Linux C/C++实现随机密码生成器

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Linux C/C++实现随机密码生成器

当您使用用户名和密码对服务进行身份验证时，强密码非常重要。一个强密码必须至少有14个字符，并有大小写字母和字母等变体。大多数时候，长密码被认为比短密码安全得多，因为它很难获得。

下面我们将学习使用Linux命令行创建安全密码的多种方法。我们将研究使用Linux命令行创建更强、更安全的密码的多种不同方法。如果要使用命令行创建强密码，可以使用多种方法和实用程序。我们将讨论其中的许多方法，可以根据需要选择其中一种方法来创建密码。

使用urandom生成密码

我们用来生成密码的第一个命令已经用tr命令过滤了/dev/urandom输出。这将允许我们删除所有不需要的字符，然后帮助我们只打印前14个字符。

cat /dev/urandom | tr -dc 'a-zA-Z0-9' | head -c 14;echo

上述命令的输出如下：

输出允许我们仅通过删除所有不需要的字符来打印前14个字符。

...
void gendigit(int size)
{ 
...f = fopen("/dev/urandom", "r");for (i=0; i<size; i++) {fread(&randval, sizeof(randval), 1, f);pass[i] = list[randval % 10];printf("%c", pass[i]);}
...
}
int main(int argc, char *argv[]) 
{
...switch (argc) {case 1: genalpha(length); break;case 2: if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {HELP} length = atoi(argv[1]);if (length < 6 || length > 32) {printf("Error: Password size must be a number between 6 and 32\n\n");HELP}genalpha(length); break;case 3:length = atoi(argv[2]);if(length < 6 || length > 32) {printf("Error: Password size must be a number between 6 and 32\n\n");HELP}/* 检查正在传递的参数 */if (!strcmp(argv[1], "-s") || !strcmp(argv[1], "--symbol")) {gensymbol(length);} else if (!strcmp(argv[1], "-a") || !strcmp(argv[1], "--alphanum")) {genalpha(length);} else if (!strcmp(argv[1], "-d") || !strcmp(argv[1], "--digits")) {gendigit(length);} else {HELP}break;default: HELP }
}
...

运行结果:

使用SHA生成密码

我们将在这个方法中使用SHA，它被设计用来使用 SHA-256 算法（SHA-2 系列，摘要长度为 256 位）校验数据完整性。

date | sha256sum

...
void sha256(const char* str)
{unsigned char hash[SHA256_DIGEST_LENGTH];SHA256_CTX sha256;SHA256_Init(&sha256);SHA256_Update(&sha256, str, strlen(str));SHA256_Final(hash, &sha256);for(int i = 0; i < SHA256_DIGEST_LENGTH; i++) {printf("%02x", (int)hash[i]);}printf("\n");
}int main(int argc, char *argv[]) 
{sha256("asdfqwr12");return 0;
}

编译运行：

通过md5sum简单的方式生成密码

使用命令行可以很容易地生成密码。虽然它不是随机的，但如果我们使用整个密码，它仍然很有用。为此，最简单的命令如下：

date | md5sum

一种获取可用作密码的随机字符串的方法是计算 MD5 校验值！校验值看起来确实像是随机字符串组合在一起，我们可以用作密码。确保你的计算源是个变量，这样的话每次运行命令时生成的校验值都不一样。date 命令 总会生成不同的输出。

static void Transform (UINT4 *buf, UINT4 *in) {UINT4 a = buf[0], b = buf[1], c = buf[2], d = buf[3];#define S11 7
#define S12 12
#define S13 17
#define S14 22FF ( a, b, c, d, in[ 0], S11, 3614090360UL);FF ( d, a, b, c, in[ 1], S12, 3905402710UL);FF ( c, d, a, b, in[ 2], S13,	606105819);FF ( b, c, d, a, in[ 3], S14, 3250441966UL);FF ( a, b, c, d, in[ 4], S11, 4118548399UL);FF ( d, a, b, c, in[ 5], S12, 1200080426);FF ( c, d, a, b, in[ 6], S13, 2821735955UL);FF ( b, c, d, a, in[ 7], S14, 4249261313UL);FF ( a, b, c, d, in[ 8], S11, 1770035416);FF ( d, a, b, c, in[ 9], S12, 2336552879UL);FF ( c, d, a, b, in[10], S13, 4294925233UL);FF ( b, c, d, a, in[11], S14, 2304563134UL);FF ( a, b, c, d, in[12], S11, 1804603682);FF ( d, a, b, c, in[13], S12, 4254626195UL);FF ( c, d, a, b, in[14], S13, 2792965006UL);FF ( b, c, d, a, in[15], S14, 1236535329);#define S21 5
#define S22 9
#define S23 14
#define S24 20GG ( a, b, c, d, in[ 1], S21, 4129170786UL);GG ( d, a, b, c, in[ 6], S22, 3225465664UL);GG ( c, d, a, b, in[11], S23,	643717713);GG ( b, c, d, a, in[ 0], S24, 3921069994UL);GG ( a, b, c, d, in[ 5], S21, 3593408605UL);GG ( d, a, b, c, in[10], S22,	38016083);GG ( c, d, a, b, in[15], S23, 3634488961UL);GG ( b, c, d, a, in[ 4], S24, 3889429448UL);GG ( a, b, c, d, in[ 9], S21,	568446438);GG ( d, a, b, c, in[14], S22, 3275163606UL);GG ( c, d, a, b, in[ 3], S23, 4107603335UL);GG ( b, c, d, a, in[ 8], S24, 1163531501);GG ( a, b, c, d, in[13], S21, 2850285829UL);GG ( d, a, b, c, in[ 2], S22, 4243563512UL);GG ( c, d, a, b, in[ 7], S23, 1735328473);GG ( b, c, d, a, in[12], S24, 2368359562UL);#define S31 4
#define S32 11
#define S33 16
#define S34 23HH ( a, b, c, d, in[ 5], S31, 4294588738UL);HH ( d, a, b, c, in[ 8], S32, 2272392833UL);HH ( c, d, a, b, in[11], S33, 1839030562);HH ( b, c, d, a, in[14], S34, 4259657740UL);HH ( a, b, c, d, in[ 1], S31, 2763975236UL);HH ( d, a, b, c, in[ 4], S32, 1272893353);HH ( c, d, a, b, in[ 7], S33, 4139469664UL);HH ( b, c, d, a, in[10], S34, 3200236656UL);HH ( a, b, c, d, in[13], S31,	681279174);HH ( d, a, b, c, in[ 0], S32, 3936430074UL);HH ( c, d, a, b, in[ 3], S33, 3572445317UL);HH ( b, c, d, a, in[ 6], S34,	76029189);HH ( a, b, c, d, in[ 9], S31, 3654602809UL);HH ( d, a, b, c, in[12], S32, 3873151461UL);HH ( c, d, a, b, in[15], S33,	530742520);HH ( b, c, d, a, in[ 2], S34, 3299628645UL);#define S41 6
#define S42 10
#define S43 15
#define S44 21II ( a, b, c, d, in[ 0], S41, 4096336452UL);II ( d, a, b, c, in[ 7], S42, 1126891415);II ( c, d, a, b, in[14], S43, 2878612391UL);II ( b, c, d, a, in[ 5], S44, 4237533241UL);II ( a, b, c, d, in[12], S41, 1700485571);II ( d, a, b, c, in[ 3], S42, 2399980690UL);II ( c, d, a, b, in[10], S43, 4293915773UL);II ( b, c, d, a, in[ 1], S44, 2240044497UL);II ( a, b, c, d, in[ 8], S41, 1873313359);II ( d, a, b, c, in[15], S42, 4264355552UL);II ( c, d, a, b, in[ 6], S43, 2734768916UL);II ( b, c, d, a, in[13], S44, 1309151649);II ( a, b, c, d, in[ 4], S41, 4149444226UL);II ( d, a, b, c, in[11], S42, 3174756917UL);II ( c, d, a, b, in[ 2], S43,	718787259);II ( b, c, d, a, in[ 9], S44, 3951481745UL);buf[0] += a;buf[1] += b;buf[2] += c;buf[3] += d;
}void MD5Update (MD5_CTX *mdContext, unsigned char *inBuf, unsigned int inLen) {UINT4 in[16];int mdi;unsigned int i, ii;mdi = (int)((mdContext->i[0] >> 3) & 0x3F);if ((mdContext->i[0] + ((UINT4)inLen << 3)) < mdContext->i[0])mdContext->i[1]++;mdContext->i[0] += ((UINT4)inLen << 3);mdContext->i[1] += ((UINT4)inLen >> 29);while (inLen--) {mdContext->in[mdi++] = *inBuf++;if (mdi == 0x40) {for (i = 0, ii = 0; i < 16; i++, ii += 4)in[i] = (((UINT4)mdContext->in[ii+3]) << 24) |(((UINT4)mdContext->in[ii+2]) << 16) |(((UINT4)mdContext->in[ii+1]) << 8) |((UINT4)mdContext->in[ii]);Transform (mdContext->buf, in);mdi = 0;}}
}void MD5Final (MD5_CTX *mdContext) {UINT4 in[16];int mdi;unsigned int i, ii;unsigned int padLen;in[14] = mdContext->i[0];in[15] = mdContext->i[1];mdi = (int)((mdContext->i[0] >> 3) & 0x3F);padLen = (mdi < 56) ? (56 - mdi) : (120 - mdi);MD5Update (mdContext, PADDING, padLen);for (i = 0, ii = 0; i < 14; i++, ii += 4)in[i] = (((UINT4)mdContext->in[ii+3]) << 24) |(((UINT4)mdContext->in[ii+2]) << 16) |(((UINT4)mdContext->in[ii+1]) << 8) |((UINT4)mdContext->in[ii]);Transform (mdContext->buf, in);for (i = 0, ii = 0; i < 4; i++, ii += 4) {mdContext->digest[ii] = (unsigned char)(mdContext->buf[i] & 0xFF);mdContext->digest[ii+1] = (unsigned char)((mdContext->buf[i] >> 8) & 0xFF);mdContext->digest[ii+2] = (unsigned char)((mdContext->buf[i] >> 16) & 0xFF);mdContext->digest[ii+3] = (unsigned char)((mdContext->buf[i] >> 24) & 0xFF);}
}static void MDPrint (MD5_CTX *mdContext) {sprintf(master_pass,"%02x%02x%02x%02x", mdContext->digest[0], mdContext->digest[1],mdContext->digest[2],mdContext->digest[3]);
}...int main (int argn, char **argv) 
{if (argn < 2)usage(*argv);MDString(*(++argv));printf("\nPassword Master: %s\n\n", master_pass);return 0;
}

运行结果：

使用openssl生成密码

Linux中有几种方法可以为Linux命令行创建和生成密码。我们正在尝试的第一个方法是使用openssl。用于生成更强密码的命令包括openssl rand函数。这将帮助我们在一个字符串中生成14个随机字符。命令是：

openssl rand -base64 14

结果将是一个14个字符的强密码，如下所示。

#include <openssl/rand.h>
#include <openssl/crypto.h>
...
static char symbols[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I','J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'S','R', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b','c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k','l', 'm', 'n', 'o', 'p', 'q', 's', 'r', 'u','v', 'w', 'x', 'y', 'z', '1', '2', '3', '4','5', '6', '7', '8', '9', '0', '!', '~', '@','#', '$', '%', '<', '>', ';', '^', '&', '*','(', ')', '-', '+', '=', '_', '?', '|', '/'
};int get_random_ascii_string(char *str, size_t in_size, generator_mode_t mode) {...switch (mode) {case FULL_ASCII_MODE:boundary = sizeof(symbols);break;case SHORT_ASCII_MODE:boundary = sizeof(symbols) - 21;break;default:return EXIT_FAILURE;} if (gen_random_bytes(buffer, in_size) != EXIT_SUCCESS) {return EXIT_FAILURE;}for (size_t i = 0; i < in_size; ++i) {index = buffer[i];/* 转换间隔的随机数 */index %= boundary;str[i] = symbols[index];if ((i + 1) == in_size) {str[(i + 1)] = '\0';}}...
}int main(int argc, char *const argv[]) 
{...rv = parse_argv(argc, argv);if (rv) {fprintf(stderr, "openssl_pg: invalid option -- \"%s\"\n", argv[rv]);show_help_info();return 1;}if (show_help) {show_help_info();return 0;}if (!result_len) {fprintf(stderr, "You need to specify password length\n");return 1;}else if (result_len < 0) {fprintf(stderr, "Password length must be positive number\n");return 1;}else if (result_len > MAX_PASSWDLEN) {fprintf(stderr, "Length of password is too big.\n");return 1;}if (without_spec) {err = get_random_ascii_string(buf, result_len, SHORT_ASCII_MODE);}else {err = get_random_ascii_string(buf, result_len, FULL_ASCII_MODE);}if (err != EXIT_SUCCESS) {fprintf(stderr, "Failed to generate random bytes.\n");return EXIT_FAILURE;}fprintf(stdout, "%s\n", buf);explicit_memzero(buf, result_len);...
}

运行结果：

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总结

我们讨论了几个从Linux命令行生成密码的方法。在本文中，我们讨论了实用程序openssh、urandom、md5sum、sha256sum。所有这些命令都可以保证从Linux命令行生成更强的密码，并且对用户确保系统安全非常有用。

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