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Code Issues Releases Wiki Activity

Check PNG file compliance (#171)

pull/177/head
Emeric Planet 2018-01-30 22:50:38 +01:00 committed by Michael Stapelberg
parent 6b53758e14
commit b34ae89d30
1 changed files with 33 additions and 2 deletions
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35
i3lock.c
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@ -19,6 +19,7 @@
#include <xcb/xcb.h>
#include <xcb/xkb.h>
#include <err.h>
#include <errno.h>
#include <assert.h>
#ifdef __OpenBSD__
#include <bsd_auth.h>
@ -632,6 +633,36 @@ void handle_screen_resize(void) {
redraw_screen();
}
static bool verify_png_image(const char *image_path) {
if (!image_path) {
return false;
}
/* Check file exists and has correct PNG header */
FILE *png_file = fopen(image_path, "r");
if (png_file == NULL) {
fprintf(stderr, "Image file path \"%s\" cannot be opened: %s\n", image_path, strerror(errno));
return false;
}
unsigned char png_header[8];
memset(png_header, '\0', sizeof(png_header));
int bytes_read = fread(png_header, 1, sizeof(png_header), png_file);
fclose(png_file);
if (bytes_read != sizeof(png_header)) {
fprintf(stderr, "Could not read PNG header from \"%s\"\n", image_path);
return false;
}
// Check PNG header according to the specification, available at:
// https://www.w3.org/TR/2003/REC-PNG-20031110/#5PNG-file-signature
static unsigned char PNG_REFERENCE_HEADER[8] = { 137, 80, 78, 71, 13, 10, 26, 10 };
if (memcmp(PNG_REFERENCE_HEADER, png_header, sizeof(png_header)) != 0) {
fprintf(stderr, "File \"%s\" does not start with a PNG header. i3lock currently only supports loading PNG files.\n", image_path);
return false;
}
return true;
}
#ifndef __OpenBSD__
/*
* Callback function for PAM. We only react on password request callbacks.
@ -1012,7 +1043,7 @@ int main(int argc, char *argv[]) {
xcb_change_window_attributes(conn, screen->root, XCB_CW_EVENT_MASK,
(uint32_t[]){XCB_EVENT_MASK_STRUCTURE_NOTIFY});
if (image_path) {
if (verify_png_image(image_path)) {
/* Create a pixmap to render on, fill it with the background color */
img = cairo_image_surface_create_from_png(image_path);
/* In case loading failed, we just pretend no -i was specified. */
@ -1021,8 +1052,8 @@ int main(int argc, char *argv[]) {
image_path, cairo_status_to_string(cairo_surface_status(img)));
img = NULL;
}
free(image_path);
}
free(image_path);
/* Pixmap on which the image is rendered to (if any) */
xcb_pixmap_t bg_pixmap = draw_image(last_resolution);