Initial tool for OBB manipulation

Add "obbtool" host command for adding, removing, and querying Opaque
Binary Blob (OBB) information from a file.

Change-Id: Id2ac41e687ad2a500c362616d6738a8ae7e8f5c3

include/utils/ObbFile.h

@@ -35,6 +35,8 @@ public:
     bool readFrom(int fd);
     bool writeTo(const char* filename);
     bool writeTo(int fd);
+    bool removeFrom(const char* filename);
+    bool removeFrom(int fd);
 
     const char* getFileName() const {
         return mFileName;
@@ -78,6 +80,8 @@ private:
 
     size_t mFileSize;
 
+    size_t mFooterStart;
+
     unsigned char* mReadBuf;
 
     bool parseObbFile(int fd);

libs/utils/ObbFile.cpp

@@ -156,9 +156,9 @@ bool ObbFile::parseObbFile(int fd)
             return false;
         }
 
-        if (footerSize < kFooterMinSize) {
-            LOGW("claimed footer size is too small (%08zx; minimum size is 0x%x)\n",
-                    footerSize, kFooterMinSize);
+        if (footerSize < (kFooterMinSize - kFooterTagSize)) {
+            LOGW("claimed footer size is too small (0x%zx; minimum size is 0x%x)\n",
+                    footerSize, kFooterMinSize - kFooterTagSize);
             return false;
         }
     }
@@ -169,6 +169,8 @@ bool ObbFile::parseObbFile(int fd)
         return false;
     }
 
+    mFooterStart = fileOffset;
+
     char* scanBuf = (char*)malloc(footerSize);
     if (scanBuf == NULL) {
         LOGW("couldn't allocate scanBuf: %s\n", strerror(errno));
@@ -293,4 +295,38 @@ bool ObbFile::writeTo(int fd)
     return true;
 }
 
+bool ObbFile::removeFrom(const char* filename)
+{
+    int fd;
+    bool success = false;
+
+    fd = ::open(filename, O_RDWR);
+    if (fd < 0) {
+        goto out;
+    }
+    success = removeFrom(fd);
+    close(fd);
+
+out:
+    if (!success) {
+        LOGW("failed to remove signature from %s: %s\n", filename, strerror(errno));
+    }
+    return success;
+}
+
+bool ObbFile::removeFrom(int fd)
+{
+    if (fd < 0) {
+        return false;
+    }
+
+    if (!readFrom(fd)) {
+        return false;
+    }
+
+    ftruncate(fd, mFooterStart);
+
+    return true;
+}
+
 }