30496461195

Committed 29 Jul 2026 08:43PM UTC coverage: 89.519% (+0.09%) from 89.425%

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Merge pull request #5776 from Rohde-Schwarz/fix/tls_anvil

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87.96

/src/lib/pubkey/ecdsa/ecdsa.cpp

/*
* ECDSA implementation
* (C) 2007 Manuel Hartl, FlexSecure GmbH
*     2007 Falko Strenzke, FlexSecure GmbH
*     2008-2010,2015,2016,2018,2024 Jack Lloyd
*     2016 René Korthaus
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/ecdsa.h>

#include <botan/ec_group.h>
#include <botan/internal/keypair.h>
#include <botan/internal/pk_ops_impl.h>

#if defined(BOTAN_HAS_RFC6979_GENERATOR)
   #include <botan/internal/rfc6979.h>
#endif

namespace Botan {

namespace {

EC_AffinePoint recover_ecdsa_public_key(
   const EC_Group& group, const std::vector<uint8_t>& msg, const BigInt& r, const BigInt& s, uint8_t v) {
   if(group.has_cofactor()) {
      throw Invalid_Argument("ECDSA public key recovery only supported for prime order groups");
   }

   if(v >= 4) {
      throw Invalid_Argument("Unexpected v param for ECDSA public key recovery");
   }

   const BigInt& group_order = group.get_order();

   if(r <= 0 || r >= group_order || s <= 0 || s >= group_order) {
      throw Invalid_Argument("Out of range r/s cannot recover ECDSA public key");
   }

   const uint8_t y_odd = v % 2;
   const bool add_order = (v >> 1) == 0x01;
   const size_t p_bytes = group.get_p_bytes();

   BigInt x = r;

   if(add_order) {
      x += group_order;
   }

   if(x.bytes() <= p_bytes) {
      std::vector<uint8_t> X(p_bytes + 1);

      X[0] = 0x02 | y_odd;
      x.serialize_to(std::span{X}.subspan(1));

      if(auto R = EC_AffinePoint::deserialize_compressed(group, X)) {
         // Compute r_inv * (-eG + s*R)
         const auto ne = EC_Scalar::from_bytes_with_trunc(group, msg).negate();
         const auto ss = EC_Scalar::from_bigint(group, s);

         const auto r_inv = EC_Scalar::from_bigint(group, r).invert_vartime();

         const EC_Group::Mul2Table GR_mul(R.value());
         if(auto egsr = GR_mul.mul2_vartime(ne * r_inv, ss * r_inv)) {
            return egsr.value();
         }
      }
   }

   throw Decoding_Error("Failed to recover ECDSA public key from signature/msg pair");
}

}  // namespace

ECDSA_PublicKey::ECDSA_PublicKey(
   const EC_Group& group, const std::vector<uint8_t>& msg, const BigInt& r, const BigInt& s, uint8_t v) :
      EC_PublicKey(group, recover_ecdsa_public_key(group, msg, r, s, v)) {}

std::optional<size_t> ECDSA_PublicKey::_signature_element_size_for_DER_encoding() const {
   return domain().get_order_bytes();
}

std::unique_ptr<Private_Key> ECDSA_PublicKey::generate_another(RandomNumberGenerator& rng) const {
   return std::make_unique<ECDSA_PrivateKey>(rng, domain());
}

uint8_t ECDSA_PublicKey::recovery_param(const std::vector<uint8_t>& msg, const BigInt& r, const BigInt& s) const {
   const auto this_key = this->_public_ec_point().serialize_compressed();

   for(uint8_t v = 0; v != 4; ++v) {
      try {
         const auto R = recover_ecdsa_public_key(this->domain(), msg, r, s, v);

         if(R.serialize_compressed() == this_key) {
            return v;
         }
      } catch(Decoding_Error&) {
         // try the next v
      }
   }

   throw Internal_Error("Could not determine ECDSA recovery parameter");
}

std::unique_ptr<Public_Key> ECDSA_PrivateKey::public_key() const {
   return std::make_unique<ECDSA_PublicKey>(domain(), _public_ec_point());
}

bool ECDSA_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const {
   if(!EC_PrivateKey::check_key(rng, strong)) {
      return false;
   }

   if(!strong) {
      return true;
   }

   return KeyPair::signature_consistency_check(rng, *this, "SHA-256");
}

namespace {

/**
* ECDSA signature operation
*/
class ECDSA_Signature_Operation final : public PK_Ops::Signature_with_Hash {
   public:
      ECDSA_Signature_Operation(const ECDSA_PrivateKey& ecdsa, std::string_view padding, RandomNumberGenerator& rng) :
            PK_Ops::Signature_with_Hash(padding),
            m_group(ecdsa.domain()),
            m_x(ecdsa._private_key()),
            m_b(EC_Scalar::random(m_group, rng)) {
#if defined(BOTAN_HAS_RFC6979_GENERATOR)
         m_rfc6979 = std::make_unique<RFC6979_Nonce_Generator>(
            this->rfc6979_hash_function(), m_group.get_order_bits(), ecdsa._private_key());
#endif
      }

      size_t signature_length() const override { return 2 * m_group.get_order_bytes(); }

      std::vector<uint8_t> raw_sign(std::span<const uint8_t> msg, RandomNumberGenerator& rng) override;

      AlgorithmIdentifier algorithm_identifier() const override;

   private:
      const EC_Group m_group;
      const EC_Scalar m_x;

#if defined(BOTAN_HAS_RFC6979_GENERATOR)
      std::unique_ptr<RFC6979_Nonce_Generator> m_rfc6979;
#endif

      EC_Scalar m_b;
};

AlgorithmIdentifier ECDSA_Signature_Operation::algorithm_identifier() const {
   const std::string full_name = "ECDSA/" + hash_function();
   const OID oid = OID::from_string(full_name);
   return AlgorithmIdentifier(oid, AlgorithmIdentifier::USE_EMPTY_PARAM);
}

std::vector<uint8_t> ECDSA_Signature_Operation::raw_sign(std::span<const uint8_t> msg, RandomNumberGenerator& rng) {
   const auto m = EC_Scalar::from_bytes_with_trunc(m_group, msg);

#if defined(BOTAN_HAS_RFC6979_GENERATOR)
   const auto k = m_rfc6979->nonce_for(m_group, m);
#else
   const auto k = EC_Scalar::random(m_group, rng);
#endif

   /*
   * Blind the inputs
   *
   * Here we are computing (x*r+m)/k
   *
   * Instead have a random b and compute (k*b)^-1
   *
   * Then compute (x*r+m) as (x*r*b + m*b)
   *
   * Finally (x*r*b + m*b)/(k*b) = (x*r+m)/k
   *
   * This effectively blinds both the inversion as well as the various scalar
   * multiplications. All of these operations should be constant-time anyway but
   * blinding is very cheap and may help if either the compiler introduces
   * variable-time behavior, or for the case of EM/power side channel attacks [1].
   *
   * [1] But note that such attacks are currently outside of Botan's threat model.
   *
   * NOTE: if you change anything here also update ECDSA_Timing_Test
   * in cli/timing_tests.cpp to use the same formulas
   */
   const auto r = EC_Scalar::gk_x_mod_order(k, rng);

   const auto k_inv = (m_b * k).invert();

   const auto xr_m = ((m_x * m_b) * r) + (m * m_b);

   const auto s = (k_inv * xr_m);

   // Generate the next blinding value via modular squaring
   m_b.square_self();

   // With overwhelming probability, a bug rather than actual zero r/s
   if(r.is_zero() || s.is_zero()) {
      throw Internal_Error("During ECDSA signature generated zero r/s");
   }

   return EC_Scalar::serialize_pair(r, s);
}

/**
* ECDSA verification operation
*/
class ECDSA_Verification_Operation final : public PK_Ops::Verification_with_Hash {
   public:
      ECDSA_Verification_Operation(const ECDSA_PublicKey& ecdsa, std::string_view padding) :
            PK_Ops::Verification_with_Hash(padding), m_group(ecdsa.domain()), m_gy_mul(ecdsa._public_ec_point()) {}

      ECDSA_Verification_Operation(const ECDSA_PublicKey& ecdsa, const AlgorithmIdentifier& alg_id) :
            /*
            * RFC 5758 Section 3.2 is clear that for ECDSA signatures the parameters field is empty
            *
            *    When the [ecdsa-with-SHA*] algorithm identifier appears in the algorithm
            *    field as an AlgorithmIdentifier, the encoding MUST omit the parameters
            *    field. That is, the AlgorithmIdentifier SHALL be a SEQUENCE of one
            *    component, the OID [ecdsa-with-SHA*].
            *
            * However ECDSA is old enough and widely implemented enough that many non-conformant
            * implementations which emit X509 signatures using an explicit NULL parameter do exist,
            * so accept it here.
            */
            PK_Ops::Verification_with_Hash(alg_id, "ECDSA", true),
            m_group(ecdsa.domain()),
            m_gy_mul(ecdsa._public_ec_point()) {}

      bool verify(std::span<const uint8_t> msg, std::span<const uint8_t> sig) override;

   private:
      const EC_Group m_group;
      const EC_Group::Mul2Table m_gy_mul;
};

bool ECDSA_Verification_Operation::verify(std::span<const uint8_t> msg, std::span<const uint8_t> sig) {
   if(auto rs = EC_Scalar::deserialize_pair(m_group, sig)) {
      const auto& [r, s] = rs.value();

      if(r.is_nonzero() && s.is_nonzero()) {
         const auto m = EC_Scalar::from_bytes_with_trunc(m_group, msg);

         const auto w = s.invert_vartime();

         // Check if r == x_coord(g*w*m + y*w*r) % n
         return m_gy_mul.mul2_vartime_x_mod_order_eq(r, w, m, r);
      }
   }

   return false;
}

}  // namespace

std::unique_ptr<PK_Ops::Verification> ECDSA_PublicKey::create_verification_op(std::string_view params,
                                                                              std::string_view provider) const {
   if(provider == "base" || provider.empty()) {
      return std::make_unique<ECDSA_Verification_Operation>(*this, params);
   }

   throw Provider_Not_Found(algo_name(), provider);
}

std::unique_ptr<PK_Ops::Verification> ECDSA_PublicKey::create_x509_verification_op(
   const AlgorithmIdentifier& signature_algorithm, std::string_view provider) const {
   if(provider == "base" || provider.empty()) {
      return std::make_unique<ECDSA_Verification_Operation>(*this, signature_algorithm);
   }

   throw Provider_Not_Found(algo_name(), provider);
}

std::unique_ptr<PK_Ops::Signature> ECDSA_PrivateKey::create_signature_op(RandomNumberGenerator& rng,
                                                                         std::string_view params,
                                                                         std::string_view provider) const {
   if(provider == "base" || provider.empty()) {
      return std::make_unique<ECDSA_Signature_Operation>(*this, params, rng);
   }

   throw Provider_Not_Found(algo_name(), provider);
}

}  // namespace Botan

1	/*
2	* ECDSA implementation
3	* (C) 2007 Manuel Hartl, FlexSecure GmbH
4	* 2007 Falko Strenzke, FlexSecure GmbH
5	* 2008-2010,2015,2016,2018,2024 Jack Lloyd
6	* 2016 René Korthaus
7	*
8	* Botan is released under the Simplified BSD License (see license.txt)
9	*/
10
11	#include <botan/ecdsa.h>
12
13	#include <botan/ec_group.h>
14	#include <botan/internal/keypair.h>
15	#include <botan/internal/pk_ops_impl.h>
16
17	#if defined(BOTAN_HAS_RFC6979_GENERATOR)
18	#include <botan/internal/rfc6979.h>
19	#endif
20
21	namespace Botan {
22
23	namespace {
24
25	EC_AffinePoint recover_ecdsa_public_key(	21✔
26	const EC_Group& group, const std::vector<uint8_t>& msg, const BigInt& r, const BigInt& s, uint8_t v) {
27	if(group.has_cofactor()) {	21✔
28	throw Invalid_Argument("ECDSA public key recovery only supported for prime order groups");	×
29	}
30
31	if(v >= 4) {	21✔
32	throw Invalid_Argument("Unexpected v param for ECDSA public key recovery");	×
33	}
34
35	const BigInt& group_order = group.get_order();	21✔
36
37	if(r <= 0 \|\| r >= group_order \|\| s <= 0 \|\| s >= group_order) {	84✔
38	throw Invalid_Argument("Out of range r/s cannot recover ECDSA public key");	×
39	}
40
41	const uint8_t y_odd = v % 2;	21✔
42	const bool add_order = (v >> 1) == 0x01;	21✔
43	const size_t p_bytes = group.get_p_bytes();	21✔
44
45	BigInt x = r;	21✔
46
47	if(add_order) {	21✔
48	x += group_order;	×
49	}
50
51	if(x.bytes() <= p_bytes) {	21✔
52	std::vector<uint8_t> X(p_bytes + 1);	21✔
53
54	X[0] = 0x02 \| y_odd;	21✔
55	x.serialize_to(std::span{X}.subspan(1));	21✔
56
57	if(auto R = EC_AffinePoint::deserialize_compressed(group, X)) {	21✔
58	// Compute r_inv * (-eG + s*R)
59	const auto ne = EC_Scalar::from_bytes_with_trunc(group, msg).negate();	21✔
60	const auto ss = EC_Scalar::from_bigint(group, s);	21✔
61
62	const auto r_inv = EC_Scalar::from_bigint(group, r).invert_vartime();	21✔
63
64	const EC_Group::Mul2Table GR_mul(R.value());	21✔
65	if(auto egsr = GR_mul.mul2_vartime(ne * r_inv, ss * r_inv)) {	21✔
66	return egsr.value();	42✔
67	}	×
68	}	42✔
69	}	×
70
71	throw Decoding_Error("Failed to recover ECDSA public key from signature/msg pair");	×
72	}	42✔
73
74	} // namespace
75
76	ECDSA_PublicKey::ECDSA_PublicKey(	10✔
77	const EC_Group& group, const std::vector<uint8_t>& msg, const BigInt& r, const BigInt& s, uint8_t v) :	10✔
78	EC_PublicKey(group, recover_ecdsa_public_key(group, msg, r, s, v)) {}	10✔
79
80	std::optional<size_t> ECDSA_PublicKey::_signature_element_size_for_DER_encoding() const {	20,503✔
81	return domain().get_order_bytes();	20,503✔
82	}
83
84	std::unique_ptr<Private_Key> ECDSA_PublicKey::generate_another(RandomNumberGenerator& rng) const {	96✔
85	return std::make_unique<ECDSA_PrivateKey>(rng, domain());	192✔
86	}
87
88	uint8_t ECDSA_PublicKey::recovery_param(const std::vector<uint8_t>& msg, const BigInt& r, const BigInt& s) const {	10✔
89	const auto this_key = this->_public_ec_point().serialize_compressed();	10✔
90
91	for(uint8_t v = 0; v != 4; ++v) {	11✔
92	try {	11✔
93	const auto R = recover_ecdsa_public_key(this->domain(), msg, r, s, v);	11✔
94
95	if(R.serialize_compressed() == this_key) {	22✔
96	return v;	20✔
97	}
98	} catch(Decoding_Error&) {	11✔
99	// try the next v
100	}	×
101	}
102
103	throw Internal_Error("Could not determine ECDSA recovery parameter");	×
104	}	10✔
105
106	std::unique_ptr<Public_Key> ECDSA_PrivateKey::public_key() const {	549✔
107	return std::make_unique<ECDSA_PublicKey>(domain(), _public_ec_point());	549✔
108	}
109
110	bool ECDSA_PrivateKey::check_key(RandomNumberGenerator& rng, bool strong) const {	43✔
111	if(!EC_PrivateKey::check_key(rng, strong)) {	43✔
112	return false;
113	}
114
115	if(!strong) {	43✔
116	return true;
117	}
118
119	return KeyPair::signature_consistency_check(rng, *this, "SHA-256");	42✔
120	}
121
122	namespace {
123
124	/**
125	* ECDSA signature operation
126	*/
127	class ECDSA_Signature_Operation final : public PK_Ops::Signature_with_Hash {	×
128	public:
129	ECDSA_Signature_Operation(const ECDSA_PrivateKey& ecdsa, std::string_view padding, RandomNumberGenerator& rng) :	2,253✔
130	PK_Ops::Signature_with_Hash(padding),
131	m_group(ecdsa.domain()),	2,253✔
132	m_x(ecdsa._private_key()),	2,253✔
133	m_b(EC_Scalar::random(m_group, rng)) {	4,506✔
134	#if defined(BOTAN_HAS_RFC6979_GENERATOR)
135	m_rfc6979 = std::make_unique<RFC6979_Nonce_Generator>(	6,759✔
136	this->rfc6979_hash_function(), m_group.get_order_bits(), ecdsa._private_key());	4,506✔
137	#endif
138	}	2,253✔
139
140	size_t signature_length() const override { return 2 * m_group.get_order_bytes(); }	127✔
141
142	std::vector<uint8_t> raw_sign(std::span<const uint8_t> msg, RandomNumberGenerator& rng) override;
143
144	AlgorithmIdentifier algorithm_identifier() const override;
145
146	private:
147	const EC_Group m_group;
148	const EC_Scalar m_x;
149
150	#if defined(BOTAN_HAS_RFC6979_GENERATOR)
151	std::unique_ptr<RFC6979_Nonce_Generator> m_rfc6979;
152	#endif
153
154	EC_Scalar m_b;
155	};
156
157	AlgorithmIdentifier ECDSA_Signature_Operation::algorithm_identifier() const {	1,649✔
158	const std::string full_name = "ECDSA/" + hash_function();	3,298✔
159	const OID oid = OID::from_string(full_name);	1,649✔
160	return AlgorithmIdentifier(oid, AlgorithmIdentifier::USE_EMPTY_PARAM);	1,649✔
161	}	1,649✔
162
163	std::vector<uint8_t> ECDSA_Signature_Operation::raw_sign(std::span<const uint8_t> msg, RandomNumberGenerator& rng) {	6,019✔
164	const auto m = EC_Scalar::from_bytes_with_trunc(m_group, msg);	6,019✔
165
166	#if defined(BOTAN_HAS_RFC6979_GENERATOR)
167	const auto k = m_rfc6979->nonce_for(m_group, m);	6,019✔
168	#else
169	const auto k = EC_Scalar::random(m_group, rng);
170	#endif
171
172	/*
173	* Blind the inputs
174	*
175	* Here we are computing (x*r+m)/k
176	*
177	* Instead have a random b and compute (k*b)^-1
178	*
179	* Then compute (xr+m) as (xrb + mb)
180	*
181	* Finally (xrb + mb)/(kb) = (x*r+m)/k
182	*
183	* This effectively blinds both the inversion as well as the various scalar
184	* multiplications. All of these operations should be constant-time anyway but
185	* blinding is very cheap and may help if either the compiler introduces
186	* variable-time behavior, or for the case of EM/power side channel attacks [1].
187	*
188	* [1] But note that such attacks are currently outside of Botan's threat model.
189	*
190	* NOTE: if you change anything here also update ECDSA_Timing_Test
191	* in cli/timing_tests.cpp to use the same formulas
192	*/
193	const auto r = EC_Scalar::gk_x_mod_order(k, rng);	6,019✔
194
195	const auto k_inv = (m_b * k).invert();	6,019✔
196
197	const auto xr_m = ((m_x * m_b) * r) + (m * m_b);	6,019✔
198
199	const auto s = (k_inv * xr_m);	6,019✔
200
201	// Generate the next blinding value via modular squaring
202	m_b.square_self();	6,019✔
203
204	// With overwhelming probability, a bug rather than actual zero r/s
205	if(r.is_zero() \|\| s.is_zero()) {	6,019✔
206	throw Internal_Error("During ECDSA signature generated zero r/s");	×
207	}
208
209	return EC_Scalar::serialize_pair(r, s);	12,038✔
210	}	6,019✔
211
212	/**
213	* ECDSA verification operation
214	*/
215	class ECDSA_Verification_Operation final : public PK_Ops::Verification_with_Hash {	×
216	public:
217	ECDSA_Verification_Operation(const ECDSA_PublicKey& ecdsa, std::string_view padding) :	12,855✔
218	PK_Ops::Verification_with_Hash(padding), m_group(ecdsa.domain()), m_gy_mul(ecdsa._public_ec_point()) {}	12,855✔
219
220	ECDSA_Verification_Operation(const ECDSA_PublicKey& ecdsa, const AlgorithmIdentifier& alg_id) :	3,838✔
221	/*
222	* RFC 5758 Section 3.2 is clear that for ECDSA signatures the parameters field is empty
223	*
224	* When the [ecdsa-with-SHA*] algorithm identifier appears in the algorithm
225	* field as an AlgorithmIdentifier, the encoding MUST omit the parameters
226	* field. That is, the AlgorithmIdentifier SHALL be a SEQUENCE of one
227	* component, the OID [ecdsa-with-SHA*].
228	*
229	* However ECDSA is old enough and widely implemented enough that many non-conformant
230	* implementations which emit X509 signatures using an explicit NULL parameter do exist,
231	* so accept it here.
232	*/
233	PK_Ops::Verification_with_Hash(alg_id, "ECDSA", true),
234	m_group(ecdsa.domain()),	3,838✔
235	m_gy_mul(ecdsa._public_ec_point()) {}	7,676✔
236
237	bool verify(std::span<const uint8_t> msg, std::span<const uint8_t> sig) override;
238
239	private:
240	const EC_Group m_group;
241	const EC_Group::Mul2Table m_gy_mul;
242	};
243
244	bool ECDSA_Verification_Operation::verify(std::span<const uint8_t> msg, std::span<const uint8_t> sig) {	39,150✔
245	if(auto rs = EC_Scalar::deserialize_pair(m_group, sig)) {	39,150✔
246	const auto& [r, s] = rs.value();	33,026✔
247
248	if(r.is_nonzero() && s.is_nonzero()) {	66,052✔
249	const auto m = EC_Scalar::from_bytes_with_trunc(m_group, msg);	33,026✔
250
251	const auto w = s.invert_vartime();	33,026✔
252
253	// Check if r == x_coord(gwm + ywr) % n
254	return m_gy_mul.mul2_vartime_x_mod_order_eq(r, w, m, r);	33,026✔
255	}	33,026✔
256	}	33,026✔
257
258	return false;	6,124✔
259	}
260
261	} // namespace
262
263	std::unique_ptr<PK_Ops::Verification> ECDSA_PublicKey::create_verification_op(std::string_view params,	49,605✔
264	std::string_view provider) const {
265	if(provider == "base" \|\| provider.empty()) {	61,865✔
266	return std::make_unique<ECDSA_Verification_Operation>(*this, params);	12,855✔
267	}
268
269	throw Provider_Not_Found(algo_name(), provider);	73,500✔
270	}
271
272	std::unique_ptr<PK_Ops::Verification> ECDSA_PublicKey::create_x509_verification_op(	3,838✔
273	const AlgorithmIdentifier& signature_algorithm, std::string_view provider) const {
274	if(provider == "base" \|\| provider.empty()) {	3,838✔
275	return std::make_unique<ECDSA_Verification_Operation>(*this, signature_algorithm);	3,838✔
276	}
277
278	throw Provider_Not_Found(algo_name(), provider);	×
279	}
280
281	std::unique_ptr<PK_Ops::Signature> ECDSA_PrivateKey::create_signature_op(RandomNumberGenerator& rng,	2,565✔
282	std::string_view params,
283	std::string_view provider) const {
284	if(provider == "base" \|\| provider.empty()) {	2,671✔
285	return std::make_unique<ECDSA_Signature_Operation>(*this, params, rng);	2,253✔
286	}
287
288	throw Provider_Not_Found(algo_name(), provider);	624✔
289	}
290
291	} // namespace Botan

randombit / botan / 30496461195

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