Fix potential null pointer dereference in FlutterDartProject (flutter#6035)

jamesderlin · web-flow · commit 4ff4a5cc995e · 2018-08-16T17:40:33.000-07:00
If `FlutterDartProject` found an `FLTLibraryPath` entry in an iOS
application's `Info.plist`, it assumed that values that were valid
filesystem paths were paths to bundles.  If the attempt to retrieve
the `NSBundle` fails, `FlutterDartProject` ignored the failure and
then would assign `nil` to a C++ `std::string`, resulting in a null
pointer dereference.

Add some failure checks to prevent this.
diff --git a/shell/platform/darwin/ios/framework/Source/FlutterDartProject.mm b/shell/platform/darwin/ios/framework/Source/FlutterDartProject.mm
@@ -73,8 +73,10 @@
       NSString* libraryName = [mainBundle objectForInfoDictionaryKey:@"FLTLibraryPath"];
       NSString* libraryPath = [mainBundle pathForResource:libraryName ofType:@""];
       if (libraryPath.length > 0) {
-        settings.application_library_path =
-            [NSBundle bundleWithPath:libraryPath].executablePath.UTF8String;
+        NSString* executablePath = [NSBundle bundleWithPath:libraryPath].executablePath;
+        if (executablePath.length > 0) {
+          settings.application_library_path = executablePath.UTF8String;
+        }
       }
     }
 
@@ -84,8 +86,11 @@
       NSString* applicationFrameworkPath =
           [mainBundle pathForResource:@"Frameworks/App.framework" ofType:@""];
       if (applicationFrameworkPath.length > 0) {
-        settings.application_library_path =
-            [NSBundle bundleWithPath:applicationFrameworkPath].executablePath.UTF8String;
+        NSString* executablePath =
+            [NSBundle bundleWithPath:applicationFrameworkPath].executablePath;
+        if (executablePath.length > 0) {
+          settings.application_library_path = executablePath.UTF8String;
+        }
       }
     }
   }

Original file line number	Diff line number	Diff line change
`@@ -73,8 +73,10 @@`
`73`	`73`	`NSString* libraryName = [mainBundle objectForInfoDictionaryKey:@"FLTLibraryPath"];`
`74`	`74`	`NSString* libraryPath = [mainBundle pathForResource:libraryName ofType:@""];`
`75`	`75`	`if (libraryPath.length > 0) {`
`76`		`- settings.application_library_path =`
`77`		`- [NSBundle bundleWithPath:libraryPath].executablePath.UTF8String;`
	`76`	`+ NSString* executablePath = [NSBundle bundleWithPath:libraryPath].executablePath;`
	`77`	`+ if (executablePath.length > 0) {`
	`78`	`+ settings.application_library_path = executablePath.UTF8String;`
	`79`	`+ }`
`78`	`80`	`}`
`79`	`81`	`}`
`80`	`82`
`@@ -84,8 +86,11 @@`
`84`	`86`	`NSString* applicationFrameworkPath =`
`85`	`87`	`[mainBundle pathForResource:@"Frameworks/App.framework" ofType:@""];`
`86`	`88`	`if (applicationFrameworkPath.length > 0) {`
`87`		`- settings.application_library_path =`
`88`		`- [NSBundle bundleWithPath:applicationFrameworkPath].executablePath.UTF8String;`
	`89`	`+ NSString* executablePath =`
	`90`	`+ [NSBundle bundleWithPath:applicationFrameworkPath].executablePath;`
	`91`	`+ if (executablePath.length > 0) {`
	`92`	`+ settings.application_library_path = executablePath.UTF8String;`
	`93`	`+ }`
`89`	`94`	`}`
`90`	`95`	`}`
`91`	`96`	`}`