macOS Default Sandbox Debug

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In this page you can find how to create an app to launch arbitrary commands from inside the default macOS sandbox:

1. Compile the application:

#include <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        while (true) {
            char input[512];

            printf("Enter command to run (or 'exit' to quit): ");
            if (fgets(input, sizeof(input), stdin) == NULL) {
                break;
            }

            // Remove newline character
            size_t len = strlen(input);
            if (len > 0 && input[len - 1] == '\n') {
                input[len - 1] = '\0';
            }

            if (strcmp(input, "exit") == 0) {
                break;
            }

            system(input);
        }
    }
    return 0;
}

Compile it running: clang -framework Foundation -o SandboxedShellApp main.m

2. Build the .app bundle

mkdir -p SandboxedShellApp.app/Contents/MacOS
mv SandboxedShellApp SandboxedShellApp.app/Contents/MacOS/

cat << EOF > SandboxedShellApp.app/Contents/Info.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>CFBundleIdentifier</key>
    <string>com.example.SandboxedShellApp</string>
    <key>CFBundleName</key>
    <string>SandboxedShellApp</string>
    <key>CFBundleVersion</key>
    <string>1.0</string>
    <key>CFBundleExecutable</key>
    <string>SandboxedShellApp</string>
</dict>
</plist>
EOF

3. Define the entitlements

cat << EOF > entitlements.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>com.apple.security.app-sandbox</key>
    <true/>
</dict>
</plist>
EOF

cat << EOF > entitlements.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>com.apple.security.app-sandbox</key>
    <true/>
    <key>com.apple.security.files.downloads.read-write</key>
    <true/>
</dict>
</plist>
EOF

4. Sign the app (you need to create a certificate in the keychain)

codesign --entitlements entitlements.plist -s "YourIdentity" SandboxedShellApp.app
./SandboxedShellApp.app/Contents/MacOS/SandboxedShellApp

# An d in case you need this in the future
codesign --remove-signature SandboxedShellApp.app