[Kimchi-devel] [PATCH] bug fix: Avoid equals sign in VM console URL

[Sheldon]

On 07/28/2014 08:28 PM, Aline Manera wrote:
>
> On 07/28/2014 06:15 AM, Sheldon wrote:
>> On 07/26/2014 05:01 AM, alinefm at linux.vnet.ibm.com wrote:
>>> From: Aline Manera <alinefm at linux.vnet.ibm.com>
>>>
>>> >From python documentation, base64.urlsafe_b64encode(s) substitutes 
>>> - instead
>>> of + and _ instead of / in the standard Base64 alphabet, BUT the 
>>> result can
>>> still contain = which is not safe in a URL query component.
>>> As token value is not decoded nowhere, replace = by A
>>
>> what about other character instead of A? such as "." or "~"
>>
>> This is the base64 alphabet:
>> 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
>>
>> "A" is in the alphabet.
>>
>
> Ok. I will use . to replace =
>
>>
>> or do not pad the encode string.
>> some base64 variant has no pad character.
>> http://en.wikipedia.org/wiki/Base64#Implementations_and_history
>>
>
> I think we can have problem in not using the pad if you have the same 
> code string to different sentence
> Example:
>
> "abcd"  = "YWJjZA="
> "jdcf" = "YWJjZA"

in python, I have try:

In [51]: base64.urlsafe_b64encode("jdcf")
Out[51]: 'amRjZg=='

In [52]: base64.urlsafe_b64encode("abcd")
Out[52]: 'YWJjZA=='


and in UI I also try:
atob("YWJjZA")
"abcd"
atob("YWJjZA=")
[Exception... "String contains an invalid character"  code: "5" 
nsresult: "0x80530005 (InvalidCharacterError)"  location: "<unknown>"]
atob("YWJjZA==")
"abcd"


>
> If we ignore the = in the first string we will have 2 matches to the 
> different values.
> Not sure it can happen in real world, but I think it is safe to use . 
> instead of =
>
>>
>> Then in python, it can easy strip the "="
>> In [21]: s1 = base64.urlsafe_b64encode("abcd")
>> In [22]: s1.rstrip("=")
>> Out[22]: 'YWJjZA'
>>
>> and In js add a funtion to
>> $ git diff
>> diff --git a/ui/js/src/kimchi.utils.js b/ui/js/src/kimchi.utils.js
>> index 480b9b5..2d252a7 100644
>> --- a/ui/js/src/kimchi.utils.js
>> +++ b/ui/js/src/kimchi.utils.js
>> @@ -191,3 +191,8 @@ kimchi.urlSafeB64Decode = function(str) {
>> kimchi.urlSafeB64Encode = function(str) {
>> return btoa(str).replace(/\+/g, '-').replace(/\//g, '_');
>> }
>> +
>> +kimchi.padBase64 = function(str) {
>> + padLen = str.length % 4;
>> + return str + new Array(padLen? 4 - padLen + 1 : 0).join("=");
>> +}
>>
>>
>> Now test this method:
>> in python:
>> In [40]: base64.urlsafe_b64encode("abcd")
>> Out[40]: 'YWJjZA=='
>>
>> In [41]: base64.urlsafe_b64encode("abcde")
>> Out[41]: 'YWJjZGU='
>>
>> In UI:
>> kimchi.padBase64("YWJjZA")
>> "YWJjZA=="
>>
>> kimchi.padBase64("YWJjZGU")
>> "YWJjZGU="
>>
>>
>>>
>>> The problem with equals sign was only identified on Spice connections.
>>> noVNC can deal well with that.
>>>
>>> For reference: https://docs.python.org/2/library/base64.html
>>>
>>> Signed-off-by: Aline Manera <alinefm at linux.vnet.ibm.com>
>>> ---
>>>   src/kimchi/vnc.py       |  9 ++++++++-
>>>   ui/js/src/kimchi.api.js | 18 ++++++++++++++++--
>>>   2 files changed, 24 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/src/kimchi/vnc.py b/src/kimchi/vnc.py
>>> index 9380e21..4159049 100644
>>> --- a/src/kimchi/vnc.py
>>> +++ b/src/kimchi/vnc.py
>>> @@ -54,7 +54,14 @@ def new_ws_proxy():
>>>
>>>   def add_proxy_token(name, port):
>>>       with open(os.path.join(WS_TOKENS_DIR, name), 'w') as f:
>>> -        name = base64.urlsafe_b64encode(name)
>>> +        """
>>> +        From python documentation base64.urlsafe_b64encode(s)
>>> +        substitutes - instead of + and _ instead of / in the
>>> +        standard Base64 alphabet, BUT the result can still
>>> +        contain = which is not safe in a URL query component.
>>> +        As token value is not decoded nowhere, replace = by A
>>> +        """
>>> +        name = base64.urlsafe_b64encode(name).replace('=', 'A')
>>>           f.write('%s: localhost:%s' % (name.encode('utf-8'), port))
>>>
>>>
>>> diff --git a/ui/js/src/kimchi.api.js b/ui/js/src/kimchi.api.js
>>> index 8f5b68f..30360c5 100644
>>> --- a/ui/js/src/kimchi.api.js
>>> +++ b/ui/js/src/kimchi.api.js
>>> @@ -352,7 +352,14 @@ var kimchi = {
>>>               }).done(function() {
>>>                   url = 'https://' + location.hostname + ':' + 
>>> proxy_port;
>>>                   url += "/console.html?url=vnc_auto.html&port=" + 
>>> proxy_port;
>>> -                url += "&path=?token=" + kimchi.urlSafeB64Encode(vm);
>>> +                /*
>>> +                 * From python documentation 
>>> base64.urlsafe_b64encode(s)
>>> +                 * substitutes - instead of + and _ instead of / in 
>>> the
>>> +                 * standard Base64 alphabet, BUT the result can still
>>> +                 * contain = which is not safe in a URL query 
>>> component.
>>> +                 * As token value is not decoded nowhere, replace = 
>>> by A
>>> +                 * */
>>> +                url += "&path=?token=" + 
>>> kimchi.urlSafeB64Encode(vm).replace(/=/g, 'A');
>>>                   url += "&kimchi=" + location.port;
>>>                   url += '&encrypt=1';
>>>                   window.open(url);
>>> @@ -377,7 +384,14 @@ var kimchi = {
>>>                   url = 'https://' + location.hostname + ':' + 
>>> proxy_port;
>>>                   url += "/console.html?url=spice.html&port=" + 
>>> proxy_port;
>>>                   url += "&listen=" + location.hostname;
>>> -                url += "&token=" + kimchi.urlSafeB64Encode(vm);
>>> +                /*
>>> +                 * From python documentation 
>>> base64.urlsafe_b64encode(s)
>>> +                 * substitutes - instead of + and _ instead of / in 
>>> the
>>> +                 * standard Base64 alphabet, BUT the result can still
>>> +                 * contain = which is not safe in a URL query 
>>> component.
>>> +                 * As token value is not decoded nowhere, replace = 
>>> by A
>>> +                 * */
>>> +                url += "&token=" + 
>>> kimchi.urlSafeB64Encode(vm).replace(/=/g, 'A');
>>>                   url += "&kimchi=" + location.port;
>>>                   url += '&encrypt=1';
>>>                   window.open(url);
>>
>>
>
>
>


-- 
Thanks and best regards!

Sheldon Feng(冯少合)<shaohef at linux.vnet.ibm.com>
IBM Linux Technology Center