22855031980

Committed 09 Mar 2026 01:10PM UTC coverage: 90.173% (-0.01%) from 90.184%

Build # 22855031980

Build Type

Pull #5425

github

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web-flow

Commit Message

Merge 058be2a86 into cdaa9c0ff

Pull Request Pull Request #5425: BigInt encoding cleanups

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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/exceptn.h>
#include <botan/internal/bit_ops.h>
#include <botan/internal/ct_utils.h>
#include <botan/internal/loadstor.h>
#include <botan/internal/mem_utils.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;
}

BigInt BigInt::from_string(std::string_view str) {
   size_t prefix_bytes = 0;
   bool negative = false;
   size_t radix = 10;

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

   if(str.length() > prefix_bytes + 2 && str[prefix_bytes] == '0' && str[prefix_bytes + 1] == 'x') {
      prefix_bytes += 2;
      radix = 16;
   }

   BigInt r = BigInt::from_radix_digits(str.substr(prefix_bytes), radix);

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

   return r;
}

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

   return bigint_ct_is_lt(this->_data(), this->size(), other._data(), other.size()).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(;;) {
      const word borrow = bigint_sub3(ws.data(), _data(), p_words + 1, p._data(), p_words);
      if(borrow > 0) {
         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) {
      const 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");
   }
   const size_t v_words = value.sig_words();

   this->grow_to(1 + v_words);

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

   word carry = 0;

   word* x = this->mutable_data();
   const word* y = value._data();

   for(size_t i = 0; i != v_words; ++i) {
      x[i] = word_add(x[i], y[i] & mask, &carry);
   }

   for(size_t i = v_words; i != size(); ++i) {
      x[i] = word_add(x[i], static_cast<word>(0), &carry);
   }
}

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_bool(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_bool(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/exceptn.h>
11	#include <botan/internal/bit_ops.h>
12	#include <botan/internal/ct_utils.h>
13	#include <botan/internal/loadstor.h>
14	#include <botan/internal/mem_utils.h>
15	#include <botan/internal/mp_core.h>
16	#include <botan/internal/rounding.h>
17
18	namespace Botan {
19
20	BigInt::BigInt(uint64_t n) {	362,077✔
21	if constexpr(sizeof(word) == 8) {	362,077✔
22	m_data.set_word_at(0, static_cast<word>(n));	362,077✔
23	} else {
24	m_data.set_word_at(1, static_cast<word>(n >> 32));
25	m_data.set_word_at(0, static_cast<word>(n));
26	}
27	}	362,077✔
28
29	//static
30	BigInt BigInt::from_u64(uint64_t n) {	182,989✔
31	return BigInt(n);	182,989✔
32	}
33
34	//static
35	BigInt BigInt::from_word(word n) {	473,654✔
36	BigInt bn;	473,654✔
37	bn.set_word_at(0, n);	473,654✔
38	return bn;	473,654✔
39	}	×
40
41	//static
42	BigInt BigInt::from_s32(int32_t n) {	70,866✔
43	if(n >= 0) {	70,866✔
44	return BigInt::from_u64(static_cast<uint64_t>(n));	70,734✔
45	} else {
46	return -BigInt::from_u64(static_cast<uint64_t>(-n));	132✔
47	}
48	}
49
50	//static
51	BigInt BigInt::with_capacity(size_t size) {	8,829,922✔
52	BigInt bn;	8,829,922✔
53	bn.grow_to(size);	8,829,922✔
54	return bn;	8,829,922✔
55	}	×
56
57	BigInt BigInt::from_string(std::string_view str) {	47,079✔
58	size_t prefix_bytes = 0;	47,079✔
59	bool negative = false;	47,079✔
60	size_t radix = 10;	47,079✔
61
62	if(!str.empty() && str[0] == '-') {	47,079✔
63	prefix_bytes += 1;
64	negative = true;
65	}
66
67	if(str.length() > prefix_bytes + 2 && str[prefix_bytes] == '0' && str[prefix_bytes + 1] == 'x') {	47,079✔
68	prefix_bytes += 2;
69	radix = 16;
70	}
71
72	BigInt r = BigInt::from_radix_digits(str.substr(prefix_bytes), radix);	47,079✔
73
74	if(negative) {	47,079✔
75	r.set_sign(Negative);	904✔
76	} else {
77	r.set_sign(Positive);	46,627✔
78	}
79
80	return r;	47,079✔
81	}	×
82
83	BigInt BigInt::from_bytes(std::span<const uint8_t> input) {	169,732✔
84	BigInt r;	169,732✔
85	r.assign_from_bytes(input);	169,732✔
86	return r;	169,732✔
87	}	×
88
89	/*
90	* Construct a BigInt from an encoded BigInt
91	*/
92	BigInt::BigInt(const uint8_t input[], size_t length, Base base) {	×
93	*this = decode(input, length, base);	×
94	}	×
95
96	//static
97	BigInt BigInt::from_bytes_with_max_bits(const uint8_t input[], size_t length, size_t max_bits) {	6,986✔
98	const size_t input_bits = 8 * length;	6,986✔
99
100	auto bn = BigInt::from_bytes(std::span{input, length});	6,986✔
101
102	if(input_bits > max_bits) {	6,986✔
103	const size_t bits_to_shift = input_bits - max_bits;	3,793✔
104
105	bn >>= bits_to_shift;	3,793✔
106	}
107
108	return bn;	6,986✔
109	}	×
110
111	/*
112	* Construct a BigInt from an encoded BigInt
113	*/
114	BigInt::BigInt(RandomNumberGenerator& rng, size_t bits, bool set_high_bit) {	97,613✔
115	randomize(rng, bits, set_high_bit);	97,613✔
116	}	97,613✔
117
118	uint8_t BigInt::byte_at(size_t n) const {	346,362✔
119	return get_byte_var(sizeof(word) - (n % sizeof(word)) - 1, word_at(n / sizeof(word)));	346,362✔
120	}
121
122	int32_t BigInt::cmp_word(word other) const {	3,244,532✔
123	if(is_negative()) {	3,244,532✔
124	return -1; // other is positive ...
125	}
126
127	const size_t sw = this->sig_words();	3,178,964✔
128	if(sw > 1) {	3,178,964✔
129	return 1; // must be larger since other is just one word ...
130	}
131
132	return bigint_cmp(this->_data(), sw, &other, 1);	2,417,840✔
133	}
134
135	/*
136	* Comparison Function
137	*/
138	int32_t BigInt::cmp(const BigInt& other, bool check_signs) const {	1,031,590✔
139	if(check_signs) {	1,031,590✔
140	if(other.is_positive() && this->is_negative()) {	1,031,463✔
141	return -1;
142	}
143
144	if(other.is_negative() && this->is_positive()) {	1,031,391✔
145	return 1;
146	}
147
148	if(other.is_negative() && this->is_negative()) {	1,031,323✔
149	return (-bigint_cmp(this->_data(), this->size(), other._data(), other.size()));	72✔
150	}
151	}
152
153	return bigint_cmp(this->_data(), this->size(), other._data(), other.size());	1,031,378✔
154	}
155
156	bool BigInt::is_equal(const BigInt& other) const {	584,181✔
157	if(this->sign() != other.sign()) {	584,181✔
158	return false;
159	}
160
161	return bigint_ct_is_eq(this->_data(), this->size(), other._data(), other.size()).as_bool();	584,112✔
162	}
163
164	bool BigInt::is_less_than(const BigInt& other) const {	1,613,703✔
165	if(this->is_negative() && other.is_positive()) {	1,613,703✔
166	return true;
167	}
168
169	if(this->is_positive() && other.is_negative()) {	1,613,632✔
170	return false;
171	}
172
173	if(other.is_negative() && this->is_negative()) {	1,613,564✔
174	return bigint_ct_is_lt(other._data(), other.size(), this->_data(), this->size()).as_bool();	71✔
175	}
176
177	return bigint_ct_is_lt(this->_data(), this->size(), other._data(), other.size()).as_bool();	1,613,493✔
178	}
179
180	void BigInt::encode_words(word out[], size_t size) const {	283,534✔
181	const size_t words = sig_words();	283,534✔
182
183	if(words > size) {	283,534✔
184	throw Encoding_Error("BigInt::encode_words value too large to encode");	×
185	}
186
187	clear_mem(out, size);	283,534✔
188	copy_mem(out, _data(), words);	283,534✔
189	}	283,534✔
190
191	void BigInt::Data::set_to_zero() {	900,820✔
192	m_reg.resize(m_reg.capacity());	900,820✔
193	clear_mem(m_reg.data(), m_reg.size());	900,820✔
194	m_sig_words = 0;	900,820✔
195	}	900,820✔
196
197	void BigInt::Data::mask_bits(size_t n) {	45,115✔
198	if(n == 0) {	45,115✔
199	return set_to_zero();	×
200	}
201
202	const size_t top_word = n / WordInfo<word>::bits;	45,115✔
203
204	if(top_word < size()) {	45,115✔
205	const word mask = (static_cast<word>(1) << (n % WordInfo<word>::bits)) - 1;	43,065✔
206	const size_t len = size() - (top_word + 1);	43,065✔
207	if(len > 0) {	43,065✔
208	clear_mem(&m_reg[top_word + 1], len);	43,065✔
209	}
210	m_reg[top_word] &= mask;	43,065✔
211	invalidate_sig_words();	43,065✔
212	}
213	}
214
215	size_t BigInt::Data::calc_sig_words() const {	42,776,643✔
216	const size_t sz = m_reg.size();	42,776,643✔
217	size_t sig = sz;	42,776,643✔
218
219	word sub = 1;	42,776,643✔
220
221	for(size_t i = 0; i != sz; ++i) {	1,144,427,933✔
222	const word w = m_reg[sz - i - 1];	1,101,651,290✔
223	sub &= ct_is_zero(w);	1,101,651,290✔
224	sig -= sub;	1,101,651,290✔
225	}
226
227	/*
228	* This depends on the data so is poisoned, but unpoison it here as
229	* later conditionals are made on the size.
230	*/
231	CT::unpoison(sig);	42,776,643✔
232
233	return sig;	42,776,643✔
234	}
235
236	/*
237	* Return bits {offset...offset+length}
238	*/
239	uint32_t BigInt::get_substring(size_t offset, size_t length) const {	12,208,210✔
240	if(length == 0 \|\| length > 32) {	12,208,210✔
241	throw Invalid_Argument("BigInt::get_substring invalid substring length");	×
242	}
243
244	const uint32_t mask = 0xFFFFFFFF >> (32 - length);	12,208,210✔
245
246	const size_t word_offset = offset / WordInfo<word>::bits;	12,208,210✔
247	const size_t wshift = (offset % WordInfo<word>::bits);	12,208,210✔
248
249	/*
250	* The substring is contained within one or at most two words. The
251	* offset and length are not secret, so we can perform conditional
252	* operations on those values.
253	*/
254	const word w0 = word_at(word_offset);	12,208,210✔
255
256	if(wshift == 0 \|\| (offset + length) / WordInfo<word>::bits == word_offset) {	12,208,210✔
257	return static_cast<uint32_t>(w0 >> wshift) & mask;	11,607,273✔
258	} else {
259	const word w1 = word_at(word_offset + 1);	600,937✔
260	return static_cast<uint32_t>((w0 >> wshift) \| (w1 << (WordInfo<word>::bits - wshift))) & mask;	600,937✔
261	}
262	}
263
264	/*
265	* Convert this number to a uint32_t, if possible
266	*/
267	uint32_t BigInt::to_u32bit() const {	34,952✔
268	if(is_negative()) {	34,952✔
269	throw Encoding_Error("BigInt::to_u32bit: Number is negative");	×
270	}
271	if(bits() > 32) {	34,952✔
272	throw Encoding_Error("BigInt::to_u32bit: Number is too big to convert");	15✔
273	}
274
275	uint32_t out = 0;
276	for(size_t i = 0; i != 4; ++i) {	174,685✔
277	out = (out << 8) \| byte_at(3 - i);	139,748✔
278	}
279	return out;	34,937✔
280	}
281
282	/*
283	* Clear bit number n
284	*/
285	void BigInt::clear_bit(size_t n) {	83✔
286	const size_t which = n / WordInfo<word>::bits;	83✔
287
288	if(which < size()) {	83✔
289	const word mask = ~(static_cast<word>(1) << (n % WordInfo<word>::bits));	83✔
290	m_data.set_word_at(which, word_at(which) & mask);	83✔
291	}
292	}	83✔
293
294	size_t BigInt::bytes() const {	372,377✔
295	return round_up(bits(), 8) / 8;	372,377✔
296	}
297
298	size_t BigInt::top_bits_free() const {	2,241,653✔
299	const size_t words = sig_words();	2,241,653✔
300
301	const word top_word = word_at(words - 1);	2,241,653✔
302	const size_t bits_used = high_bit(CT::value_barrier(top_word));	2,241,653✔
303	CT::unpoison(bits_used);	2,241,653✔
304	return WordInfo<word>::bits - bits_used;	2,241,653✔
305	}
306
307	size_t BigInt::bits() const {	1,754,149✔
308	const size_t words = sig_words();	1,754,149✔
309
310	if(words == 0) {	1,754,149✔
311	return 0;
312	}
313
314	const size_t full_words = (words - 1) * WordInfo<word>::bits;	1,734,693✔
315	const size_t top_bits = WordInfo<word>::bits - top_bits_free();	1,734,693✔
316
317	return full_words + top_bits;	1,734,693✔
318	}
319
320	/*
321	* Return the negation of this number
322	*/
323	BigInt BigInt::operator-() const {	143✔
324	BigInt x = (*this);	143✔
325	x.flip_sign();	143✔
326	return x;	143✔
327	}	×
328
329	size_t BigInt::reduce_below(const BigInt& p, secure_vector<word>& ws) {	7,429,568✔
330	if(p.is_negative() \|\| this->is_negative()) {	7,429,568✔
331	throw Invalid_Argument("BigInt::reduce_below both values must be positive");	×
332	}
333
334	const size_t p_words = p.sig_words();	7,429,568✔
335
336	if(size() < p_words + 1) {	7,429,568✔
337	grow_to(p_words + 1);	39,050✔
338	}
339
340	if(ws.size() < p_words + 1) {	7,429,568✔
341	ws.resize(p_words + 1);	506,960✔
342	}
343
344	clear_mem(ws.data(), ws.size());	7,429,568✔
345
346	size_t reductions = 0;	7,429,568✔
347
348	for(;;) {	11,277,095✔
349	const word borrow = bigint_sub3(ws.data(), _data(), p_words + 1, p._data(), p_words);	18,706,663✔
350	if(borrow > 0) {	18,706,663✔
351	break;
352	}
353
354	++reductions;	11,277,095✔
355	swap_reg(ws);	11,277,095✔
356	}
357
358	return reductions;	7,429,568✔
359	}
360
361	void BigInt::ct_reduce_below(const BigInt& mod, secure_vector<word>& ws, size_t bound) {	×
362	if(mod.is_negative() \|\| this->is_negative()) {	×
363	throw Invalid_Argument("BigInt::ct_reduce_below both values must be positive");	×
364	}
365
366	const size_t mod_words = mod.sig_words();	×
367
368	grow_to(mod_words);	×
369
370	const size_t sz = size();	×
371
372	ws.resize(sz);	×
373
374	clear_mem(ws.data(), sz);	×
375
376	for(size_t i = 0; i != bound; ++i) {	×
377	const word borrow = bigint_sub3(ws.data(), _data(), sz, mod._data(), mod_words);	×
378
379	CT::Mask<word>::is_zero(borrow).select_n(mutable_data(), ws.data(), _data(), sz);	×
380	}
381	}	×
382
383	/*
384	* Return the absolute value of this number
385	*/
386	BigInt BigInt::abs() const {	894✔
387	BigInt x = (*this);	894✔
388	x.set_sign(Positive);	894✔
389	return x;	894✔
390	}
391
392	/*
393	* Encode this number into bytes
394	*/
395	void BigInt::serialize_to(std::span<uint8_t> output) const {	232,204✔
396	BOTAN_ARG_CHECK(this->bytes() <= output.size(), "Insufficient output space");	232,204✔
397
398	this->binary_encode(output.data(), output.size());	231,975✔
399	}	231,975✔
400
401	/*
402	* Encode this number into bytes
403	*/
404	void BigInt::binary_encode(uint8_t output[], size_t len) const {	231,980✔
405	const size_t full_words = len / sizeof(word);	231,980✔
406	const size_t extra_bytes = len % sizeof(word);	231,980✔
407
408	for(size_t i = 0; i != full_words; ++i) {	2,058,029✔
409	const word w = word_at(i);	1,826,049✔
410	store_be(w, output + (len - (i + 1) * sizeof(word)));	1,826,049✔
411	}
412
413	if(extra_bytes > 0) {	231,980✔
414	const word w = word_at(full_words);	132,007✔
415
416	for(size_t i = 0; i != extra_bytes; ++i) {	606,515✔
417	output[extra_bytes - i - 1] = get_byte_var(sizeof(word) - i - 1, w);	474,508✔
418	}
419	}
420	}	231,980✔
421
422	/*
423	* Set this number to the value in buf
424	*/
425	void BigInt::assign_from_bytes(std::span<const uint8_t> bytes) {	898,108✔
426	clear();	898,108✔
427
428	const size_t length = bytes.size();	898,108✔
429	const size_t full_words = length / sizeof(word);	898,108✔
430	const size_t extra_bytes = length % sizeof(word);	898,108✔
431
432	secure_vector<word> reg((round_up(full_words + (extra_bytes > 0 ? 1 : 0), 8)));	1,138,190✔
433
434	for(size_t i = 0; i != full_words; ++i) {	9,079,812✔
435	reg[i] = load_be<word>(bytes.last<sizeof(word)>());	8,181,704✔
436	bytes = bytes.first(bytes.size() - sizeof(word));	8,181,704✔
437	}
438
439	if(!bytes.empty()) {	898,108✔
440	BOTAN_ASSERT_NOMSG(extra_bytes == bytes.size());	658,026✔
441	std::array<uint8_t, sizeof(word)> last_partial_word = {0};	658,026✔
442	copy_mem(std::span{last_partial_word}.last(extra_bytes), bytes);	658,026✔
443	reg[full_words] = load_be<word>(last_partial_word);	658,026✔
444	}
445
446	m_data.swap(reg);	898,108✔
447	}	898,108✔
448
449	void BigInt::ct_cond_add(bool predicate, const BigInt& value) {	2,434,679✔
450	if(this->is_negative() \|\| value.is_negative()) {	2,434,679✔
451	throw Invalid_Argument("BigInt::ct_cond_add requires both values to be positive");	×
452	}
453	const size_t v_words = value.sig_words();	2,434,679✔
454
455	this->grow_to(1 + v_words);	2,434,679✔
456
457	const auto mask = CT::Mask<word>::expand(static_cast<word>(predicate)).value();	2,434,679✔
458
459	word carry = 0;	2,434,679✔
460
461	word* x = this->mutable_data();	2,434,679✔
462	const word* y = value._data();	2,434,679✔
463
464	for(size_t i = 0; i != v_words; ++i) {	12,475,938✔
465	x[i] = word_add(x[i], y[i] & mask, &carry);	10,041,259✔
466	}
467
468	for(size_t i = v_words; i != size(); ++i) {	22,215,906✔
469	x[i] = word_add(x[i], static_cast<word>(0), &carry);	19,781,227✔
470	}
471	}	2,434,679✔
472
473	void BigInt::ct_shift_left(size_t shift) {	30,727✔
474	auto shl_bit = [](const BigInt& a, BigInt& result) {	3,834,304✔
475	BOTAN_DEBUG_ASSERT(a.size() + 1 == result.size());	3,803,577✔
476	bigint_shl2(result.mutable_data(), a._data(), a.size(), 1);	3,803,577✔
477	// shl2 may have shifted a bit into the next word, which must be dropped
478	clear_mem(result.mutable_data() + result.size() - 1, 1);	3,803,577✔
479	};	3,803,577✔
480
481	auto shl_word = [](const BigInt& a, BigInt& result) {	3,834,304✔
482	// the most significant word is not copied, aka. shifted out
483	bigint_shl2(result.mutable_data(), a._data(), a.size() - 1 /* ignore msw */, WordInfo<word>::bits);	3,803,577✔
484	// we left-shifted by a full word, the least significant word must be zero'ed
485	clear_mem(result.mutable_data(), 1);	3,803,577✔
486	};	3,803,577✔
487
488	BOTAN_ASSERT_NOMSG(size() > 0);	30,727✔
489
490	constexpr size_t bits_in_word = sizeof(word) * 8;	30,727✔
491	const size_t word_shift = shift >> ceil_log2(bits_in_word); // shift / bits_in_word	30,727✔
492	const size_t bit_shift = shift & ((1 << ceil_log2(bits_in_word)) - 1); // shift % bits_in_word	30,727✔
493	const size_t iterations = std::max(size(), bits_in_word) - 1; // uint64_t i; i << 64 is undefined behaviour	30,727✔
494
495	// In every iteration, shift one bit and one word to the left and use the
496	// shift results only when they are within the shift range.
497	BigInt tmp;	30,727✔
498	tmp.resize(size() + 1 /* to hold the shifted-out word */);	30,727✔
499	for(size_t i = 0; i < iterations; ++i) {	3,834,304✔
500	shl_bit(*this, tmp);	3,803,577✔
501	ct_cond_assign(i < bit_shift, tmp);	3,803,577✔
502	shl_word(*this, tmp);	3,803,577✔
503	ct_cond_assign(i < word_shift, tmp);	3,803,577✔
504	}
505	}	30,727✔
506
507	void BigInt::ct_cond_swap(bool predicate, BigInt& other) {	11,477,902✔
508	const size_t max_words = std::max(size(), other.size());	11,477,902✔
509	grow_to(max_words);	11,477,902✔
510	other.grow_to(max_words);	11,477,902✔
511
512	bigint_cnd_swap(static_cast<word>(predicate), this->mutable_data(), other.mutable_data(), max_words);	11,477,902✔
513	}	11,477,902✔
514
515	void BigInt::cond_flip_sign(bool predicate) {	32,480,019✔
516	// This code is assuming Negative == 0, Positive == 1
517
518	const auto mask = CT::Mask<uint8_t>::expand_bool(predicate);	32,480,019✔
519
520	const uint8_t current_sign = static_cast<uint8_t>(sign());	32,480,019✔
521
522	const uint8_t new_sign = mask.select(current_sign ^ 1, current_sign);	32,480,019✔
523
524	set_sign(static_cast<Sign>(new_sign));	32,480,019✔
525	}	32,480,019✔
526
527	void BigInt::ct_cond_assign(bool predicate, const BigInt& other) {	32,079,953✔
528	const size_t t_words = size();	32,079,953✔
529	const size_t o_words = other.size();	32,079,953✔
530
531	if(o_words < t_words) {	32,079,953✔
532	grow_to(o_words);	367✔
533	}
534
535	const size_t r_words = std::max(t_words, o_words);	32,079,953✔
536
537	const auto mask = CT::Mask<word>::expand_bool(predicate);	32,079,953✔
538
539	for(size_t i = 0; i != r_words; ++i) {	2,147,483,647✔
540	const word o_word = other.word_at(i);	2,147,483,647✔
541	const word t_word = this->word_at(i);	2,147,483,647✔
542	this->set_word_at(i, mask.select(o_word, t_word));	2,147,483,647✔
543	}
544
545	const auto same_sign = CT::Mask<word>::is_equal(sign(), other.sign()).as_choice();	32,079,953✔
546	cond_flip_sign((mask.as_choice() && !same_sign).as_bool());	32,079,953✔
547	}	32,079,953✔
548
549	void BigInt::_const_time_poison() const {	57,518✔
550	CT::poison(m_data.const_data(), m_data.size());	57,518✔
551	}	57,518✔
552
553	void BigInt::_const_time_unpoison() const {	25,430,563✔
554	CT::unpoison(m_data.const_data(), m_data.size());	25,430,563✔
555	}	25,430,563✔
556
557	} // namespace Botan

randombit / botan / 22855031980

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