This adds SCRIPT_VERIFY_LOW_S to STANDARD_SCRIPT_VERIFY_FLAGS which
will make the node require the canonical 'low-s' encoding for
ECDSA signatures when relaying or mining.
Consensus behavior is unchanged.
The rational is explained in a81cd96805ce6b65cca3a40ebbd3b2eb428abb7b:
Absent this kind of test ECDSA is not a strong signature as given
a valid signature {r, s} both that value and {r, -s mod n} are valid.
These two encodings have different hashes allowing third parties a
vector to change users txids. These attacks are avoided by picking
a particular form as canonical and rejecting the other form(s); in
the of the LOW_S rule, the smaller of the two possible S values is
used.
If widely deployed this change would eliminate the last remaining
known vector for nuisance malleability on boring SIGHASH_ALL
p2pkh transactions. On the down-side it will block most
transactions made by sufficiently out of date software.
Unlike the other avenues to change txids on boring transactions this
one was randomly violated by all deployed bitcoin software prior to
its discovery. So, while other malleability vectors where made
non-standard as soon as they were discovered, this one has remained
permitted. Even BIP62 did not propose applying this rule to
old version transactions, but conforming implementations have become
much more common since BIP62 was initially written.
Bitcoin Core has produced compatible signatures since a28fb70e in
September 2013, but this didn't make it into a release until 0.9
in March 2014; Bitcoinj has done so for a similar span of time.
Bitcoinjs and electrum have been more recently updated.
This does not replace the need for BIP62 or similar, as miners can
still cooperate to break transactions. Nor does it replace the
need for wallet software to handle malleability sanely[1]. This
only eliminates the cheap and irritating DOS attack.
[1] On the Malleability of Bitcoin Transactions
Marcin Andrychowicz, Stefan Dziembowski, Daniel Malinowski, Łukasz Mazurek
http://fc15.ifca.ai/preproceedings/bitcoin/paper_9.pdf
* Fixes#6679
* Tested with --disable-zmq
* Tested with and without pkgconfig
* Tested with and without zmq installed
Signed-off-by: Johnathan Corgan <johnathan@corganlabs.com>
da894ab Accept any sequence of PUSHDATAs in OP_RETURN outputs (Peter Todd)
5d8709c Add IsPushOnly(const_iterator pc) (Peter Todd)
6a07eb6 Make TX_SCRIPTHASH clear vSolutionsRet first (Peter Todd)
1) created rpc-tests.py
2) deleted rpc-tests.sh
3) travis.yml points to rpc-tests.py
4) Modified Makefile.am
5) Updated README.md
6) Added tests_config.py and deleted tests-config.sh
7) Modified configure.ac with script to set correct path in tests_config.py
Prevent these warnings in clang 3.6:
./serialize.h:96:9: warning: explicitly assigning value of variable of type 'uint64_t' (aka 'unsigned long') to itself [-Wself-assign]
obj = (obj);
~~~ ^ ~~~
Previously only one PUSHDATA was allowed, needlessly limiting
applications such as matching OP_RETURN contents with bloom filters that
operate on a per-PUSHDATA level. Now any combination that passes
IsPushOnly() is allowed, so long as the total size of the scriptPubKey
is less than 42 bytes. (unchanged modulo non-minimal PUSHDATA encodings)
Also, this fixes the odd bug where previously the PUSHDATA could be
replaced by any single opcode, even sigops consuming opcodes such as
CHECKMULTISIG. (20 sigops!)
Previously unlike other transaction types the TX_SCRIPTHASH would not
clear vSolutionsRet, which means that unlike other transaction types if
it was called twice in a row you would get the result of the previous
invocation as well.
a3874c7 doc: no longer require use of openssl in OpenBSD build guide (Wladimir J. van der Laan)
5978388 build: remove libressl check (Wladimir J. van der Laan)
Now that BIP66 passed, OpenSSL is no longer directly part of the
consensus. What matters is that DER signatures are correctly parsed, and
secp256k1 crypto is implemented correctly (as well as the other
functions we use from OpenSSL, such as random number generation)
This means that effectively, using LibreSSL is not a larger risk than
using another version of OpenSSL.
Remove the specific check for LibreSSL.
Includes the still-relevant part of #6729: make sure CHECK_HEADER is
called using the right CXXFLAGS, not CFLAGS (as AC_LANG is c++).
Wladimir J. van der Laan