[PATCH v2] Fix buffer overflow in config parser

[Thomas Jarosch <thomas.jarosch@intra2net.com>]

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.

Signed-off-by: Thomas Jarosch <thomas.jarosch@intra2net.com>
---
 config.c                |    2 +-
 t/t1303-wacky-config.sh |    9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/config.c b/config.c
index b76fe4c..2d70398 100644
--- a/config.c
+++ b/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)
diff --git a/t/t1303-wacky-config.sh b/t/t1303-wacky-config.sh
index 1983076..a7d8d25 100755
--- a/t/t1303-wacky-config.sh
+++ b/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=`perl -e 'print "x" x 1023," a"'`
+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
-- 
1.6.1.3