Now unspendable outs are determined by attempting to create a minimal
satisfying input script. If this can't be done, the output is unspendable.
(Unfortunately this "minimal satisfying script" is not (yet) something
that can be shown to the user, since it is more a bundle of constraints
than actual data pushes.)
Current limitations:
- OP_ADD and friends mean the checker gives the script a free pass.
There is no fundamental reason for this, I just didn't get to it
yet.
- Pubkeys are checked for DER encoding but signatures aren't. This
is because secp256k1 exposes a method for pubkeys, but not one
for sigs :). Signatures are loosely length checked.
Sorry for so many things in one commit ... it was an iterative
process depending as I worked on BIP32 to get the other stuff
working. (And I was too lazy to separate it out after the fact.)
A breaking change by the array newtyping is that Show for Sha256dHash
now outputs the slice Show. You have to use `{:x}` to get the old hex
output.
We no longer confirm that chained transactions occur in the correct order
in blocks, which is a minor consensus regression and should be dealt with
in future.
Looks like to implement the crypto opcodes I may need to switch from
rust-crypto to rust-openssl.. or implement RIPEMD-160 for rust-crypto.
In either case I will need to generalize the hash.rs stuff to support
other hashes, so I'm committing here as a checkpoint before doing all
that.
I noticed that the little/big endian hex string functions for Sha256dHash
did not match my intuition. What we should have is that the raw bytes
correspond to a little-endian representation (since we convert to Uint256
by transmuting, and Uint256's have little-endian representation) while
the reversed raw bytes are big-endian.
This means that the output from `sha256sum` is "little-endian", while the
standard "zeros on the left" output from bitcoind is "big-endian". This
is correct since we think of blockhashes as being "below the target" when
they have lots of zeros on the left, and we also notice that when hashing
Bitcoin objects with sha256sum that the output hashes are always reversed.
These two functions le_hex_string and be_hex_string should really not be
used outside of the library; the Encodable trait should give access to a
"big endian" representation while ConsensusEncodable gives access to a
"little endian" representation. That way we describe the split in terms
of user-facing/consensus code rather than big/little endian code, which
is a better way of thinking about it. After all, a hash is a collection
of bytes, not a number --- it doesn't have an intrinsic endianness.
Oh, and by the way, to compute a sha256d hash from sha256sum, you do
echo -n 'data' | sha256sum | xxd -r -p | sha256dsum
Andrew Poelstra
Jerzy Kozera