cmds/idmap/scan.cpp

#include <dirent.h>
#include <inttypes.h>
#include <sys/file.h>
#include <sys/stat.h>

#include "idmap.h"

#include <memory>
#include <androidfw/ResourceTypes.h>
#include <androidfw/StreamingZipInflater.h>
#include <androidfw/ZipFileRO.h>
#include <cutils/properties.h>
#include <private/android_filesystem_config.h> // for AID_SYSTEM
#include <utils/SortedVector.h>
#include <utils/String16.h>
#include <utils/String8.h>

#define NO_OVERLAY_TAG (-1000)

using namespace android;

namespace {
    struct Overlay {
        Overlay() {}
        Overlay(const String8& a, const String8& i, int p) :
            apk_path(a), idmap_path(i), priority(p) {}

        bool operator<(Overlay const& rhs) const
        {
            return rhs.priority > priority;
        }

        String8 apk_path;
        String8 idmap_path;
        int priority;
    };

    bool writePackagesList(const char *filename, const SortedVector<Overlay>& overlayVector)
    {
        // the file is opened for appending so that it doesn't get truncated
        // before we can guarantee mutual exclusion via the flock
        FILE* fout = fopen(filename, "a");
        if (fout == NULL) {
            return false;
        }

        if (TEMP_FAILURE_RETRY(flock(fileno(fout), LOCK_EX)) != 0) {
            fclose(fout);
            return false;
        }

        if (TEMP_FAILURE_RETRY(ftruncate(fileno(fout), 0)) != 0) {
            TEMP_FAILURE_RETRY(flock(fileno(fout), LOCK_UN));
            fclose(fout);
            return false;
        }

        for (size_t i = 0; i < overlayVector.size(); ++i) {
            const Overlay& overlay = overlayVector[i];
            fprintf(fout, "%s %s\n", overlay.apk_path.string(), overlay.idmap_path.string());
        }

        TEMP_FAILURE_RETRY(fflush(fout));
        TEMP_FAILURE_RETRY(flock(fileno(fout), LOCK_UN));
        fclose(fout);

        // Make file world readable since Zygote (running as root) will read
        // it when creating the initial AssetManger object
        const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH; // 0644
        if (chmod(filename, mode) == -1) {
            unlink(filename);
            return false;
        }

        return true;
    }

    String8 flatten_path(const char *path)
    {
        String16 tmp(path);
        tmp.replaceAll('/', '@');
        return String8(tmp);
    }

    bool check_property(String16 property, String16 value) {
        char propBuf[PROPERTY_VALUE_MAX];
        property_get(String8(property).c_str(), propBuf, NULL);
        return String8(value) == propBuf;
    }

    int parse_overlay_tag(const ResXMLTree& parser, const char *target_package_name,
            bool* is_static_overlay)
    {
        const size_t N = parser.getAttributeCount();
        String16 target;
        int priority = -1;
        String16 propName = String16();
        String16 propValue = String16();
        for (size_t i = 0; i < N; ++i) {
            size_t len;
            String16 key(parser.getAttributeName(i, &len));
            if (key == String16("targetPackage")) {
                const char16_t *p = parser.getAttributeStringValue(i, &len);
                if (p != NULL) {
                    target = String16(p, len);
                }
            } else if (key == String16("priority")) {
                Res_value v;
                if (parser.getAttributeValue(i, &v) == sizeof(Res_value)) {
                    priority = v.data;
                    if (priority < 0 || priority > 9999) {
                        return -1;
                    }
                }
            } else if (key == String16("isStatic")) {
                Res_value v;
                if (parser.getAttributeValue(i, &v) == sizeof(Res_value)) {
                    *is_static_overlay = (v.data != 0);
                }
            } else if (key == String16("requiredSystemPropertyName")) {
                const char16_t *p = parser.getAttributeStringValue(i, &len);
                if (p != NULL) {
                    propName = String16(p, len);
                }
            } else if (key == String16("requiredSystemPropertyValue")) {
                const char16_t *p = parser.getAttributeStringValue(i, &len);
                if (p != NULL) {
                    propValue = String16(p, len);
                }
            }
        }

        // Note that conditional property enablement/exclusion only applies if
        // the attribute is present. In its absence, all overlays are presumed enabled.
        if (propName.size() > 0 && propValue.size() > 0) {
            // if property set & equal to value, then include overlay - otherwise skip
            if (!check_property(propName, propValue)) {
                return NO_OVERLAY_TAG;
            }
        }

        if (target == String16(target_package_name)) {
            return priority;
        }
        return NO_OVERLAY_TAG;
    }

    int parse_manifest(const void *data, size_t size, const char *target_package_name)
    {
        ResXMLTree parser;
        parser.setTo(data, size);
        if (parser.getError() != NO_ERROR) {
            ALOGD("%s failed to init xml parser, error=0x%08x\n", __FUNCTION__, parser.getError());
            return -1;
        }

        ResXMLParser::event_code_t type;
        bool is_static_overlay = false;
        int priority = NO_OVERLAY_TAG;
        do {
            type = parser.next();
            if (type == ResXMLParser::START_TAG) {
                size_t len;
                String16 tag(parser.getElementName(&len));
                if (tag == String16("overlay")) {
                    priority = parse_overlay_tag(parser, target_package_name, &is_static_overlay);
                    break;
                }
            }
        } while (type != ResXMLParser::BAD_DOCUMENT && type != ResXMLParser::END_DOCUMENT);

        if (is_static_overlay) {
            return priority;
        }
        return NO_OVERLAY_TAG;
    }

    int parse_apk(const char *path, const char *target_package_name)
    {
        std::unique_ptr<ZipFileRO> zip(ZipFileRO::open(path));
        if (zip.get() == NULL) {
            ALOGW("%s: failed to open zip %s\n", __FUNCTION__, path);
            return -1;
        }
        ZipEntryRO entry;
        if ((entry = zip->findEntryByName("AndroidManifest.xml")) == NULL) {
            ALOGW("%s: failed to find entry AndroidManifest.xml\n", __FUNCTION__);
            return -1;
        }
        uint32_t uncompLen = 0;
        uint16_t method;
        if (!zip->getEntryInfo(entry, &method, &uncompLen, NULL, NULL, NULL, NULL)) {
            ALOGW("%s: failed to read entry info\n", __FUNCTION__);
            return -1;
        }
        if (method != ZipFileRO::kCompressDeflated) {
            ALOGW("%s: cannot handle zip compression method %" PRIu16 "\n", __FUNCTION__, method);
            return -1;
        }
        FileMap *dataMap = zip->createEntryFileMap(entry);
        if (dataMap == NULL) {
            ALOGW("%s: failed to create FileMap\n", __FUNCTION__);
            return -1;
        }
        char *buf = new char[uncompLen];
        if (NULL == buf) {
            ALOGW("%s: failed to allocate %" PRIu32 " byte\n", __FUNCTION__, uncompLen);
            delete dataMap;
            return -1;
        }
        StreamingZipInflater inflater(dataMap, uncompLen);
        if (inflater.read(buf, uncompLen) < 0) {
            ALOGW("%s: failed to inflate %" PRIu32 " byte\n", __FUNCTION__, uncompLen);
            delete[] buf;
            delete dataMap;
            return -1;
        }

        int priority = parse_manifest(buf, static_cast<size_t>(uncompLen), target_package_name);
        delete[] buf;
        delete dataMap;
        return priority;
    }
}

int idmap_scan(const char *target_package_name, const char *target_apk_path,
        const char *idmap_dir, const android::Vector<const char *> *overlay_dirs)
{
    String8 filename = String8(idmap_dir);
    filename.appendPath("overlays.list");

    SortedVector<Overlay> overlayVector;
    const size_t N = overlay_dirs->size();
    for (size_t i = 0; i < N; ++i) {
        const char *overlay_dir = overlay_dirs->itemAt(i);
        DIR *dir = opendir(overlay_dir);
        if (dir == NULL) {
            return EXIT_FAILURE;
        }

        struct dirent *dirent;
        while ((dirent = readdir(dir)) != NULL) {
            struct stat st;
            char overlay_apk_path[PATH_MAX + 1];
            snprintf(overlay_apk_path, PATH_MAX, "%s/%s", overlay_dir, dirent->d_name);
            if (stat(overlay_apk_path, &st) < 0) {
                continue;
            }
            if (!S_ISREG(st.st_mode)) {
                continue;
            }

            int priority = parse_apk(overlay_apk_path, target_package_name);
            if (priority < 0) {
                continue;
            }

            String8 idmap_path(idmap_dir);
            idmap_path.appendPath(flatten_path(overlay_apk_path + 1));
            idmap_path.append("@idmap");

            if (idmap_create_path(target_apk_path, overlay_apk_path, idmap_path.string()) != 0) {
                ALOGE("error: failed to create idmap for target=%s overlay=%s idmap=%s\n",
                        target_apk_path, overlay_apk_path, idmap_path.string());
                continue;
            }

            Overlay overlay(String8(overlay_apk_path), idmap_path, priority);
            overlayVector.add(overlay);
        }

        closedir(dir);
    }

    if (!writePackagesList(filename.string(), overlayVector)) {
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}