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crypto: constant-time pss (if it survives optimization)

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This commit is contained in:
Michael Scire 2020-02-24 02:27:01 -08:00
parent 5fa534fb71
commit c3656aae30
2 changed files with 22 additions and 18 deletions
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38
libraries/libvapours/include/vapours/crypto/impl/crypto_rsa_pss_impl.hpp
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@ -73,9 +73,7 @@ namespace ams::crypto::impl {
bool Verify(u8 *buf, size_t size, Hash *hash) { bool Verify(u8 *buf, size_t size, Hash *hash) {
/* Validate sanity byte. */ /* Validate sanity byte. */
if (buf[size - 1] != TailMagic) { bool is_valid = buf[size - 1] == TailMagic;
return false;
}
/* Decrypt maskedDB */ /* Decrypt maskedDB */
const size_t db_len = size - HashSize - 1; const size_t db_len = size - HashSize - 1;
@ -87,33 +85,37 @@ namespace ams::crypto::impl {
db[0] &= 0x7F; db[0] &= 0x7F;
/* Verify that DB is of the form 0000...0001 */ /* Verify that DB is of the form 0000...0001 */
s32 salt_ofs = -1; s32 salt_ofs = 0;
for (size_t i = 0; i < db_len; i++) { {
if (db[i] != 0) { int looking_for_one = 1;
salt_ofs = static_cast<s32>(i) + 1; int invalid_db_padding = 0;
break; int is_zero;
int is_one;
for (size_t i = 0; i < db_len; /* ... */) {
is_zero = (db[i] == 0);
is_one = (db[i] == 1);
salt_ofs += (looking_for_one & is_one) * (static_cast<s32>(++i));
looking_for_one &= ~is_one;
invalid_db_padding |= (looking_for_one & ~is_zero);
} }
}
if (salt_ofs == -1) { is_valid &= (invalid_db_padding == 0);
return false;
}
if (db[salt_ofs - 1] != 1) {
return false;
} }
/* Verify salt. */ /* Verify salt. */
const u8 *salt = db + salt_ofs; const u8 *salt = db + salt_ofs;
const size_t salt_size = db_len - salt_ofs; const size_t salt_size = db_len - salt_ofs;
if (salt_size == 0) { is_valid &= (salt_size != 0);
return false;
}
/* Verify hash. */ /* Verify hash. */
u8 cmp_hash[HashSize]; u8 cmp_hash[HashSize];
ON_SCOPE_EXIT { ClearMemory(cmp_hash, sizeof(cmp_hash)); }; ON_SCOPE_EXIT { ClearMemory(cmp_hash, sizeof(cmp_hash)); };
ComputeHashWithPadding(cmp_hash, hash, salt, salt_size); ComputeHashWithPadding(cmp_hash, hash, salt, salt_size);
return IsSameBytes(cmp_hash, h, HashSize); is_valid &= IsSameBytes(cmp_hash, h, HashSize);
/* Succeed if all our checks succeeded. */
return is_valid;
} }
}; };

2
libraries/libvapours/include/vapours/svc/svc_types_common.hpp
View file

@ -58,6 +58,8 @@ namespace ams::svc {
static constexpr bool IsInput = std::is_const<typename std::remove_pointer<T>::type>::value; static constexpr bool IsInput = std::is_const<typename std::remove_pointer<T>::type>::value;
private: private:
T pointer; T pointer;
public:
constexpr ALWAYS_INLINE UserPointer(T p) : pointer(p) { /* ... */ }
}; };
template<typename T> template<typename T>