AUTOSAR C++14 Rule A26-5-1

Pseudorandom numbers shall not be generated using std::rand()

Description

Rule Definition

Pseudorandom numbers shall not be generated using std::rand().

Rationale

This cryptographically weak routines is predictable and must not be used for security purposes. When a predictable random value controls the execution flow, your program is vulnerable to malicious attacks.

Troubleshooting

If you expect a rule violation but Polyspace^® does not report it, see Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

Random Loop Numbers

#include <stdio.h>
#include <stdlib.h>

volatile int rd = 1;
int main(int argc, char *argv[])
{   
    int j, r, nloops;
    struct random_data buf;
    int i = 0;
    
    nloops = rand();
    
    for (j = 0; j < nloops; j++) {
        if (random_r(&buf, &i))
            exit(1);
        printf("random_r: %ld\n", (long)i);
    }
    return 0;
}

This example uses rand and random_r to generate random numbers. If you use these functions for security purposes, these PRNGs can be the source of malicious attacks.

Correction — Use Stronger PRNG

One possible correction is to replace the vulnerable PRNG with a stronger random number generator.

#include <stdio.h>
#include <stdlib.h>
#include <openssl/rand.h>

volatile int rd = 1;
int main(int argc, char* argv[])
{   
    int j, r, nloops;
    unsigned char buf;
    unsigned int seed;
    int i = 0;
    
    if (argc != 3) 
    {
        fprintf(stderr, "Usage: %s <seed> <nloops>\n", argv[0]);
        exit(EXIT_FAILURE);
    }
    
    seed = atoi(argv[1]);
    nloops = atoi(argv[2]);
    
    for (j = 0; j < nloops; j++) {
        if (RAND_bytes(&buf, i) != 1)
            exit(1);
        printf("RAND_bytes: %u\n", (unsigned)buf);
    }
    return 0;
}

Check Information

Group: Algorithms library

Category: Required, Automated

Version History

Introduced in R2019a