Add missing range checks on number of multi primes in rsa_ossl_mod_exp #4862
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Why is this needed? I've had the time to check now, and I'm finding checks here (general RSA key checker), here (RSA key generation) and here (RSA security bits). Before |
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It is at least not obvious at all why there is no buffer overrun at Line 760 in f47270e I may be wrong, but what if a manipulated 19-key prime ASN.1 is read in, and the app does not call RSA_check_key or RSA_security_bits and goes directly to RSA_private_decrypt or RSA_sign ? |
levitte
reviewed
Dec 7, 2017
| @@ -618,7 +618,8 @@ static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx) | |||
| goto err; | |||
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| if (rsa->version == RSA_ASN1_VERSION_MULTI | |||
| && (ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0) | |||
| && ((ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0 | |||
| || ex_primes > RSA_MAX_PRIME_NUM - 2)) | |||
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You could make that || ex_primes > sizeof(m))...
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I totally missed the intent with this PR. Sorry 'bout that, brain now awake. |
levitte
approved these changes
Dec 7, 2017
mattcaswell
added
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approval: done
levitte
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Dec 8, 2017
Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from #4862)
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Merged. Thanks! |
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I think this could even crash when the imported RSA key has too many primes.