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GUACAMOLE-2262: Heap-allocate clipboard buffers to prevent stack overflow. #659

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GUACAMOLE-2262: Heap-allocate clipboard buffers to prevent stack overflow. #659

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16 changes: 11 additions & 5 deletions src/protocols/rdp/channels/cliprdr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -371,7 +371,8 @@ static UINT guac_rdp_cliprdr_format_data_request(CliprdrClientContext* cliprdr,

guac_iconv_write* remote_writer;
const char* input = clipboard->clipboard->buffer;
char* output = guac_mem_alloc(GUAC_COMMON_CLIPBOARD_MAX_LENGTH);
int output_buf_size = clipboard->clipboard->available;
char* output = guac_mem_alloc(output_buf_size);

/* Map requested clipboard format to a guac_iconv writer */
switch (format_data_request->requestedFormatId) {
Expand Down Expand Up @@ -402,7 +403,7 @@ static UINT guac_rdp_cliprdr_format_data_request(CliprdrClientContext* cliprdr,
BYTE* start = (BYTE*) output;
guac_iconv_read* local_reader = settings->normalize_clipboard ? GUAC_READ_UTF8_NORMALIZED : GUAC_READ_UTF8;
guac_iconv(local_reader, &input, clipboard->clipboard->length,
remote_writer, &output, GUAC_COMMON_CLIPBOARD_MAX_LENGTH);
remote_writer, &output, output_buf_size);

CLIPRDR_FORMAT_DATA_RESPONSE data_response = {
.requestedFormatData = (BYTE*) start,
Expand Down Expand Up @@ -470,7 +471,10 @@ static UINT guac_rdp_cliprdr_format_data_response(CliprdrClientContext* cliprdr,
return CHANNEL_RC_OK;
}

char received_data[GUAC_COMMON_CLIPBOARD_MAX_LENGTH];
/* Heap-allocate the receive buffer to avoid stack overflow when the
* configured clipboard limit exceeds the default thread stack size */
int recv_buf_size = clipboard->clipboard->available;
char* received_data = guac_mem_alloc(recv_buf_size);

guac_iconv_read* remote_reader;
const char* input = (char*) format_data_response->requestedFormatData;
Expand Down Expand Up @@ -498,6 +502,7 @@ static UINT guac_rdp_cliprdr_format_data_response(CliprdrClientContext* cliprdr,
default:
guac_client_log(client, GUAC_LOG_DEBUG, "Requested clipboard data "
"in unsupported format (0x%X).", clipboard->requested_format);
guac_mem_free(received_data);
return CHANNEL_RC_OK;

}
Expand All @@ -512,13 +517,14 @@ static UINT guac_rdp_cliprdr_format_data_response(CliprdrClientContext* cliprdr,
/* Convert, store, and forward the clipboard data received from RDP
* server */
if (guac_iconv(remote_reader, &input, data_len,
GUAC_WRITE_UTF8, &output, sizeof(received_data))) {
int length = strnlen(received_data, sizeof(received_data));
GUAC_WRITE_UTF8, &output, recv_buf_size)) {
int length = strnlen(received_data, recv_buf_size);
guac_common_clipboard_reset(clipboard->clipboard, "text/plain");
guac_common_clipboard_append(clipboard->clipboard, received_data, length);
guac_common_clipboard_send(clipboard->clipboard, client);
}

guac_mem_free(received_data);
return CHANNEL_RC_OK;

}
Expand Down