add configurable checkpoint to blockchain verification; use genesis as default

8 years ago · dd0b018a35
3 changed files with 48 additions and 11 deletions
--- a/lib/bitcoin.py
+++ b/lib/bitcoin.py
@ -45,11 +45,13 @@ ADDRTYPE_P2WPKH = 6
 XPRV_HEADER = 0x0488ade4
 XPUB_HEADER = 0x0488b21e
 HEADERS_URL = "https://headers.electrum.org/blockchain_headers"
+GENESIS = "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"

 def set_testnet():
    global ADDRTYPE_P2PKH, ADDRTYPE_P2SH, ADDRTYPE_P2WPKH
    global XPRV_HEADER, XPUB_HEADER
    global TESTNET, HEADERS_URL
+    global GENESIS
    TESTNET = True
    ADDRTYPE_P2PKH = 111
    ADDRTYPE_P2SH = 196
@ -57,18 +59,21 @@ def set_testnet():
    XPRV_HEADER = 0x04358394
    XPUB_HEADER = 0x043587cf
    HEADERS_URL = "https://headers.electrum.org/testnet_headers"
+    GENESIS = "000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943"

 def set_nolnet():
    global ADDRTYPE_P2PKH, ADDRTYPE_P2SH, ADDRTYPE_P2WPKH
    global XPRV_HEADER, XPUB_HEADER
    global NOLNET, HEADERS_URL
-    NOLNET = True
+    global GENESIS
+    TESTNET = True
    ADDRTYPE_P2PKH = 0
    ADDRTYPE_P2SH = 5
    ADDRTYPE_P2WPKH = 6
    XPRV_HEADER = 0x0488ade4
    XPUB_HEADER = 0x0488b21e
    HEADERS_URL = "https://headers.electrum.org/nolnet_headers"
+    GENESIS = "663c88be18d07c45f87f910b93a1a71ed9ef1946cad50eb6a6f3af4c424625c6"



--- a/lib/blockchain.py
+++ b/lib/blockchain.py
@ -37,7 +37,9 @@ class Blockchain(util.PrintError):
    def __init__(self, config, network):
        self.config = config
        self.network = network
-        self.local_height = 0
+        self.checkpoint_height = self.config.get('checkpoint_height', 0)
+        self.checkpoint_hash = self.config.get('checkpoint_value', bitcoin.GENESIS)
+        self.check_truncate_headers()
        self.set_local_height()

    def height(self):
@ -55,11 +57,19 @@ class Blockchain(util.PrintError):

    def verify_header(self, header, prev_header, bits, target):
        prev_hash = self.hash_header(prev_header)
-        assert prev_hash == header.get('prev_block_hash'), "prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash'))
-        if bitcoin.TESTNET or bitcoin.NOLNET: return
-        assert bits == header.get('bits'), "bits mismatch: %s vs %s" % (bits, header.get('bits'))
        _hash = self.hash_header(header)
-        assert int('0x' + _hash, 16) <= target, "insufficient proof of work: %s vs target %s" % (int('0x' + _hash, 16), target)
+        if prev_hash != header.get('prev_block_hash'):
+            raise BaseException("prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash')))
+        if self.checkpoint_height == header.get('block_height') and self.checkpoint_hash != _hash:
+            raise BaseException('failed checkpoint')
+        if self.checkpoint_height == header.get('block_height'):
+            self.print_error("validated checkpoint", self.checkpoint_height)
+        if bitcoin.TESTNET:
+            return
+        if bits != header.get('bits'):
+            raise BaseException("bits mismatch: %s vs %s" % (bits, header.get('bits')))
+        if int('0x' + _hash, 16) > target:
+            raise BaseException("insufficient proof of work: %s vs target %s" % (int('0x' + _hash, 16), target))

    def verify_chain(self, chain):
        first_header = chain[0]
@ -78,7 +88,7 @@ class Blockchain(util.PrintError):
        bits, target = self.get_target(index)
        for i in range(num):
            raw_header = data[i*80:(i+1) * 80]
-            header = self.deserialize_header(raw_header)
+            header = self.deserialize_header(raw_header, index*2016 + i)
            self.verify_header(header, prev_header, bits, target)
            prev_header = header

@ -91,7 +101,7 @@ class Blockchain(util.PrintError):
            + int_to_hex(int(res.get('nonce')), 4)
        return s

-    def deserialize_header(self, s):
+    def deserialize_header(self, s, height):
        hex_to_int = lambda s: int('0x' + s[::-1].encode('hex'), 16)
        h = {}
        h['version'] = hex_to_int(s[0:4])
@ -100,6 +110,7 @@ class Blockchain(util.PrintError):
        h['timestamp'] = hex_to_int(s[68:72])
        h['bits'] = hex_to_int(s[72:76])
        h['nonce'] = hex_to_int(s[76:80])
+        h['block_height'] = height
        return h

    def hash_header(self, header):
@ -146,6 +157,7 @@ class Blockchain(util.PrintError):
        self.set_local_height()

    def set_local_height(self):
+        self.local_height = 0
        name = self.path()
        if os.path.exists(name):
            h = os.path.getsize(name)/80 - 1
@ -160,10 +172,25 @@ class Blockchain(util.PrintError):
            h = f.read(80)
            f.close()
            if len(h) == 80:
-                h = self.deserialize_header(h)
+                h = self.deserialize_header(h, block_height)
                return h

+    def check_truncate_headers(self):
+        checkpoint = self.read_header(self.checkpoint_height)
+        if checkpoint is None:
+            return
+        if self.hash_header(checkpoint) == self.checkpoint_hash:
+            return
+        self.print_error('Truncating headers file at height %d'%self.checkpoint_height)
+        name = self.path()
+        f = open(name, 'rwb+')
+        f.seek(self.checkpoint_height * 80)
+        f.truncate()
+        f.close()
+
    def get_target(self, index, chain=None):
+        if bitcoin.TESTNET:
+            return 0, 0
        if index == 0:
            return 0x1d00ffff, MAX_TARGET
        first = self.read_header((index-1) * 2016)
@ -176,9 +203,11 @@ class Blockchain(util.PrintError):
        # bits to target
        bits = last.get('bits')
        bitsN = (bits >> 24) & 0xff
-        assert bitsN >= 0x03 and bitsN <= 0x1d, "First part of bits should be in [0x03, 0x1d]"
+        if not (bitsN >= 0x03 and bitsN <= 0x1d):
+            raise BaseException("First part of bits should be in [0x03, 0x1d]")
        bitsBase = bits & 0xffffff
-        assert bitsBase >= 0x8000 and bitsBase <= 0x7fffff, "Second part of bits should be in [0x8000, 0x7fffff]"
+        if not (bitsBase >= 0x8000 and bitsBase <= 0x7fffff):
+            raise BaseException("Second part of bits should be in [0x8000, 0x7fffff]")
        target = bitsBase << (8 * (bitsN-3))
        # new target
        nActualTimespan = last.get('timestamp') - first.get('timestamp')
--- a/lib/network.py
+++ b/lib/network.py
@ -737,6 +737,9 @@ class Network(util.DaemonThread):

    def on_get_chunk(self, interface, response):
        '''Handle receiving a chunk of block headers'''
+        if response.get('error'):
+            interface.print_error(response.get('error'))
+            return
        if self.bc_requests:
            req_if, data = self.bc_requests[0]
            req_idx = data.get('chunk_idx')