[OpenWrt-Devel] [PATCH] [libubox][v3] b64: add base64 support

[Felix Fietkau]

On 2015-04-14 18:24, Luka Perkov wrote:
> Hi,
> 
> On Tue, Apr 14, 2015 at 06:00:32PM +0200, Felix Fietkau wrote:
>> >> +	if (data[len - 1] == '=')
>> >> +		ret--;
>> >> +
>> >> +	if (data[len - 2] == '=')
>> >> +		ret--;
>> > 
>> > the 2 if clauses look redundant and i guess you could solve it with a loop
> 
> Ok. I'll fix it.
> 
>> I'd prefer not passing in the input buffer here at all - a tiny
>> overestimation of the decode size doesn't hurt.
> 
> I don't think that is a good idea since we do not have NULL terminating
> output buffer in b64decode(). If you really want a function without
> input buffer we can make another one called:
> 
> static inline int b64_decode_size_approx(size_t len);
> 
> The overestimation is likely going to cause problems in cases like this:
> 
> buf = malloc(b64_decode_size(data, data_len));
> if (!buf)
> 	return -1
> 
> buf_len = b64decode(rbuf, data, data_len);
> if (!buf_len)
> 	return -1
> 
> write(fd, buf, buf_len);
> 
> In this case end of buf could be foobared and because of that extra
> bytes could be written.
As long as buf_len only returns the actual number of output bytes, I
don't see how overestimation is going to cause problems here.
Also, I think it would be nice to have a 0-terminated output. The extra
0-byte should be counted only in b64_decode_size and not in the result
of b64decode.
I think that will make the API harder to misuse, as calling C-string
functions on the result will be safe by default.

- Felix
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