Merge Android U (ab/10368041)

Bug: 291102124
Merged-In: I3c9e9d15786fbead1b874636b46844f6c24bccc2
Change-Id: Id6cf6cc13baef4e67486c6271a1510146204affa

1 files changed, 110 insertions, 0 deletions

diff --git a/libs/androidfw/ApkParsing.cpp b/libs/androidfw/ApkParsing.cpp
new file mode 100644
index 000000000000..32d2c5b05acb
--- /dev/null
+++ b/libs/androidfw/ApkParsing.cpp
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2022 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 "androidfw/ApkParsing.h"
+#include <algorithm>
+#include <array>
+#include <stdlib.h>
+#include <string_view>
+#include <sys/types.h>
+
+const std::string_view APK_LIB = "lib/";
+const size_t APK_LIB_LEN = APK_LIB.size();
+
+const std::string_view LIB_PREFIX = "/lib";
+const size_t LIB_PREFIX_LEN = LIB_PREFIX.size();
+
+const std::string_view LIB_SUFFIX = ".so";
+const size_t LIB_SUFFIX_LEN = LIB_SUFFIX.size();
+
+static const std::array<std::string_view, 2> abis = {"arm64-v8a", "x86_64"};
+
+namespace android::util {
+const char* ValidLibraryPathLastSlash(const char* fileName, bool suppress64Bit, bool debuggable) {
+    // Make sure the filename is at least to the minimum library name size.
+    const size_t fileNameLen = strlen(fileName);
+    static const size_t minLength = APK_LIB_LEN + 2 + LIB_PREFIX_LEN + 1 + LIB_SUFFIX_LEN;
+    if (fileNameLen < minLength) {
+        return nullptr;
+    }
+
+    const char* lastSlash = strrchr(fileName, '/');
+    if (!lastSlash) {
+        return nullptr;
+    }
+
+    // Skip directories.
+    if (*(lastSlash + 1) == 0) {
+        return nullptr;
+    }
+
+    // Make sure the filename is safe.
+    if (!isFilenameSafe(lastSlash + 1)) {
+        return nullptr;
+    }
+
+    // Make sure there aren't subdirectories by checking if the next / after lib/ is the last slash
+    if (memchr(fileName + APK_LIB_LEN, '/', fileNameLen - APK_LIB_LEN) != lastSlash) {
+        return nullptr;
+    }
+
+    if (!debuggable) {
+        // Make sure the filename starts with lib and ends with ".so".
+        if (strncmp(fileName + fileNameLen - LIB_SUFFIX_LEN, LIB_SUFFIX.data(), LIB_SUFFIX_LEN) != 0
+            || strncmp(lastSlash, LIB_PREFIX.data(), LIB_PREFIX_LEN) != 0) {
+            return nullptr;
+        }
+    }
+
+    // Don't include 64 bit versions if they are suppressed
+    if (suppress64Bit && std::find(abis.begin(), abis.end(), std::string_view(
+        fileName + APK_LIB_LEN, lastSlash - fileName - APK_LIB_LEN)) != abis.end()) {
+      return nullptr;
+    }
+
+    return lastSlash;
+}
+
+bool isFilenameSafe(const char* filename) {
+    off_t offset = 0;
+    for (;;) {
+        switch (*(filename + offset)) {
+        case 0:
+            // Null.
+            // If we've reached the end, all the other characters are good.
+            return true;
+
+        case 'A' ... 'Z':
+        case 'a' ... 'z':
+        case '0' ... '9':
+        case '+':
+        case ',':
+        case '-':
+        case '.':
+        case '/':
+        case '=':
+        case '_':
+            offset++;
+            break;
+
+        default:
+            // We found something that is not good.
+            return false;
+        }
+    }
+    // Should not reach here.
+}
+}
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