lix/src/libutil/hash.cc
Tuomas Tynkkynen 546f98dace libutil: Fix invalid assert on decoding base64 hashes
The assertion is broken because there is no one-to-one mapping from
length of a base64 string to the length of the output.

E.g.

"1q69lz7Empb06nzfkj651413n9icx0njmyr3xzq1j9q=" results in a 32-byte output.
"1q69lz7Empb06nzfkj651413n9icx0njmyr3xzq1j9qy" results in a 33-byte output.

To reproduce, evaluate:

builtins.derivationStrict {
    name = "0";
    builder = "0";
    system = "0";
    outputHashAlgo = "sha256";
    outputHash = "1q69lz7Empb06nzfkj651413n9icx0njmyr3xzq1j9qy";
}

Found by afl-fuzz.
2018-02-19 23:20:26 +02:00

349 lines
8 KiB
C++

#include <iostream>
#include <cstring>
#include <openssl/md5.h>
#include <openssl/sha.h>
#include "hash.hh"
#include "archive.hh"
#include "util.hh"
#include "istringstream_nocopy.hh"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
namespace nix {
void Hash::init()
{
if (type == htMD5) hashSize = md5HashSize;
else if (type == htSHA1) hashSize = sha1HashSize;
else if (type == htSHA256) hashSize = sha256HashSize;
else if (type == htSHA512) hashSize = sha512HashSize;
else abort();
assert(hashSize <= maxHashSize);
memset(hash, 0, maxHashSize);
}
bool Hash::operator == (const Hash & h2) const
{
if (hashSize != h2.hashSize) return false;
for (unsigned int i = 0; i < hashSize; i++)
if (hash[i] != h2.hash[i]) return false;
return true;
}
bool Hash::operator != (const Hash & h2) const
{
return !(*this == h2);
}
bool Hash::operator < (const Hash & h) const
{
if (hashSize < h.hashSize) return true;
if (hashSize > h.hashSize) return false;
for (unsigned int i = 0; i < hashSize; i++) {
if (hash[i] < h.hash[i]) return true;
if (hash[i] > h.hash[i]) return false;
}
return false;
}
const string base16Chars = "0123456789abcdef";
static string printHash16(const Hash & hash)
{
char buf[hash.hashSize * 2];
for (unsigned int i = 0; i < hash.hashSize; i++) {
buf[i * 2] = base16Chars[hash.hash[i] >> 4];
buf[i * 2 + 1] = base16Chars[hash.hash[i] & 0x0f];
}
return string(buf, hash.hashSize * 2);
}
// omitted: E O U T
const string base32Chars = "0123456789abcdfghijklmnpqrsvwxyz";
static string printHash32(const Hash & hash)
{
assert(hash.hashSize);
size_t len = hash.base32Len();
assert(len);
string s;
s.reserve(len);
for (int n = len - 1; n >= 0; n--) {
unsigned int b = n * 5;
unsigned int i = b / 8;
unsigned int j = b % 8;
unsigned char c =
(hash.hash[i] >> j)
| (i >= hash.hashSize - 1 ? 0 : hash.hash[i + 1] << (8 - j));
s.push_back(base32Chars[c & 0x1f]);
}
return s;
}
string printHash16or32(const Hash & hash)
{
return hash.to_string(hash.type == htMD5 ? Base16 : Base32, false);
}
std::string Hash::to_string(Base base, bool includeType) const
{
std::string s;
if (includeType) {
s += printHashType(type);
s += ':';
}
switch (base) {
case Base16:
s += printHash16(*this);
break;
case Base32:
s += printHash32(*this);
break;
case Base64:
s += base64Encode(std::string((const char *) hash, hashSize));
break;
}
return s;
}
Hash::Hash(const std::string & s, HashType type)
: type(type)
{
auto colon = s.find(':');
size_t pos = 0;
if (colon == string::npos) {
if (type == htUnknown)
throw BadHash("hash '%s' does not include a type", s);
} else {
string hts = string(s, 0, colon);
this->type = parseHashType(hts);
if (this->type == htUnknown)
throw BadHash("unknown hash type '%s'", hts);
if (type != htUnknown && type != this->type)
throw BadHash("hash '%s' should have type '%s'", s, printHashType(type));
pos = colon + 1;
}
init();
size_t size = s.size() - pos;
if (size == base16Len()) {
auto parseHexDigit = [&](char c) {
if (c >= '0' && c <= '9') return c - '0';
if (c >= 'A' && c <= 'F') return c - 'A' + 10;
if (c >= 'a' && c <= 'f') return c - 'a' + 10;
throw BadHash("invalid base-16 hash '%s'", s);
};
for (unsigned int i = 0; i < hashSize; i++) {
hash[i] =
parseHexDigit(s[pos + i * 2]) << 4
| parseHexDigit(s[pos + i * 2 + 1]);
}
}
else if (size == base32Len()) {
for (unsigned int n = 0; n < size; ++n) {
char c = s[pos + size - n - 1];
unsigned char digit;
for (digit = 0; digit < base32Chars.size(); ++digit) /* !!! slow */
if (base32Chars[digit] == c) break;
if (digit >= 32)
throw BadHash("invalid base-32 hash '%s'", s);
unsigned int b = n * 5;
unsigned int i = b / 8;
unsigned int j = b % 8;
hash[i] |= digit << j;
if (i < hashSize - 1) {
hash[i + 1] |= digit >> (8 - j);
} else {
if (digit >> (8 - j))
throw BadHash("invalid base-32 hash '%s'", s);
}
}
}
else if (size == base64Len()) {
auto d = base64Decode(std::string(s, pos));
if (d.size() != hashSize)
throw BadHash("invalid base-64 hash '%s'", s);
memcpy(hash, d.data(), hashSize);
}
else
throw BadHash("hash '%s' has wrong length for hash type '%s'", s, printHashType(type));
}
union Ctx
{
MD5_CTX md5;
SHA_CTX sha1;
SHA256_CTX sha256;
SHA512_CTX sha512;
};
static void start(HashType ht, Ctx & ctx)
{
if (ht == htMD5) MD5_Init(&ctx.md5);
else if (ht == htSHA1) SHA1_Init(&ctx.sha1);
else if (ht == htSHA256) SHA256_Init(&ctx.sha256);
else if (ht == htSHA512) SHA512_Init(&ctx.sha512);
}
static void update(HashType ht, Ctx & ctx,
const unsigned char * bytes, size_t len)
{
if (ht == htMD5) MD5_Update(&ctx.md5, bytes, len);
else if (ht == htSHA1) SHA1_Update(&ctx.sha1, bytes, len);
else if (ht == htSHA256) SHA256_Update(&ctx.sha256, bytes, len);
else if (ht == htSHA512) SHA512_Update(&ctx.sha512, bytes, len);
}
static void finish(HashType ht, Ctx & ctx, unsigned char * hash)
{
if (ht == htMD5) MD5_Final(hash, &ctx.md5);
else if (ht == htSHA1) SHA1_Final(hash, &ctx.sha1);
else if (ht == htSHA256) SHA256_Final(hash, &ctx.sha256);
else if (ht == htSHA512) SHA512_Final(hash, &ctx.sha512);
}
Hash hashString(HashType ht, const string & s)
{
Ctx ctx;
Hash hash(ht);
start(ht, ctx);
update(ht, ctx, (const unsigned char *) s.data(), s.length());
finish(ht, ctx, hash.hash);
return hash;
}
Hash hashFile(HashType ht, const Path & path)
{
Ctx ctx;
Hash hash(ht);
start(ht, ctx);
AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
if (!fd) throw SysError(format("opening file '%1%'") % path);
unsigned char buf[8192];
ssize_t n;
while ((n = read(fd.get(), buf, sizeof(buf)))) {
checkInterrupt();
if (n == -1) throw SysError(format("reading file '%1%'") % path);
update(ht, ctx, buf, n);
}
finish(ht, ctx, hash.hash);
return hash;
}
HashSink::HashSink(HashType ht) : ht(ht)
{
ctx = new Ctx;
bytes = 0;
start(ht, *ctx);
}
HashSink::~HashSink()
{
bufPos = 0;
delete ctx;
}
void HashSink::write(const unsigned char * data, size_t len)
{
bytes += len;
update(ht, *ctx, data, len);
}
HashResult HashSink::finish()
{
flush();
Hash hash(ht);
nix::finish(ht, *ctx, hash.hash);
return HashResult(hash, bytes);
}
HashResult HashSink::currentHash()
{
flush();
Ctx ctx2 = *ctx;
Hash hash(ht);
nix::finish(ht, ctx2, hash.hash);
return HashResult(hash, bytes);
}
HashResult hashPath(
HashType ht, const Path & path, PathFilter & filter)
{
HashSink sink(ht);
dumpPath(path, sink, filter);
return sink.finish();
}
Hash compressHash(const Hash & hash, unsigned int newSize)
{
Hash h;
h.hashSize = newSize;
for (unsigned int i = 0; i < hash.hashSize; ++i)
h.hash[i % newSize] ^= hash.hash[i];
return h;
}
HashType parseHashType(const string & s)
{
if (s == "md5") return htMD5;
else if (s == "sha1") return htSHA1;
else if (s == "sha256") return htSHA256;
else if (s == "sha512") return htSHA512;
else return htUnknown;
}
string printHashType(HashType ht)
{
if (ht == htMD5) return "md5";
else if (ht == htSHA1) return "sha1";
else if (ht == htSHA256) return "sha256";
else if (ht == htSHA512) return "sha512";
else abort();
}
}