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/*************************************************
* CMS Decoding Operations Source File *
* (C) 1999-2006 The Botan Project *
*************************************************/
#include <botan/cms_dec.h>
#include <botan/ber_dec.h>
#include <botan/oids.h>
#include <botan/lookup.h>
#include <botan/look_pk.h>
#include <botan/bigint.h>
#include <memory>
namespace Botan {
namespace {
/*************************************************
* Compute the hash of some content *
*************************************************/
SecureVector<byte> hash_of(const SecureVector<byte>& content,
const AlgorithmIdentifier& hash_algo,
std::string& hash_name)
{
hash_name = OIDS::lookup(hash_algo.oid);
std::auto_ptr<HashFunction> hash_fn(get_hash(hash_name));
return hash_fn->process(content);
}
/*************************************************
* Find a cert based on SignerIdentifier *
*************************************************/
std::vector<X509_Certificate> get_cert(BER_Decoder& signer_info,
X509_Store& store)
{
BER_Object id = signer_info.get_next_object();
std::vector<X509_Certificate> found;
if(id.type_tag == SEQUENCE && id.class_tag == CONSTRUCTED)
{
X509_DN issuer;
BigInt serial;
BER_Decoder iands(id.value);
iands.decode(issuer);
iands.decode(serial);
found = X509_Store_Search::by_iands(store, issuer,
BigInt::encode(serial));
}
else if(id.type_tag == 0 && id.class_tag == CONSTRUCTED)
found = X509_Store_Search::by_SKID(store, id.value);
else
throw Decoding_Error("CMS: Unknown tag for cert identifier");
// verify cert if found
if(found.size() > 1)
throw Internal_Error("CMS: Found more than one match in get_cert");
return found;
}
/*************************************************
* Read OriginatorInfo *
*************************************************/
void read_orig_info(BER_Decoder& info, X509_Store& store)
{
BER_Object next = info.get_next_object();
if(next.type_tag == 0 &&
next.class_tag == ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
{
DataSource_Memory certs(next.value);
while(!certs.end_of_data())
{
// FIXME: can be attribute certs too
// FIXME: DoS?
X509_Certificate cert(certs);
store.add_cert(cert);
}
next = info.get_next_object();
}
if(next.type_tag == 1 &&
next.class_tag == ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
{
DataSource_Memory crls(next.value);
while(!crls.end_of_data())
{
// FIXME: DoS?
X509_CRL crl(crls);
store.add_crl(crl);
}
next = info.get_next_object();
}
info.push_back(next);
}
/*************************************************
* Decode any Attributes, and check type *
*************************************************/
SecureVector<byte> decode_attributes(BER_Decoder& ber, const OID& type,
bool& bad_attributes)
{
BER_Object obj = ber.get_next_object();
SecureVector<byte> digest;
bool got_digest = false;
bool got_content_type = false;
if(obj.type_tag == 0 &&
obj.class_tag == ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
ber.push_back(obj);
else
{
BER_Decoder attributes(obj.value);
while(attributes.more_items())
{
Attribute attr;
attributes.decode(attr);
BER_Decoder attr_value(attr.parameters);
if(attr.oid == OIDS::lookup("PKCS9.MessageDigest"))
{
got_digest = true;
attr_value.decode(digest, OCTET_STRING);
}
else if(attr.oid == OIDS::lookup("PKCS9.ContentType"))
{
got_content_type = true;
OID inner_type;
attr_value.decode(inner_type);
if(inner_type != type)
bad_attributes = true;
}
else
throw Decoding_Error("Unknown/unhandled CMS attribute found: " +
OIDS::lookup(attr.oid));
}
if(!got_digest || !got_content_type)
bad_attributes = true;
}
return digest;
}
}
/*************************************************
* Decode this layer of CMS encoding *
*************************************************/
void CMS_Decoder::decode_layer()
{
try {
if(status == FAILURE)
throw Invalid_State("CMS: Decoder is in FAILURE state");
status = GOOD;
info = "";
type = next_type;
if(type == OIDS::lookup("CMS.DataContent"))
return;
BER_Decoder decoder(data);
if(type == OIDS::lookup("CMS.CompressedData"))
decompress(decoder);
else if(type == OIDS::lookup("CMS.DigestedData"))
{
u32bit version;
AlgorithmIdentifier hash_algo;
SecureVector<byte> digest;
BER_Decoder hash_info = decoder.start_cons(SEQUENCE);
hash_info.decode(version);
if(version != 0 && version != 2)
throw Decoding_Error("CMS: Unknown version for DigestedData");
hash_info.decode(hash_algo);
read_econtent(hash_info);
hash_info.decode(digest, OCTET_STRING);
hash_info.end_cons();
if(digest != hash_of(data, hash_algo, info))
status = BAD;
}
else if(type == OIDS::lookup("CMS.SignedData"))
{
#if 1
throw Exception("FIXME: not implemented");
#else
u32bit version;
BER_Decoder sig_info = BER::get_subsequence(decoder);
BER::decode(sig_info, version);
if(version != 1 && version != 3)
throw Decoding_Error("CMS: Unknown version for SignedData");
BER::get_subset(sig_info); // hash algos (do something with these?)
read_econtent(sig_info);
read_orig_info(sig_info, store);
BER_Decoder signer_infos = BER::get_subset(sig_info);
while(signer_infos.more_items())
{
AlgorithmIdentifier sig_algo, hash_algo;
SecureVector<byte> signature, digest;
u32bit version;
BER_Decoder signer_info = BER::get_subsequence(signer_infos);
BER::decode(signer_info, version);
if(version != 1 && version != 3)
throw Decoding_Error("CMS: Unknown version for SignerInfo");
std::vector<X509_Certificate> certs = get_cert(signer_info, store);
if(certs.size() == 0) { status = NO_KEY; continue; }
BER::decode(signer_info, hash_algo);
bool bad_attr = false;
digest = decode_attributes(signer_info, next_type, bad_attr);
if(bad_attr) { status = BAD; continue; }
BER::decode(signer_info, sig_algo);
BER::decode(signer_info, signature, OCTET_STRING);
// unsigned attributes
signer_info.verify_end();
if(digest.has_items())
{
std::string hash;
if(digest != hash_of(data, hash_algo, hash))
{
status = BAD;
continue;
}
status = check_sig(signed_attr, sig_algo, signature, certs[0]);
}
else
status = check_sig(data, sig_algo, signature, certs[0]);
if(status == BAD)
continue;
// fix this (gets only last signer, for one thing)
// maybe some way for the user to get all certs that signed the
// message? that would be useful
info = "CN=" + cert.subject_info("CommonName") +
",O=" + cert.subject_info("Organization") +
",OU=" + cert.subject_info("Organizational Unit");
}
#endif
}
else if(type == OIDS::lookup("CMS.EnvelopedData"))
{
throw Exception("FIXME: not implemented");
}
else if(type == OIDS::lookup("CMS.AuthenticatedData"))
{
throw Exception("FIXME: not implemented");
}
else
throw Decoding_Error("CMS: Unknown content ID " + type.as_string());
}
catch(std::exception)
{
status = FAILURE;
}
}
}
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