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src: fix CSPRNG when length exceeds INT_MAX #47515

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Merged
nodejs-github-bot merged 1 commit into from
Apr 15, 2023
Merged

src: fix CSPRNG when length exceeds INT_MAX #47515

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src: fix CSPRNG when length exceeds INT_MAX 
CSPRNG implicitly casts the size_t length argument to a signed int when
calling RAND_bytes(), which leaves it up to the caller to ensure that
the length argument actually fits into such a signed int. However, not
all call sites explicitly ensure that, which could lead to subtle bugs.

In OpenSSL 3, use RAND_bytes_ex() instead, which does not require
casting the length to a signed int.

In OpenSSL 1.1.1, RAND_bytes_ex() is not supported, thus we have to
process blocks of size INT_MAX one by one.
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@tniessen
tniessen committed Apr 11, 2023
commit 0ae69719541e42ace846a9f32a88302932b2c4db
14 changes: 12 additions & 2 deletions src/crypto/crypto_util.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -61,10 +61,20 @@ int VerifyCallback(int preverify_ok, X509_STORE_CTX* ctx) {
}

MUST_USE_RESULT CSPRNGResult CSPRNG(void* buffer, size_t length) {
unsigned char* buf = static_cast<unsigned char*>(buffer);
do {
if (1 == RAND_status())
if (1 == RAND_bytes(static_cast<unsigned char*>(buffer), length))
if (1 == RAND_status()) {
#if OPENSSL_VERSION_MAJOR >= 3
if (1 == RAND_bytes_ex(nullptr, buf, length, 0)) return {true};
#else
while (length > INT_MAX && 1 == RAND_bytes(buf, INT_MAX)) {
buf += INT_MAX;
length -= INT_MAX;
}
if (length <= INT_MAX && 1 == RAND_bytes(buf, static_cast<int>(length)))
return {true};
#endif
}
#if OPENSSL_VERSION_MAJOR >= 3
const auto code = ERR_peek_last_error();
// A misconfigured OpenSSL 3 installation may report 1 from RAND_poll()
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