Be more careful with user-supplied buffersrb/fix-2333

This adds in missing calls to `git_buf_sanitize` and fixes a
number of places where `git_buf` APIs could inadvertently write
NUL terminator bytes into invalid buffers.  This also changes the
behavior of `git_buf_sanitize` to NUL terminate a buffer if it can
and of `git_buf_shorten` to do nothing if it can.

Adds tests of filtering code with zeroed (i.e. unsanitized) buffer
which was previously triggering a segfault.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/config.c b/src/config.c
index f9d697197..4dddab6df 100644
--- a/src/config.c
+++ b/src/config.c
@@ -967,16 +967,19 @@ void git_config_iterator_free(git_config_iterator *iter)
 
 int git_config_find_global(git_buf *path)
 {
+	git_buf_sanitize(path);
 	return git_sysdir_find_global_file(path, GIT_CONFIG_FILENAME_GLOBAL);
 }
 
 int git_config_find_xdg(git_buf *path)
 {
+	git_buf_sanitize(path);
 	return git_sysdir_find_xdg_file(path, GIT_CONFIG_FILENAME_XDG);
 }
 
 int git_config_find_system(git_buf *path)
 {
+	git_buf_sanitize(path);
 	return git_sysdir_find_system_file(path, GIT_CONFIG_FILENAME_SYSTEM);
 }