crypto,tls: do not ignore BN_get_word error

This changes `BignumPointer::GetWord` such that it does not hide errors
from the caller. In the context of RSA keys within X.509 certificates,
we should eventually compute the public exponent correctly regardless of
its size. This patch, however, is designed to be a minimal change that
prevents callers from using erroneous return values of `BN_get_word`.
Signed-off-by: Tobias Nießen <tniessen@tnie.de>
PR-URL: #63895
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: tniessen

deps/ncrypto/ncrypto.cc

@@ -408,12 +408,16 @@ bool BignumPointer::setWord(unsigned long w) { // NOLINT(runtime/int)
 returnBN_set_word(bn_.get(), w) == 1;
 }
 
-unsignedlongBignumPointer::GetWord(constBIGNUM* bn) { // NOLINT(runtime/int)
-returnBN_get_word(bn);
+std::optional<unsignedlong> BignumPointer::GetWord( // NOLINT(runtime/int)
+constBIGNUM* bn) {
+BN_ULONG ret = BN_get_word(bn);
+if (ret == static_cast<BN_ULONG>(-1)) return std::nullopt;
+return ret;
 }
 
-unsignedlongBignumPointer::getWord() const { // NOLINT(runtime/int)
-if (!bn_) return0;
+std::optional<unsignedlong> BignumPointer::getWord() // NOLINT(runtime/int)
+const {
+if (!bn_) return std::nullopt;
 returnGetWord(bn_.get());
 }
 

deps/ncrypto/ncrypto.h

@@ -743,7 +743,7 @@ class BignumPointer final {
 boolisOne() const;
 
 boolsetWord(unsignedlong w); // NOLINT(runtime/int)
-unsignedlonggetWord() const; // NOLINT(runtime/int)
+std::optional<unsignedlong>getWord() const; // NOLINT(runtime/int)
 
 size_tbyteLength() const;
 
@@ -782,7 +782,8 @@ class BignumPointer final {
 size_t size);
 staticintGetBitCount(constBIGNUM* bn);
 staticintGetByteCount(constBIGNUM* bn);
-staticunsignedlongGetWord(constBIGNUM* bn); // NOLINT(runtime/int)
+static std::optional<unsignedlong> GetWord( // NOLINT(runtime/int)
+constBIGNUM* bn);
 staticconstBIGNUM* One();
 
  BignumPointer clone();

src/crypto/crypto_aes.cc

@@ -384,7 +384,9 @@ WebCryptoCipherStatus AES_CTR_Cipher(Environment* env,
 return status;
  }
 
-BN_ULONG input_size_part1 = remaining_until_reset.getWord() * kAesBlockSize;
+ std::optional<BN_ULONG> remaining_blocks = remaining_until_reset.getWord();
+CHECK(remaining_blocks.has_value());
+BN_ULONG input_size_part1 = remaining_blocks.value() * kAesBlockSize;
 
 // Encrypt the first part...
 auto status =

src/crypto/crypto_x509.cc

@@ -44,6 +44,7 @@ using v8::Local;
 using v8::LocalVector;
 using v8::MaybeLocal;
 using v8::NewStringType;
+using v8::Null;
 using v8::Object;
 using v8::String;
 using v8::Uint32;
@@ -688,11 +689,12 @@ MaybeLocal<Value> GetModulusString(Environment* env, const BIGNUM* n) {
 }
 
 MaybeLocal<Value> GetExponentString(Environment* env, constBIGNUM* e) {
-uint64_t exponent_word = static_cast<uint64_t>(BignumPointer::GetWord(e));
+auto exponent_word = BignumPointer::GetWord(e);
+if (!exponent_word) returnNull(env->isolate());
 auto bio = BIOPointer::NewMem();
 if (!bio) [[unlikely]]
 return {};
-BIO_printf(bio.get(), "0x%" PRIx64, exponent_word);
+BIO_printf(bio.get(), "0x%" PRIx64, static_cast<uint64_t>(*exponent_word));
 returnToV8Value(env->context(), bio);
 }