/*
* CheckBodyHash()
*
* Validate the message according to rfc6376
*/
void Validatory::CheckBodyHash(const DKIM::Signature& sig)
throw (DKIM::PermanentError)
{
std::unique_ptr<EVP_MD_CTX, std::function<void(EVP_MD_CTX*)>> evpmdbody(EVP_MD_CTX_create(), [] (EVP_MD_CTX* p) { EVP_MD_CTX_destroy(p); });
// create signature for our body (message data)
switch (sig.GetDigestAlgorithm())
{
case DKIM::DKIM_A_SHA1:
EVP_DigestInit_ex(evpmdbody.get(), EVP_sha1(), nullptr);
break;
case DKIM::DKIM_A_SHA256:
EVP_DigestInit_ex(evpmdbody.get(), EVP_sha256(), nullptr);
break;
}
DKIM::Conversion::EVPDigest evpupd;
evpupd.ctx = evpmdbody.get();
CanonicalizationBody(m_file,
sig.GetCanonModeBody(),
m_msg.GetBodyOffset(),
sig.GetBodySizeLimit(),
sig.GetBodySize(),
std::bind(&DKIM::Conversion::EVPDigest::update, &evpupd, std::placeholders::_1, std::placeholders::_2));
unsigned char md_value[EVP_MAX_MD_SIZE];
unsigned int md_len;
EVP_DigestFinal_ex(evpmdbody.get(), md_value, &md_len);
if (sig.GetBodyHash().size() != md_len ||
memcmp(sig.GetBodyHash().c_str(), md_value, md_len) != 0)
{
throw DKIM::PermanentError("Body hash did not verify");
}
}
/*
* GetSignature()
*
* Get the signature from supported header iterator
*/
void Validatory::GetSignature(const Message::HeaderList::const_iterator& headerIter,
DKIM::Signature& sig)
throw (DKIM::PermanentError)
{
sig.Parse((*headerIter)->GetHeader().substr((*headerIter)->GetValueOffset()));
// create signature for our body (message data)
switch (sig.GetAlgorithm())
{
case DKIM::DKIM_A_SHA1:
EVP_DigestInit(&m_ctx_body, EVP_sha1());
break;
case DKIM::DKIM_A_SHA256:
EVP_DigestInit(&m_ctx_body, EVP_sha256());
break;
}
CanonicalizationBody canonicalbody(sig.GetCanonModeBody());
// if we should limit the size of the body we hash
bool limitBody = sig.GetBodySizeLimit();
size_t bodySize = sig.GetBodySize();
// if we have a message: seek to GetBodyOffset()
if (m_msg.GetBodyOffset() != -1)
{
m_file.clear();
m_file.seekg(m_msg.GetBodyOffset(), std::istream::beg);
std::string s;
while (std::getline(m_file, s) || m_file.peek() != EOF)
{
// double dots (postfix file may have .., instead of .)
if (m_doubleDots && s.substr(0, 2) == "..")
{
s.erase(0, 1);
}
// remove possible \r (if not removed by getline *probably not*)
if (s.size() > 0 && s[s.size()-1] == '\r')
s.erase(s.size()-1);
// canonical body
std::vector<std::string> output;
if (canonicalbody.FilterLine(s, output))
{
for (std::vector<std::string>::const_iterator i = output.begin();
i != output.end(); ++i)
{
if (limitBody && bodySize == 0) break;
#ifdef DEBUG
if (*i == "\r\n") printf("[CRLF]\n");
else printf("[%s]\n", i->c_str());
#endif
EVP_DigestUpdate(&m_ctx_body, i->c_str(),
limitBody?std::min(i->size(), bodySize):i->size());
bodySize -= std::min(i->size(), bodySize);
}
}
}
}
// else call (Done) -- which may insert a last CRLF if the body was empty
if (m_msg.GetBodyOffset() != -1 || m_file.peek() == EOF)
{
std::vector<std::string> output;
if (canonicalbody.Done(output))
{
for (std::vector<std::string>::const_iterator i = output.begin();
i != output.end(); ++i)
{
if (limitBody && bodySize == 0) break;
#ifdef DEBUG
if (*i == "\r\n") printf("[CRLF]\n");
else printf("[%s]\n", i->c_str());
#endif
EVP_DigestUpdate(&m_ctx_body, i->c_str(),
limitBody?std::min(i->size(), bodySize):i->size());
bodySize -= std::min(i->size(), bodySize);
}
}
}
unsigned char md_value[EVP_MAX_MD_SIZE];
unsigned int md_len;
EVP_DigestFinal_ex(&m_ctx_body, md_value, &md_len);
EVP_MD_CTX_cleanup(&m_ctx_body);
if (sig.GetBodyHash().size() != md_len ||
memcmp(sig.GetBodyHash().c_str(), md_value, md_len) != 0)
{
throw DKIM::PermanentError("Body hash did not verify");
}
}