* Shorten SHA-256 hashes used in store path name generation to 160
bits, then encode them in a radix-32 representation (using digits and letters except e, o, u, and t). This produces store paths like /nix/store/4i0zb0z7f88mwghjirkz702a71dcfivn-aterm-2.3.1. The nice thing about this is that the hash part of the file name is still 32 characters, as before with MD5. (Of course, shortening SHA-256 to 160 bits makes it no better than SHA-160 in theory, but hopefully it's a bit more resistant to attacks; it's certainly a lot slower.)
This commit is contained in:
Eelco Dolstra
parent
9530cc3170
commit
d58a11e019
7 changed files with 108 additions and 36 deletions
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@ -39,7 +39,7 @@ static Hash hashDerivation(EvalState & state, StoreExpr ne)
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DrvHashes::iterator j = state.drvHashes.find(*i);
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if (j == state.drvHashes.end())
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throw Error(format("don't know expression `%1%'") % (string) *i);
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inputs2.insert(j->second);
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inputs2.insert(printHash(j->second));
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}
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ne.derivation.inputs = inputs2;
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}
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@ -60,7 +60,7 @@ static Path copyAtom(EvalState & state, const Path & srcPath)
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Hash drvHash = hashDerivation(state, ne);
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Path drvPath = writeTerm(unparseStoreExpr(ne), "c");
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state.drvHashes.insert(make_pair(drvPath, drvHash));
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state.drvHashes[drvPath] = drvHash;
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state.drvRoots[drvPath] = ne.closure.roots;
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@ -111,14 +111,14 @@ static void processBinding(EvalState & state, Expr e, StoreExpr & ne,
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a = queryAttr(e, "drvHash");
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if (!a) throw Error("derivation hash missing");
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Hash drvHash = parseHash(evalString(state, a));
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Hash drvHash = parseHash(htMD5, evalString(state, a));
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a = queryAttr(e, "outPath");
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if (!a) throw Error("output path missing");
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PathSet drvRoots;
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drvRoots.insert(evalPath(state, a));
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state.drvHashes.insert(make_pair(drvPath, drvHash));
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state.drvHashes[drvPath] = drvHash;
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state.drvRoots[drvPath] = drvRoots;
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ss.push_back(addInput(state, drvPath, ne));
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@ -188,7 +188,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
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ne.type = StoreExpr::neDerivation;
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string drvName;
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Hash outHash(htMD5);
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Hash outHash;
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bool outHashGiven = false;
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for (ATermIterator i(attrs.keys()); i; ++i) {
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@ -223,7 +223,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
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else if (key == "system") ne.derivation.platform = s;
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else if (key == "name") drvName = s;
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else if (key == "id") {
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outHash = parseHash(s);
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outHash = parseHash(htMD5, s);
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outHashGiven = true;
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}
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}
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@ -273,7 +273,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
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/* Write the resulting term into the Nix store directory. */
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Hash drvHash = outHashGiven
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? hashString((string) outHash + outPath, htMD5)
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? hashString(printHash(outHash) + outPath, htMD5)
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: hashDerivation(state, ne);
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Path drvPath = writeTerm(unparseStoreExpr(ne), "d-" + drvName);
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@ -283,7 +283,7 @@ static Expr primDerivation(EvalState & state, const ATermVector & _args)
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attrs.set("outPath", makeAttrRHS(makePath(toATerm(outPath)), makeNoPos()));
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attrs.set("drvPath", makeAttrRHS(makePath(toATerm(drvPath)), makeNoPos()));
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attrs.set("drvHash",
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makeAttrRHS(makeStr(toATerm((string) drvHash)), makeNoPos()));
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makeAttrRHS(makeStr(toATerm(printHash(drvHash))), makeNoPos()));
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attrs.set("type", makeAttrRHS(makeStr(toATerm("derivation")), makeNoPos()));
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return makeAttrs(attrs);
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@ -81,8 +81,12 @@ Strings filterReferences(const string & path, const Strings & paths)
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for (Strings::const_iterator i = paths.begin();
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i != paths.end(); i++)
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{
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string s = string(baseNameOf(*i), 0, 32);
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parseHash(s);
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string baseName = baseNameOf(*i);
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unsigned int pos = baseName.find('-');
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if (pos == string::npos)
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throw Error(format("bad reference `%1%'") % *i);
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string s = string(baseName, 0, pos);
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// parseHash(htSHA256, s);
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ids.push_back(s);
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backMap[s] = *i;
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}
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@ -415,14 +415,12 @@ Path makeStorePath(const string & type,
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Hash & hash, const string & suffix)
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{
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/* e.g., "source:sha256:1abc...:/nix/store:foo.tar.gz" */
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string s = type + ":sha256:" + (string) hash + ":"
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string s = type + ":sha256:" + printHash(hash) + ":"
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+ nixStore + ":" + suffix;
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Hash nameHash = hashString(s, htSHA256);
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printMsg(lvlError, format("name input: %1% -> %2%") % s % (string) nameHash);
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return nixStore + "/" + (string) nameHash + "-" + suffix;
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return nixStore + "/"
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+ printHash32(compressHash(hashString(s, htSHA256), 20))
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+ "-" + suffix;
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}
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@ -461,7 +459,7 @@ Path addToStore(const Path & _srcPath)
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Hash h2 = hashPath(dstPath, htSHA256);
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if (h != h2)
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throw Error(format("contents of `%1%' changed while copying it to `%2%' (%3% -> %4%)")
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% srcPath % dstPath % (string) h % (string) h2);
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% srcPath % dstPath % printHash(h) % printHash(h2));
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makePathReadOnly(dstPath);
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@ -15,6 +15,14 @@ extern "C" {
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Hash::Hash()
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{
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type = htUnknown;
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hashSize = 0;
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memset(hash, 0, maxHashSize);
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}
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Hash::Hash(HashType type)
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{
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this->type = type;
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@ -23,7 +31,7 @@ Hash::Hash(HashType type)
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else if (type == htSHA256) hashSize = sha256HashSize;
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else throw Error("unknown hash type");
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assert(hashSize <= maxHashSize);
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memset(hash, 0, hashSize);
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memset(hash, 0, maxHashSize);
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}
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@ -52,21 +60,21 @@ bool Hash::operator < (const Hash & h) const
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}
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Hash::operator string() const
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string printHash(const Hash & hash)
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{
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ostringstream str;
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for (unsigned int i = 0; i < hashSize; i++) {
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for (unsigned int i = 0; i < hash.hashSize; i++) {
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str.fill('0');
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str.width(2);
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str << hex << (int) hash[i];
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str << hex << (int) hash.hash[i];
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}
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return str.str();
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}
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Hash parseHash(const string & s)
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Hash parseHash(HashType ht, const string & s)
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{
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Hash hash(htMD5);
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Hash hash(ht);
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if (s.length() != hash.hashSize * 2)
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throw Error(format("invalid hash `%1%'") % s);
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for (unsigned int i = 0; i < hash.hashSize; i++) {
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@ -82,6 +90,48 @@ Hash parseHash(const string & s)
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}
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static unsigned short divMod(uint16_t * words, unsigned short y)
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{
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unsigned int borrow = 0;
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int pos = (Hash::maxHashSize / 2) - 1;
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while (pos >= 0 && !words[pos]) --pos;
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for ( ; pos >= 0; --pos) {
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unsigned int s = words[pos] + (borrow << 16);
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unsigned int d = s / y;
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borrow = s % y;
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words[pos] = d;
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}
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return borrow;
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}
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// omitted: E O U T
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char chars[] = "0123456789abcdfghijklmnpqrsvwxyz";
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string printHash32(const Hash & hash)
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{
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Hash hash2(hash);
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unsigned int len = (hash.hashSize * 8 - 1) / 5 + 1;
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string s(len, '0');
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int pos = len - 1;
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while (pos >= 0) {
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unsigned short digit = divMod((uint16_t *) hash2.hash, 32);
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s[pos--] = chars[digit];
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}
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for (unsigned int i = 0; i < hash2.maxHashSize; ++i)
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assert(hash2.hash[i] == 0);
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return s;
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}
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bool isHash(const string & s)
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{
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if (s.length() != 32) return false;
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@ -186,3 +236,13 @@ Hash hashPath(const Path & path, HashType ht)
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finish(ht, sink.ctx, hash.hash);
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return hash;
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}
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Hash compressHash(const Hash & hash, unsigned int newSize)
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{
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Hash h;
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h.hashSize = newSize;
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for (unsigned int i = 0; i < hash.hashSize; ++i)
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h.hash[i % newSize] ^= hash.hash[i];
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return h;
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}
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@ -8,7 +8,7 @@
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using namespace std;
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typedef enum { htMD5, htSHA1, htSHA256 } HashType;
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typedef enum { htUnknown, htMD5, htSHA1, htSHA256 } HashType;
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const int md5HashSize = 16;
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@ -24,7 +24,10 @@ struct Hash
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HashType type;
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/* Create a zeroed hash object. */
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/* Create an unusable hash object. */
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Hash();
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/* Create a zero-filled hash object. */
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Hash(HashType type);
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/* Check whether two hash are equal. */
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@ -36,13 +39,20 @@ struct Hash
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/* For sorting. */
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bool operator < (const Hash & h) const;
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/* Convert a hash code into a hexadecimal representation. */
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operator string() const;
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};
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/* Convert a hash to a hexadecimal representation. */
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string printHash(const Hash & hash);
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/* Parse a hexadecimal representation of a hash code. */
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Hash parseHash(const string & s);
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Hash parseHash(HashType ht, const string & s);
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/* Convert a hash to a base-32 representation. */
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string printHash32(const Hash & hash);
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/* Parse a base-32 representation of a hash code. */
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Hash parseHash32(HashType ht, const string & s);
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/* Verify that the given string is a valid hash code. */
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bool isHash(const string & s);
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@ -57,5 +67,9 @@ Hash hashFile(const Path & path, HashType ht);
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md5(dump(path)). */
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Hash hashPath(const Path & path, HashType ht);
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/* Compress a hash to the specified number of bytes by cyclically
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XORing bytes together. */
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Hash compressHash(const Hash & hash, unsigned int newSize);
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#endif /* !__HASH_H */
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@ -34,10 +34,6 @@ struct DrvInfo
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Path drvPath;
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Path outPath;
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Hash drvHash;
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DrvInfo() : drvHash(htMD5)
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{
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}
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};
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typedef map<Path, DrvInfo> DrvInfos;
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@ -74,7 +70,7 @@ bool parseDerivation(EvalState & state, Expr e, DrvInfo & drv)
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a = queryAttr(e, "drvHash");
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if (!a) throw badTerm("derivation hash missing", e);
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drv.drvHash = parseHash(evalString(state, a));
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drv.drvHash = parseHash(htMD5, evalString(state, a));
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a = queryAttr(e, "outPath");
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if (!a) throw badTerm("output path missing", e);
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@ -205,7 +201,7 @@ void createUserEnv(EvalState & state, const DrvInfos & drvs,
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makeBind(toATerm("drvPath"),
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makePath(toATerm(i->second.drvPath)), makeNoPos()),
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makeBind(toATerm("drvHash"),
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makeStr(toATerm((string) i->second.drvHash)), makeNoPos()),
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makeStr(toATerm(printHash(i->second.drvHash))), makeNoPos()),
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makeBind(toATerm("outPath"),
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makePath(toATerm(i->second.outPath)), makeNoPos())
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));
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@ -29,8 +29,8 @@ void run(Strings args)
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else throw UsageError(format("unknown hash type `%1%'") % *i);
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}
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else
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cout << format("%1%\n") % (string)
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(flat ? hashFile(*i, ht) : hashPath(*i, ht));
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cout << format("%1%\n") % printHash(
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(flat ? hashFile(*i, ht) : hashPath(*i, ht)));
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}
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}
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