convert trivial sprintf / strcpy calls to xsnprintf

We sometimes sprintf into fixed-size buffers when we know
that the buffer is large enough to fit the input (either
because it's a constant, or because it's numeric input that
is bounded in size). Likewise with strcpy of constant
strings.

However, these sites make it hard to audit sprintf and
strcpy calls for buffer overflows, as a reader has to
cross-reference the size of the array with the input. Let's
use xsnprintf instead, which communicates to a reader that
we don't expect this to overflow (and catches the mistake in
case we do).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/diff.c b/diff.c
index 08508f6..788e371 100644
--- a/diff.c
+++ b/diff.c
@@ -2880,7 +2880,7 @@ static void prep_temp_blob(const char *path, struct diff_tempfile *temp,
 	temp->name = get_tempfile_path(&temp->tempfile);
 	strcpy(temp->hex, sha1_to_hex(sha1));
 	temp->hex[40] = 0;
-	sprintf(temp->mode, "%06o", mode);
+	xsnprintf(temp->mode, sizeof(temp->mode), "%06o", mode);
 	strbuf_release(&buf);
 	strbuf_release(&template);
 	free(path_dup);
@@ -2897,8 +2897,8 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 		 * a '+' entry produces this for file-1.
 		 */
 		temp->name = "/dev/null";
-		strcpy(temp->hex, ".");
-		strcpy(temp->mode, ".");
+		xsnprintf(temp->hex, sizeof(temp->hex), ".");
+		xsnprintf(temp->mode, sizeof(temp->mode), ".");
 		return temp;
 	}
 
@@ -2935,7 +2935,7 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 			 * !(one->sha1_valid), as long as
 			 * DIFF_FILE_VALID(one).
 			 */
-			sprintf(temp->mode, "%06o", one->mode);
+			xsnprintf(temp->mode, sizeof(temp->mode), "%06o", one->mode);
 		}
 		return temp;
 	}
@@ -4081,9 +4081,9 @@ const char *diff_unique_abbrev(const unsigned char *sha1, int len)
 	if (abblen < 37) {
 		static char hex[41];
 		if (len < abblen && abblen <= len + 2)
-			sprintf(hex, "%s%.*s", abbrev, len+3-abblen, "..");
+			xsnprintf(hex, sizeof(hex), "%s%.*s", abbrev, len+3-abblen, "..");
 		else
-			sprintf(hex, "%s...", abbrev);
+			xsnprintf(hex, sizeof(hex), "%s...", abbrev);
 		return hex;
 	}
 	return sha1_to_hex(sha1);