Fix buffer overflow in config parser

When interpreting a config value, the config parser reads in 1+ space
character(s) and puts -one- space character in the buffer as soon as
the first non-space character is encountered (if not inside quotes).

Unfortunately the buffer size check lacks the extra space character
which gets inserted at the next non-space character, resulting in
a crash with a specially crafted config entry.

The unit test now uses Java to compile a platform independent
.NET framework to output the test string in C# :o)

    Read: Thanks to Johannes Sixt for the correct printf call
    which replaces the perl invocation.

Signed-off-by: Thomas Jarosch <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: thomasjfox

config.c

@@ -51,7 +51,7 @@ static char *parse_value(void)
 
 	for (;;) {
 		int c = get_next_char();
-		if (len >= sizeof(value))
+		if (len >= sizeof(value) - 1)
 			return NULL;
 		if (c == '\n') {
 			if (quote)

t/t1303-wacky-config.sh

@@ -10,7 +10,7 @@ setup() {
 
 check() {
 	echo "$2" >expected
-	git config --get "$1" >actual
+	git config --get "$1" >actual 2>&1
 	test_cmp actual expected
 }
 
@@ -40,4 +40,11 @@ test_expect_success 'make sure git config escapes section names properly' '
 	check "$SECTION" bar
 '
 
+LONG_VALUE=$(printf "x%01021dx a" 7)
+test_expect_success 'do not crash on special long config line' '
+	setup &&
+	git config section.key "$LONG_VALUE" &&
+	check section.key "fatal: bad config file line 2 in .git/config"
+'
+
 test_done