diff options
| -rw-r--r-- | crypto/rsa/rsa_eay.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/crypto/rsa/rsa_eay.c b/crypto/rsa/rsa_eay.c index 06f73fc8ff..f325050c1c 100644 --- a/crypto/rsa/rsa_eay.c +++ b/crypto/rsa/rsa_eay.c @@ -545,10 +545,19 @@ static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa) if (rsa->e && rsa->n) { if (!meth->bn_mod_exp(&vrfy,r0,rsa->e,rsa->n,ctx,NULL)) goto err; - if (BN_cmp(I, &vrfy) != 0) - { + /* If 'I' was greater than (or equal to) rsa->n, the operation + * will be equivalent to using 'I mod n'. However, the result of + * the verify will *always* be less than 'n' so we don't check + * for absolute equality, just congruency. */ + if (!BN_sub(&vrfy, &vrfy, I)) goto err; + if (!BN_mod(&vrfy, &vrfy, rsa->n, ctx)) goto err; + if (vrfy.neg) + if (!BN_add(&vrfy, &vrfy, rsa->n)) goto err; + if (!BN_is_zero(&vrfy)) + /* 'I' and 'vrfy' aren't congruent mod n. Don't leak + * miscalculated CRT output, just do a raw (slower) + * mod_exp and return that instead. */ if (!meth->bn_mod_exp(r0,I,rsa->d,rsa->n,ctx,NULL)) goto err; - } } ret=1; err: |