Merge "Check if idsig size is within IncFs limits." into sc-dev

core/java/android/os/incremental/V4Signature.java

@@ -41,6 +41,8 @@ public class V4Signature {
     public static final int HASHING_ALGORITHM_SHA256 = 1;
     public static final byte LOG2_BLOCK_SIZE_4096_BYTES = 12;
 
+    public static final int INCFS_MAX_SIGNATURE_SIZE = 8096;  // incrementalfs.h
+
     /**
      * IncFS hashing data.
      */
@@ -191,8 +193,12 @@ public class V4Signature {
 
     private static V4Signature readFrom(InputStream stream) throws IOException {
         final int version = readIntLE(stream);
-        final byte[] hashingInfo = readBytes(stream);
-        final byte[] signingInfo = readBytes(stream);
+        int maxSize = INCFS_MAX_SIGNATURE_SIZE;
+        final byte[] hashingInfo = readBytes(stream, maxSize);
+        if (hashingInfo != null) {
+            maxSize -= hashingInfo.length;
+        }
+        final byte[] signingInfo = readBytes(stream, maxSize);
         return new V4Signature(version, hashingInfo, signingInfo);
     }
 
@@ -231,9 +237,13 @@ public class V4Signature {
         stream.write(buffer);
     }
 
-    private static byte[] readBytes(InputStream stream) throws IOException {
+    private static byte[] readBytes(InputStream stream, int maxSize) throws IOException {
         try {
             final int size = readIntLE(stream);
+            if (size > maxSize) {
+                throw new IOException(
+                        "Signature is too long. Max allowed is " + INCFS_MAX_SIGNATURE_SIZE);
+            }
             final byte[] bytes = new byte[size];
             readFully(stream, bytes);
             return bytes;

services/core/jni/com_android_server_pm_PackageManagerShellCommandDataLoader.cpp

@@ -171,17 +171,23 @@ static inline int32_t readLEInt32(borrowed_fd fd) {
     return result;
 }
 
-static inline std::vector<char> readBytes(borrowed_fd fd) {
-    int32_t size = readLEInt32(fd);
-    std::vector<char> result(size);
-    android::base::ReadFully(fd, result.data(), size);
-    return result;
+static inline bool skipBytes(borrowed_fd fd, int* max_size) {
+    int32_t size = std::min(readLEInt32(fd), *max_size);
+    if (size <= 0) {
+        return false;
+    }
+    *max_size -= size;
+    return (TEMP_FAILURE_RETRY(lseek64(fd.get(), size, SEEK_CUR)) >= 0);
 }
 
 static inline int32_t skipIdSigHeaders(borrowed_fd fd) {
-    readLEInt32(fd);        // version
-    readBytes(fd);          // hashingInfo
-    readBytes(fd);          // signingInfo
+    // version
+    auto version = readLEInt32(fd);
+    int max_size = INCFS_MAX_SIGNATURE_SIZE - sizeof(version);
+    // hashingInfo and signingInfo
+    if (!skipBytes(fd, &max_size) || !skipBytes(fd, &max_size)) {
+        return -1;
+    }
     return readLEInt32(fd); // size of the verity tree
 }
 
@@ -253,8 +259,12 @@ static inline InputDescs openLocalFile(JNIEnv* env, const JniIds& jni, jobject s
 
     unique_fd idsigFd = openLocalFile(env, jni, shellCommand, idsigPath);
     if (idsigFd.ok()) {
-        auto treeSize = verityTreeSizeForFile(size);
         auto actualTreeSize = skipIdSigHeaders(idsigFd);
+        if (actualTreeSize < 0) {
+            ALOGE("Error reading .idsig file: wrong format.");
+            return {};
+        }
+        auto treeSize = verityTreeSizeForFile(size);
         if (treeSize != actualTreeSize) {
             ALOGE("Verity tree size mismatch: %d vs .idsig: %d.", int(treeSize),
                   int(actualTreeSize));