Hard-code a special nId=max int alert, to be broadcast if the
alert key is ever compromised. It applies to all versions, never
expires, cancels all previous alerts, and has a fixed message:
URGENT: Alert key compromised, upgrade required
Variations are not allowed (ignored), so an attacker with
the private key cannot broadcast empty-message nId=max alerts.
This fixes two alert system vulnerabilities found by
Sergio Lerner; you could send peers unlimited numbers
of invalid alert message to try to either fill up their
debug.log with messages and/or keep their CPU busy
checking signatures.
Fixed by disconnecting/banning peers if they send 10 or more
bad (invalid/expired/cancelled) alerts.
Windows & WindowsXP style have a problem with displaying the block progress.
Add a custom stylesheet as workaround, but only when one of those renderers is active,
otherwise leave the theme alone (issue #1071).
If 950 of the last 1,000 blocks are nVersion=2, reject nVersion=1
(or zero, but no bitcoin release has created block.nVersion=0) blocks
-- 75 of last 100 on testnet3.
This rule is being put in place now so that we don't have to go
through another "express support" process to get what we really
want, which is for every single new block to include the block height
in the coinbase.
"Version 2" blocks are blocks that have nVersion=2 and
have the block height as the first item in their coinbase.
Block-height-in-the-coinbase is strictly enforced when
version=2 blocks are a supermajority in the block chain
(750 of the last 1,000 blocks on main net, 51 of 100 for
testnet). This does not affect old clients/miners at all,
which will continue producing nVersion=1 blocks, and
which will continue to be valid.
Since the minimum signed integer cannot be represented as positive so long as its type is signed, and it's not well-defined what happens if you make it unsigned before negating it, we instead increment the negative integer by 1, convert it, then increment the (now positive) unsigned integer by 1 to compensate
As noticed by sipa (Pieter Wuille), this can happen when CBigNum::setint64() is
called with an integer value of INT64_MIN (-2^63).
When compiled with -ftrapv, the program would crash. Otherwise, it would
execute an undefined operation (although in practice, usually the correct one).
Bitcoin will not make an outbound connection to a network group
(/16 for IPv4) that it is already connected to. This means that
if an attacker wants good odds of capturing all a nodes outbound
connections he must have hosts on a a large number of distinct
groups.
Previously both inbound and outbound connections were used to
feed this exclusion. The use of inbound connections, which can be
controlled by the attacker, actually has the potential of making
sibyl attacks _easier_: An attacker can start up hosts in groups
which house many honest nodes and make outbound connections to
the victim to exclude big swaths of honest nodes. Because the
attacker chooses to make the outbound connection he can always
beat out honest nodes for the consumption of inbound slots.
At _best_ the old behavior increases attacker costs by a single
group (e.g. one distinct group to use to fill up all your inbound
slots), but at worst it allows the attacker to select whole
networks you won't connect to.
This commit makes the nodes use only outbound links to exclude
network groups for outbound connections. Fancier things could
be done, like weaker exclusion for inbound groups... but
simplicity is good and I don't believe more complexity is
currently needed.
