[PATCH 15/67] convert trivial sprintf / strcpy calls to xsnprintf

From: Jeff King <peff@peff.net>
Date: Sep 15, 2015, 15:36 UTC
Message-ID: <20150915153637.GO29753@sigill.intra.peff.net>
In-Reply-To: <20150915152125.GA27504@sigill.intra.peff.net>

We sometimes sprintf into static buffers when we know that the size of 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>
---
These are all pretty trivial; the obvious thing to get wrong is that
"sizeof(buf)" is not the correct length if "buf" is a pointer. I
considered a macro wrapper like:

  #define xsnprintf_array(dst, fmt, ...) \
	xsnprintf(dst, sizeof(dst) + BARF_UNLESS_AN_ARRAY(dst), \
		  fmt, __VA_ARGS__)

but obviously that requires variadic macro support.

 archive-tar.c             |  2 +-
 builtin/gc.c              |  2 +-
 builtin/init-db.c         | 11 ++++++-----
 builtin/ls-tree.c         |  9 +++++----
 builtin/merge-index.c     |  2 +-
 builtin/merge-recursive.c |  2 +-
 builtin/read-tree.c       |  2 +-
 builtin/unpack-file.c     |  2 +-
 compat/mingw.c            |  8 +++++---
 compat/winansi.c          |  2 +-
 connect.c                 |  2 +-
 convert.c                 |  3 ++-
 daemon.c                  |  4 ++--
 diff.c                    | 12 ++++++------
 http-push.c               |  2 +-
 http.c                    |  6 +++---
 ll-merge.c                | 12 ++++++------
 refs.c                    |  8 ++++----
 sideband.c                |  4 ++--
 strbuf.c                  |  4 ++--
 20 files changed, 52 insertions(+), 47 deletions(-)

diff --git a/archive-tar.c b/archive-tar.c
index b6b30bb..d543f93 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -301,7 +301,7 @@ static int write_global_extended_header(struct archiver_args *args)
 	memset(&header, 0, sizeof(header));
 	*header.typeflag = TYPEFLAG_GLOBAL_HEADER;
 	mode = 0100666;
-	strcpy(header.name, "pax_global_header");
+	xsnprintf(header.name, sizeof(header.name), "pax_global_header");
 	prepare_header(args, &header, mode, ext_header.len);
 	write_blocked(&header, sizeof(header));
 	write_blocked(ext_header.buf, ext_header.len);
diff --git a/builtin/gc.c b/builtin/gc.c
index 0ad8d30..57584bc 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -194,7 +194,7 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 		return NULL;
 
 	if (gethostname(my_host, sizeof(my_host)))
-		strcpy(my_host, "unknown");
+		xsnprintf(my_host, sizeof(my_host), "unknown");
 
 	pidfile_path = git_pathdup("gc.pid");
 	fd = hold_lock_file_for_update(&lock, pidfile_path,
diff --git a/builtin/init-db.c b/builtin/init-db.c
index 69323e1..e7d0e31 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -262,7 +262,8 @@ static int create_default_files(const char *template_path)
 	}
 
 	/* This forces creation of new config file */
-	sprintf(repo_version_string, "%d", GIT_REPO_VERSION);
+	xsnprintf(repo_version_string, sizeof(repo_version_string),
+		  "%d", GIT_REPO_VERSION);
 	git_config_set("core.repositoryformatversion", repo_version_string);
 
 	path[len] = 0;
@@ -414,13 +415,13 @@ int init_db(const char *template_dir, unsigned int flags)
 		 */
 		if (shared_repository < 0)
 			/* force to the mode value */
-			sprintf(buf, "0%o", -shared_repository);
+			xsnprintf(buf, sizeof(buf), "0%o", -shared_repository);
 		else if (shared_repository == PERM_GROUP)
-			sprintf(buf, "%d", OLD_PERM_GROUP);
+			xsnprintf(buf, sizeof(buf), "%d", OLD_PERM_GROUP);
 		else if (shared_repository == PERM_EVERYBODY)
-			sprintf(buf, "%d", OLD_PERM_EVERYBODY);
+			xsnprintf(buf, sizeof(buf), "%d", OLD_PERM_EVERYBODY);
 		else
-			die("oops");
+			die("BUG: invalid value for shared_repository");
 		git_config_set("core.sharedrepository", buf);
 		git_config_set("receive.denyNonFastforwards", "true");
 	}
diff --git a/builtin/ls-tree.c b/builtin/ls-tree.c
index 3b04a0f..0e30d86 100644
--- a/builtin/ls-tree.c
+++ b/builtin/ls-tree.c
@@ -96,12 +96,13 @@ static int show_tree(const unsigned char *sha1, struct strbuf *base,
 			if (!strcmp(type, blob_type)) {
 				unsigned long size;
 				if (sha1_object_info(sha1, &size) == OBJ_BAD)
-					strcpy(size_text, "BAD");
+					xsnprintf(size_text, sizeof(size_text),
+						  "BAD");
 				else
-					snprintf(size_text, sizeof(size_text),
-						 "%lu", size);
+					xsnprintf(size_text, sizeof(size_text),
+						  "%lu", size);
 			} else
-				strcpy(size_text, "-");
+				xsnprintf(size_text, sizeof(size_text), "-");
 			printf("%06o %s %s %7s\t", mode, type,
 			       find_unique_abbrev(sha1, abbrev),
 			       size_text);
diff --git a/builtin/merge-index.c b/builtin/merge-index.c
index 1a1eafa..1d66111 100644
--- a/builtin/merge-index.c
+++ b/builtin/merge-index.c
@@ -23,7 +23,7 @@ static int merge_entry(int pos, const char *path)
 			break;
 		found++;
 		strcpy(hexbuf[stage], sha1_to_hex(ce->sha1));
-		sprintf(ownbuf[stage], "%o", ce->ce_mode);
+		xsnprintf(ownbuf[stage], sizeof(ownbuf[stage]), "%o", ce->ce_mode);
 		arguments[stage] = hexbuf[stage];
 		arguments[stage + 4] = ownbuf[stage];
 	} while (++pos < active_nr);
diff --git a/builtin/merge-recursive.c b/builtin/merge-recursive.c
index a90f28f..491efd5 100644
--- a/builtin/merge-recursive.c
+++ b/builtin/merge-recursive.c
@@ -14,7 +14,7 @@ static const char *better_branch_name(const char *branch)
 
 	if (strlen(branch) != 40)
 		return branch;
-	sprintf(githead_env, "GITHEAD_%s", branch);
+	xsnprintf(githead_env, sizeof(githead_env), "GITHEAD_%s", branch);
 	name = getenv(githead_env);
 	return name ? name : branch;
 }
diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index 2379e11..8c693e7 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c
@@ -90,7 +90,7 @@ static int debug_merge(const struct cache_entry * const *stages,
 	debug_stage("index", stages[0], o);
 	for (i = 1; i <= o->merge_size; i++) {
 		char buf[24];
-		sprintf(buf, "ent#%d", i);
+		xsnprintf(buf, sizeof(buf), "ent#%d", i);
 		debug_stage(buf, stages[i], o);
 	}
 	return 0;
diff --git a/builtin/unpack-file.c b/builtin/unpack-file.c
index 1920029..6fc6bcd 100644
--- a/builtin/unpack-file.c
+++ b/builtin/unpack-file.c
@@ -12,7 +12,7 @@ static char *create_temp_file(unsigned char *sha1)
 	if (!buf || type != OBJ_BLOB)
 		die("unable to read blob object %s", sha1_to_hex(sha1));
 
-	strcpy(path, ".merge_file_XXXXXX");
+	xsnprintf(path, sizeof(path), ".merge_file_XXXXXX");
 	fd = xmkstemp(path);
 	if (write_in_full(fd, buf, size) != size)
 		die_errno("unable to write temp-file");
diff --git a/compat/mingw.c b/compat/mingw.c
index f74da23..a168800 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -2133,9 +2133,11 @@ int uname(struct utsname *buf)
 {
 	DWORD v = GetVersion();
 	memset(buf, 0, sizeof(*buf));
-	strcpy(buf->sysname, "Windows");
-	sprintf(buf->release, "%u.%u", v & 0xff, (v >> 8) & 0xff);
+	xsnprintf(buf->sysname, sizeof(buf->sysname), "Windows");
+	xsnprintf(buf->release, sizeof(buf->release),
+		 "%u.%u", v & 0xff, (v >> 8) & 0xff);
 	/* assuming NT variants only.. */
-	sprintf(buf->version, "%u", (v >> 16) & 0x7fff);
+	xsnprintf(buf->version, sizeof(buf->version),
+		  "%u", (v >> 16) & 0x7fff);
 	return 0;
 }
diff --git a/compat/winansi.c b/compat/winansi.c
index efc5bb3..ceff55b 100644
--- a/compat/winansi.c
+++ b/compat/winansi.c
@@ -539,7 +539,7 @@ void winansi_init(void)
 		return;
 
 	/* create a named pipe to communicate with the console thread */
-	sprintf(name, "\\\\.\\pipe\\winansi%lu", GetCurrentProcessId());
+	xsnprintf(name, sizeof(name), "\\\\.\\pipe\\winansi%lu", GetCurrentProcessId());
 	hwrite = CreateNamedPipe(name, PIPE_ACCESS_OUTBOUND,
 		PIPE_TYPE_BYTE | PIPE_WAIT, 1, BUFFER_SIZE, 0, 0, NULL);
 	if (hwrite == INVALID_HANDLE_VALUE)
diff --git a/connect.c b/connect.c
index c0144d8..1d5c5e0 100644
--- a/connect.c
+++ b/connect.c
@@ -332,7 +332,7 @@ static const char *ai_name(const struct addrinfo *ai)
 	static char addr[NI_MAXHOST];
 	if (getnameinfo(ai->ai_addr, ai->ai_addrlen, addr, sizeof(addr), NULL, 0,
 			NI_NUMERICHOST) != 0)
-		strcpy(addr, "(unknown)");
+		xsnprintf(addr, sizeof(addr), "(unknown)");
 
 	return addr;
 }
diff --git a/convert.c b/convert.c
index f3bd3e9..814e814 100644
--- a/convert.c
+++ b/convert.c
@@ -1289,7 +1289,8 @@ static struct stream_filter *ident_filter(const unsigned char *sha1)
 {
 	struct ident_filter *ident = xmalloc(sizeof(*ident));
 
-	sprintf(ident->ident, ": %s $", sha1_to_hex(sha1));
+	xsnprintf(ident->ident, sizeof(ident->ident),
+		  ": %s $", sha1_to_hex(sha1));
 	strbuf_init(&ident->left, 0);
 	ident->filter.vtbl = &ident_vtbl;
 	ident->state = 0;
diff --git a/daemon.c b/daemon.c
index f9eb296..5218a3f 100644
--- a/daemon.c
+++ b/daemon.c
@@ -901,7 +901,7 @@ static const char *ip2str(int family, struct sockaddr *sin, socklen_t len)
 		inet_ntop(family, &((struct sockaddr_in*)sin)->sin_addr, ip, len);
 		break;
 	default:
-		strcpy(ip, "<unknown>");
+		xsnprintf(ip, sizeof(ip), "<unknown>");
 	}
 	return ip;
 }
@@ -916,7 +916,7 @@ static int setup_named_sock(char *listen_addr, int listen_port, struct socketlis
 	int gai;
 	long flags;
 
-	sprintf(pbuf, "%d", listen_port);
+	xsnprintf(pbuf, sizeof(pbuf), "%d", listen_port);
 	memset(&hints, 0, sizeof(hints));
 	hints.ai_family = AF_UNSPEC;
 	hints.ai_socktype = SOCK_STREAM;
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);
diff --git a/http-push.c b/http-push.c
index c98dad2..154e67b 100644
--- a/http-push.c
+++ b/http-push.c
@@ -881,7 +881,7 @@ static struct remote_lock *lock_remote(const char *path, long timeout)
 	strbuf_addf(&out_buffer.buf, LOCK_REQUEST, escaped);
 	free(escaped);
 
-	sprintf(timeout_header, "Timeout: Second-%ld", timeout);
+	xsnprintf(timeout_header, sizeof(timeout_header), "Timeout: Second-%ld", timeout);
 	dav_headers = curl_slist_append(dav_headers, timeout_header);
 	dav_headers = curl_slist_append(dav_headers, "Content-Type: text/xml");
 
diff --git a/http.c b/http.c
index 9dce380..7b02259 100644
--- a/http.c
+++ b/http.c
@@ -1104,7 +1104,7 @@ static void write_accept_language(struct strbuf *buf)
 		     decimal_places++, max_q *= 10)
 			;
 
-		sprintf(q_format, ";q=0.%%0%dd", decimal_places);
+		xsnprintf(q_format, sizeof(q_format), ";q=0.%%0%dd", decimal_places);
 
 		strbuf_addstr(buf, "Accept-Language: ");
 
@@ -1601,7 +1601,7 @@ struct http_pack_request *new_http_pack_request(
 			fprintf(stderr,
 				"Resuming fetch of pack %s at byte %ld\n",
 				sha1_to_hex(target->sha1), prev_posn);
-		sprintf(range, "Range: bytes=%ld-", prev_posn);
+		xsnprintf(range, sizeof(range), "Range: bytes=%ld-", prev_posn);
 		preq->range_header = curl_slist_append(NULL, range);
 		curl_easy_setopt(preq->slot->curl, CURLOPT_HTTPHEADER,
 			preq->range_header);
@@ -1761,7 +1761,7 @@ struct http_object_request *new_http_object_request(const char *base_url,
 			fprintf(stderr,
 				"Resuming fetch of object %s at byte %ld\n",
 				hex, prev_posn);
-		sprintf(range, "Range: bytes=%ld-", prev_posn);
+		xsnprintf(range, sizeof(range), "Range: bytes=%ld-", prev_posn);
 		range_header = curl_slist_append(range_header, range);
 		curl_easy_setopt(freq->slot->curl,
 				 CURLOPT_HTTPHEADER, range_header);
diff --git a/ll-merge.c b/ll-merge.c
index fc3c049..56f73b3 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -142,11 +142,11 @@ static struct ll_merge_driver ll_merge_drv[] = {
 	{ "union", "built-in union merge", ll_union_merge },
 };
 
-static void create_temp(mmfile_t *src, char *path)
+static void create_temp(mmfile_t *src, char *path, size_t len)
 {
 	int fd;
 
-	strcpy(path, ".merge_file_XXXXXX");
+	xsnprintf(path, len, ".merge_file_XXXXXX");
 	fd = xmkstemp(path);
 	if (write_in_full(fd, src->ptr, src->size) != src->size)
 		die_errno("unable to write temp-file");
@@ -187,10 +187,10 @@ static int ll_ext_merge(const struct ll_merge_driver *fn,
 
 	result->ptr = NULL;
 	result->size = 0;
-	create_temp(orig, temp[0]);
-	create_temp(src1, temp[1]);
-	create_temp(src2, temp[2]);
-	sprintf(temp[3], "%d", marker_size);
+	create_temp(orig, temp[0], sizeof(temp[0]));
+	create_temp(src1, temp[1], sizeof(temp[1]));
+	create_temp(src2, temp[2], sizeof(temp[2]));
+	xsnprintf(temp[3], sizeof(temp[3]), "%d", marker_size);
 
 	strbuf_expand(&cmd, fn->cmdline, strbuf_expand_dict_cb, &dict);
 
diff --git a/refs.c b/refs.c
index 4e15f60..d5c8b2f 100644
--- a/refs.c
+++ b/refs.c
@@ -3326,10 +3326,10 @@ static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
 	msglen = msg ? strlen(msg) : 0;
 	maxlen = strlen(committer) + msglen + 100;
 	logrec = xmalloc(maxlen);
-	len = sprintf(logrec, "%s %s %s\n",
-		      sha1_to_hex(old_sha1),
-		      sha1_to_hex(new_sha1),
-		      committer);
+	len = xsnprintf(logrec, maxlen, "%s %s %s\n",
+			sha1_to_hex(old_sha1),
+			sha1_to_hex(new_sha1),
+			committer);
 	if (msglen)
 		len += copy_msg(logrec + len - 1, msg) - 1;
 
diff --git a/sideband.c b/sideband.c
index 7f9dc22..fde8adc 100644
--- a/sideband.c
+++ b/sideband.c
@@ -137,11 +137,11 @@ ssize_t send_sideband(int fd, int band, const char *data, ssize_t sz, int packet
 		if (packet_max - 5 < n)
 			n = packet_max - 5;
 		if (0 <= band) {
-			sprintf(hdr, "%04x", n + 5);
+			xsnprintf(hdr, sizeof(hdr), "%04x", n + 5);
 			hdr[4] = band;
 			write_or_die(fd, hdr, 5);
 		} else {
-			sprintf(hdr, "%04x", n + 4);
+			xsnprintf(hdr, sizeof(hdr), "%04x", n + 4);
 			write_or_die(fd, hdr, 4);
 		}
 		write_or_die(fd, p, n);
diff --git a/strbuf.c b/strbuf.c
index 6c1b577..46a3d20 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -245,8 +245,8 @@ void strbuf_add_commented_lines(struct strbuf *out, const char *buf, size_t size
 	static char prefix2[2];
 
 	if (prefix1[0] != comment_line_char) {
-		sprintf(prefix1, "%c ", comment_line_char);
-		sprintf(prefix2, "%c", comment_line_char);
+		xsnprintf(prefix1, sizeof(prefix1), "%c ", comment_line_char);
+		xsnprintf(prefix2, sizeof(prefix2), "%c", comment_line_char);
 	}
 	add_lines(out, prefix1, prefix2, buf, size);
 }

-- 
2.6.0.rc2.408.ga2926b9