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fix(quic): bound decrypt header associated data #11

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fix(quic): bound decrypt header associated data #11

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2c8eee9
fix(quic): bound decrypt header associated data
alanhoff Mar 17, 2026
51538e1
fix(packet): validate decrypt payload bounds
alanhoff Mar 17, 2026
2f13b45
fix(packet): bound decrypt associated data rebuild
alanhoff Mar 17, 2026
bb3bde2
fix(packet): narrow helper error set
alanhoff Mar 17, 2026
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16 changes: 14 additions & 2 deletions src/quic/packet.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -375,7 +375,13 @@ pub fn decrypt(header: *Header, fbs: anytype, space: PacketNumSpace) ![]u8 {
// Skip the packet number bytes in the buffer
try fbs.seekBy(@intCast(header.packet_number_len));

if (header.remainder_len < header.packet_number_len) {
return error.InvalidPacket;
}
const payload_len = header.remainder_len - header.packet_number_len;
if (payload_len > (fbs.buffer.len - fbs.pos)) {
return error.InvalidPacket;
}

// RFC 9001 Section 5.2: AD includes the unprotected first byte and everything up to and including packet number
// For coalesced packets, use packet_start to get the correct offset within the buffer
Expand All @@ -387,7 +393,7 @@ pub fn decrypt(header: *Header, fbs: anytype, space: PacketNumSpace) ![]u8 {
// Copy the rest of the header and packet number (from byte after first to current position)
@memcpy(header_bytes_buf[1..][0..(header_len - 1)], fbs.buffer[(pkt_start + 1)..fbs.pos]);
const header_bytes = header_bytes_buf[0..header_len];
const encrypted_payload = fbs.buffer[(fbs.pos)..(fbs.pos + payload_len)];
const encrypted_payload = fbs.buffer[fbs.pos..(fbs.pos + payload_len)];

// Decode packet number
header.packet_number = decodePacketNumber(space.next_packet_number, truncated_packet_number, header.packet_number_len * 8);
Expand Down Expand Up @@ -457,7 +463,13 @@ pub fn decryptWithKeyUpdate(header: *Header, fbs: anytype, space: *PacketNumSpac

try fbs.seekBy(@intCast(header.packet_number_len));

if (header.remainder_len < header.packet_number_len) {
return error.InvalidPacket;
}
const payload_len = header.remainder_len - header.packet_number_len;
if (payload_len > (fbs.buffer.len - fbs.pos)) {
return error.InvalidPacket;
}

// Build associated data
const pkt_start = header.packet_start;
Expand All @@ -466,7 +478,7 @@ pub fn decryptWithKeyUpdate(header: *Header, fbs: anytype, space: *PacketNumSpac
header_bytes_buf[0] = first_byte;
@memcpy(header_bytes_buf[1..][0..(header_len - 1)], fbs.buffer[(pkt_start + 1)..fbs.pos]);
const header_bytes = header_bytes_buf[0..header_len];
const encrypted_payload = fbs.buffer[(fbs.pos)..(fbs.pos + payload_len)];
const encrypted_payload = fbs.buffer[fbs.pos..(fbs.pos + payload_len)];

// Decode packet number
header.packet_number = decodePacketNumber(space.next_packet_number, truncated_packet_number, header.packet_number_len * 8);
Expand Down
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