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/*************************************************
* OpenSSL DSA Engine Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/eng_ossl.h>
#include <botan/bn_wrap.h>
#include <openssl/opensslv.h>
#if OPENSSL_VERSION_NUMBER < 0x0090700F
#error Your OpenSSL install is too old, upgrade to 0.9.7 or later
#endif
namespace Botan {
#if defined(BOTAN_HAS_DSA)
namespace {
/*************************************************
* OpenSSL DSA Operation *
*************************************************/
class OpenSSL_DSA_Op : public DSA_Operation
{
public:
bool verify(const byte[], u32bit, const byte[], u32bit) const;
SecureVector<byte> sign(const byte[], u32bit, const BigInt&) const;
DSA_Operation* clone() const { return new OpenSSL_DSA_Op(*this); }
OpenSSL_DSA_Op(const DL_Group& group, const BigInt& y1,
const BigInt& x1) :
x(x1), y(y1), p(group.get_p()), q(group.get_q()), g(group.get_g()) {}
private:
const OSSL_BN x, y, p, q, g;
OSSL_BN_CTX ctx;
};
/*************************************************
* OpenSSL DSA Verify Operation *
*************************************************/
bool OpenSSL_DSA_Op::verify(const byte msg[], u32bit msg_len,
const byte sig[], u32bit sig_len) const
{
const u32bit q_bytes = q.bytes();
if(sig_len != 2*q_bytes || msg_len > q_bytes)
return false;
OSSL_BN r(sig, q_bytes);
OSSL_BN s(sig + q_bytes, q_bytes);
OSSL_BN i(msg, msg_len);
if(BN_is_zero(r.value) || BN_cmp(r.value, q.value) >= 0)
return false;
if(BN_is_zero(s.value) || BN_cmp(s.value, q.value) >= 0)
return false;
if(BN_mod_inverse(s.value, s.value, q.value, ctx.value) == 0)
return false;
OSSL_BN si;
BN_mod_mul(si.value, s.value, i.value, q.value, ctx.value);
BN_mod_exp(si.value, g.value, si.value, p.value, ctx.value);
OSSL_BN sr;
BN_mod_mul(sr.value, s.value, r.value, q.value, ctx.value);
BN_mod_exp(sr.value, y.value, sr.value, p.value, ctx.value);
BN_mod_mul(si.value, si.value, sr.value, p.value, ctx.value);
BN_nnmod(si.value, si.value, q.value, ctx.value);
if(BN_cmp(si.value, r.value) == 0)
return true;
return false;
}
/*************************************************
* OpenSSL DSA Sign Operation *
*************************************************/
SecureVector<byte> OpenSSL_DSA_Op::sign(const byte in[], u32bit length,
const BigInt& k_bn) const
{
if(BN_is_zero(x.value))
throw Internal_Error("OpenSSL_DSA_Op::sign: No private key");
OSSL_BN i(in, length);
OSSL_BN k(k_bn);
OSSL_BN r;
BN_mod_exp(r.value, g.value, k.value, p.value, ctx.value);
BN_nnmod(r.value, r.value, q.value, ctx.value);
BN_mod_inverse(k.value, k.value, q.value, ctx.value);
OSSL_BN s;
BN_mul(s.value, x.value, r.value, ctx.value);
BN_add(s.value, s.value, i.value);
BN_mod_mul(s.value, s.value, k.value, q.value, ctx.value);
if(BN_is_zero(r.value) || BN_is_zero(s.value))
throw Internal_Error("OpenSSL_DSA_Op::sign: r or s was zero");
const u32bit q_bytes = q.bytes();
SecureVector<byte> output(2*q_bytes);
r.encode(output, q_bytes);
s.encode(output + q_bytes, q_bytes);
return output;
}
}
/*************************************************
* Acquire a DSA op *
*************************************************/
DSA_Operation* OpenSSL_Engine::dsa_op(const DL_Group& group, const BigInt& y,
const BigInt& x) const
{
return new OpenSSL_DSA_Op(group, y, x);
}
#endif
}
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