.h"
#include "selinux_error.h"
#include "selinux_klog.h"
#include "contexts_trie.h"

using namespace Selinux;

namespace {
static const std::string PARAMETER_CONTEXTS_FILE = "/system/etc/selinux/targeted/contexts/parameter_contexts";
static const std::string TYPE_PREFIX = "u:object_r:";
static const char *DEFAULT_CONTEXT = "u:object_r:default_param:s0";
static pthread_once_t FC_ONCE = PTHREAD_ONCE_INIT;
static std::unique_ptr<ParamContextsTrie> g_contextsTrie = nullptr;
static ParamContextsList *g_contextsList = nullptr;
static const int CONTEXTS_LENGTH_MIN = 16; // sizeof("x u:object_r:x:s0")
static const int CONTEXTS_LENGTH_MAX = 1024;
} // namespace

struct AuditMsg {
    const ucred *ucred;
    const char *name;
};

static int SelinuxAuditCallback(void *data, security_class_t cls, char *buf, size_t len)
{
    if (data == nullptr || buf == nullptr) {
        return -1;
    }
    auto *msg = reinterpret_cast<AuditMsg *>(data);
    if (!msg->name || !msg->ucred) {
        selinux_log(SELINUX_ERROR, "Selinux audit msg invalid argument\n");
        return -1;
    }
    if (snprintf_s(buf, len, len - 1, "parameter=%s pid=%d uid=%d gid=%d", msg->name, msg->ucred->pid, msg->ucred->uid,
                   msg->ucred->gid) <= 0) {
        return -1;
    }
    return 0;
}

static void SelinuxSetCallback()
{
    union selinux_callback cb;
    cb.func_log = SelinuKLog;
    selinux_set_callback(SELINUX_CB_LOG, cb);
    cb.func_audit = SelinuxAuditCallback;
    selinux_set_callback(SELINUX_CB_AUDIT, cb);
}

static void ReleaseMem()
{
    DestroyParamList(&g_contextsList);
    if (g_contextsTrie != nullptr) {
        g_contextsTrie->Clear();
        g_contextsTrie = nullptr;
    }
}

static int CheckParaNameValid(const char *paraName)
{
    if (paraName == nullptr) {
        return -SELINUX_PTR_NULL;
    }
    std::string para = paraName;
    if (para.empty() || para[0] == '.' || para[para.size() - 1] == '.' || para.find("..") != std::string::npos) {
        return -SELINUX_ARG_INVALID;
    }
    std::regex paraReg("^[a-zA-Z0-9_\\-@:](([\\.]{0,1})[a-zA-Z0-9_\\-@:])*");
    if (std::regex_match(para, paraReg)) {
        return SELINUX_SUCC;
    }
    return -SELINUX_ARG_INVALID;
}

static bool CouldSkip(const std::string &line)
{
    if (line.size() < CONTEXTS_LENGTH_MIN || line.size() > CONTEXTS_LENGTH_MAX) {
        return true;
    }
    int i = 0;
    while (isspace(line[i])) {
        i++;
    }
    if (line[i] == '#') {
        return true;
    }
    if (line.find(TYPE_PREFIX) == line.npos) {
        return true;
    }
    return false;
}

static bool StartWith(const std::string &dst, const std::string &prefix)
{
    return dst.compare(0, prefix.size(), prefix) == 0;
}

static struct ParameterInfo DecodeString(const std::string &line)
{
    std::stringstream input(line);
    struct ParameterInfo contextBuff = {"", ""};
    std::string name;
    if (input >> name) {
        contextBuff.paraName = name;
    }
    std::string context;
    if (input >> context) {
        if (StartWith(context, TYPE_PREFIX)) {
            contextBuff.paraContext = context;
        }
    }
    return contextBuff;
}

static bool InsertContextsList(const ParameterInfo &tmpInfo, ParamContextsList **head)
{
    ParamContextsList *node = (ParamContextsList *)malloc(sizeof(ParamContextsList));
    if (node == nullptr) {
        return false;
    }
    struct ParameterNode contextBuff = {nullptr, nullptr};
    contextBuff.paraName = strdup(tmpInfo.paraName.c_str());
    contextBuff.paraContext = strdup(tmpInfo.paraContext.c_str());
    node->info = contextBuff;
    node->next = nullptr;
    (*head)->next = node;
    *head = (*head)->next;
    return true;
}

static bool ParameterContextsLoad()
{
    ReleaseMem();
    std::ifstream contextsFile(PARAMETER_CONTEXTS_FILE);
    if (!contextsFile) {
        selinux_log(SELINUX_ERROR, "Load parameter_contexts fail, no such file: %s\n", PARAMETER_CONTEXTS_FILE.c_str());
        return false;
    }
    g_contextsTrie = std::make_unique<ParamContextsTrie>();
    g_contextsList = (ParamContextsList *)malloc(sizeof(ParamContextsList));
    if (g_contextsList == nullptr) {
        selinux_log(SELINUX_ERROR, "malloc param info list head fail\n");
        return false;
    }
    ParamContextsList *head = g_contextsList;
    int lineNum = 0;
    std::string line;
    while (getline(contextsFile, line)) {
        lineNum++;
        if (CouldSkip(line))
            continue;
        struct ParameterInfo tmpInfo = DecodeString(line);
        if (tmpInfo.paraContext.empty() || tmpInfo.paraName.empty()) {
            selinux_log(SELINUX_ERROR, "parameter_contexts read fail in line %d\n", lineNum);
            continue;
        }
        if (!g_contextsTrie->Insert(tmpInfo.paraName, tmpInfo.paraContext)) {
            selinux_log(SELINUX_ERROR, "insert contexts trie node fail\n");
            contextsFile.close();
            ReleaseMem();
            return false;
        }
        if (!InsertContextsList(tmpInfo, &head)) {
            selinux_log(SELINUX_ERROR, "malloc param info list node fail\n");
            contextsFile.close();
            ReleaseMem();
            return false;
        }
    }
    head = g_contextsList->next;
    free(g_contextsList);
    g_contextsList = head;
    selinux_log(SELINUX_INFO, "Load parameter_contexts succes: %s\n", PARAMETER_CONTEXTS_FILE.c_str());
    contextsFile.close();
    return true;
}

static int CheckPerm(const std::string &paraName, const char *srcContext, const char *destContext, const ucred &uc)
{
    if (srcContext == nullptr || destContext == nullptr) {
        selinux_log(SELINUX_INFO, "context empty!\n");
        return -SELINUX_PTR_NULL;
    }
    selinux_log(SELINUX_INFO, "srcContext[%s] is setting param[%s] destContext[%s]\n", srcContext, paraName.c_str(),
                destContext);
    AuditMsg msg;
    msg.name = paraName.c_str();
    msg.ucred = &uc;
    int res = selinux_check_access(srcContext, destContext, "parameter_service", "set", &msg);
    return res == 0 ? SELINUX_SUCC : -SELINUX_PERMISSION_DENY;
}

void SetSelinuxLogCallback()
{
    __selinux_once(FC_ONCE, SelinuxSetCallback);
    return;
}

void DestroyParamList(ParamContextsList **list)
{
    if (list == nullptr) {
        return;
    }
    ParamContextsList *tmpNode;
    ParamContextsList *listHead = *list;
    while (listHead != nullptr) {
        tmpNode = listHead->next;
        free(listHead->info.paraName);
        listHead->info.paraName = nullptr;
        free(listHead->info.paraContext);
        listHead->info.paraContext = nullptr;
        free(listHead);
        listHead = tmpNode;
    }
    *list = nullptr;
    return;
}

ParamContextsList *GetParamList()
{
    if (g_contextsList == nullptr) {
        if (!ParameterContextsLoad()) {
            return nullptr;
        }
    }
    return g_contextsList;
}

int GetParamLabel(const char *paraName, char **context)
{
    if (paraName == nullptr || context == nullptr) {
        return -SELINUX_PTR_NULL;
    }

    int ret = CheckParaNameValid(paraName);
    if (ret != 0) {
        selinux_log(SELINUX_ERROR, "paraName invalid!\n");
        return ret;
    }

    if (g_contextsTrie == nullptr) {
        if (!ParameterContextsLoad()) {
            return -SELINUX_CONTEXTS_FILE_LOAD_ERROR;
        }
    }

    if (!g_contextsTrie->Search(std::string(paraName), context)) {
        return -SELINUX_KEY_NOT_FOUND;
    }
    selinux_log(SELINUX_INFO, "find context: %s\n", *context);
    return SELINUX_SUCC;
}

int ReadParamCheck(const char *paraName)
{
    int ret = CheckParaNameValid(paraName);
    if (ret != 0) {
        selinux_log(SELINUX_ERROR, "paraName invalid!\n");
        return ret;
    }

    char *srcContext = nullptr;
    int rc = getcon(&srcContext);
    if (rc < 0) {
        selinux_log(SELINUX_ERROR, "getcon failed!\n");
        return -SELINUX_GET_CONTEXT_ERROR;
    }

    AuditMsg msg;
    msg.name = paraName;
    ucred uc = {.pid = getpid(), .uid = getuid(), .gid = getgid()};
    msg.ucred = &uc;
    char *destContext = nullptr;
    if (GetParamLabel(paraName, &destContext) != 0) {
        destContext = strdup(DEFAULT_CONTEXT);
    }
    if (srcContext == nullptr || destContext == nullptr) {
        freecon(srcContext);
        return -SELINUX_PTR_NULL;
    }
    selinux_log(SELINUX_INFO, "srcContext[%s] is reading param[%s] destContext[%s]\n", srcContext, paraName,
                destContext);
    int res = selinux_check_access(srcContext, destContext, "file", "read", &msg);
    freecon(srcContext);
    free(destContext);
    return res == 0 ? SELINUX_SUCC : -SELINUX_PERMISSION_DENY;
}

int SetParamCheck(const char *paraName, struct ucred *uc)
{
    if (paraName == nullptr || uc == nullptr) {
        return -SELINUX_PTR_NULL;
    }

    int ret = CheckParaNameValid(paraName);
    if (ret != 0) {
        selinux_log(SELINUX_ERROR, "paraName invalid!\n");
        return ret;
    }

    char *srcContext = nullptr;

    int rc = getpidcon(uc->pid, &srcContext);
    if (rc < 0) {
        selinux_log(SELINUX_ERROR, "getpidcon failed!\n");
        return -SELINUX_GET_CONTEXT_ERROR;
    }
    char *destContext = nullptr;
    if (GetParamLabel(paraName, &destContext) != 0) {
        destContext = strdup(DEFAULT_CONTEXT);
    }
    int res = CheckPerm(std::string(paraName), srcContext, destContext, *uc);
    freecon(srcContext);
    free(destContext);
    return res;
}