14644214898

Committed 24 Apr 2025 02:29PM UTC coverage: 91.324% (-0.02%) from 91.344%

Build # 14644214898

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Commit Message

Merge pull request #4835 from randombit/jack/reducer-api-work

New Barrett Reduction implementation

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80.39

/src/lib/misc/fpe_fe1/fpe_fe1.cpp

/*
* Format Preserving Encryption (FE1 scheme)
* (C) 2009,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/fpe_fe1.h>

#include <botan/mac.h>
#include <botan/numthry.h>
#include <botan/internal/divide.h>
#include <botan/internal/fmt.h>
#include <botan/internal/loadstor.h>

namespace Botan {

namespace {

// Normally FPE is for SSNs, CC#s, etc, nothing too big
const size_t MAX_N_BYTES = 128 / 8;

/*
* Factor n into a and b which are as close together as possible.
* Assumes n is composed mostly of small factors which is the case for
* typical uses of FPE (typically, n is a power of 10)
*/
void factor(BigInt n, BigInt& a, BigInt& b) {
   BOTAN_ARG_CHECK(n >= 2, "Invalid FPE modulus");

   a = BigInt::one();
   b = BigInt::one();

   /*
   * This algorithm was poorly designed. It should have fully factored n (to the
   * extent possible) and then built a/b starting from the largest factor first.
   *
   * This can't be fixed now without breaking existing users but if some
   * incompatible change (or new flag, etc) is added in the future, consider
   * fixing the factoring for those users.
   */

   size_t n_low_zero = low_zero_bits(n);

   a <<= (n_low_zero / 2);
   b <<= n_low_zero - (n_low_zero / 2);
   n >>= n_low_zero;

   for(size_t i = 0; i != PRIME_TABLE_SIZE; ++i) {
      while(n % PRIMES[i] == 0) {
         a *= PRIMES[i];
         if(a > b) {
            std::swap(a, b);
         }
         n /= BigInt::from_word(PRIMES[i]);
      }
   }

   if(a > b) {
      std::swap(a, b);
   }
   a *= n;

   if(a <= 1 || b <= 1) {
      throw Internal_Error("Could not factor n for use in FPE");
   }
}

}  // namespace

FPE_FE1::FPE_FE1(const BigInt& n, size_t rounds, bool compat_mode, std::string_view mac_algo) : m_rounds(rounds) {
   if(m_rounds < 3) {
      throw Invalid_Argument("FPE_FE1 rounds too small");
   }

   m_mac = MessageAuthenticationCode::create_or_throw(mac_algo);

   m_n_bytes = n.serialize();

   if(m_n_bytes.size() > MAX_N_BYTES) {
      throw Invalid_Argument("N is too large for FPE encryption");
   }

   factor(n, m_a, m_b);

   if(compat_mode) {
      if(m_a < m_b) {
         std::swap(m_a, m_b);
      }
   } else {
      if(m_a > m_b) {
         std::swap(m_a, m_b);
      }
   }
}

FPE_FE1::~FPE_FE1() = default;

void FPE_FE1::clear() {
   m_mac->clear();
}

std::string FPE_FE1::name() const {
   return fmt("FPE_FE1({},{})", m_mac->name(), m_rounds);
}

Key_Length_Specification FPE_FE1::key_spec() const {
   return m_mac->key_spec();
}

bool FPE_FE1::has_keying_material() const {
   return m_mac->has_keying_material();
}

void FPE_FE1::key_schedule(std::span<const uint8_t> key) {
   m_mac->set_key(key);
}

BigInt FPE_FE1::F(const BigInt& R,
                  size_t round,
                  const secure_vector<uint8_t>& tweak_mac,
                  secure_vector<uint8_t>& tmp) const {
   tmp = R.serialize<secure_vector<uint8_t>>();

   m_mac->update(tweak_mac);
   m_mac->update_be(static_cast<uint32_t>(round));

   m_mac->update_be(static_cast<uint32_t>(tmp.size()));
   m_mac->update(tmp.data(), tmp.size());

   tmp = m_mac->final();
   return BigInt::from_bytes(tmp);
}

secure_vector<uint8_t> FPE_FE1::compute_tweak_mac(const uint8_t tweak[], size_t tweak_len) const {
   m_mac->update_be(static_cast<uint32_t>(m_n_bytes.size()));
   m_mac->update(m_n_bytes.data(), m_n_bytes.size());

   m_mac->update_be(static_cast<uint32_t>(tweak_len));
   if(tweak_len > 0) {
      m_mac->update(tweak, tweak_len);
   }

   return m_mac->final();
}

BigInt FPE_FE1::encrypt(const BigInt& input, const uint8_t tweak[], size_t tweak_len) const {
   const secure_vector<uint8_t> tweak_mac = compute_tweak_mac(tweak, tweak_len);

   BigInt X = input;

   secure_vector<uint8_t> tmp;

   BigInt L, R, Fi;
   for(size_t i = 0; i != m_rounds; ++i) {
      ct_divide(X, m_b, L, R);
      Fi = F(R, i, tweak_mac, tmp);
      X = m_a * R + ct_modulo(L + Fi, m_a);
   }

   return X;
}

BigInt FPE_FE1::decrypt(const BigInt& input, const uint8_t tweak[], size_t tweak_len) const {
   const secure_vector<uint8_t> tweak_mac = compute_tweak_mac(tweak, tweak_len);

   BigInt X = input;
   secure_vector<uint8_t> tmp;

   BigInt W, R, Fi;
   for(size_t i = 0; i != m_rounds; ++i) {
      ct_divide(X, m_a, R, W);

      Fi = F(R, m_rounds - i - 1, tweak_mac, tmp);
      X = m_b * ct_modulo(W - Fi, m_a) + R;
   }

   return X;
}

BigInt FPE_FE1::encrypt(const BigInt& x, uint64_t tweak) const {
   uint8_t tweak8[8];
   store_be(tweak, tweak8);
   return encrypt(x, tweak8, sizeof(tweak8));
}

BigInt FPE_FE1::decrypt(const BigInt& x, uint64_t tweak) const {
   uint8_t tweak8[8];
   store_be(tweak, tweak8);
   return decrypt(x, tweak8, sizeof(tweak8));
}

namespace FPE {

BigInt fe1_encrypt(const BigInt& n, const BigInt& X, const SymmetricKey& key, const std::vector<uint8_t>& tweak) {
   FPE_FE1 fpe(n, 3, true, "HMAC(SHA-256)");
   fpe.set_key(key);
   return fpe.encrypt(X, tweak.data(), tweak.size());
}

BigInt fe1_decrypt(const BigInt& n, const BigInt& X, const SymmetricKey& key, const std::vector<uint8_t>& tweak) {
   FPE_FE1 fpe(n, 3, true, "HMAC(SHA-256)");
   fpe.set_key(key);
   return fpe.decrypt(X, tweak.data(), tweak.size());
}

}  // namespace FPE

}  // namespace Botan

1	/*
2	* Format Preserving Encryption (FE1 scheme)
3	* (C) 2009,2018 Jack Lloyd
4	*
5	* Botan is released under the Simplified BSD License (see license.txt)
6	*/
7
8	#include <botan/fpe_fe1.h>
9
10	#include <botan/mac.h>
11	#include <botan/numthry.h>
12	#include <botan/internal/divide.h>
13	#include <botan/internal/fmt.h>
14	#include <botan/internal/loadstor.h>
15
16	namespace Botan {
17
18	namespace {
19
20	// Normally FPE is for SSNs, CC#s, etc, nothing too big
21	const size_t MAX_N_BYTES = 128 / 8;
22
23	/*
24	* Factor n into a and b which are as close together as possible.
25	* Assumes n is composed mostly of small factors which is the case for
26	* typical uses of FPE (typically, n is a power of 10)
27	*/
28	void factor(BigInt n, BigInt& a, BigInt& b) {	15✔
29	BOTAN_ARG_CHECK(n >= 2, "Invalid FPE modulus");	15✔
30
31	a = BigInt::one();	15✔
32	b = BigInt::one();	15✔
33
34	/*
35	* This algorithm was poorly designed. It should have fully factored n (to the
36	* extent possible) and then built a/b starting from the largest factor first.
37	*
38	* This can't be fixed now without breaking existing users but if some
39	* incompatible change (or new flag, etc) is added in the future, consider
40	* fixing the factoring for those users.
41	*/
42
43	size_t n_low_zero = low_zero_bits(n);	15✔
44
45	a <<= (n_low_zero / 2);	15✔
46	b <<= n_low_zero - (n_low_zero / 2);	15✔
47	n >>= n_low_zero;	15✔
48
49	for(size_t i = 0; i != PRIME_TABLE_SIZE; ++i) {	98,130✔
50	while(n % PRIMES[i] == 0) {	98,256✔
51	a *= PRIMES[i];	141✔
52	if(a > b) {	141✔
53	std::swap(a, b);	141✔
54	}
55	n /= BigInt::from_word(PRIMES[i]);	141✔
56	}
57	}
58
59	if(a > b) {	15✔
60	std::swap(a, b);	×
61	}
62	a *= n;	15✔
63
64	if(a <= 1 \|\| b <= 1) {	30✔
65	throw Internal_Error("Could not factor n for use in FPE");	×
66	}
67	}	15✔
68
69	} // namespace
70
71	FPE_FE1::FPE_FE1(const BigInt& n, size_t rounds, bool compat_mode, std::string_view mac_algo) : m_rounds(rounds) {	15✔
72	if(m_rounds < 3) {	15✔
73	throw Invalid_Argument("FPE_FE1 rounds too small");	×
74	}
75
76	m_mac = MessageAuthenticationCode::create_or_throw(mac_algo);	15✔
77
78	m_n_bytes = n.serialize();	30✔
79
80	if(m_n_bytes.size() > MAX_N_BYTES) {	15✔
81	throw Invalid_Argument("N is too large for FPE encryption");	×
82	}
83
84	factor(n, m_a, m_b);	15✔
85
86	if(compat_mode) {	15✔
87	if(m_a < m_b) {	12✔
88	std::swap(m_a, m_b);	12✔
89	}
90	} else {
91	if(m_a > m_b) {	3✔
92	std::swap(m_a, m_b);	×
93	}
94	}
95	}	15✔
96
97	FPE_FE1::~FPE_FE1() = default;	32✔
98
99	void FPE_FE1::clear() {	×
100	m_mac->clear();	×
101	}	×
102
103	std::string FPE_FE1::name() const {	×
104	return fmt("FPE_FE1({},{})", m_mac->name(), m_rounds);	×
105	}
106
107	Key_Length_Specification FPE_FE1::key_spec() const {	15✔
108	return m_mac->key_spec();	15✔
109	}
110
111	bool FPE_FE1::has_keying_material() const {	×
112	return m_mac->has_keying_material();	×
113	}
114
115	void FPE_FE1::key_schedule(std::span<const uint8_t> key) {	15✔
116	m_mac->set_key(key);	15✔
117	}	15✔
118
119	BigInt FPE_FE1::F(const BigInt& R,	106✔
120	size_t round,
121	const secure_vector<uint8_t>& tweak_mac,
122	secure_vector<uint8_t>& tmp) const {
123	tmp = R.serialize<secure_vector<uint8_t>>();	212✔
124
125	m_mac->update(tweak_mac);	106✔
126	m_mac->update_be(static_cast<uint32_t>(round));	106✔
127
128	m_mac->update_be(static_cast<uint32_t>(tmp.size()));	106✔
129	m_mac->update(tmp.data(), tmp.size());	106✔
130
131	tmp = m_mac->final();	212✔
132	return BigInt::from_bytes(tmp);	106✔
133	}
134
135	secure_vector<uint8_t> FPE_FE1::compute_tweak_mac(const uint8_t tweak[], size_t tweak_len) const {	26✔
136	m_mac->update_be(static_cast<uint32_t>(m_n_bytes.size()));	26✔
137	m_mac->update(m_n_bytes.data(), m_n_bytes.size());	26✔
138
139	m_mac->update_be(static_cast<uint32_t>(tweak_len));	26✔
140	if(tweak_len > 0) {	26✔
141	m_mac->update(tweak, tweak_len);	20✔
142	}
143
144	return m_mac->final();	26✔
145	}
146
147	BigInt FPE_FE1::encrypt(const BigInt& input, const uint8_t tweak[], size_t tweak_len) const {	13✔
148	const secure_vector<uint8_t> tweak_mac = compute_tweak_mac(tweak, tweak_len);	13✔
149
150	BigInt X = input;	13✔
151
152	secure_vector<uint8_t> tmp;	13✔
153
154	BigInt L, R, Fi;	13✔
155	for(size_t i = 0; i != m_rounds; ++i) {	66✔
156	ct_divide(X, m_b, L, R);	53✔
157	Fi = F(R, i, tweak_mac, tmp);	53✔
158	X = m_a * R + ct_modulo(L + Fi, m_a);	53✔
159	}
160
161	return X;	26✔
162	}	39✔
163
164	BigInt FPE_FE1::decrypt(const BigInt& input, const uint8_t tweak[], size_t tweak_len) const {	13✔
165	const secure_vector<uint8_t> tweak_mac = compute_tweak_mac(tweak, tweak_len);	13✔
166
167	BigInt X = input;	13✔
168	secure_vector<uint8_t> tmp;	13✔
169
170	BigInt W, R, Fi;	13✔
171	for(size_t i = 0; i != m_rounds; ++i) {	66✔
172	ct_divide(X, m_a, R, W);	53✔
173
174	Fi = F(R, m_rounds - i - 1, tweak_mac, tmp);	53✔
175	X = m_b * ct_modulo(W - Fi, m_a) + R;	53✔
176	}
177
178	return X;	26✔
179	}	39✔
180
181	BigInt FPE_FE1::encrypt(const BigInt& x, uint64_t tweak) const {	×
182	uint8_t tweak8[8];	×
183	store_be(tweak, tweak8);	×
184	return encrypt(x, tweak8, sizeof(tweak8));	×
185	}
186
187	BigInt FPE_FE1::decrypt(const BigInt& x, uint64_t tweak) const {	×
188	uint8_t tweak8[8];	×
189	store_be(tweak, tweak8);	×
190	return decrypt(x, tweak8, sizeof(tweak8));	×
191	}
192
193	namespace FPE {
194
195	BigInt fe1_encrypt(const BigInt& n, const BigInt& X, const SymmetricKey& key, const std::vector<uint8_t>& tweak) {	6✔
196	FPE_FE1 fpe(n, 3, true, "HMAC(SHA-256)");	6✔
197	fpe.set_key(key);	6✔
198	return fpe.encrypt(X, tweak.data(), tweak.size());	12✔
199	}	6✔
200
201	BigInt fe1_decrypt(const BigInt& n, const BigInt& X, const SymmetricKey& key, const std::vector<uint8_t>& tweak) {	6✔
202	FPE_FE1 fpe(n, 3, true, "HMAC(SHA-256)");	6✔
203	fpe.set_key(key);	6✔
204	return fpe.decrypt(X, tweak.data(), tweak.size());	12✔
205	}	6✔
206
207	} // namespace FPE
208
209	} // namespace Botan

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