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Fix plaintext length check for UTF-8 strings #193

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Fix plaintext length check for UTF-8 strings #193

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11 changes: 8 additions & 3 deletions RSA.xs
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Original file line number Diff line number Diff line change
Expand Up @@ -426,10 +426,15 @@ EVP_PKEY* _load_rsa_key(SV* p_keyStringSv,
return rsa;
}

static void check_max_message_length(rsaData* p_rsa, STRLEN from_length) {
static void check_max_message_length(rsaData* p_rsa, SV* from_sv) {
int size;
int max_len = -1;
const char *pad_name = NULL;
STRLEN from_length;

/* sv_len() returns character count for UTF-8 SVs, but encryption
operates on bytes. SvPV always returns the byte length. */
(void)SvPV(from_sv, from_length);

size = EVP_PKEY_get_size(p_rsa->rsa);

Expand Down Expand Up @@ -1204,7 +1209,7 @@ encrypt(p_rsa, p_plaintext)
rsaData* p_rsa;
SV* p_plaintext;
CODE:
check_max_message_length(p_rsa, sv_len(p_plaintext));
check_max_message_length(p_rsa, p_plaintext);
#if OPENSSL_VERSION_NUMBER >= 0x30000000L
RETVAL = rsa_crypt(p_rsa, p_plaintext, EVP_PKEY_encrypt, EVP_PKEY_encrypt_init, 1 /* is_encrypt */);
#else
Expand Down Expand Up @@ -1247,7 +1252,7 @@ private_encrypt(p_rsa, p_plaintext)
croak("PSS padding with private_encrypt/public_decrypt is not supported. "
"Use sign()/verify() for PSS signatures.");
}
check_max_message_length(p_rsa, sv_len(p_plaintext));
check_max_message_length(p_rsa, p_plaintext);
#if OPENSSL_VERSION_NUMBER >= 0x30000000L
RETVAL = rsa_crypt(p_rsa, p_plaintext, EVP_PKEY_sign, EVP_PKEY_sign_init, 0 /* is_encrypt */);
#else
Expand Down
19 changes: 18 additions & 1 deletion t/crypto.t
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ use Crypt::OpenSSL::RSA;
# Tests for encrypt/decrypt error paths, boundary conditions, and edge cases.
# These cover gaps not addressed by rsa.t or padding.t.

plan tests => 20;
plan tests => 22;

Crypt::OpenSSL::Random::random_seed("OpenSSL needs at least 32 bytes.");
Crypt::OpenSSL::RSA->import_random_seed();
Expand Down Expand Up @@ -156,6 +156,23 @@ $rsa->use_pkcs1_oaep_padding();
"no-padding oversized plaintext gives clear error message");
}

# --- UTF-8 byte-length validation ---
# sv_len() returns character count for UTF-8 SVs, which is shorter than the
# byte count. The length check must use byte count since OpenSSL operates
# on bytes. Construct a UTF-8 string where chars <= max but bytes > max.

{
$rsa->use_pkcs1_oaep_padding();
my $utf8_str = "\xe9" x 120;
utf8::upgrade($utf8_str); # 120 chars, 240 UTF-8 bytes
require bytes;
ok(bytes::length($utf8_str) > $oaep_max,
"UTF-8 test string byte length exceeds OAEP max");
eval { $rsa->encrypt($utf8_str) };
like($@, qr/plaintext too long/,
"length check uses byte count for UTF-8 strings");
}

# Decrypt still works (no false positive from validation)
{
$rsa->use_pkcs1_oaep_padding();
Expand Down
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