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

int WifiCore_GetPassword(unsigned char input_pwd[],unsigned int input_size)
{
    unsigned char password[] = {
    '0','1','2','3','4','5','6','7','8','9',
    'Q','W','E','R','T','Y','U','I','O','P',
    'A','S','D','F','G','H','J','K','L',
    'Z','X','C','V','B','N','M',
    'q','w','e','r','t','y','u','i','o','p',
    'a','s','d','f','g','h','j','k','l',
    'z','x','c','v','b','n','m'};
    unsigned int index = 0x00U;

    if(input_pwd == NULL)
        return -1;
    
    if(input_size == 0U)
        return -2;

    srand((unsigned)time(NULL));

    for(unsigned loop = 0x00U;loop < input_size;loop++)
    {   
        index = rand() % sizeof(password);
        input_pwd[loop] = password[index];
/*        printf("%c \n",input_pwd[loop]);  */
    }

    return 0;
}

int main(){

    unsigned char input_pwd[12+1];

    memset(input_pwd,0x00U,sizeof(input_pwd));

    int res = WifiCore_GetPassword(input_pwd,sizeof(input_pwd)-1);

    if(0 == res)
    {
        printf(" Succes \n");
        printf(" Password [%s] \n",input_pwd);
    }
    else
    {
        printf(" fail %d \n",res);
    }

    return 0;
}

平时写着玩，略显简陋。