From 281cff0b604735407e1ffbee439086c8780b2f65 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 3 Apr 2026 21:13:41 +0530
Subject: [PATCH] base64 decode present dnd source data

---
 kitty/base64.h | 12 ++++++++++++
 kitty/dnd.c    |  9 +++++++--
 kitty/state.h  |  5 ++++-
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/kitty/base64.h b/kitty/base64.h
index 331443763..bef8b8ad8 100644
--- a/kitty/base64.h
+++ b/kitty/base64.h
@@ -10,9 +10,21 @@
 #include <stdbool.h>
 #include "../3rdparty/base64/include/libbase64.h"
 
+typedef struct base64_state base64_state;
+
 static inline size_t required_buffer_size_for_base64_decode(size_t src_sz) { return (src_sz / 4 * 3 + 2); }
 static inline size_t required_buffer_size_for_base64_encode(size_t src_sz) { return ((src_sz + 2) / 3 * 4); }
 
+static inline void
+base64_init_stream_decoder(base64_state *state) {
+    base64_stream_decode_init(state, 0);
+}
+
+static inline bool
+base64_decode_stream(base64_state *state, const uint8_t *src, size_t src_sz, uint8_t *dest, size_t *dest_sz) {
+    if (*dest_sz < required_buffer_size_for_base64_decode(src_sz)) return false;
+    return base64_stream_decode(state, (const char*)src, src_sz, (char*)dest, dest_sz) == 1;
+}
 
 static inline bool
 base64_decode8(const uint8_t *src, size_t src_sz, uint8_t *dest, size_t *dest_sz) {
diff --git a/kitty/dnd.c b/kitty/dnd.c
index 7f68dd8f1..306294612 100644
--- a/kitty/dnd.c
+++ b/kitty/dnd.c
@@ -912,14 +912,19 @@ drag_add_pre_sent_data(Window *w, unsigned idx, const uint8_t *payload, size_t s
     if (sz + ds.pre_sent_total_sz > 64 * 1024 * 1024) abrt(EFBIG);
     ds.pre_sent_total_sz += sz;
     DragSourceItem *item = ds.items + idx;
+    if (!item->data_decode_initialized) {
+        item->data_decode_initialized = true;
+        base64_init_stream_decoder(&item->base64_state);
+    }
     if (item->data_capacity < sz + item->data_size) {
         size_t newcap = MAX(item->data_size * 2, sz + item->data_size);
         item->optional_data = realloc(item->optional_data, newcap);
         if (!item->optional_data) abrt(ENOMEM);
         item->data_capacity = newcap;
     }
-    memcpy(item->optional_data + item->data_size, payload, sz);
-    item->data_size += sz;
+    size_t outlen = item->data_capacity - item->data_size;
+    if (!base64_decode_stream(&item->base64_state, payload, sz, item->optional_data + item->data_size, &outlen)) abrt(EINVAL);
+    item->data_size += outlen;
 }
 
 #undef abrt
diff --git a/kitty/state.h b/kitty/state.h
index 7524d0eb8..68025b262 100644
--- a/kitty/state.h
+++ b/kitty/state.h
@@ -10,6 +10,7 @@
 #include "screen.h"
 #include "monotonic.h"
 #include "window_logo.h"
+#include "base64.h"
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wpedantic"
 #include <hb.h>
@@ -235,8 +236,10 @@ typedef struct DirHandle {
 
 typedef struct DragSourceItem {
     const char *mime_type;
-    char *optional_data;
+    uint8_t *optional_data;
     size_t data_size, data_capacity;
+    base64_state base64_state;
+    bool data_decode_initialized;
 } DragSourceItem;
 
 typedef struct Window {