MissingZeroization.md

Missing zeroization of random BIGNUMs

Randomly generated BIGNUMs often represent sensitive data (e.g. like ECDSA nonces). These should be cleared as they go out of scope to ensure that sensitive data does not remain in memory longer than required.

This query identifies OpenSSL BIGNUMs which are inititialized using BN_rand but not which are not zeroized using BN_clear before they go out of scope. The following example function would be flagged as an issue by the query.

void compute() {
    BIGNUM *n = BN_new();
    BN_rand(n, 128, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY);
    
    // Perform sensitive computation using `n`.

    BN_free(n);
}