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Use new APDU parser in CTAP1 code
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@krkhan
krkhan committed Dec 8, 2020
1 parent f475aa5 commit 4c84e94
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Showing 2 changed files with 47 additions and 45 deletions.
33 changes: 19 additions & 14 deletions src/ctap/apdu.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,10 +53,10 @@ pub enum ApduInstructions {
#[allow(dead_code)]
#[derive(Default, PartialEq)]
pub struct ApduHeader {
cla: u8,
ins: u8,
p1: u8,
p2: u8,
pub cla: u8,
pub ins: u8,
pub p1: u8,
pub p2: u8,
}

impl From<&[u8; APDU_HEADER_LEN]> for ApduHeader {
Expand Down Expand Up @@ -96,11 +96,11 @@ pub enum ApduType {
#[allow(dead_code)]
#[derive(PartialEq)]
pub struct APDU {
header: ApduHeader,
lc: u16,
data: Vec<u8>,
le: u32,
case_type: ApduType,
pub header: ApduHeader,
pub lc: u16,
pub data: Vec<u8>,
pub le: u32,
pub case_type: ApduType,
}

impl TryFrom<&[u8]> for APDU {
Expand Down Expand Up @@ -168,12 +168,17 @@ impl TryFrom<&[u8]> for APDU {
}
if payload.len() > 2 {
// Lc is possibly three-bytes long
let extended_apdu_lc: usize = BigEndian::read_u16(&payload[1..]) as usize;
let extended_apdu_le_len: usize = if payload.len() > extended_apdu_lc {
payload.len() - extended_apdu_lc - 3
} else {
0
let extended_apdu_lc: usize = BigEndian::read_u16(&payload[1..3]) as usize;
if payload.len() < extended_apdu_lc + 3 {
return Err(ApduStatusCode::SW_WRONG_LENGTH);
}
let extended_apdu_le_len: usize = match payload.len() - extended_apdu_lc {
// There's some possible Le bytes at the end
2..=5 => payload.len() - extended_apdu_lc - 3,
// There are more bytes than even Le3 can consume, return an error
_ => return Err(ApduStatusCode::SW_WRONG_LENGTH),
};

if byte_0 == 0 && extended_apdu_le_len <= 3 {
// If first byte is zero AND the next two bytes can be parsed as a big-endian
// length that covers the rest of the block (plus few additional bytes for Le), we
Expand Down
59 changes: 28 additions & 31 deletions src/ctap/ctap1.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
// See the License for the specific language governing permissions and
// limitations under the License.

use super::apdu::{ApduStatusCode, APDU};
use super::hid::ChannelID;
use super::status_code::Ctap2StatusCode;
use super::CtapState;
Expand Down Expand Up @@ -118,11 +119,16 @@ impl TryFrom<&[u8]> for U2fCommand {
type Error = Ctap1StatusCode;

fn try_from(message: &[u8]) -> Result<Self, Ctap1StatusCode> {
if message.len() < Ctap1Command::APDU_HEADER_LEN as usize {
return Err(Ctap1StatusCode::SW_WRONG_DATA);
}

let (apdu, payload) = message.split_at(Ctap1Command::APDU_HEADER_LEN as usize);
let apdu: APDU = match APDU::try_from(message) {
Ok(apdu) => apdu,
// Todo: Better conversion between ApduStatusCode and Ctap1StatusCode
// Maybe use TryFrom?
Err(apdu_status_code) => match apdu_status_code {
ApduStatusCode::SW_WRONG_LENGTH => return Err(Ctap1StatusCode::SW_WRONG_LENGTH),
ApduStatusCode::SW_WRONG_DATA => return Err(Ctap1StatusCode::SW_WRONG_DATA),
_ => return Err(Ctap1StatusCode::SW_COMMAND_ABORTED),
},
};

// ISO7816 APDU Header format. Each cell is 1 byte. Note that the CTAP flavor always
// encodes the length on 3 bytes and doesn't use the field "Le" (Length Expected).
Expand All @@ -131,30 +137,29 @@ impl TryFrom<&[u8]> for U2fCommand {
// +-----+-----+----+----+-----+-----+-----+
// | CLA | INS | P1 | P2 | Lc1 | Lc2 | Lc3 |
// +-----+-----+----+----+-----+-----+-----+
if apdu[0] != Ctap1Command::CTAP1_CLA {
if apdu.header.cla != Ctap1Command::CTAP1_CLA {
return Err(Ctap1StatusCode::SW_CLA_NOT_SUPPORTED);
}

let lc = (((apdu[4] as u32) << 16) | ((apdu[5] as u32) << 8) | (apdu[6] as u32)) as usize;

// Since there is always request data, the expected length is either omitted or
// encoded in 2 bytes.
if lc != payload.len() && lc + 2 != payload.len() {
// Todo: support extended APDUs now that the new parser can work with those
if apdu.lc as usize != apdu.data.len() && (apdu.lc as usize) + 2 != apdu.data.len() {
return Err(Ctap1StatusCode::SW_WRONG_LENGTH);
}

match apdu[1] {
match apdu.header.ins {
// U2F raw message format specification, Section 4.1
// +-----------------+-------------------+
// + Challenge (32B) | Application (32B) |
// +-----------------+-------------------+
Ctap1Command::U2F_REGISTER => {
if lc != 64 {
if apdu.lc != 64 {
return Err(Ctap1StatusCode::SW_WRONG_LENGTH);
}
Ok(Self::Register {
challenge: *array_ref!(payload, 0, 32),
application: *array_ref!(payload, 32, 32),
challenge: *array_ref!(apdu.data, 0, 32),
application: *array_ref!(apdu.data, 32, 32),
})
}

Expand All @@ -163,25 +168,25 @@ impl TryFrom<&[u8]> for U2fCommand {
// + Challenge (32B) | Application (32B) | key handle len (1B) | key handle |
// +-----------------+-------------------+---------------------+------------+
Ctap1Command::U2F_AUTHENTICATE => {
if lc < 65 {
if apdu.lc < 65 {
return Err(Ctap1StatusCode::SW_WRONG_LENGTH);
}
let handle_length = payload[64] as usize;
if lc != 65 + handle_length {
let handle_length = apdu.data[64] as usize;
if apdu.lc as usize != 65 + handle_length {
return Err(Ctap1StatusCode::SW_WRONG_LENGTH);
}
let flag = Ctap1Flags::try_from(apdu[2])?;
let flag = Ctap1Flags::try_from(apdu.header.p1)?;
Ok(Self::Authenticate {
challenge: *array_ref!(payload, 0, 32),
application: *array_ref!(payload, 32, 32),
key_handle: payload[65..lc].to_vec(),
challenge: *array_ref!(apdu.data, 0, 32),
application: *array_ref!(apdu.data, 32, 32),
key_handle: apdu.data[65..].to_vec(),
flags: flag,
})
}

// U2F raw message format specification, Section 6.1
Ctap1Command::U2F_VERSION => {
if lc != 0 {
if apdu.lc != 0 {
return Err(Ctap1StatusCode::SW_WRONG_LENGTH);
}
Ok(Self::Version)
Expand All @@ -190,7 +195,7 @@ impl TryFrom<&[u8]> for U2fCommand {
// For Vendor specific command.
Ctap1Command::VENDOR_SPECIFIC_FIRST..=Ctap1Command::VENDOR_SPECIFIC_LAST => {
Ok(Self::VendorSpecific {
payload: payload.to_vec(),
payload: apdu.data.to_vec(),
})
}

Expand All @@ -202,8 +207,6 @@ impl TryFrom<&[u8]> for U2fCommand {
pub struct Ctap1Command {}

impl Ctap1Command {
const APDU_HEADER_LEN: u32 = 7; // CLA + INS + P1 + P2 + LC1-3

const CTAP1_CLA: u8 = 0;
// This byte is used in Register, but only serves backwards compatibility.
const LEGACY_BYTE: u8 = 0x05;
Expand Down Expand Up @@ -571,13 +574,7 @@ mod test {
let mut message =
create_authenticate_message(&application, Ctap1Flags::CheckOnly, &key_handle);

message.push(0x00);
let response = Ctap1Command::process_command(&message, &mut ctap_state, START_CLOCK_VALUE);
assert_eq!(response, Err(Ctap1StatusCode::SW_WRONG_LENGTH));

// Two extra zeros are okay, they could encode the expected response length.
message.push(0x00);
message.push(0x00);
message.extend_from_slice(&[0x00, 0x00, 0x00, 0x00]);
let response = Ctap1Command::process_command(&message, &mut ctap_state, START_CLOCK_VALUE);
assert_eq!(response, Err(Ctap1StatusCode::SW_WRONG_LENGTH));
}
Expand Down

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