Metadata-Version: 2.1
Name: evalidate
Version: 0.7.7
Summary: Validation and secure evaluation untrusted python expressions
Home-page: http://bitbucket.org/yaroslaff/evalidate
Author: Yaroslav Polyakov
Author-email: xenon@sysattack.com
License: MIT
Description: ﻿Evalidate
        ===
        Evalidate is simple python module for safe eval()'uating user-supplied (possible malicious) logical expressions in python syntax.
        
        Purpose
        ---
        Originally it's developed for filtering (performing boolean expressions) complex data structures e.g. raise salary if 
        
        ```python
        person.age>30 and person.salary>5000 or "Jack" in person.children
        ```
        or, like simple firewall, allow inbound traffic if:
        
        ```python
        (packet.tcp.dstport==22 or packet.tcp.dstport==80) and packet.tcp.srcip in WhiteListIP
        ```
        But also, it can be used for other expressions, e.g. arithmetical, like
        ```python
        a+b-100
        ```
        
        Install
        ---
        ```shell
        pip install evalidate
        ```
            
        Security
        ---
        Built-in python features such as compile() or eval() is quite powerful to run any kind of user-supplied code, but could be insecure if used code is malicious like os.system("rm -rf /"). Evalidate works on whitelist principle, allowing code only if it consist only  of safe operations (based on authors views about what is safe and what is not, your mileage may vary - but you can supply your list of safe operations)
        
        Very basic example
        ---
        ```python
        import evalidate
        
        src="a+b" # source code
        c={'a': 1, 'b': 2} # context, variables which will be available for code
        
        success,result = evalidate.safeeval(src,c)
        if success:
            print result
        else:
            print "ERROR:",result
        ```
        
        Gives output:
        
            3
        
        In case of dangerous code:
        ```python
        src="__import__('os').system('clear')"
        ```    
            
        output will be:
        
            ERROR: Validation error: Operaton type Call is not allowed
            
        # Extending evalidate, safenodes and addnodes #
        Evalidate has built-in set of python operations, which are considered 'safe' (from author point of view). Code is considered valid only if all of it's operations are in this lisst. You can override this list by adding argument *safenodes* like:
        ```python
        success,result = evalidate.safeeval(src,c, safenodes=['Expression','BinOp','Num','Add'])
        ```
        this will be enough for '1+1' expression (in src argument), but not for '1-1'. If you will try '1-1', it will report error:
        
            ERROR: Validation error: Operaton type Sub is not allowed
        
        
        This way you can start from scratch and allow only required operations. As an alternative, you can use built-in list of allowed operations and extend it if needed, using *addnodes* argument.
        
        For example, "1*1" will give error:
        
          ERROR: Validation error: Operaton type Mult is not allowed
        
        
        But it will work with addnodes:
        ```python
        success,result = evalidate.safeeval(src,c, addnodes=['Mult'])
        ```    
        Please note, using 'Mult' operation isn't very secure, because for strings it can lead to Out-of-memory:
        ```python
        src='"a"=="a"*100*100*100*100*100'
        ```    
            ERROR: Runtime error (OverflowError): repeated string is too long
        
        # Allowing function calls
        Evalidate does not allows any function calls by default:
        ```
        >>> import evalidate
        >>> evalidate.safeeval('1+int(2)')
        (False, 'Validation error: Operaton type Call is not allowed')
        ```
        To enable int() function, need to allow 'Call' node and  add this function to list of allowed function:
        ```
        >>> evalidate.safeeval('1+int(2)', addnodes=['Call'], funcs=['int'])
        (True, 3)
        ```
        Attempt to call other functions will fail (because it's not in funcs list):
        ```
        >>> evalidate.safeeval('1+round(2)', addnodes=['Call'], funcs=['int'])
        (False, 'Validation error: Call to function round() is not allowed')
        ```
        
        Functions
        ---
        
        ### safeeval()
        
        ```python
        success,result = safeeval(src,context={}, safenodes=None, addnodes=None, funcs=None, attrs=None)
        ```
        
        *safeeval* is C-style higher-level wrapper of evalidate(), which validates code and runs it (if validation is successful)
        
        *src* - source expression like "person['Age']>30 and salary==10000"
        
        *context* - dictionary of variables, available for evaluated code.
        
        *safenodes*, *addnodes*, *funcs* and *attrs* are same as in evalidate()
        
        return values:
        
        *success* - binary, True if validation is successul and evaluation didn't thrown any exceptions. (False in this case) 
        
        *result* - if success==True, result is result of expression. If success==False, result is string with error message, like "ERROR: Runtime error (NameError): name 'aaa' is not defined"
            
        safeeval doesn't throws any exceptions
        
        ### evalidate()     
        ```python
        node = evalidate(expression, safenodes=None, addnodes=None, funcs=None, attrs=None)
        ```
        evalidate() is main (and recommended to use) method, performs parsing of python expession, validates it, and returns python AST (Abstract Syntax Tree) structure, which can be later compiled and executed
        ```python            
        
        >>> import evalidate
        >>> node = evalidate.evalidate('1+2')
        >>> code = compile(node,'<usercode>','eval')
        >>> eval(code)
        3
        ```    
            
        - *expression* - string with python expressions like '1+2' or 'a+b' or 'a if a>0 else b' or 'p.salary * 1.2'
        - *safenodes* - list of allowed nodes. This will *override* built-in list of allowed nodes. e.g. `safenodes=['Expression','BinOp','Num','Add'])`
        - *addnodes* - list of allowed nodes. This will *extend* built-in lsit of allowed nodes. e.g. `addnodes=['Mult']`
        - *funcs* - list of allowed function calls. You need to add 'Call' to safe nodes. e.g. `funcs=['int']`
        - *attrs* - list of allowed attributes. You need to add 'Attribute' to attrs. e.g. `attrs=['salary']`.
        
            
        evalidate() throws ValueError if it doesn't like source code (if code has unsafe operations).
            
        Even if evalidate is successful, this doesn't guarantees that code will run well, For example, code still can have NameError (if tries to access undefined variable) or ZeroDivisionError.
        
        Examples
        ---
        
        ### Filtering by user-supplied condition ###
        ```python
        import evalidate
            
        depot = [
            {
                'book': 'Sirens of Titan',
                'price': 12,
                'stock': 4
            },
            {
                'book': 'Gone Girl',
                'price': 9.8,
                'stock': 0
            },
            {
                'book': 'Choke',
                'price': 14,
                'stock': 2
            },
            {
                'book': 'Pulp',
                'price': 7.45,
                'stock': 4
            }
        ]
            
        #src='stock==0' # books out of stock
        src='stock>0 and price>8' # expensive book available for sale
            
        for book in depot:
            success, result = evalidate.safeeval(src,book)
            
            if success:
                if result:
                    print book
            else:
                print "ERR:", result
        ```    
            
        With first src line ('stock==0') it gives:
        
            {'price': 9.8, 'book': 'Gone Girl', 'stock': 0}
        
        With second src line ('stock>0 and price>8') it gives:
        
            {'price': 12, 'book': 'Sirens of Titan', 'stock': 4}
            {'price': 14, 'book': 'Choke', 'stock': 2}
            
        
        
        ### Data as objects ###
        Data represented as object with attributes (not as dictionary) (we have to add 'Attribute' to safe nodes). Increase salary for person for 200, and additionaly 25 for each year (s)he works in company.
        ```python
        import evalidate
                                
        class Person:
            pass
                                
        p = Person()
        p.salary=1000
        p.age=5
                                
        data = {'p':p}
        src = 'p.salary+200+p.age*25'
                                
        success, result = evalidate.safeeval(src,data,addnodes=['Attribute','Mult'], attrs=['salary', 'age'])
                                
        if success:
            print "result", result
        else:
            print "ERR:", result
        ```
                                                        
        ### Validate, compile and evaluate code ###
        ```python
        import evalidate
        import os
            
        data={'one':1,'two':2}
        src='one+two+3'
        #src='one+two+3+os.system("clear")'
            
        try:
            node = evalidate.evalidate(src)
            code = compile(node,'<usercode>','eval')
            result = eval(code,{},data)
            print "result:",result
        except ValueError:
            print "Bad source code:", src
        ```    
                     
        More info
        ---
        Want more info? Check source code of module, it's very short and simple, easy to modify
        
        Contact
        ---
        Write me: yaroslaff@gmail.com
        
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