security/keymint/support/keymint_utils.cpp


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/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * 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 <regex.h>

#include <android-base/properties.h>
#include <hardware/hw_auth_token.h>

namespace aidl::android::hardware::security::keymint {

namespace {

constexpr char kPlatformVersionProp[] = "ro.build.version.release";
constexpr char kPlatformVersionRegex[] = "^([0-9]{1,2})(\\.([0-9]{1,2}))?(\\.([0-9]{1,2}))?";
constexpr size_t kMajorVersionMatch = 1;
constexpr size_t kMinorVersionMatch = 3;
constexpr size_t kSubminorVersionMatch = 5;
constexpr size_t kPlatformVersionMatchCount = kSubminorVersionMatch + 1;

constexpr char kPlatformPatchlevelProp[] = "ro.build.version.security_patch";
constexpr char kVendorPatchlevelProp[] = "ro.vendor.build.security_patch";
constexpr char kPatchlevelRegex[] = "^([0-9]{4})-([0-9]{2})-([0-9]{2})$";
constexpr size_t kYearMatch = 1;
constexpr size_t kMonthMatch = 2;
constexpr size_t kDayMatch = 3;
constexpr size_t kPatchlevelMatchCount = kDayMatch + 1;

uint32_t match_to_uint32(const char* expression, const regmatch_t& match) {
    if (match.rm_so == -1) return 0;

    size_t len = match.rm_eo - match.rm_so;
    std::string s(expression + match.rm_so, len);
    return std::stoul(s);
}

std::string wait_and_get_property(const char* prop) {
    std::string prop_value;
    while (!::android::base::WaitForPropertyCreation(prop))
        ;
    prop_value = ::android::base::GetProperty(prop, "" /* default */);
    return prop_value;
}

uint32_t getOsVersion(const char* version_str) {
    regex_t regex;
    if (regcomp(&regex, kPlatformVersionRegex, REG_EXTENDED)) {
        return 0;
    }

    regmatch_t matches[kPlatformVersionMatchCount];
    int not_match =
            regexec(&regex, version_str, kPlatformVersionMatchCount, matches, 0 /* flags */);
    regfree(&regex);
    if (not_match) {
        return 0;
    }

    uint32_t major = match_to_uint32(version_str, matches[kMajorVersionMatch]);
    uint32_t minor = match_to_uint32(version_str, matches[kMinorVersionMatch]);
    uint32_t subminor = match_to_uint32(version_str, matches[kSubminorVersionMatch]);

    return (major * 100 + minor) * 100 + subminor;
}

enum class PatchlevelOutput { kYearMonthDay, kYearMonth };

uint32_t getPatchlevel(const char* patchlevel_str, PatchlevelOutput detail) {
    regex_t regex;
    if (regcomp(&regex, kPatchlevelRegex, REG_EXTENDED) != 0) {
        return 0;
    }

    regmatch_t matches[kPatchlevelMatchCount];
    int not_match = regexec(&regex, patchlevel_str, kPatchlevelMatchCount, matches, 0 /* flags */);
    regfree(&regex);
    if (not_match) {
        return 0;
    }

    uint32_t year = match_to_uint32(patchlevel_str, matches[kYearMatch]);
    uint32_t month = match_to_uint32(patchlevel_str, matches[kMonthMatch]);

    if (month < 1 || month > 12) {
        return 0;
    }

    switch (detail) {
        case PatchlevelOutput::kYearMonthDay: {
            uint32_t day = match_to_uint32(patchlevel_str, matches[kDayMatch]);
            if (day < 1 || day > 31) {
                return 0;
            }
            return year * 10000 + month * 100 + day;
        }
        case PatchlevelOutput::kYearMonth:
            return year * 100 + month;
    }
}

}  // anonymous namespace

uint32_t getOsVersion() {
    std::string version = wait_and_get_property(kPlatformVersionProp);
    return getOsVersion(version.c_str());
}

uint32_t getOsPatchlevel() {
    std::string patchlevel = wait_and_get_property(kPlatformPatchlevelProp);
    return getPatchlevel(patchlevel.c_str(), PatchlevelOutput::kYearMonth);
}

uint32_t getVendorPatchlevel() {
    std::string patchlevel = wait_and_get_property(kVendorPatchlevelProp);
    return getPatchlevel(patchlevel.c_str(), PatchlevelOutput::kYearMonthDay);
}

}  // namespace aidl::android::hardware::security::keymint