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Fix RSA-OAEP to allow zero-length plaintext per RFC 8017 #10012

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Fix RSA-OAEP to allow zero-length plaintext per RFC 8017 #10012

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19 changes: 16 additions & 3 deletions wolfcrypt/src/rsa.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3318,7 +3318,15 @@ static int RsaPublicEncryptEx(const byte* in, word32 inLen, byte* out,
RsaPadding padding;
#endif

if (in == NULL || inLen == 0 || out == NULL || key == NULL) {
if (out == NULL || key == NULL) {
return BAD_FUNC_ARG;
}

/* For OAEP padding (RFC 8017, Section 7.1.1), zero-length messages are
* permitted: the spec requires mLen <= k - 2*hLen - 2, and mLen = 0
* satisfies this for all supported key sizes. For other padding types,
* a zero-length input is invalid. */
Comment on lines +3326 to +3328
if (in == NULL || (inLen == 0 && pad_type != WC_RSA_OAEP_PAD)) {
Comment on lines +3328 to +3329
return BAD_FUNC_ARG;
}

Expand Down Expand Up @@ -3706,8 +3714,13 @@ static int RsaPrivateDecryptEx(const byte* in, word32 inLen, byte* out,
ret = ctMaskSelInt(ctMaskLTE(ret, (int)outLen), ret,
WC_NO_ERR_TRACE(RSA_BUFFER_E));
#ifndef WOLFSSL_RSA_DECRYPT_TO_0_LEN
ret = ctMaskSelInt(ctMaskNotEq(ret, 0), ret,
WC_NO_ERR_TRACE(RSA_BUFFER_E));
/* RFC 8017 Section 7.1.2: OAEP decryption may produce a valid
* zero-length message. Only reject ret==0 for non-OAEP types. */
{
int zeroOk = ctMaskEq(pad_type, WC_RSA_OAEP_PAD);
ret = ctMaskSelInt(ctMaskNotEq(ret, 0) | zeroOk, ret,
Comment on lines +3720 to +3721
WC_NO_ERR_TRACE(RSA_BUFFER_E));
}
#endif
#else
if (outLen < (word32)ret)
Expand Down
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