From e6b343d880f50d52390c5af8623afa15fcbc65a2 Mon Sep 17 00:00:00 2001 From: Pieter Wuille Date: Wed, 18 Mar 2015 09:31:49 -0700 Subject: Make addrman's bucket placement deterministic. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Give each address a single fixed location in the new and tried tables, which become simple fixed-size arrays instead of sets and vectors. This prevents attackers from having an advantages by inserting an address multiple times. This change was suggested as Countermeasure 1 in Eclipse Attacks on Bitcoin’s Peer-to-Peer Network, Ethan Heilman, Alison Kendler, Aviv Zohar, Sharon Goldberg. ePrint Archive Report 2015/263. March 2015. It is also more efficient. --- src/addrman.h | 167 +++++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 107 insertions(+), 60 deletions(-) (limited to 'src/addrman.h') diff --git a/src/addrman.h b/src/addrman.h index 04c7b32eaf..f7c6318448 100644 --- a/src/addrman.h +++ b/src/addrman.h @@ -10,7 +10,6 @@ #include "random.h" #include "sync.h" #include "timedata.h" -#include "uint256.h" #include "util.h" #include @@ -91,6 +90,9 @@ public: return GetNewBucket(nKey, source); } + //! Calculate in which position of a bucket to store this entry. + int GetBucketPosition(const uint256 &nKey, bool fNew, int nBucket) const; + //! Determine whether the statistics about this entry are bad enough so that it can just be deleted bool IsTerrible(int64_t nNow = GetAdjustedTime()) const; @@ -128,14 +130,11 @@ public: //! total number of buckets for tried addresses #define ADDRMAN_TRIED_BUCKET_COUNT 64 -//! maximum allowed number of entries in buckets for tried addresses -#define ADDRMAN_TRIED_BUCKET_SIZE 64 - //! total number of buckets for new addresses #define ADDRMAN_NEW_BUCKET_COUNT 256 -//! maximum allowed number of entries in buckets for new addresses -#define ADDRMAN_NEW_BUCKET_SIZE 64 +//! maximum allowed number of entries in buckets for new and tried addresses +#define ADDRMAN_BUCKET_SIZE 64 //! over how many buckets entries with tried addresses from a single group (/16 for IPv4) are spread #define ADDRMAN_TRIED_BUCKETS_PER_GROUP 4 @@ -146,9 +145,6 @@ public: //! in how many buckets for entries with new addresses a single address may occur #define ADDRMAN_NEW_BUCKETS_PER_ADDRESS 4 -//! how many entries in a bucket with tried addresses are inspected, when selecting one to replace -#define ADDRMAN_TRIED_ENTRIES_INSPECT_ON_EVICT 4 - //! how old addresses can maximally be #define ADDRMAN_HORIZON_DAYS 30 @@ -195,13 +191,13 @@ private: int nTried; //! list of "tried" buckets - std::vector > vvTried; + int vvTried[ADDRMAN_TRIED_BUCKET_COUNT][ADDRMAN_BUCKET_SIZE]; //! number of (unique) "new" entries int nNew; //! list of "new" buckets - std::vector > vvNew; + int vvNew[ADDRMAN_NEW_BUCKET_COUNT][ADDRMAN_BUCKET_SIZE]; protected: @@ -215,17 +211,14 @@ protected: //! Swap two elements in vRandom. void SwapRandom(unsigned int nRandomPos1, unsigned int nRandomPos2); - //! Return position in given bucket to replace. - int SelectTried(int nKBucket); + //! Move an entry from the "new" table(s) to the "tried" table + void MakeTried(CAddrInfo& info, int nId); - //! Remove an element from a "new" bucket. - //! This is the only place where actual deletions occur. - //! Elements are never deleted while in the "tried" table, only possibly evicted back to the "new" table. - int ShrinkNew(int nUBucket); + //! Delete an entry. It must not be in tried, and have refcount 0. + void Delete(int nId); - //! Move an entry from the "new" table(s) to the "tried" table - //! @pre vvUnkown[nOrigin].count(nId) != 0 - void MakeTried(CAddrInfo& info, int nId, int nOrigin); + //! Clear a position in a "new" table. This is the only place where entries are actually deleted. + void ClearNew(int nUBucket, int nUBucketPos); //! Mark an entry "good", possibly moving it from "new" to "tried". void Good_(const CService &addr, int64_t nTime); @@ -254,17 +247,21 @@ protected: public: /** * serialized format: - * * version byte (currently 0) - * * nKey + * * version byte (currently 1) + * * 0x20 + nKey (serialized as if it were a vector, for backward compatibility) * * nNew * * nTried - * * number of "new" buckets + * * number of "new" buckets XOR 2**30 * * all nNew addrinfos in vvNew * * all nTried addrinfos in vvTried * * for each bucket: * * number of elements * * for each element: index * + * 2**30 is xorred with the number of buckets to make addrman deserializer v0 detect it + * as incompatible. This is necessary because it did not check the version number on + * deserialization. + * * Notice that vvTried, mapAddr and vVector are never encoded explicitly; * they are instead reconstructed from the other information. * @@ -276,49 +273,53 @@ public: * * We don't use ADD_SERIALIZE_METHODS since the serialization and deserialization code has * very little in common. - * */ template void Serialize(Stream &s, int nType, int nVersionDummy) const { LOCK(cs); - unsigned char nVersion = 0; + unsigned char nVersion = 1; s << nVersion; s << ((unsigned char)32); s << nKey; s << nNew; s << nTried; - int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT; + int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT ^ (1 << 30); s << nUBuckets; std::map mapUnkIds; int nIds = 0; for (std::map::const_iterator it = mapInfo.begin(); it != mapInfo.end(); it++) { - if (nIds == nNew) break; // this means nNew was wrong, oh ow mapUnkIds[(*it).first] = nIds; const CAddrInfo &info = (*it).second; if (info.nRefCount) { + assert(nIds != nNew); // this means nNew was wrong, oh ow s << info; nIds++; } } nIds = 0; for (std::map::const_iterator it = mapInfo.begin(); it != mapInfo.end(); it++) { - if (nIds == nTried) break; // this means nTried was wrong, oh ow const CAddrInfo &info = (*it).second; if (info.fInTried) { + assert(nIds != nTried); // this means nTried was wrong, oh ow s << info; nIds++; } } - for (std::vector >::const_iterator it = vvNew.begin(); it != vvNew.end(); it++) { - const std::set &vNew = (*it); - int nSize = vNew.size(); + for (int bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; bucket++) { + int nSize = 0; + for (int i = 0; i < ADDRMAN_BUCKET_SIZE; i++) { + if (vvNew[bucket][i] != -1) + nSize++; + } s << nSize; - for (std::set::const_iterator it2 = vNew.begin(); it2 != vNew.end(); it2++) { - int nIndex = mapUnkIds[*it2]; - s << nIndex; + for (int i = 0; i < ADDRMAN_BUCKET_SIZE; i++) { + if (vvNew[bucket][i] != -1) { + int nIndex = mapUnkIds[vvNew[bucket][i]]; + s << nIndex; + } } } } @@ -328,67 +329,97 @@ public: { LOCK(cs); + Clear(); + unsigned char nVersion; s >> nVersion; unsigned char nKeySize; s >> nKeySize; - if (nKeySize != 32) throw std::ios_base::failure("Incorrect keysize in addrman"); + if (nKeySize != 32) throw std::ios_base::failure("Incorrect keysize in addrman deserialization"); s >> nKey; s >> nNew; s >> nTried; - int nUBuckets = 0; s >> nUBuckets; - nIdCount = 0; - mapInfo.clear(); - mapAddr.clear(); - vRandom.clear(); - vvTried = std::vector >(ADDRMAN_TRIED_BUCKET_COUNT, std::vector(0)); - vvNew = std::vector >(ADDRMAN_NEW_BUCKET_COUNT, std::set()); + if (nVersion != 0) { + nUBuckets ^= (1 << 30); + } + + // Deserialize entries from the new table. for (int n = 0; n < nNew; n++) { CAddrInfo &info = mapInfo[n]; s >> info; mapAddr[info] = n; info.nRandomPos = vRandom.size(); vRandom.push_back(n); - if (nUBuckets != ADDRMAN_NEW_BUCKET_COUNT) { - vvNew[info.GetNewBucket(nKey)].insert(n); - info.nRefCount++; + if (nVersion != 1 || nUBuckets != ADDRMAN_NEW_BUCKET_COUNT) { + // In case the new table data cannot be used (nVersion unknown, or bucket count wrong), + // immediately try to give them a reference based on their primary source address. + int nUBucket = info.GetNewBucket(nKey); + int nUBucketPos = info.GetBucketPosition(nKey, true, nUBucket); + if (vvNew[nUBucket][nUBucketPos] == -1) { + vvNew[nUBucket][nUBucketPos] = n; + info.nRefCount++; + } } } nIdCount = nNew; + + // Deserialize entries from the tried table. int nLost = 0; for (int n = 0; n < nTried; n++) { CAddrInfo info; s >> info; - std::vector &vTried = vvTried[info.GetTriedBucket(nKey)]; - if (vTried.size() < ADDRMAN_TRIED_BUCKET_SIZE) { + int nKBucket = info.GetTriedBucket(nKey); + int nKBucketPos = info.GetBucketPosition(nKey, false, nKBucket); + if (vvTried[nKBucket][nKBucketPos] == -1) { info.nRandomPos = vRandom.size(); info.fInTried = true; vRandom.push_back(nIdCount); mapInfo[nIdCount] = info; mapAddr[info] = nIdCount; - vTried.push_back(nIdCount); + vvTried[nKBucket][nKBucketPos] = nIdCount; nIdCount++; } else { nLost++; } } nTried -= nLost; - for (int b = 0; b < nUBuckets; b++) { - std::set &vNew = vvNew[b]; + + // Deserialize positions in the new table (if possible). + for (int bucket = 0; bucket < nUBuckets; bucket++) { int nSize = 0; s >> nSize; for (int n = 0; n < nSize; n++) { int nIndex = 0; s >> nIndex; - CAddrInfo &info = mapInfo[nIndex]; - if (nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS) { - info.nRefCount++; - vNew.insert(nIndex); + if (nIndex >= 0 && nIndex < nNew) { + CAddrInfo &info = mapInfo[nIndex]; + int nUBucketPos = info.GetBucketPosition(nKey, true, bucket); + if (nVersion == 1 && nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && vvNew[bucket][nUBucketPos] == -1 && info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS) { + info.nRefCount++; + vvNew[bucket][nUBucketPos] = nIndex; + } } } } + + // Prune new entries with refcount 0 (as a result of collisions). + int nLostUnk = 0; + for (std::map::const_iterator it = mapInfo.begin(); it != mapInfo.end(); ) { + if (it->second.fInTried == false && it->second.nRefCount == 0) { + std::map::const_iterator itCopy = it++; + Delete(itCopy->first); + nLostUnk++; + } else { + it++; + } + } + if (nLost + nLostUnk > 0) { + LogPrint("addrman", "addrman lost %i new and %i tried addresses due to collisions\n", nLostUnk, nLost); + } + + Check(); } unsigned int GetSerializeSize(int nType, int nVersion) const @@ -396,18 +427,34 @@ public: return (CSizeComputer(nType, nVersion) << *this).size(); } - CAddrMan() : vRandom(0), vvTried(ADDRMAN_TRIED_BUCKET_COUNT, std::vector(0)), vvNew(ADDRMAN_NEW_BUCKET_COUNT, std::set()) + void Clear() { - nKey = GetRandHash(); + std::vector().swap(vRandom); + nKey = GetRandHash(); + for (size_t bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; bucket++) { + for (size_t entry = 0; entry < ADDRMAN_BUCKET_SIZE; entry++) { + vvNew[bucket][entry] = -1; + } + } + for (size_t bucket = 0; bucket < ADDRMAN_TRIED_BUCKET_COUNT; bucket++) { + for (size_t entry = 0; entry < ADDRMAN_BUCKET_SIZE; entry++) { + vvTried[bucket][entry] = -1; + } + } - nIdCount = 0; - nTried = 0; - nNew = 0; + nIdCount = 0; + nTried = 0; + nNew = 0; + } + + CAddrMan() + { + Clear(); } ~CAddrMan() { - nKey.SetNull(); + nKey.SetNull(); } //! Return the number of (unique) addresses in all tables. -- cgit v1.2.3