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>

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);

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,

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");
 	}

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);

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);

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;
 }

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;

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");

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;
 }

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)

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;
 }

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;

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.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);

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");
 

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);

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);
 

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;
 

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);

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);
 }