From ef1286d3c0ba714c6c2ae87e14edf3c462aef114 Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Thu, 24 Sep 2015 17:06:42 -0400
Subject: use xsnprintf for generating git object headers

We generally use 32-byte buffers to format git's "type size"
header fields. These should not generally overflow unless
you can produce some truly gigantic objects (and our types
come from our internal array of constant strings). But it is
a good idea to use xsnprintf to make sure this is the case.

Note that we slightly modify the interface to
write_sha1_file_prepare, which nows uses "hdrlen" as an "in"
parameter as well as an "out" (on the way in it stores the
allocated size of the header, and on the way out it returns
the ultimate size of the header).

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

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 3431de2..1ad1bde 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -441,7 +441,7 @@ static void *unpack_entry_data(unsigned long offset, unsigned long size,
 	int hdrlen;
 
 	if (!is_delta_type(type)) {
-		hdrlen = sprintf(hdr, "%s %lu", typename(type), size) + 1;
+		hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", typename(type), size) + 1;
 		git_SHA1_Init(&c);
 		git_SHA1_Update(&c, hdr, hdrlen);
 	} else
diff --git a/bulk-checkin.c b/bulk-checkin.c
index 7cffc3a..4347f5c 100644
--- a/bulk-checkin.c
+++ b/bulk-checkin.c
@@ -200,8 +200,8 @@ static int deflate_to_pack(struct bulk_checkin_state *state,
 	if (seekback == (off_t) -1)
 		return error("cannot find the current offset");
 
-	header_len = sprintf((char *)obuf, "%s %" PRIuMAX,
-			     typename(type), (uintmax_t)size) + 1;
+	header_len = xsnprintf((char *)obuf, sizeof(obuf), "%s %" PRIuMAX,
+			       typename(type), (uintmax_t)size) + 1;
 	git_SHA1_Init(&ctx);
 	git_SHA1_Update(&ctx, obuf, header_len);
 
diff --git a/fast-import.c b/fast-import.c
index 6c7c3c9..d0c2502 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -1035,8 +1035,8 @@ static int store_object(
 	git_SHA_CTX c;
 	git_zstream s;
 
-	hdrlen = sprintf((char *)hdr,"%s %lu", typename(type),
-		(unsigned long)dat->len) + 1;
+	hdrlen = xsnprintf((char *)hdr, sizeof(hdr), "%s %lu",
+			   typename(type), (unsigned long)dat->len) + 1;
 	git_SHA1_Init(&c);
 	git_SHA1_Update(&c, hdr, hdrlen);
 	git_SHA1_Update(&c, dat->buf, dat->len);
diff --git a/http-push.c b/http-push.c
index 154e67b..1f3788f 100644
--- a/http-push.c
+++ b/http-push.c
@@ -361,7 +361,7 @@ static void start_put(struct transfer_request *request)
 	git_zstream stream;
 
 	unpacked = read_sha1_file(request->obj->sha1, &type, &len);
-	hdrlen = sprintf(hdr, "%s %lu", typename(type), len) + 1;
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", typename(type), len) + 1;
 
 	/* Set it up */
 	git_deflate_init(&stream, zlib_compression_level);
diff --git a/sha1_file.c b/sha1_file.c
index d295a32..f106091 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1464,7 +1464,7 @@ int check_sha1_signature(const unsigned char *sha1, void *map,
 		return -1;
 
 	/* Generate the header */
-	hdrlen = sprintf(hdr, "%s %lu", typename(obj_type), size) + 1;
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", typename(obj_type), size) + 1;
 
 	/* Sha1.. */
 	git_SHA1_Init(&c);
@@ -2930,7 +2930,7 @@ static void write_sha1_file_prepare(const void *buf, unsigned long len,
 	git_SHA_CTX c;
 
 	/* Generate the header */
-	*hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
+	*hdrlen = xsnprintf(hdr, *hdrlen, "%s %lu", type, len)+1;
 
 	/* Sha1.. */
 	git_SHA1_Init(&c);
@@ -2993,7 +2993,7 @@ int hash_sha1_file(const void *buf, unsigned long len, const char *type,
                    unsigned char *sha1)
 {
 	char hdr[32];
-	int hdrlen;
+	int hdrlen = sizeof(hdr);
 	write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
 	return 0;
 }
@@ -3139,7 +3139,7 @@ static int freshen_packed_object(const unsigned char *sha1)
 int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1)
 {
 	char hdr[32];
-	int hdrlen;
+	int hdrlen = sizeof(hdr);
 
 	/* Normally if we have it in the pack then we do not bother writing
 	 * it out into .git/objects/??/?{38} file.
@@ -3157,7 +3157,8 @@ int hash_sha1_file_literally(const void *buf, unsigned long len, const char *typ
 	int hdrlen, status = 0;
 
 	/* type string, SP, %lu of the length plus NUL must fit this */
-	header = xmalloc(strlen(type) + 32);
+	hdrlen = strlen(type) + 32;
+	header = xmalloc(hdrlen);
 	write_sha1_file_prepare(buf, len, type, sha1, header, &hdrlen);
 
 	if (!(flags & HASH_WRITE_OBJECT))
@@ -3185,7 +3186,7 @@ int force_object_loose(const unsigned char *sha1, time_t mtime)
 	buf = read_packed_sha1(sha1, &type, &len);
 	if (!buf)
 		return error("cannot read sha1_file for %s", sha1_to_hex(sha1));
-	hdrlen = sprintf(hdr, "%s %lu", typename(type), len) + 1;
+	hdrlen = xsnprintf(hdr, sizeof(hdr), "%s %lu", typename(type), len) + 1;
 	ret = write_loose_object(sha1, hdr, hdrlen, buf, len, mtime);
 	free(buf);
 
-- 
cgit v0.10.2-6-g49f6