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>

7 files changed, 16 insertions, 14 deletions

diff --git a/builtin/gc.c b/builtin/gc.c
index 0ad8d30b56..57584bc99f 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 69323e186c..e7d0e31f46 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 3b04a0f082..0e30d86230 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 1a1eafa6fd..1d66111917 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 a90f28f34d..491efd556e 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 2379e11069..8c693e7568 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 19200291a2..6fc6bcdf7f 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");