Re: [PATCH 1/2] mailinfo: extract is_from_line from mailsplit

[Junio C Hamano <gitster@pobox.com>]

Andreas Schwab <schwab@linux-m68k.org> writes:

>> +	colon = line + len - 2;
>> +	line += 5;
>> +	for (;;) {
>> +		if (colon < line)
>> +			return 0;
>> +		if (*--colon == ':')
>> +			break;
>> +	}
>> +
>> +	if (!isdigit(colon[-4]) ||
>> +	    !isdigit(colon[-2]) ||
>> +	    !isdigit(colon[-1]) ||
>> +	    !isdigit(colon[ 1]) ||
>> +	    !isdigit(colon[ 2]))
>> +		return 0;
>> +
>> +	/* year */
>> +	if (strtol(colon+3, NULL, 10) <= 90)
>> +		return 0;
>> +
>> +	/* Ok, close enough */
>> +	return 1;
>> +}
>
> Should this be made more strict, like by checking for a space before the
> year?

The function seems to judge the line to be "close enough" by
checking these places (please view with fixed-width font ;-):

    From me Mon Jul 25 01:23:45 2016
    xxxxx               x xxxxx ....

We only see if the year part is more than 90 but we do not even
ensure that it is at the end of the line without any further
garbage, which I think is probably OK for the purpose of "close
enough".

We also do not bother rejecting a single-digit hour, or there is a
colon between the hour and minute part.

I would say requiring SP between the year and the second, and
requiring colon between hour and minute, would probably be a good
change, i.e. something like this:

	if (!isdigit(colon[-4]) ||
	    colon[-3] != ':' ||
	    !isdigit(colon[-2]) ||
	    !isdigit(colon[-1]) ||
	    !isdigit(colon[ 1]) ||
	    !isdigit(colon[ 2]) ||
	    colon[3] != ' ')

would be safe enough without increasing the false negatives too
much.