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reuse vchan::Client to add the general header and break messages in…
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…to chunks (#11714)
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Isaiah Becker-Mayer authored Apr 13, 2022
1 parent d266456 commit c4deb1c
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Showing 5 changed files with 187 additions and 126 deletions.
177 changes: 82 additions & 95 deletions lib/srv/desktop/rdp/rdpclient/src/cliprdr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
// limitations under the License.

use crate::errors::invalid_data_error;
use crate::util;
use crate::{vchan, Payload};
use bitflags::bitflags;
use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
Expand Down Expand Up @@ -130,7 +131,7 @@ impl Client {
self.clipboard
.insert(ClipboardFormat::CF_OEMTEXT as u32, converted);

encode_message(
self.add_headers_and_chunkify(
ClipboardPDUType::CB_FORMAT_LIST,
FormatListPDU {
format_names: vec![LongFormatName::id(ClipboardFormat::CF_OEMTEXT as u32)],
Expand Down Expand Up @@ -164,7 +165,7 @@ impl Client {
// 1. Send our clipboard capabilities
// 2. Mimic a "copy" operation by sending a format list PDU
// This completes the initialization process.
let mut result = encode_message(
let mut result = self.add_headers_and_chunkify(
ClipboardPDUType::CB_CLIP_CAPS,
ClipboardCapabilitiesPDU {
general: Some(GeneralClipboardCapabilitySet {
Expand All @@ -174,13 +175,15 @@ impl Client {
}
.encode()?,
)?;
result.extend(encode_message(
ClipboardPDUType::CB_FORMAT_LIST,
FormatListPDU::<LongFormatName> {
format_names: vec![LongFormatName::id(0)],
}
.encode()?,
)?);
result.extend(
self.add_headers_and_chunkify(
ClipboardPDUType::CB_FORMAT_LIST,
FormatListPDU::<LongFormatName> {
format_names: vec![LongFormatName::id(0)],
}
.encode()?,
)?,
);

Ok(result)
}
Expand All @@ -205,14 +208,15 @@ impl Client {
//
// see section 3.1.1.1 for details

let mut result = encode_message(ClipboardPDUType::CB_FORMAT_LIST_RESPONSE, vec![])?;
let mut result =
self.add_headers_and_chunkify(ClipboardPDUType::CB_FORMAT_LIST_RESPONSE, vec![])?;

for name in list.format_names {
match FromPrimitive::from_u32(name.format_id) {
// TODO(zmb3): support CF_TEXT, CF_UNICODETEXT, ...
Some(ClipboardFormat::CF_OEMTEXT) => {
// request the data by imitating a paste event
result.extend(encode_message(
result.extend(self.add_headers_and_chunkify(
ClipboardPDUType::CB_FORMAT_DATA_REQUEST,
FormatDataRequestPDU::for_id(name.format_id).encode()?,
)?);
Expand Down Expand Up @@ -254,7 +258,7 @@ impl Client {
}
};

encode_message(
self.add_headers_and_chunkify(
ClipboardPDUType::CB_FORMAT_DATA_RESPONSE,
FormatDataResponsePDU { data }.encode()?,
)
Expand Down Expand Up @@ -284,6 +288,50 @@ impl Client {

Ok(vec![])
}

/// add_headers_and_chunkify takes an encoded PDU ready to be sent over a virtual channel (payload),
/// adds on the Clipboard PDU Header based the passed msg_type, adds the appropriate (virtual) Channel PDU Header,
/// and splits the entire payload into chunks if the payload exceeds the maximum size.
fn add_headers_and_chunkify(
&self,
msg_type: ClipboardPDUType,
payload: Vec<u8>,
) -> RdpResult<Vec<Vec<u8>>> {
let msg_flags = match msg_type {
// the spec requires 0 for these messages
ClipboardPDUType::CB_CLIP_CAPS => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_TEMP_DIRECTORY => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_LOCK_CLIPDATA => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_UNLOCK_CLIPDATA => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_FORMAT_DATA_REQUEST => ClipboardHeaderFlags::from_bits_truncate(0),

// assume success for now
ClipboardPDUType::CB_FORMAT_DATA_RESPONSE => ClipboardHeaderFlags::CB_RESPONSE_OK,
ClipboardPDUType::CB_FORMAT_LIST_RESPONSE => ClipboardHeaderFlags::CB_RESPONSE_OK,

// we don't advertise support for file transfers, so the server should never send this,
// but if it does, ensure the response indicates a failure
ClipboardPDUType::CB_FILECONTENTS_RESPONSE => ClipboardHeaderFlags::CB_RESPONSE_FAIL,

_ => ClipboardHeaderFlags::from_bits_truncate(0),
};

let channel_flags = match msg_type {
ClipboardPDUType::CB_FORMAT_LIST
| ClipboardPDUType::CB_CLIP_CAPS
| ClipboardPDUType::CB_FORMAT_DATA_REQUEST
| ClipboardPDUType::CB_FORMAT_DATA_RESPONSE => {
Some(vchan::ChannelPDUFlags::CHANNEL_FLAG_SHOW_PROTOCOL)
}
_ => None,
};

let mut inner =
ClipboardPDUHeader::new(msg_type, msg_flags, payload.len() as u32).encode()?;
inner.extend(payload);

self.vchan.add_header_and_chunkify(channel_flags, inner)
}
}

bitflags! {
Expand Down Expand Up @@ -577,10 +625,7 @@ impl FormatName for LongFormatName {
// must be encoded as a single Unicode null character (two zero bytes)
None => w.write_u16::<LittleEndian>(0)?,
Some(name) => {
for c in str::encode_utf16(name) {
w.write_u16::<LittleEndian>(c)?;
}
w.write_u16::<LittleEndian>(0)?; // terminating null
w.append(&mut util::to_unicode(name));
}
};

Expand Down Expand Up @@ -707,69 +752,6 @@ impl FormatDataResponsePDU {
}
}

/// encode_message encodes a message by wrapping it in the appropriate
/// channel header. If the payload exceeds the maximum size, the message
/// is split into multiple messages.
fn encode_message(msg_type: ClipboardPDUType, payload: Vec<u8>) -> RdpResult<Vec<Vec<u8>>> {
let msg_flags = match msg_type {
// the spec requires 0 for these messages
ClipboardPDUType::CB_CLIP_CAPS => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_TEMP_DIRECTORY => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_LOCK_CLIPDATA => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_UNLOCK_CLIPDATA => ClipboardHeaderFlags::from_bits_truncate(0),
ClipboardPDUType::CB_FORMAT_DATA_REQUEST => ClipboardHeaderFlags::from_bits_truncate(0),

// assume success for now
ClipboardPDUType::CB_FORMAT_DATA_RESPONSE => ClipboardHeaderFlags::CB_RESPONSE_OK,
ClipboardPDUType::CB_FORMAT_LIST_RESPONSE => ClipboardHeaderFlags::CB_RESPONSE_OK,

// we don't advertise support for file transfers, so the server should never send this,
// but if it does, ensure the response indicates a failure
ClipboardPDUType::CB_FILECONTENTS_RESPONSE => ClipboardHeaderFlags::CB_RESPONSE_FAIL,

_ => ClipboardHeaderFlags::from_bits_truncate(0),
};
let mut inner = ClipboardPDUHeader::new(msg_type, msg_flags, payload.len() as u32).encode()?;
inner.extend(payload);
let total_len = inner.len() as u32;

let mut result = Vec::new();
let mut first = true;
while !inner.is_empty() {
let i = std::cmp::min(inner.len(), vchan::CHANNEL_CHUNK_LEGNTH);
let leftover = inner.split_off(i);

let mut channel_flags = match msg_type {
ClipboardPDUType::CB_FORMAT_LIST
| ClipboardPDUType::CB_CLIP_CAPS
| ClipboardPDUType::CB_FORMAT_DATA_REQUEST
| ClipboardPDUType::CB_FORMAT_DATA_RESPONSE => {
vchan::ChannelPDUFlags::CHANNEL_FLAG_SHOW_PROTOCOL
}
_ => vchan::ChannelPDUFlags::from_bits_truncate(0),
};

if first {
channel_flags.set(vchan::ChannelPDUFlags::CHANNEL_FLAG_FIRST, true);
first = false;
}
if leftover.is_empty() {
channel_flags.set(vchan::ChannelPDUFlags::CHANNEL_FLAG_LAST, true);
}

// the Channel PDU Header always specifies the *total length* of the PDU,
// even if it has to be split into multpile chunks:
// https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/a542bf19-1c86-4c80-ab3e-61449653abf6
let mut outer = vchan::ChannelPDUHeader::new(total_len, channel_flags).encode()?;
outer.extend(inner);
result.push(outer);

inner = leftover;
}

Ok(result)
}

#[cfg(test)]
mod tests {
use crate::vchan::ChannelPDUFlags;
Expand All @@ -780,15 +762,17 @@ mod tests {

#[test]
fn encode_format_list_short() {
let msg = encode_message(
ClipboardPDUType::CB_FORMAT_LIST,
FormatListPDU {
format_names: vec![ShortFormatName::id(ClipboardFormat::CF_TEXT as u32)],
}
.encode()
.unwrap(),
)
.unwrap();
let client = Client::default();
let msg = client
.add_headers_and_chunkify(
ClipboardPDUType::CB_FORMAT_LIST,
FormatListPDU {
format_names: vec![ShortFormatName::id(ClipboardFormat::CF_TEXT as u32)],
}
.encode()
.unwrap(),
)
.unwrap();

assert_eq!(
msg[0],
Expand Down Expand Up @@ -816,8 +800,11 @@ mod tests {
format_names: vec![LongFormatName::id(0)],
};

let encoded =
encode_message(ClipboardPDUType::CB_FORMAT_LIST, empty.encode().unwrap()).unwrap();
let client = Client::default();

let encoded = client
.add_headers_and_chunkify(ClipboardPDUType::CB_FORMAT_LIST, empty.encode().unwrap())
.unwrap();

assert_eq!(
encoded[0],
Expand Down Expand Up @@ -976,7 +963,10 @@ mod tests {
}
let pdu = FormatDataResponsePDU { data };
let encoded = pdu.encode().unwrap();
let messages = encode_message(ClipboardPDUType::CB_FORMAT_DATA_RESPONSE, encoded).unwrap();
let client = Client::default();
let messages = client
.add_headers_and_chunkify(ClipboardPDUType::CB_FORMAT_DATA_RESPONSE, encoded)
.unwrap();
assert_eq!(2, messages.len());

let header0 =
Expand All @@ -996,10 +986,7 @@ mod tests {
#[test]
fn responds_to_format_data_request_hasdata() {
// a null-terminated utf-16 string, represented as a Vec<u8>
let test_data: Vec<u8> = "test\0"
.encode_utf16()
.flat_map(|v| v.to_le_bytes())
.collect();
let test_data = util::to_unicode("test");

let mut c: Client = Default::default();
c.clipboard
Expand Down
1 change: 1 addition & 0 deletions lib/srv/desktop/rdp/rdpclient/src/lib.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ pub mod errors;
pub mod piv;
pub mod rdpdr;
pub mod scard;
pub mod util;
pub mod vchan;

#[macro_use]
Expand Down
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