14644214898

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

Build # 14644214898

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

New Barrett Reduction implementation

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/src/lib/math/bigint/bigint.cpp

/*
* BigInt Base
* (C) 1999-2011,2012,2014,2019 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/bigint.h>

#include <botan/internal/bit_ops.h>
#include <botan/internal/ct_utils.h>
#include <botan/internal/loadstor.h>
#include <botan/internal/mp_core.h>
#include <botan/internal/rounding.h>

namespace Botan {

BigInt::BigInt(uint64_t n) {
   if constexpr(sizeof(word) == 8) {
      m_data.set_word_at(0, static_cast<word>(n));
   } else {
      m_data.set_word_at(1, static_cast<word>(n >> 32));
      m_data.set_word_at(0, static_cast<word>(n));
   }
}

//static
BigInt BigInt::from_u64(uint64_t n) {
   return BigInt(n);
}

//static
BigInt BigInt::from_word(word n) {
   BigInt bn;
   bn.set_word_at(0, n);
   return bn;
}

//static
BigInt BigInt::from_s32(int32_t n) {
   if(n >= 0) {
      return BigInt::from_u64(static_cast<uint64_t>(n));
   } else {
      return -BigInt::from_u64(static_cast<uint64_t>(-n));
   }
}

//static
BigInt BigInt::with_capacity(size_t size) {
   BigInt bn;
   bn.grow_to(size);
   return bn;
}

/*
* Construct a BigInt from a string
*/
BigInt::BigInt(std::string_view str) {
   Base base = Decimal;
   size_t markers = 0;
   bool negative = false;

   if(!str.empty() && str[0] == '-') {
      markers += 1;
      negative = true;
   }

   if(str.length() > markers + 2 && str[markers] == '0' && str[markers + 1] == 'x') {
      markers += 2;
      base = Hexadecimal;
   }

   *this = decode(cast_char_ptr_to_uint8(str.data()) + markers, str.length() - markers, base);

   if(negative) {
      set_sign(Negative);
   } else {
      set_sign(Positive);
   }
}

BigInt BigInt::from_string(std::string_view str) {
   return BigInt(str);
}

BigInt BigInt::from_bytes(std::span<const uint8_t> input) {
   BigInt r;
   r.assign_from_bytes(input);
   return r;
}

/*
* Construct a BigInt from an encoded BigInt
*/
BigInt::BigInt(const uint8_t input[], size_t length, Base base) {
   *this = decode(input, length, base);
}

//static
BigInt BigInt::from_bytes_with_max_bits(const uint8_t input[], size_t length, size_t max_bits) {
   const size_t input_bits = 8 * length;

   auto bn = BigInt::from_bytes(std::span{input, length});

   if(input_bits > max_bits) {
      const size_t bits_to_shift = input_bits - max_bits;

      bn >>= bits_to_shift;
   }

   return bn;
}

/*
* Construct a BigInt from an encoded BigInt
*/
BigInt::BigInt(RandomNumberGenerator& rng, size_t bits, bool set_high_bit) {
   randomize(rng, bits, set_high_bit);
}

uint8_t BigInt::byte_at(size_t n) const {
   return get_byte_var(sizeof(word) - (n % sizeof(word)) - 1, word_at(n / sizeof(word)));
}

int32_t BigInt::cmp_word(word other) const {
   if(is_negative()) {
      return -1;  // other is positive ...
   }

   const size_t sw = this->sig_words();
   if(sw > 1) {
      return 1;  // must be larger since other is just one word ...
   }

   return bigint_cmp(this->_data(), sw, &other, 1);
}

/*
* Comparison Function
*/
int32_t BigInt::cmp(const BigInt& other, bool check_signs) const {
   if(check_signs) {
      if(other.is_positive() && this->is_negative()) {
         return -1;
      }

      if(other.is_negative() && this->is_positive()) {
         return 1;
      }

      if(other.is_negative() && this->is_negative()) {
         return (-bigint_cmp(this->_data(), this->size(), other._data(), other.size()));
      }
   }

   return bigint_cmp(this->_data(), this->size(), other._data(), other.size());
}

bool BigInt::is_equal(const BigInt& other) const {
   if(this->sign() != other.sign()) {
      return false;
   }

   return bigint_ct_is_eq(this->_data(), this->sig_words(), other._data(), other.sig_words()).as_bool();
}

bool BigInt::is_less_than(const BigInt& other) const {
   if(this->is_negative() && other.is_positive()) {
      return true;
   }

   if(this->is_positive() && other.is_negative()) {
      return false;
   }

   if(other.is_negative() && this->is_negative()) {
      return bigint_ct_is_lt(other._data(), other.sig_words(), this->_data(), this->sig_words()).as_bool();
   }

   return bigint_ct_is_lt(this->_data(), this->sig_words(), other._data(), other.sig_words()).as_bool();
}

void BigInt::encode_words(word out[], size_t size) const {
   const size_t words = sig_words();

   if(words > size) {
      throw Encoding_Error("BigInt::encode_words value too large to encode");
   }

   clear_mem(out, size);
   copy_mem(out, _data(), words);
}

void BigInt::Data::set_to_zero() {
   m_reg.resize(m_reg.capacity());
   clear_mem(m_reg.data(), m_reg.size());
   m_sig_words = 0;
}

void BigInt::Data::mask_bits(size_t n) {
   if(n == 0) {
      return set_to_zero();
   }

   const size_t top_word = n / WordInfo<word>::bits;

   if(top_word < size()) {
      const word mask = (static_cast<word>(1) << (n % WordInfo<word>::bits)) - 1;
      const size_t len = size() - (top_word + 1);
      if(len > 0) {
         clear_mem(&m_reg[top_word + 1], len);
      }
      m_reg[top_word] &= mask;
      invalidate_sig_words();
   }
}

size_t BigInt::Data::calc_sig_words() const {
   const size_t sz = m_reg.size();
   size_t sig = sz;

   word sub = 1;

   for(size_t i = 0; i != sz; ++i) {
      const word w = m_reg[sz - i - 1];
      sub &= ct_is_zero(w);
      sig -= sub;
   }

   /*
   * This depends on the data so is poisoned, but unpoison it here as
   * later conditionals are made on the size.
   */
   CT::unpoison(sig);

   return sig;
}

/*
* Return bits {offset...offset+length}
*/
uint32_t BigInt::get_substring(size_t offset, size_t length) const {
   if(length == 0 || length > 32) {
      throw Invalid_Argument("BigInt::get_substring invalid substring length");
   }

   const uint32_t mask = 0xFFFFFFFF >> (32 - length);

   const size_t word_offset = offset / WordInfo<word>::bits;
   const size_t wshift = (offset % WordInfo<word>::bits);

   /*
   * The substring is contained within one or at most two words. The
   * offset and length are not secret, so we can perform conditional
   * operations on those values.
   */
   const word w0 = word_at(word_offset);

   if(wshift == 0 || (offset + length) / WordInfo<word>::bits == word_offset) {
      return static_cast<uint32_t>(w0 >> wshift) & mask;
   } else {
      const word w1 = word_at(word_offset + 1);
      return static_cast<uint32_t>((w0 >> wshift) | (w1 << (WordInfo<word>::bits - wshift))) & mask;
   }
}

/*
* Convert this number to a uint32_t, if possible
*/
uint32_t BigInt::to_u32bit() const {
   if(is_negative()) {
      throw Encoding_Error("BigInt::to_u32bit: Number is negative");
   }
   if(bits() > 32) {
      throw Encoding_Error("BigInt::to_u32bit: Number is too big to convert");
   }

   uint32_t out = 0;
   for(size_t i = 0; i != 4; ++i) {
      out = (out << 8) | byte_at(3 - i);
   }
   return out;
}

/*
* Clear bit number n
*/
void BigInt::clear_bit(size_t n) {
   const size_t which = n / WordInfo<word>::bits;

   if(which < size()) {
      const word mask = ~(static_cast<word>(1) << (n % WordInfo<word>::bits));
      m_data.set_word_at(which, word_at(which) & mask);
   }
}

size_t BigInt::bytes() const {
   return round_up(bits(), 8) / 8;
}

size_t BigInt::top_bits_free() const {
   const size_t words = sig_words();

   const word top_word = word_at(words - 1);
   const size_t bits_used = high_bit(CT::value_barrier(top_word));
   CT::unpoison(bits_used);
   return WordInfo<word>::bits - bits_used;
}

size_t BigInt::bits() const {
   const size_t words = sig_words();

   if(words == 0) {
      return 0;
   }

   const size_t full_words = (words - 1) * WordInfo<word>::bits;
   const size_t top_bits = WordInfo<word>::bits - top_bits_free();

   return full_words + top_bits;
}

/*
* Return the negation of this number
*/
BigInt BigInt::operator-() const {
   BigInt x = (*this);
   x.flip_sign();
   return x;
}

size_t BigInt::reduce_below(const BigInt& p, secure_vector<word>& ws) {
   if(p.is_negative() || this->is_negative()) {
      throw Invalid_Argument("BigInt::reduce_below both values must be positive");
   }

   const size_t p_words = p.sig_words();

   if(size() < p_words + 1) {
      grow_to(p_words + 1);
   }

   if(ws.size() < p_words + 1) {
      ws.resize(p_words + 1);
   }

   clear_mem(ws.data(), ws.size());

   size_t reductions = 0;

   for(;;) {
      word borrow = bigint_sub3(ws.data(), _data(), p_words + 1, p._data(), p_words);
      if(borrow) {
         break;
      }

      ++reductions;
      swap_reg(ws);
   }

   return reductions;
}

void BigInt::ct_reduce_below(const BigInt& mod, secure_vector<word>& ws, size_t bound) {
   if(mod.is_negative() || this->is_negative()) {
      throw Invalid_Argument("BigInt::ct_reduce_below both values must be positive");
   }

   const size_t mod_words = mod.sig_words();

   grow_to(mod_words);

   const size_t sz = size();

   ws.resize(sz);

   clear_mem(ws.data(), sz);

   for(size_t i = 0; i != bound; ++i) {
      word borrow = bigint_sub3(ws.data(), _data(), sz, mod._data(), mod_words);

      CT::Mask<word>::is_zero(borrow).select_n(mutable_data(), ws.data(), _data(), sz);
   }
}

/*
* Return the absolute value of this number
*/
BigInt BigInt::abs() const {
   BigInt x = (*this);
   x.set_sign(Positive);
   return x;
}

/*
* Encode this number into bytes
*/
void BigInt::serialize_to(std::span<uint8_t> output) const {
   BOTAN_ARG_CHECK(this->bytes() <= output.size(), "Insufficient output space");

   this->binary_encode(output.data(), output.size());
}

/*
* Encode this number into bytes
*/
void BigInt::binary_encode(uint8_t output[], size_t len) const {
   const size_t full_words = len / sizeof(word);
   const size_t extra_bytes = len % sizeof(word);

   for(size_t i = 0; i != full_words; ++i) {
      const word w = word_at(i);
      store_be(w, output + (len - (i + 1) * sizeof(word)));
   }

   if(extra_bytes > 0) {
      const word w = word_at(full_words);

      for(size_t i = 0; i != extra_bytes; ++i) {
         output[extra_bytes - i - 1] = get_byte_var(sizeof(word) - i - 1, w);
      }
   }
}

/*
* Set this number to the value in buf
*/
void BigInt::assign_from_bytes(std::span<const uint8_t> bytes) {
   clear();

   const size_t length = bytes.size();
   const size_t full_words = length / sizeof(word);
   const size_t extra_bytes = length % sizeof(word);

   secure_vector<word> reg((round_up(full_words + (extra_bytes > 0 ? 1 : 0), 8)));

   for(size_t i = 0; i != full_words; ++i) {
      reg[i] = load_be<word>(bytes.last<sizeof(word)>());
      bytes = bytes.first(bytes.size() - sizeof(word));
   }

   if(!bytes.empty()) {
      BOTAN_ASSERT_NOMSG(extra_bytes == bytes.size());
      std::array<uint8_t, sizeof(word)> last_partial_word = {0};
      copy_mem(std::span{last_partial_word}.last(extra_bytes), bytes);
      reg[full_words] = load_be<word>(last_partial_word);
   }

   m_data.swap(reg);
}

void BigInt::ct_cond_add(bool predicate, const BigInt& value) {
   if(this->is_negative() || value.is_negative()) {
      throw Invalid_Argument("BigInt::ct_cond_add requires both values to be positive");
   }
   this->grow_to(1 + value.sig_words());

   bigint_cnd_add(static_cast<word>(predicate), this->mutable_data(), this->size(), value._data(), value.sig_words());
}

void BigInt::ct_shift_left(size_t shift) {
   auto shl_bit = [](const BigInt& a, BigInt& result) {
      BOTAN_DEBUG_ASSERT(a.size() + 1 == result.size());
      bigint_shl2(result.mutable_data(), a._data(), a.size(), 1);
      // shl2 may have shifted a bit into the next word, which must be dropped
      clear_mem(result.mutable_data() + result.size() - 1, 1);
   };

   auto shl_word = [](const BigInt& a, BigInt& result) {
      // the most significant word is not copied, aka. shifted out
      bigint_shl2(result.mutable_data(), a._data(), a.size() - 1 /* ignore msw */, WordInfo<word>::bits);
      // we left-shifted by a full word, the least significant word must be zero'ed
      clear_mem(result.mutable_data(), 1);
   };

   BOTAN_ASSERT_NOMSG(size() > 0);

   constexpr size_t bits_in_word = sizeof(word) * 8;
   const size_t word_shift = shift >> ceil_log2(bits_in_word);             // shift / bits_in_word
   const size_t bit_shift = shift & ((1 << ceil_log2(bits_in_word)) - 1);  // shift % bits_in_word
   const size_t iterations = std::max(size(), bits_in_word) - 1;           // uint64_t i; i << 64 is undefined behaviour

   // In every iteration, shift one bit and one word to the left and use the
   // shift results only when they are within the shift range.
   BigInt tmp;
   tmp.resize(size() + 1 /* to hold the shifted-out word */);
   for(size_t i = 0; i < iterations; ++i) {
      shl_bit(*this, tmp);
      ct_cond_assign(i < bit_shift, tmp);
      shl_word(*this, tmp);
      ct_cond_assign(i < word_shift, tmp);
   }
}

void BigInt::ct_cond_swap(bool predicate, BigInt& other) {
   const size_t max_words = std::max(size(), other.size());
   grow_to(max_words);
   other.grow_to(max_words);

   bigint_cnd_swap(static_cast<word>(predicate), this->mutable_data(), other.mutable_data(), max_words);
}

void BigInt::cond_flip_sign(bool predicate) {
   // This code is assuming Negative == 0, Positive == 1

   const auto mask = CT::Mask<uint8_t>::expand(predicate);

   const uint8_t current_sign = static_cast<uint8_t>(sign());

   const uint8_t new_sign = mask.select(current_sign ^ 1, current_sign);

   set_sign(static_cast<Sign>(new_sign));
}

void BigInt::ct_cond_assign(bool predicate, const BigInt& other) {
   const size_t t_words = size();
   const size_t o_words = other.size();

   if(o_words < t_words) {
      grow_to(o_words);
   }

   const size_t r_words = std::max(t_words, o_words);

   const auto mask = CT::Mask<word>::expand(predicate);

   for(size_t i = 0; i != r_words; ++i) {
      const word o_word = other.word_at(i);
      const word t_word = this->word_at(i);
      this->set_word_at(i, mask.select(o_word, t_word));
   }

   const auto same_sign = CT::Mask<word>::is_equal(sign(), other.sign()).as_choice();
   cond_flip_sign((mask.as_choice() && !same_sign).as_bool());
}

void BigInt::_const_time_poison() const {
   CT::poison(m_data.const_data(), m_data.size());
}

void BigInt::_const_time_unpoison() const {
   CT::unpoison(m_data.const_data(), m_data.size());
}

}  // namespace Botan

1	/*
2	* BigInt Base
3	* (C) 1999-2011,2012,2014,2019 Jack Lloyd
4	*
5	* Botan is released under the Simplified BSD License (see license.txt)
6	*/
7
8	#include <botan/bigint.h>
9
10	#include <botan/internal/bit_ops.h>
11	#include <botan/internal/ct_utils.h>
12	#include <botan/internal/loadstor.h>
13	#include <botan/internal/mp_core.h>
14	#include <botan/internal/rounding.h>
15
16	namespace Botan {
17
18	BigInt::BigInt(uint64_t n) {	360,253✔
19	if constexpr(sizeof(word) == 8) {	360,253✔
20	m_data.set_word_at(0, static_cast<word>(n));	360,253✔
21	} else {
22	m_data.set_word_at(1, static_cast<word>(n >> 32));
23	m_data.set_word_at(0, static_cast<word>(n));
24	}
25	}	360,253✔
26
27	//static
28	BigInt BigInt::from_u64(uint64_t n) {	110,570✔
29	return BigInt(n);	110,570✔
30	}
31
32	//static
33	BigInt BigInt::from_word(word n) {	410,473✔
34	BigInt bn;	410,473✔
35	bn.set_word_at(0, n);	410,473✔
36	return bn;	410,473✔
37	}	×
38
39	//static
40	BigInt BigInt::from_s32(int32_t n) {	110✔
41	if(n >= 0) {	110✔
42	return BigInt::from_u64(static_cast<uint64_t>(n));	2✔
43	} else {
44	return -BigInt::from_u64(static_cast<uint64_t>(-n));	108✔
45	}
46	}
47
48	//static
49	BigInt BigInt::with_capacity(size_t size) {	12,605,256✔
50	BigInt bn;	12,605,256✔
51	bn.grow_to(size);	12,605,256✔
52	return bn;	12,605,256✔
53	}	×
54
55	/*
56	* Construct a BigInt from a string
57	*/
58	BigInt::BigInt(std::string_view str) {	46,601✔
59	Base base = Decimal;	46,601✔
60	size_t markers = 0;	46,601✔
61	bool negative = false;	46,601✔
62
63	if(!str.empty() && str[0] == '-') {	46,601✔
64	markers += 1;
65	negative = true;
66	}
67
68	if(str.length() > markers + 2 && str[markers] == '0' && str[markers + 1] == 'x') {	46,601✔
69	markers += 2;
70	base = Hexadecimal;
71	}
72
73	*this = decode(cast_char_ptr_to_uint8(str.data()) + markers, str.length() - markers, base);	46,601✔
74
75	if(negative) {	46,601✔
76	set_sign(Negative);	890✔
77	} else {
78	set_sign(Positive);	46,156✔
79	}
80	}	46,601✔
81
82	BigInt BigInt::from_string(std::string_view str) {	6✔
83	return BigInt(str);	6✔
84	}
85
86	BigInt BigInt::from_bytes(std::span<const uint8_t> input) {	110,472✔
87	BigInt r;	110,472✔
88	r.assign_from_bytes(input);	110,472✔
89	return r;	110,472✔
90	}	×
91
92	/*
93	* Construct a BigInt from an encoded BigInt
94	*/
95	BigInt::BigInt(const uint8_t input[], size_t length, Base base) {	10✔
96	*this = decode(input, length, base);	10✔
97	}	10✔
98
99	//static
100	BigInt BigInt::from_bytes_with_max_bits(const uint8_t input[], size_t length, size_t max_bits) {	6,896✔
101	const size_t input_bits = 8 * length;	6,896✔
102
103	auto bn = BigInt::from_bytes(std::span{input, length});	6,896✔
104
105	if(input_bits > max_bits) {	6,896✔
106	const size_t bits_to_shift = input_bits - max_bits;	3,722✔
107
108	bn >>= bits_to_shift;	3,722✔
109	}
110
111	return bn;	6,896✔
112	}	×
113
114	/*
115	* Construct a BigInt from an encoded BigInt
116	*/
117	BigInt::BigInt(RandomNumberGenerator& rng, size_t bits, bool set_high_bit) {	96,269✔
118	randomize(rng, bits, set_high_bit);	96,269✔
119	}	96,269✔
120
121	uint8_t BigInt::byte_at(size_t n) const {	319,818✔
122	return get_byte_var(sizeof(word) - (n % sizeof(word)) - 1, word_at(n / sizeof(word)));	319,818✔
123	}
124
125	int32_t BigInt::cmp_word(word other) const {	2,635,371✔
126	if(is_negative()) {	2,635,371✔
127	return -1; // other is positive ...
128	}
129
130	const size_t sw = this->sig_words();	2,604,226✔
131	if(sw > 1) {	2,604,226✔
132	return 1; // must be larger since other is just one word ...
133	}
134
135	return bigint_cmp(this->_data(), sw, &other, 1);	2,000,226✔
136	}
137
138	/*
139	* Comparison Function
140	*/
141	int32_t BigInt::cmp(const BigInt& other, bool check_signs) const {	960,482✔
142	if(check_signs) {	960,482✔
143	if(other.is_positive() && this->is_negative()) {	960,355✔
144	return -1;
145	}
146
147	if(other.is_negative() && this->is_positive()) {	960,297✔
148	return 1;
149	}
150
151	if(other.is_negative() && this->is_negative()) {	960,225✔
152	return (-bigint_cmp(this->_data(), this->size(), other._data(), other.size()));	70✔
153	}
154	}
155
156	return bigint_cmp(this->_data(), this->size(), other._data(), other.size());	960,282✔
157	}
158
159	bool BigInt::is_equal(const BigInt& other) const {	539,193✔
160	if(this->sign() != other.sign()) {	539,193✔
161	return false;
162	}
163
164	return bigint_ct_is_eq(this->_data(), this->sig_words(), other._data(), other.sig_words()).as_bool();	978,822✔
165	}
166
167	bool BigInt::is_less_than(const BigInt& other) const {	10,453,656✔
168	if(this->is_negative() && other.is_positive()) {	10,453,656✔
169	return true;
170	}
171
172	if(this->is_positive() && other.is_negative()) {	10,453,591✔
173	return false;
174	}
175
176	if(other.is_negative() && this->is_negative()) {	10,453,528✔
177	return bigint_ct_is_lt(other._data(), other.sig_words(), this->_data(), this->sig_words()).as_bool();	69✔
178	}
179
180	return bigint_ct_is_lt(this->_data(), this->sig_words(), other._data(), other.sig_words()).as_bool();	15,329,230✔
181	}
182
183	void BigInt::encode_words(word out[], size_t size) const {	281,742✔
184	const size_t words = sig_words();	281,742✔
185
186	if(words > size) {	281,742✔
187	throw Encoding_Error("BigInt::encode_words value too large to encode");	×
188	}
189
190	clear_mem(out, size);	281,742✔
191	copy_mem(out, _data(), words);	281,742✔
192	}	281,742✔
193
194	void BigInt::Data::set_to_zero() {	861,338✔
195	m_reg.resize(m_reg.capacity());	861,338✔
196	clear_mem(m_reg.data(), m_reg.size());	861,338✔
197	m_sig_words = 0;	861,338✔
198	}	861,338✔
199
200	void BigInt::Data::mask_bits(size_t n) {	45,280✔
201	if(n == 0) {	45,280✔
202	return set_to_zero();	×
203	}
204
205	const size_t top_word = n / WordInfo<word>::bits;	45,280✔
206
207	if(top_word < size()) {	45,280✔
208	const word mask = (static_cast<word>(1) << (n % WordInfo<word>::bits)) - 1;	43,230✔
209	const size_t len = size() - (top_word + 1);	43,230✔
210	if(len > 0) {	43,230✔
211	clear_mem(&m_reg[top_word + 1], len);	43,230✔
212	}
213	m_reg[top_word] &= mask;	43,230✔
214	invalidate_sig_words();	43,230✔
215	}
216	}
217
218	size_t BigInt::Data::calc_sig_words() const {	48,479,065✔
219	const size_t sz = m_reg.size();	48,479,065✔
220	size_t sig = sz;	48,479,065✔
221
222	word sub = 1;	48,479,065✔
223
224	for(size_t i = 0; i != sz; ++i) {	1,306,884,638✔
225	const word w = m_reg[sz - i - 1];	1,258,405,573✔
226	sub &= ct_is_zero(w);	1,258,405,573✔
227	sig -= sub;	1,258,405,573✔
228	}
229
230	/*
231	* This depends on the data so is poisoned, but unpoison it here as
232	* later conditionals are made on the size.
233	*/
234	CT::unpoison(sig);	48,479,065✔
235
236	return sig;	48,479,065✔
237	}
238
239	/*
240	* Return bits {offset...offset+length}
241	*/
242	uint32_t BigInt::get_substring(size_t offset, size_t length) const {	15,130,230✔
243	if(length == 0 \|\| length > 32) {	15,130,230✔
244	throw Invalid_Argument("BigInt::get_substring invalid substring length");	×
245	}
246
247	const uint32_t mask = 0xFFFFFFFF >> (32 - length);	15,130,230✔
248
249	const size_t word_offset = offset / WordInfo<word>::bits;	15,130,230✔
250	const size_t wshift = (offset % WordInfo<word>::bits);	15,130,230✔
251
252	/*
253	* The substring is contained within one or at most two words. The
254	* offset and length are not secret, so we can perform conditional
255	* operations on those values.
256	*/
257	const word w0 = word_at(word_offset);	15,130,230✔
258
259	if(wshift == 0 \|\| (offset + length) / WordInfo<word>::bits == word_offset) {	15,130,230✔
260	return static_cast<uint32_t>(w0 >> wshift) & mask;	14,339,040✔
261	} else {
262	const word w1 = word_at(word_offset + 1);	791,190✔
263	return static_cast<uint32_t>((w0 >> wshift) \| (w1 << (WordInfo<word>::bits - wshift))) & mask;	791,190✔
264	}
265	}
266
267	/*
268	* Convert this number to a uint32_t, if possible
269	*/
270	uint32_t BigInt::to_u32bit() const {	34,950✔
271	if(is_negative()) {	34,950✔
272	throw Encoding_Error("BigInt::to_u32bit: Number is negative");	×
273	}
274	if(bits() > 32) {	34,950✔
275	throw Encoding_Error("BigInt::to_u32bit: Number is too big to convert");	15✔
276	}
277
278	uint32_t out = 0;
279	for(size_t i = 0; i != 4; ++i) {	174,675✔
280	out = (out << 8) \| byte_at(3 - i);	139,740✔
281	}
282	return out;	34,935✔
283	}
284
285	/*
286	* Clear bit number n
287	*/
288	void BigInt::clear_bit(size_t n) {	75✔
289	const size_t which = n / WordInfo<word>::bits;	75✔
290
291	if(which < size()) {	75✔
292	const word mask = ~(static_cast<word>(1) << (n % WordInfo<word>::bits));	75✔
293	m_data.set_word_at(which, word_at(which) & mask);	75✔
294	}
295	}	75✔
296
297	size_t BigInt::bytes() const {	311,199✔
298	return round_up(bits(), 8) / 8;	311,199✔
299	}
300
301	size_t BigInt::top_bits_free() const {	2,087,941✔
302	const size_t words = sig_words();	2,087,941✔
303
304	const word top_word = word_at(words - 1);	2,087,941✔
305	const size_t bits_used = high_bit(CT::value_barrier(top_word));	2,087,941✔
306	CT::unpoison(bits_used);	2,087,941✔
307	return WordInfo<word>::bits - bits_used;	2,087,941✔
308	}
309
310	size_t BigInt::bits() const {	1,803,580✔
311	const size_t words = sig_words();	1,803,580✔
312
313	if(words == 0) {	1,803,580✔
314	return 0;
315	}
316
317	const size_t full_words = (words - 1) * WordInfo<word>::bits;	1,785,622✔
318	const size_t top_bits = WordInfo<word>::bits - top_bits_free();	1,785,622✔
319
320	return full_words + top_bits;	1,785,622✔
321	}
322
323	/*
324	* Return the negation of this number
325	*/
326	BigInt BigInt::operator-() const {	119✔
327	BigInt x = (*this);	119✔
328	x.flip_sign();	119✔
329	return x;	119✔
330	}	×
331
332	size_t BigInt::reduce_below(const BigInt& p, secure_vector<word>& ws) {	7,218,523✔
333	if(p.is_negative() \|\| this->is_negative()) {	7,218,523✔
334	throw Invalid_Argument("BigInt::reduce_below both values must be positive");	×
335	}
336
337	const size_t p_words = p.sig_words();	7,218,523✔
338
339	if(size() < p_words + 1) {	7,218,523✔
340	grow_to(p_words + 1);	21,213✔
341	}
342
343	if(ws.size() < p_words + 1) {	7,218,523✔
344	ws.resize(p_words + 1);	302,319✔
345	}
346
347	clear_mem(ws.data(), ws.size());	7,218,523✔
348
349	size_t reductions = 0;	7,218,523✔
350
351	for(;;) {	11,241,523✔
352	word borrow = bigint_sub3(ws.data(), _data(), p_words + 1, p._data(), p_words);	18,460,046✔
353	if(borrow) {	18,460,046✔
354	break;
355	}
356
357	++reductions;	11,241,523✔
358	swap_reg(ws);	11,241,523✔
359	}
360
361	return reductions;	7,218,523✔
362	}
363
364	void BigInt::ct_reduce_below(const BigInt& mod, secure_vector<word>& ws, size_t bound) {	×
365	if(mod.is_negative() \|\| this->is_negative()) {	×
366	throw Invalid_Argument("BigInt::ct_reduce_below both values must be positive");	×
367	}
368
369	const size_t mod_words = mod.sig_words();	×
370
371	grow_to(mod_words);	×
372
373	const size_t sz = size();	×
374
375	ws.resize(sz);	×
376
377	clear_mem(ws.data(), sz);	×
378
379	for(size_t i = 0; i != bound; ++i) {	×
380	word borrow = bigint_sub3(ws.data(), _data(), sz, mod._data(), mod_words);	×
381
382	CT::Mask<word>::is_zero(borrow).select_n(mutable_data(), ws.data(), _data(), sz);	×
383	}
384	}	×
385
386	/*
387	* Return the absolute value of this number
388	*/
389	BigInt BigInt::abs() const {	1,209✔
390	BigInt x = (*this);	1,209✔
391	x.set_sign(Positive);	1,209✔
392	return x;	1,209✔
393	}
394
395	/*
396	* Encode this number into bytes
397	*/
398	void BigInt::serialize_to(std::span<uint8_t> output) const {	193,906✔
399	BOTAN_ARG_CHECK(this->bytes() <= output.size(), "Insufficient output space");	193,906✔
400
401	this->binary_encode(output.data(), output.size());	193,682✔
402	}	193,682✔
403
404	/*
405	* Encode this number into bytes
406	*/
407	void BigInt::binary_encode(uint8_t output[], size_t len) const {	193,687✔
408	const size_t full_words = len / sizeof(word);	193,687✔
409	const size_t extra_bytes = len % sizeof(word);	193,687✔
410
411	for(size_t i = 0; i != full_words; ++i) {	1,800,926✔
412	const word w = word_at(i);	1,607,239✔
413	store_be(w, output + (len - (i + 1) * sizeof(word)));	1,607,239✔
414	}
415
416	if(extra_bytes > 0) {	193,687✔
417	const word w = word_at(full_words);	112,612✔
418
419	for(size_t i = 0; i != extra_bytes; ++i) {	523,114✔
420	output[extra_bytes - i - 1] = get_byte_var(sizeof(word) - i - 1, w);	410,502✔
421	}
422	}
423	}	193,687✔
424
425	/*
426	* Set this number to the value in buf
427	*/
428	void BigInt::assign_from_bytes(std::span<const uint8_t> bytes) {	858,631✔
429	clear();	858,631✔
430
431	const size_t length = bytes.size();	858,631✔
432	const size_t full_words = length / sizeof(word);	858,631✔
433	const size_t extra_bytes = length % sizeof(word);	858,631✔
434
435	secure_vector<word> reg((round_up(full_words + (extra_bytes > 0 ? 1 : 0), 8)));	1,088,213✔
436
437	for(size_t i = 0; i != full_words; ++i) {	8,969,168✔
438	reg[i] = load_be<word>(bytes.last<sizeof(word)>());	8,110,537✔
439	bytes = bytes.first(bytes.size() - sizeof(word));	8,110,537✔
440	}
441
442	if(!bytes.empty()) {	858,631✔
443	BOTAN_ASSERT_NOMSG(extra_bytes == bytes.size());	629,049✔
444	std::array<uint8_t, sizeof(word)> last_partial_word = {0};	629,049✔
445	copy_mem(std::span{last_partial_word}.last(extra_bytes), bytes);	629,049✔
446	reg[full_words] = load_be<word>(last_partial_word);	629,049✔
447	}
448
449	m_data.swap(reg);	858,631✔
450	}	858,631✔
451
452	void BigInt::ct_cond_add(bool predicate, const BigInt& value) {	3,102,427✔
453	if(this->is_negative() \|\| value.is_negative()) {	3,102,427✔
454	throw Invalid_Argument("BigInt::ct_cond_add requires both values to be positive");	×
455	}
456	this->grow_to(1 + value.sig_words());	3,102,427✔
457
458	bigint_cnd_add(static_cast<word>(predicate), this->mutable_data(), this->size(), value._data(), value.sig_words());	3,102,427✔
459	}	3,102,427✔
460
461	void BigInt::ct_shift_left(size_t shift) {	30,725✔
462	auto shl_bit = [](const BigInt& a, BigInt& result) {	3,834,176✔
463	BOTAN_DEBUG_ASSERT(a.size() + 1 == result.size());	3,803,451✔
464	bigint_shl2(result.mutable_data(), a._data(), a.size(), 1);	3,803,451✔
465	// shl2 may have shifted a bit into the next word, which must be dropped
466	clear_mem(result.mutable_data() + result.size() - 1, 1);	3,803,451✔
467	};	3,803,451✔
468
469	auto shl_word = [](const BigInt& a, BigInt& result) {	3,834,176✔
470	// the most significant word is not copied, aka. shifted out
471	bigint_shl2(result.mutable_data(), a._data(), a.size() - 1 /* ignore msw */, WordInfo<word>::bits);	3,803,451✔
472	// we left-shifted by a full word, the least significant word must be zero'ed
473	clear_mem(result.mutable_data(), 1);	3,803,451✔
474	};	3,803,451✔
475
476	BOTAN_ASSERT_NOMSG(size() > 0);	30,725✔
477
478	constexpr size_t bits_in_word = sizeof(word) * 8;	30,725✔
479	const size_t word_shift = shift >> ceil_log2(bits_in_word); // shift / bits_in_word	30,725✔
480	const size_t bit_shift = shift & ((1 << ceil_log2(bits_in_word)) - 1); // shift % bits_in_word	30,725✔
481	const size_t iterations = std::max(size(), bits_in_word) - 1; // uint64_t i; i << 64 is undefined behaviour	30,725✔
482
483	// In every iteration, shift one bit and one word to the left and use the
484	// shift results only when they are within the shift range.
485	BigInt tmp;	30,725✔
486	tmp.resize(size() + 1 /* to hold the shifted-out word */);	30,725✔
487	for(size_t i = 0; i < iterations; ++i) {	3,834,176✔
488	shl_bit(*this, tmp);	3,803,451✔
489	ct_cond_assign(i < bit_shift, tmp);	3,803,451✔
490	shl_word(*this, tmp);	3,803,451✔
491	ct_cond_assign(i < word_shift, tmp);	3,803,451✔
492	}
493	}	30,725✔
494
495	void BigInt::ct_cond_swap(bool predicate, BigInt& other) {	11,442,146✔
496	const size_t max_words = std::max(size(), other.size());	11,442,146✔
497	grow_to(max_words);	11,442,146✔
498	other.grow_to(max_words);	11,442,146✔
499
500	bigint_cnd_swap(static_cast<word>(predicate), this->mutable_data(), other.mutable_data(), max_words);	11,442,146✔
501	}	11,442,146✔
502
503	void BigInt::cond_flip_sign(bool predicate) {	32,876,649✔
504	// This code is assuming Negative == 0, Positive == 1
505
506	const auto mask = CT::Mask<uint8_t>::expand(predicate);	32,876,649✔
507
508	const uint8_t current_sign = static_cast<uint8_t>(sign());	32,876,649✔
509
510	const uint8_t new_sign = mask.select(current_sign ^ 1, current_sign);	32,876,649✔
511
512	set_sign(static_cast<Sign>(new_sign));	32,876,649✔
513	}	32,876,649✔
514
515	void BigInt::ct_cond_assign(bool predicate, const BigInt& other) {	32,515,122✔
516	const size_t t_words = size();	32,515,122✔
517	const size_t o_words = other.size();	32,515,122✔
518
519	if(o_words < t_words) {	32,515,122✔
520	grow_to(o_words);	388✔
521	}
522
523	const size_t r_words = std::max(t_words, o_words);	32,515,122✔
524
525	const auto mask = CT::Mask<word>::expand(predicate);	32,515,122✔
526
527	for(size_t i = 0; i != r_words; ++i) {	2,147,483,647✔
528	const word o_word = other.word_at(i);	2,147,483,647✔
529	const word t_word = this->word_at(i);	2,147,483,647✔
530	this->set_word_at(i, mask.select(o_word, t_word));	2,147,483,647✔
531	}
532
533	const auto same_sign = CT::Mask<word>::is_equal(sign(), other.sign()).as_choice();	32,515,122✔
534	cond_flip_sign((mask.as_choice() && !same_sign).as_bool());	32,515,122✔
535	}	32,515,122✔
536
537	void BigInt::_const_time_poison() const {	3,096,154✔
538	CT::poison(m_data.const_data(), m_data.size());	3,096,154✔
539	}	3,096,154✔
540
541	void BigInt::_const_time_unpoison() const {	37,502,691✔
542	CT::unpoison(m_data.const_data(), m_data.size());	37,502,691✔
543	}	37,502,691✔
544
545	} // namespace Botan

randombit / botan / 14644214898

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