file download poc

1 files changed, 86 insertions, 0 deletions

diff --git a/download.c b/download.c
new file mode 100644
index 0000000..ba59b68
--- /dev/null
+++ b/download.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2023, Vincent Douillet <vincent@vdouillet.fr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors
+ * may be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/mman.h>
+#include <sys/stat.h>
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "cgi.h"
+#include "config.h"
+#include "download.h"
+#include "http.h"
+#include "url.h"
+
+void
+download(struct kreq * r)
+{
+	void   *buffer;
+	struct stat st;
+	int 	st_ret, fd;
+	char 	file_path[URL_LENGTH_MAX];
+	size_t 	path_size;
+
+	/* check that the requested URL can be safely processed */
+	if (!check_request_path(r->path))
+		http_exit(r, KHTTP_400, "download: Invalid request path");
+
+	/* build requested file path */
+	path_size = url_build(file_path, URL_LENGTH_MAX, 2, DATA_DIR,
+			      "File.txt");
+	if (path_size == 0)
+		http_exit(r, KHTTP_404, "download: Unable to build file path");
+	if (path_size >= URL_LENGTH_MAX)
+		http_exit(r, KHTTP_414, NULL);
+
+	/* memory map the file */
+	fd = open(file_path, O_RDONLY);
+	if (fd < 0)
+		http_exit(r, KHTTP_404, "download: Unable to open file");
+	st_ret = fstat(fd, &st);
+	if (st_ret != 0)
+		http_exit(r, KHTTP_404, "download: Unable to open file");
+
+	/* TODO mmap does not work with empty file: st_size = 0 */
+	buffer = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	if (buffer == MAP_FAILED)
+		http_exit(r, KHTTP_500, "download: mmap failed");
+
+	/* write the file */
+	/* TODO proper filename & MIME type detection */
+	K_OK(khttp_head(r, kresps[KRESP_CONTENT_DISPOSITION], "attachment; filename=\"File.txt\""), r);
+	http_open(r, KHTTP_200, KMIME_TEXT_PLAIN);
+	K_OK(khttp_write(r, (const char *) buffer, st.st_size), r);
+
+	/* cleanup */
+	munmap(buffer, st.st_size);
+	close(fd);
+}