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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <array>
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "chrome/browser/devtools/device/usb/android_rsa.h"
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <limits>
#include <memory>
#include <numeric>
#include <string_view>
#include "base/base64.h"
#include "base/containers/span.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/common/pref_names.h"
#include "components/sync_preferences/pref_service_syncable.h"
#include "crypto/rsa_private_key.h"
#include "crypto/signature_creator.h"
#include "net/cert/asn1_util.h"
namespace {
const size_t kRSANumWords = 64;
const size_t kBigIntSize = 1024;
static const char kDummyRSAPublicKey[] =
"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA6OSJ64q+ZLg7VV2ojEPh5TRbYjwbT"
"TifSPeFIV45CHnbTWYiiIn41wrozpYizNsMWZUBjdah1N78WVhbyDrnr0bDgFp+gXjfVppa3I"
"gjiohEcemK3omXi3GDMK8ERhriLUKfQS842SXtQ8I+KoZtpCkGM//0h7+P+Rhm0WwdipIRMhR"
"8haNAeyDiiCvqJcvevv2T52vqKtS3aWz+GjaTJJLVWydEpz9WdvWeLfFVhe2ZnqwwZNa30Qoj"
"fsnvjaMwK2MU7uYfRBPuvLyK5QESWBpArNDd6ULl8Y+NU6kwNOVDc87OASCVEM1gw2IMi2mo2"
"WO5ywp0UWRiGZCkK+wOFQIDAQAB";
typedef struct RSAPublicKey {
int len; // Length of n[] in number of uint32_t
uint32_t n0inv; // -1 / n[0] mod 2^32
std::array<uint32_t, kRSANumWords> n; // modulus as little endian array
std::array<uint32_t, kRSANumWords> rr; // R^2 as little endian array
int exponent; // 3 or 65537
} RSAPublicKey;
// http://en.wikipedia.org/wiki/Extended_Euclidean_algorithm
// a * x + b * y = gcd(a, b) = d
void ExtendedEuclid(uint64_t a,
uint64_t b,
uint64_t* x,
uint64_t* y,
uint64_t* d) {
uint64_t x1 = 0, x2 = 1, y1 = 1, y2 = 0;
while (b > 0) {
uint64_t q = a / b;
uint64_t r = a % b;
*x = x2 - q * x1;
*y = y2 - q * y1;
a = b;
b = r;
x2 = x1;
x1 = *x;
y2 = y1;
y1 = *y;
}
*d = a;
*x = x2;
*y = y2;
}
uint32_t ModInverse(uint64_t a, uint64_t m) {
uint64_t d, x, y;
ExtendedEuclid(a, m, &x, &y, &d);
if (d == 1)
return static_cast<uint32_t>(x);
return 0;
}
uint32_t* BnNew() {
uint32_t* result = new uint32_t[kBigIntSize];
memset(result, 0, kBigIntSize * sizeof(uint32_t));
return result;
}
void BnFree(uint32_t* a) {
delete[] a;
}
uint32_t* BnCopy(uint32_t* a) {
uint32_t* result = new uint32_t[kBigIntSize];
memcpy(result, a, kBigIntSize * sizeof(uint32_t));
return result;
}
uint32_t* BnMul(uint32_t* a, uint32_t b) {
uint32_t* result = BnNew();
uint64_t carry_over = 0;
for (size_t i = 0; i < kBigIntSize; ++i) {
carry_over += static_cast<uint64_t>(a[i]) * b;
result[i] = carry_over & std::numeric_limits<uint32_t>::max();
carry_over >>= 32;
}
return result;
}
void BnSub(uint32_t* a, uint32_t* b) {
int carry_over = 0;
for (size_t i = 0; i < kBigIntSize; ++i) {
int64_t sub = static_cast<int64_t>(a[i]) - b[i] - carry_over;
carry_over = 0;
if (sub < 0) {
carry_over = 1;
sub += 0x100000000LL;
}
a[i] = static_cast<uint32_t>(sub);
}
}
void BnLeftShift(uint32_t* a, int offset) {
for (int i = kBigIntSize - offset - 1; i >= 0; --i)
a[i + offset] = a[i];
for (int i = 0; i < offset; ++i)
a[i] = 0;
}
int BnCompare(uint32_t* a, uint32_t* b) {
for (int i = kBigIntSize - 1; i >= 0; --i) {
if (a[i] > b[i])
return 1;
if (a[i] < b[i])
return -1;
}
return 0;
}
uint64_t BnGuess(uint32_t* a, uint32_t* b, uint64_t from, uint64_t to) {
if (from + 1 >= to)
return from;
uint64_t guess = std::midpoint(from, to);
uint32_t* t = BnMul(b, static_cast<uint32_t>(guess));
int result = BnCompare(a, t);
BnFree(t);
if (result > 0)
return BnGuess(a, b, guess, to);
if (result < 0)
return BnGuess(a, b, from, guess);
return guess;
}
void BnDiv(uint32_t* a, uint32_t* b, uint32_t** pq, uint32_t** pr) {
if (BnCompare(a, b) < 0) {
if (pq)
*pq = BnNew();
if (pr)
*pr = BnCopy(a);
return;
}
int oa = kBigIntSize - 1;
int ob = kBigIntSize - 1;
for (; oa > 0 && !a[oa]; --oa) {}
for (; ob > 0 && !b[ob]; --ob) {}
uint32_t* q = BnNew();
uint32_t* ca = BnCopy(a);
int digit = a[oa] < b[ob] ? oa - ob - 1 : oa - ob;
for (; digit >= 0; --digit) {
uint32_t* shifted_b = BnCopy(b);
BnLeftShift(shifted_b, digit);
uint32_t value = static_cast<uint32_t>(BnGuess(
ca, shifted_b, 0,
static_cast<uint64_t>(std::numeric_limits<uint32_t>::max()) + 1));
q[digit] = value;
uint32_t* t = BnMul(shifted_b, value);
BnSub(ca, t);
BnFree(t);
BnFree(shifted_b);
}
if (pq)
*pq = q;
else
BnFree(q);
if (pr)
*pr = ca;
else
BnFree(ca);
}
} // namespace
std::unique_ptr<crypto::RSAPrivateKey> AndroidRSAPrivateKey(Profile* profile) {
std::string encoded_key =
profile->GetPrefs()->GetString(prefs::kDevToolsAdbKey);
std::string decoded_key;
std::unique_ptr<crypto::RSAPrivateKey> key;
if (!encoded_key.empty() && base::Base64Decode(encoded_key, &decoded_key)) {
std::vector<uint8_t> key_info(decoded_key.begin(), decoded_key.end());
key = crypto::RSAPrivateKey::CreateFromPrivateKeyInfo(key_info);
}
if (!key) {
key = crypto::RSAPrivateKey::Create(2048);
std::vector<uint8_t> key_info;
if (!key || !key->ExportPrivateKey(&key_info))
return nullptr;
std::string key_string(key_info.begin(), key_info.end());
encoded_key = base::Base64Encode(key_string);
profile->GetPrefs()->SetString(prefs::kDevToolsAdbKey,
encoded_key);
}
return key;
}
std::string AndroidRSAPublicKey(crypto::RSAPrivateKey* key) {
std::vector<uint8_t> public_key;
if (!key)
return kDummyRSAPublicKey;
key->ExportPublicKey(&public_key);
std::string asn1(public_key.begin(), public_key.end());
std::string_view pk;
if (!net::asn1::ExtractSubjectPublicKeyFromSPKI(asn1, &pk))
return kDummyRSAPublicKey;
// Skip 10 byte asn1 prefix to the modulus.
std::vector<uint8_t> pk_data(pk.data() + 10, pk.data() + pk.length());
uint32_t* n = BnNew();
for (size_t i = 0; i < kRSANumWords; ++i) {
uint32_t t = pk_data[4 * i];
t = t << 8;
t += pk_data[4 * i + 1];
t = t << 8;
t += pk_data[4 * i + 2];
t = t << 8;
t += pk_data[4 * i + 3];
n[kRSANumWords - i - 1] = t;
}
uint64_t n0 = n[0];
RSAPublicKey pkey;
pkey.len = kRSANumWords;
pkey.exponent = 65537; // Fixed public exponent
pkey.n0inv = 0 - ModInverse(n0, 0x100000000LL);
if (pkey.n0inv == 0)
return kDummyRSAPublicKey;
uint32_t* r = BnNew();
r[kRSANumWords * 2] = 1;
uint32_t* rr;
BnDiv(r, n, nullptr, &rr);
for (size_t i = 0; i < kRSANumWords; ++i) {
pkey.n[i] = n[i];
pkey.rr[i] = rr[i];
}
BnFree(n);
BnFree(r);
BnFree(rr);
return base::Base64Encode(base::byte_span_from_ref(pkey));
}
std::string AndroidRSASign(crypto::RSAPrivateKey* key,
const std::string& body) {
std::vector<uint8_t> digest(body.begin(), body.end());
std::vector<uint8_t> result;
if (!crypto::SignatureCreator::Sign(key, crypto::SignatureCreator::SHA1,
digest.data(), digest.size(), &result)) {
return std::string();
}
return std::string(result.begin(), result.end());
}
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