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Merge pull request #136 from rust-bitcoin/2018-08-minimal-push 

script: make Instructions iterator enforce minimal pushes
This commit is contained in:
Andrew Poelstra 2018-08-22 21:17:10 +00:00 committed by GitHub
parent c89a4f5ada fc0fec7e19
commit 3f9b003348
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 165 additions and 19 deletions
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32
fuzz/fuzz_targets/deserialize_script.rs
View File

@ -1,7 +1,37 @@
extern crate bitcoin;
use bitcoin::blockdata::script;
use bitcoin::network::serialize;
fn do_test(data: &[u8]) {
let _: Result<bitcoin::blockdata::script::Script, _> = bitcoin::network::serialize::deserialize(data);
let s: Result<script::Script, _> = serialize::deserialize(data);
if let Ok(script) = s {
let _: Vec<script::Instruction> = script.iter(false).collect();
let enforce_min: Vec<script::Instruction> = script.iter(true).collect();
let mut b = script::Builder::new();
for ins in enforce_min {
match ins {
script::Instruction::Error(_) => return,
script::Instruction::Op(op) => { b = b.push_opcode(op); }
script::Instruction::PushBytes(bytes) => {
// Any one-byte pushes, except -0, which can be interpreted as numbers, should be
// reserialized as numbers. (For -1 through 16, this will use special ops; for
// others it'll just reserialize them as pushes.)
if bytes.len() == 1 && bytes[0] != 0x80 && bytes[0] != 0x00 {
if let Ok(num) = script::read_scriptint(bytes) {
b = b.push_int(num);
} else {
b = b.push_slice(bytes);
}
} else {
b = b.push_slice(bytes);
}
}
}
}
assert_eq!(b.into_script(), script);
}
}
#[cfg(feature = "afl")]

2
src/blockdata/opcodes.rs
View File

@ -194,7 +194,7 @@ pub enum All {
OP_PUSHDATA2 = 0x4d,
/// Read the next 4 bytes as N; push the next N bytes as an array onto the stack
OP_PUSHDATA4 = 0x4e,
/// Push the array [0x80] onto the stack
/// Push the array [0x81] onto the stack
OP_PUSHNUM_NEG1 = 0x4f,
/// Synonym for OP_RETURN
OP_RESERVED = 0x50,

148
src/blockdata/script.rs
View File

@ -151,6 +151,9 @@ display_from_debug!(Builder);
/// would help you.
#[derive(PartialEq, Eq, Debug, Clone)]
pub enum Error {
/// Something did a non-minimal push; for more information see
/// `https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki#Push_operators`
NonMinimalPush,
/// Some opcode expected a parameter, but it was missing or truncated
EarlyEndOfScript,
/// Tried to read an array off the stack as a number when it was more than 4 bytes
@ -180,6 +183,7 @@ impl error::Error for Error {
fn description(&self) -> &'static str {
match *self {
Error::NonMinimalPush => "non-minimal datapush",
Error::EarlyEndOfScript => "unexpected end of script",
Error::NumericOverflow => "numeric overflow (number on stack larger than 4 bytes)",
#[cfg(feature="bitcoinconsensus")]
@ -373,6 +377,17 @@ impl Script {
opcodes::All::from(self.0[0]).classify() == opcodes::Class::IllegalOp)
}
/// Iterate over the script in the form of `Instruction`s, which are an enum covering
/// opcodes, datapushes and errors. At most one error will be returned and then the
/// iterator will end. To instead iterate over the script as sequence of bytes, treat
/// it as a slice using `script[..]` or convert it to a vector using `into_bytes()`.
pub fn iter(&self, enforce_minimal: bool) -> Instructions {
Instructions {
data: &self.0[..],
enforce_minimal: enforce_minimal,
}
}
#[cfg(feature="bitcoinconsensus")]
/// verify spend of an input script
/// # Parameters
@ -408,13 +423,8 @@ pub enum Instruction<'a> {
/// Iterator over a script returning parsed opcodes
pub struct Instructions<'a> {
data: &'a [u8]
}
impl<'a> IntoIterator for &'a Script {
type Item = Instruction<'a>;
type IntoIter = Instructions<'a>;
fn into_iter(self) -> Instructions<'a> { Instructions { data: &self.0[..] } }
data: &'a [u8],
enforce_minimal: bool,
}
impl<'a> Iterator for Instructions<'a> {
@ -429,41 +439,87 @@ impl<'a> Iterator for Instructions<'a> {
opcodes::Class::PushBytes(n) => {
let n = n as usize;
if self.data.len() < n + 1 {
self.data = &[]; // Kill iterator so that it does not return an infinite stream of errors
return Some(Instruction::Error(Error::EarlyEndOfScript));
}
if self.enforce_minimal {
if n == 1 && (self.data[1] == 0x81 || (self.data[1] > 0 && self.data[1] <= 16)) {
self.data = &[];
return Some(Instruction::Error(Error::NonMinimalPush));
}
}
let ret = Some(Instruction::PushBytes(&self.data[1..n+1]));
self.data = &self.data[n + 1..];
ret
}
opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA1) => {
if self.data.len() < 2 { return Some(Instruction::Error(Error::EarlyEndOfScript)); }
if self.data.len() < 2 {
self.data = &[];
return Some(Instruction::Error(Error::EarlyEndOfScript));
}
let n = match read_uint(&self.data[1..], 1) {
Ok(n) => n,
Err(e) => { return Some(Instruction::Error(e)); }
Err(e) => {
self.data = &[];
return Some(Instruction::Error(e));
}
};
if self.data.len() < n + 2 { return Some(Instruction::Error(Error::EarlyEndOfScript)); }
if self.data.len() < n + 2 {
self.data = &[];
return Some(Instruction::Error(Error::EarlyEndOfScript));
}
if self.enforce_minimal && n < 76 {
self.data = &[];
return Some(Instruction::Error(Error::NonMinimalPush));
}
let ret = Some(Instruction::PushBytes(&self.data[2..n+2]));
self.data = &self.data[n + 2..];
ret
}
opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA2) => {
if self.data.len() < 3 { return Some(Instruction::Error(Error::EarlyEndOfScript)); }
if self.data.len() < 3 {
self.data = &[];
return Some(Instruction::Error(Error::EarlyEndOfScript));
}
let n = match read_uint(&self.data[1..], 2) {
Ok(n) => n,
Err(e) => { return Some(Instruction::Error(e)); }
Err(e) => {
self.data = &[];
return Some(Instruction::Error(e));
}
};
if self.data.len() < n + 3 { return Some(Instruction::Error(Error::EarlyEndOfScript)); }
if self.enforce_minimal && n < 0x100 {
self.data = &[];
return Some(Instruction::Error(Error::NonMinimalPush));
}
if self.data.len() < n + 3 {
self.data = &[];
return Some(Instruction::Error(Error::EarlyEndOfScript));
}
let ret = Some(Instruction::PushBytes(&self.data[3..n + 3]));
self.data = &self.data[n + 3..];
ret
}
opcodes::Class::Ordinary(opcodes::Ordinary::OP_PUSHDATA4) => {
if self.data.len() < 5 { return Some(Instruction::Error(Error::EarlyEndOfScript)); }
if self.data.len() < 5 {
self.data = &[];
return Some(Instruction::Error(Error::EarlyEndOfScript));
}
let n = match read_uint(&self.data[1..], 4) {
Ok(n) => n,
Err(e) => { return Some(Instruction::Error(e)); }
Err(e) => {
self.data = &[];
return Some(Instruction::Error(e));
}
};
if self.data.len() < n + 5 { return Some(Instruction::Error(Error::EarlyEndOfScript)); }
if self.enforce_minimal && n < 0x10000 {
self.data = &[];
return Some(Instruction::Error(Error::NonMinimalPush));
}
if self.data.len() < n + 5 {
self.data = &[];
return Some(Instruction::Error(Error::EarlyEndOfScript));
}
let ret = Some(Instruction::PushBytes(&self.data[5..n + 5]));
self.data = &self.data[n + 5..];
ret
@ -787,6 +843,66 @@ mod test {
assert_eq!(redeem_script.to_v0_p2wsh().to_p2sh(), expected_out);
}
#[test]
fn test_iterator() {
let zero = hex_script!("00");
let zeropush = hex_script!("0100");
let nonminimal = hex_script!("4c0169b2"); // PUSHDATA1 for no reason
let minimal = hex_script!("0169b2"); // minimal
let nonminimal_alt = hex_script!("026900b2"); // non-minimal number but minimal push (should be OK)
let v_zero: Vec<Instruction> = zero.iter(true).collect();
let v_zeropush: Vec<Instruction> = zeropush.iter(true).collect();
let v_min: Vec<Instruction> = minimal.iter(true).collect();
let v_nonmin: Vec<Instruction> = nonminimal.iter(true).collect();
let v_nonmin_alt: Vec<Instruction> = nonminimal_alt.iter(true).collect();
let slop_v_min: Vec<Instruction> = minimal.iter(false).collect();
let slop_v_nonmin: Vec<Instruction> = nonminimal.iter(false).collect();
let slop_v_nonmin_alt: Vec<Instruction> = nonminimal_alt.iter(false).collect();
assert_eq!(
v_zero,
vec![
Instruction::PushBytes(&[]),
]
);
assert_eq!(
v_zeropush,
vec![
Instruction::PushBytes(&[0]),
]
);
assert_eq!(
v_min,
vec![
Instruction::PushBytes(&[105]),
Instruction::Op(opcodes::All::OP_NOP3),
]
);
assert_eq!(
v_nonmin,
vec![
Instruction::Error(Error::NonMinimalPush),
]
);
assert_eq!(
v_nonmin_alt,
vec![
Instruction::PushBytes(&[105, 0]),
Instruction::Op(opcodes::All::OP_NOP3),
]
);
assert_eq!(v_min, slop_v_min);
assert_eq!(v_min, slop_v_nonmin);
assert_eq!(v_nonmin_alt, slop_v_nonmin_alt);
}
#[test]
#[cfg(feature="bitcoinconsensus")]
fn test_bitcoinconsensus () {

2
src/util/contracthash.rs
View File

@ -237,7 +237,7 @@ pub fn untemplate(script: &script::Script) -> Result<(Template, Vec<PublicKey>),
}
let mut mode = Mode::SeekingKeys;
for instruction in script.into_iter() {
for instruction in script.iter(false) {
match instruction {
script::Instruction::PushBytes(data) => {
let n = data.len();