reference_monitor.r2py

# Constants used as dictionary keys for security definitions
TYPE = "type"
ARGS = "args"
RETURN = "return"
EXCP = "exceptions"
TARGET = "target"
FUNC = "func"
OBJC = "objc"

# Definition of a class ABFile
class ABFile:
    def __init__(self, filename, create):
        # Set the 'debug' flag in the context to False
        mycontext['debug'] = False

        # Initialize variables to store file names
        self.Afn = filename + '.a'  # File 'A' name
        self.Bfn = filename + '.b'  # File 'B' name
        self.original_filename = filename

        # Depending on the 'create' flag, create or open files 'A' and 'B'
        if create:
            # If 'A' file does not exist, create both 'A' and 'B' files
            if self.Afn not in listfiles():
                self.Afile = openfile(self.Afn, True)
                self.Bfile = openfile(self.Bfn, True)
                self.Afile.writeat('SE', 0)  # Write 'SE' at the beginning of file 'A'
            else:
                # If 'A' file exists, open 'A' in read mode and 'B' in write mode
                self.Afile = openfile(self.Afn, False)
                self.Bfile = openfile(self.Bfn, True)
        else:
            # If 'create' flag is False, open 'A' in read mode and 'B' in write mode
            self.Afile = openfile(self.Afn, False)
            self.Bfile = openfile(self.Bfn, True)

    # Method to write data at a specific offset in file 'B'
    def writeat(self, data, offset):
        if offset < 0:
            raise ValueError("Offset cannot be negative")
        if not data:
            raise ValueError("Data cannot be empty")
        self.Bfile.writeat(data, offset)

    # Method to read a certain number of bytes from file 'A' at a given offset
    def readat(self, bytes, offset):
        if offset < 0:
            raise ValueError("Offset cannot be negative")
        return self.Afile.readat(bytes, offset)

    # Method to close both files 'A' and 'B' with a backup mechanism
    def close(self):
        # Read the content of file 'B' at offset 0
        backup_data = self.Bfile.readat(None, 0)
        # If the content starts with "S" and ends with "E," it's considered valid backup data
        if backup_data.startswith("S") and backup_data.endswith("E"):
            # Restore the content of file 'A' from the backup data
            self.Afile.writeat(backup_data, 0)
            # Open the original file and restore its content as well
            original_file = openfile(self.original_filename, True)
            original_file.writeat(backup_data, 0)
            original_file.close()
        # Close both files 'A' and 'B' and remove file 'B'
        self.Afile.close()
        self.Bfile.close()
        removefile(self.Bfn)

# Function to create or open instances of ABFile
def ABopenfile(filename, create):
    # Check if the filename ends with '.a' or '.b' and raise an exception if so
    if filename.endswith('.a') or filename.endswith('.b'):
        raise Exception("Security violation: Cannot open a file ending with '.a' or '.b' for writing.")
    # Create and return an ABFile object with the specified filename and create flag
    return ABFile(filename, create)

# Dictionary containing security definitions for ABFile methods
sec_file_def = {
    "obj-type": ABFile,
    "name": "ABFile",
    "writeat": {TYPE: FUNC, ARGS: (str, (int, int)), EXCP: Exception, RETURN: (int, type(None)), TARGET: ABFile.writeat},
    "readat": {TYPE: FUNC, ARGS: ((int, int, type(None)), (int, int)), EXCP: Exception, RETURN: str, TARGET: ABFile.readat},
    "close": {TYPE: FUNC, ARGS: None, EXCP: Exception, RETURN: (bool, type(None)), TARGET: ABFile.close}
}

# Add the security definitions for ABopenfile to CHILD_CONTEXT_DEF dictionary
CHILD_CONTEXT_DEF["ABopenfile"] = {TYPE: OBJC, ARGS: (str, bool), EXCP: Exception, RETURN: sec_file_def, TARGET: ABopenfile}

# Call a function secure_dispatch_module() for some security-related operation
secure_dispatch_module()