3 # Electrum - lightweight Bitcoin client
4 # Copyright (C) 2012 thomasv@ecdsa.org
6 # This program is free software: you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation, either version 3 of the License, or
9 # (at your option) any later version.
11 # This program is distributed in the hope that it will be useful,
12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 # GNU General Public License for more details.
16 # You should have received a copy of the GNU General Public License
17 # along with this program. If not, see <http://www.gnu.org/licenses/>.
20 import threading, time, Queue, os, sys, shutil
21 from util import user_dir, appdata_dir, print_error
25 class BlockchainVerifier(threading.Thread):
26 """ Simple Payment Verification """
28 def __init__(self, interface, config):
29 threading.Thread.__init__(self)
32 self.interface = interface
33 self.interface.register_channel('verifier')
34 self.lock = threading.Lock()
35 self.pending_headers = [] # headers that have not been verified
39 self.headers_url = 'http://headers.electrum.org/blockchain_headers'
43 with self.lock: self.running = False
44 self.interface.poke('verifier')
47 with self.lock: return self.running
51 self.init_headers_file()
52 self.set_local_height()
57 requested_headers = []
60 # subscribe to block headers
61 self.interface.send([ ('blockchain.headers.subscribe',[])], 'verifier')
63 while self.is_running():
64 # request missing chunks
65 if not all_chunks and self.height and not requested_chunks:
67 if self.local_height + 50 < self.height:
68 min_index = (self.local_height + 1)/2016
69 max_index = (self.height + 1)/2016
70 for i in range(min_index, max_index + 1):
71 print_error( "requesting chunk", i )
72 self.interface.send([ ('blockchain.block.get_chunk',[i])], 'verifier')
73 requested_chunks.append(i)
77 print_error("downloaded all chunks")
80 # process pending headers
81 if self.pending_headers and all_chunks:
83 for header in self.pending_headers:
84 if self.verify_header(header):
87 # request previous header
88 i = header.get('block_height') - 1
89 if i not in requested_headers:
90 print_error("requesting header %d"%i)
91 self.interface.send([ ('blockchain.block.get_header',[i])], 'verifier')
92 requested_headers.append(i)
96 self.interface.trigger_callback('updated')
98 self.pending_headers.remove(header)
101 r = self.interface.get_response('verifier',timeout=1)
107 print_error('Verifier received an error:', r)
115 if method == 'blockchain.block.get_chunk':
117 self.verify_chunk(index, result)
118 requested_chunks.remove(index)
120 elif method in ['blockchain.headers.subscribe', 'blockchain.block.get_header']:
122 self.pending_headers.append(result)
123 if method == 'blockchain.block.get_header':
124 requested_headers.remove(result.get('block_height'))
126 self.height = result.get('block_height')
127 ## fixme # self.interface.poke('synchronizer')
129 self.pending_headers.sort(key=lambda x: x.get('block_height'))
130 # print "pending headers", map(lambda x: x.get('block_height'), self.pending_headers)
136 def verify_chunk(self, index, hexdata):
137 data = hexdata.decode('hex')
140 print_error("validating headers %d"%height)
143 previous_hash = ("0"*64)
145 prev_header = self.read_header(index*2016-1)
146 if prev_header is None: raise
147 previous_hash = self.hash_header(prev_header)
149 bits, target = self.get_target(index)
152 height = index*2016 + i
153 raw_header = data[i*80:(i+1)*80]
154 header = self.header_from_string(raw_header)
155 _hash = self.hash_header(header)
156 assert previous_hash == header.get('prev_block_hash')
157 assert bits == header.get('bits')
158 assert eval('0x'+_hash) < target
160 previous_header = header
161 previous_hash = _hash
163 self.save_chunk(index, data)
166 def verify_header(self, header):
167 # add header to the blockchain file
168 # if there is a reorg, push it in a stack
170 height = header.get('block_height')
172 prev_header = self.read_header(height -1)
174 # return False to request previous header
177 prev_hash = self.hash_header(prev_header)
178 bits, target = self.get_target(height/2016)
179 _hash = self.hash_header(header)
181 assert prev_hash == header.get('prev_block_hash')
182 assert bits == header.get('bits')
183 assert eval('0x'+_hash) < target
185 # this can be caused by a reorg.
186 print_error("verify header failed"+ repr(header))
189 items = self.verified_tx.items()[:]
190 for tx_hash, item in items:
191 tx_height, timestamp, pos = item
192 if tx_height >= height:
193 print_error("redoing", tx_hash)
195 self.verified_tx.pop(tx_hash)
196 if tx_hash in self.merkle_roots:
197 self.merkle_roots.pop(tx_hash)
198 # return False to request previous header.
201 self.save_header(header)
202 print_error("verify header:", _hash, height)
208 def header_to_string(self, res):
209 s = int_to_hex(res.get('version'),4) \
210 + rev_hex(res.get('prev_block_hash')) \
211 + rev_hex(res.get('merkle_root')) \
212 + int_to_hex(int(res.get('timestamp')),4) \
213 + int_to_hex(int(res.get('bits')),4) \
214 + int_to_hex(int(res.get('nonce')),4)
218 def header_from_string(self, s):
219 hex_to_int = lambda s: eval('0x' + s[::-1].encode('hex'))
221 h['version'] = hex_to_int(s[0:4])
222 h['prev_block_hash'] = hash_encode(s[4:36])
223 h['merkle_root'] = hash_encode(s[36:68])
224 h['timestamp'] = hex_to_int(s[68:72])
225 h['bits'] = hex_to_int(s[72:76])
226 h['nonce'] = hex_to_int(s[76:80])
229 def hash_header(self, header):
230 return rev_hex(Hash(self.header_to_string(header).decode('hex')).encode('hex'))
233 wdir = self.config.get('blockchain_headers_path', user_dir())
234 if wdir and not os.path.exists( wdir ): os.mkdir(wdir)
235 return os.path.join( wdir, 'blockchain_headers')
237 def init_headers_file(self):
238 filename = self.path()
239 if os.path.exists(filename):
243 import urllib, socket
244 socket.setdefaulttimeout(30)
245 print_error("downloading ", self.headers_url )
246 urllib.urlretrieve(self.headers_url, filename)
248 print_error( "download failed. creating file", filename )
249 open(filename,'wb+').close()
251 def save_chunk(self, index, chunk):
252 filename = self.path()
253 f = open(filename,'rb+')
254 f.seek(index*2016*80)
257 self.set_local_height()
259 def save_header(self, header):
260 data = self.header_to_string(header).decode('hex')
261 assert len(data) == 80
262 height = header.get('block_height')
263 filename = self.path()
264 f = open(filename,'rb+')
268 self.set_local_height()
271 def set_local_height(self):
273 if os.path.exists(name):
274 h = os.path.getsize(name)/80 - 1
275 if self.local_height != h:
276 self.local_height = h
279 def read_header(self, block_height):
281 if os.path.exists(name):
283 f.seek(block_height*80)
287 h = self.header_from_string(h)
291 def get_target(self, index):
293 max_target = 0x00000000FFFF0000000000000000000000000000000000000000000000000000
294 if index == 0: return 0x1d00ffff, max_target
296 first = self.read_header((index-1)*2016)
297 last = self.read_header(index*2016-1)
299 nActualTimespan = last.get('timestamp') - first.get('timestamp')
300 nTargetTimespan = 14*24*60*60
301 nActualTimespan = max(nActualTimespan, nTargetTimespan/4)
302 nActualTimespan = min(nActualTimespan, nTargetTimespan*4)
304 bits = last.get('bits')
310 target = (a) * pow(2, 8 * (bits/MM - 3))
313 new_target = min( max_target, (target * nActualTimespan)/nTargetTimespan )
316 c = ("%064X"%new_target)[2:]
322 c = eval('0x'+c[0:6])
327 new_bits = c + MM * i
328 return new_bits, new_target