buf: introduce git_buf_shellquote

Introduce a helper method to quote a string in a shellsafe manner.  This
wraps the entire buffer in single quotes, escaping single-quotes and
exclamation points.

3 files changed, 72 insertions, 0 deletions

diff --git a/src/util/buffer.c b/src/util/buffer.c
index 5d84b99fc..28db5c20c 100644
--- a/src/util/buffer.c
+++ b/src/util/buffer.c
@@ -1155,3 +1155,40 @@ done:
 	git_buf_dispose(&replaced);
 	return error;
 }
+
+int git_buf_shellquote(git_buf *buf)
+{
+	git_buf quoted = GIT_BUF_INIT;
+	size_t i;
+	int error = 0;
+
+	ENSURE_SIZE(&quoted, buf->size);
+
+	git_buf_putc(&quoted, '\'');
+
+	for (i = 0; i < buf->size; i++) {
+		switch (buf->ptr[i]) {
+		case '\'':
+		case '!':
+			git_buf_puts(&quoted, "'\\");
+			git_buf_putc(&quoted, buf->ptr[i]);
+			git_buf_putc(&quoted, '\'');
+			break;
+		default:
+			git_buf_putc(&quoted, buf->ptr[i]);
+		}
+	}
+
+	git_buf_putc(&quoted, '\'');
+
+	if (git_buf_oom(&quoted)) {
+		error = -1;
+		goto done;
+	}
+
+	git_buf_swap(&quoted, buf);
+
+done:
+	git_buf_dispose(&quoted);
+	return error;
+}
diff --git a/src/util/buffer.h b/src/util/buffer.h
index bc0133465..95953082d 100644
--- a/src/util/buffer.h
+++ b/src/util/buffer.h
@@ -269,4 +269,10 @@ int git_buf_replace(
 	const char *replacements[][2],
 	size_t replacements_len);
 
+/**
+ * Quote for shell safety.  Wrap the given buffer in single quotes,
+ * escaping any single quotes and exclamation points.
+ */
+int git_buf_shellquote(git_buf *buf);
+
 #endif
diff --git a/tests/libgit2/buf/basic.c b/tests/libgit2/buf/basic.c
index 0de860983..0cb180b7f 100644
--- a/tests/libgit2/buf/basic.c
+++ b/tests/libgit2/buf/basic.c
@@ -65,3 +65,32 @@ void test_buf_basic__replace(void)
 
 	git_buf_dispose(&buf);
 }
+
+void test_buf_basic__shellquote(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+
+	cl_git_pass(git_buf_puts(&buf, "filename"));
+	cl_git_pass(git_buf_shellquote(&buf));
+	cl_assert_equal_s("\'filename\'", buf.ptr);
+
+	git_buf_clear(&buf);
+
+	cl_git_pass(git_buf_puts(&buf, "file name"));
+	cl_git_pass(git_buf_shellquote(&buf));
+	cl_assert_equal_s("\'file name\'", buf.ptr);
+
+	git_buf_clear(&buf);
+
+	cl_git_pass(git_buf_puts(&buf, "file\'name"));
+	cl_git_pass(git_buf_shellquote(&buf));
+	cl_assert_equal_s("\'file\'\\\'\'name\'", buf.ptr);
+
+	git_buf_clear(&buf);
+
+	cl_git_pass(git_buf_puts(&buf, "file!name"));
+	cl_git_pass(git_buf_shellquote(&buf));
+	cl_assert_equal_s("\'file\'\\!\'name\'", buf.ptr);
+
+	git_buf_dispose(&buf);
+}