简介
小程序是基于 md5 + password + xor 的组合方式来加密文件。程序支持跨平台（Windows/Linux）。
使用方法：
源文件清单：main.c md5.c md5.h setup.sh
完整代码（main.c）：
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <errno.h> #include <stdbool.h> #ifdef __linux__ #include <unistd.h> #define platform_popen popen #else // windows #define platform_popen _popen #endif // os platform #define log_print_error(fmt, ...) fprintf(stderr, \ "ERROR:FILE:%s:FUNC:%s:LINE:%d:" fmt, __FILE__, __func__, __LINE__, ##__VA_ARGS__); #include "md5.h" #define MD5_SIZE 16 #define MAX_PASS_LEN 512 static unsigned char g_md5_value[MD5_SIZE]; static char g_md5_string[64]; #define ENCRYPT_MAGIC 0x20231028 static int xor_buffer(unsigned char *buffer, long buflen, const char *pass); static int xor_file(const char *file, const char *pass); static int check_encrypted(const char *file, const char *pass); static void set_md5_val(const char *str); static int add_shell(const char *file, const unsigned char *md5_val, int md5_len);//加壳 static int del_shell(const char *file, const unsigned char *md5_val, int md5_len);//脱壳 static int execute_shell(const char *aa, const char *bb, const char *cc, const char *dd, const char *ee, const char *ff); int rename_file(const char *oldname, const char *newname) { #ifdef __linux__ return execute_shell("mv ", oldname, newname, " 2>/dev/null 1>/dev/null", "", ""); #else // windows return execute_shell("MOVE /Y ", oldname, newname, " 2>NUL 1>NUL", "", ""); #endif // os platform } int del_shell(const char *file, const unsigned char *md5_val, int md5_len) { int ret = 0; const char *tmpf = "tmp.delshell"; FILE *fp_r = fopen(file, "rb"); FILE *fp_w = fopen(tmpf, "wb+"); if (fp_r == NULL) { log_print_error("fopen(%s) failed, %s\n", file, strerror(errno)); fclose(fp_w); fp_w = NULL; return -1; } if (fp_w == NULL) { log_print_error("fopen(%s) failed, %s\n", tmpf, strerror(errno)); fclose(fp_r); fp_r = NULL; return -1; } long rlen = 0; long wlen = 0; unsigned char buffer[512]; // jump head fseek(fp_r, (md5_len + 4), SEEK_SET); while (!feof(fp_r)) { rlen = fread(buffer, 1, sizeof(buffer), fp_r); if (rlen < 0) { log_print_error("fread(%s) failed, %s\n", file, strerror(errno)); goto add_shell_exit; } wlen = fwrite(buffer, 1, rlen, fp_w); if (wlen < 0) { log_print_error("fwrite(%s) failed, %s\n", tmpf, strerror(errno)); goto add_shell_exit; } } if (fp_r) fclose(fp_r); fp_r = NULL; if (fp_w) fclose(fp_w); fp_w = NULL; rename_file(tmpf, file); add_shell_exit: if (fp_r) fclose(fp_r); fp_r = NULL; if (fp_w) fclose(fp_w); fp_w = NULL; return ret; } int add_shell(const char *file, const unsigned char *md5_val, int md5_len) { int ret = 0; const char *tmpf = "tmp.addshell"; FILE *fp_r = fopen(file, "rb"); FILE *fp_w = fopen(tmpf, "wb+"); if (fp_r == NULL) { log_print_error("fopen(%s) failed, %s\n", file, strerror(errno)); return -1; } if (fp_w == NULL) { log_print_error("fopen(%s) failed, %s\n", tmpf, strerror(errno)); return -1; } long rlen = 0; long wlen = 0; unsigned char buffer[512]; unsigned int magic = ENCRYPT_MAGIC; wlen = fwrite(&magic, 1, 4, fp_w); if (wlen < 0) { log_print_error("fwrite(%s) failed, %s\n", tmpf, strerror(errno)); goto add_shell_exit; } // add head wlen = fwrite(md5_val, 1, md5_len, fp_w); if (wlen < 0) { log_print_error("fwrite(%s) failed, %s\n", tmpf, strerror(errno)); goto add_shell_exit; } while (!feof(fp_r)) { rlen = fread(buffer, 1, sizeof(buffer), fp_r); if (rlen < 0) { log_print_error("fread(%s) failed, %s\n", file, strerror(errno)); goto add_shell_exit; } wlen = fwrite(buffer, 1, rlen, fp_w); if (wlen < 0) { log_print_error("fwrite(%s) failed, %s\n", tmpf, strerror(errno)); goto add_shell_exit; } } if (fp_r) fclose(fp_r); fp_r = NULL; if (fp_w) fclose(fp_w); fp_w = NULL; rename_file(tmpf, file); add_shell_exit: if (fp_r) fclose(fp_r); fp_r = NULL; if (fp_w) fclose(fp_w); fp_w = NULL; return ret; } void set_md5_val(const char *str) { MD5_CTX md5; MD5Init(&md5); MD5Update(&md5, (unsigned char *)str, strnlen(str, MAX_PASS_LEN)); MD5Final(&md5, g_md5_value); // convert md5 value to md5 string memset(g_md5_string, 0, sizeof(g_md5_string)); char *md5_str = g_md5_string; for (int i = 0; i < MD5_SIZE; i++) { snprintf(md5_str + i * 2, 2 + 1, "%02x", g_md5_value[i]); } } enum { STATUS_ENCRYPTED = 1, STATUS_DECRYPTED = 2, STATUS_INCORRECT = 3, }; //returns -1=error, 1=encrypted, 2=decrypted, 3=incorrect password int check_encrypted(const char *file, const char *pass) { FILE *fp = NULL; unsigned char dst_value[MD5_SIZE]; set_md5_val(pass); fp = fopen(file, "rb"); if (fp == NULL) { log_print_error("fopen(%s) failed, %s\n", file, strerror(errno)); return -1; } // check magic unsigned int magic = 0; long rlen = fread(&magic, 1, 4, fp); if (rlen < 0) { log_print_error("fread(%s) failed, %s\n", file, strerror(errno)); goto check_encrypted_exit; } // 表示已经加密,接下来进一步检查密码正确性 if (magic == ENCRYPT_MAGIC) { // 读取密码MD5 long rlen = fread(dst_value, 1, sizeof(dst_value), fp); if (rlen < 0) { log_print_error("fread(%s) failed, %s\n", file, strerror(errno)); goto check_encrypted_exit; } if (fp) fclose(fp); // 对比MD5一致性 if (0 == memcmp(g_md5_value, dst_value, sizeof(dst_value))) { return STATUS_ENCRYPTED; } else { return STATUS_INCORRECT; } } check_encrypted_exit: if (fp) fclose(fp); return STATUS_DECRYPTED; } int xor_buffer(unsigned char *buffer, long buflen, const char *pass) { int ret = 0; long bufidx = 0; int keyidx = 0; for (bufidx = 0; bufidx < buflen; bufidx++) { if (pass[keyidx] == 0) { keyidx = 0; continue; } buffer[bufidx] = buffer[bufidx] ^ pass[keyidx]; keyidx++; } return ret; } int encrypt_file(const char *file) { const char *tmpf = "tmp.xor"; FILE *fp_r = fopen(file, "rb"); FILE *fp_w = fopen(tmpf, "wb+"); if (fp_r == NULL) { log_print_error("fopen(%s) failed, %s\n", file, strerror(errno)); return -1; } if (fp_w == NULL) { log_print_error("fopen(%s) failed, %s\n", tmpf, strerror(errno)); return -1; } int ret = 0; long readLen = 0; long writLen = 0; unsigned char buffer[512]; while (!feof(fp_r)) { // read readLen = fread(buffer, 1, sizeof(buffer), fp_r); if (readLen < 0) { log_print_error("fread(%s) failed, %s\n", file, strerror(errno)); ret = readLen; goto encrypt_file_exit; } // calculate ret = xor_buffer(buffer, readLen, g_md5_string); // write writLen = fwrite(buffer, 1, readLen, fp_w); if (writLen < 0) { log_print_error("fwrite(%s) failed, %s\n", tmpf, strerror(errno)); ret = writLen; goto encrypt_file_exit; } if (readLen < sizeof(buffer)) { break; } } encrypt_file_exit: if (fp_r) fclose(fp_r); fp_r = NULL; if (fp_w) fclose(fp_w); fp_w = NULL; rename_file(tmpf, file); return 0; } int xor_file(const char *file, const char *pass) { // 如果已经加密,则该动作表示解密 int status = check_encrypted(file, pass); switch (status) { case STATUS_ENCRYPTED: { del_shell(file, g_md5_value, sizeof(g_md5_value)); encrypt_file(file); fprintf(stdout, "SUCCESS: DECRYPT %s\n", file); break; } case STATUS_DECRYPTED: { encrypt_file(file); add_shell(file, g_md5_value, sizeof(g_md5_value)); fprintf(stdout, "SUCCESS: ENCRYPT %s\n", file); break; } case STATUS_INCORRECT: { fprintf(stdout, "ERROR: Incorrect password %s\n", pass); break; } default: break; } return 0; } int del_strspace(char *filename, int size) { char *ptr = filename + size; while ( ptr != filename) { if ((*ptr) == '\r' || (*ptr) == '\n') { *ptr = 0; } ptr--; } } int execute_shell(const char *aa, const char *bb, const char *cc, const char *dd, const char *ee, const char *ff) { char cmdline[1024]; memset(cmdline, 0, sizeof(cmdline)); snprintf(cmdline, sizeof(cmdline), "%s %s %s %s %s %s", aa,bb,cc,dd,ee,ff); return system(cmdline); } int cmdline_lsall(char *cmdline, int cmdlen) { memset(cmdline, 0, cmdlen); #ifdef __linux__ snprintf(cmdline, cmdlen, "ls"); #else // windows snprintf(cmdline, cmdlen, "dir /b"); #endif // os platform return 0; } int del_tmpfile(void) { #ifdef __linux__ system("rm -rf tmp.* 2>/dev/null 1>/dev/null"); #else // windows system("del /s /q /f tmp.* 2>NUL 1>NUL"); #endif // os platform return 0; } int main(int argc, const char *argv[]) { if (argc != 4) { fprintf(stderr, "usage:%s -f <filename> <password>\n", argv[0]); fprintf(stderr, "usage:%s -d <dirname> <password>\n", argv[0]); fprintf(stderr, " e.g:%s -f test.mp4 abc123\n", argv[0]); fprintf(stderr, " e.g:%s -d testdir abc123\n", argv[0]); return -1; } const char *input_opt = argv[1]; const char *input_file = argv[2]; const char *input_pass = argv[3]; if (strncmp(input_opt, "-f", 2) == 0) { xor_file(input_file, input_pass); del_tmpfile(); return 0; } if (strncmp(input_opt, "-d", 2) == 0) { char cmdline[64]; // cd testdir chdir(input_file); cmdline_lsall(cmdline, sizeof(cmdline)); FILE *fp_d = platform_popen(cmdline, "r"); if (fp_d == NULL) { log_print_error("_popen failed, %s\n", strerror(errno)); return -1; } long file_cnt = 0; char filename[512]; while (!feof(fp_d)) { memset(filename, 0, sizeof(filename)); fgets(filename, sizeof(filename), fp_d); if (strlen(filename) == 0) { break; } file_cnt++; del_strspace(filename, strnlen(filename, sizeof(filename)) + 4); xor_file(filename, input_pass); del_tmpfile(); } return 0; } return 0; }
完整代码（md5.c）：
#include "md5.h" #include <memory.h> unsigned char PADDING[] = { 0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 }; void MD5Init(MD5_CTX *context) { context->count[0] = 0; context->count[1] = 0; context->state[0] = 0x67452301; context->state[1] = 0xEFCDAB89; context->state[2] = 0x98BADCFE; context->state[3] = 0x10325476; } void MD5Update(MD5_CTX *context, unsigned char *input, unsigned int inputlen) { unsigned int i = 0; unsigned int index = 0; unsigned int partlen = 0; index = (context->count[0] >> 3) & 0x3F; partlen = 64 - index; context->count[0] += inputlen << 3; if (context->count[0] < (inputlen << 3)) context->count[1]++; context->count[1] += inputlen >> 29; if (inputlen >= partlen) { memcpy(&context->buffer[index], input, partlen); MD5Transform(context->state, context->buffer); for (i = partlen; i + 64 <= inputlen; i += 64) MD5Transform(context->state, &input[i]); index = 0; } else { i = 0; } memcpy(&context->buffer[index], &input[i], inputlen - i); } void MD5Final(MD5_CTX *context, unsigned char digest[16]) { unsigned int index = 0, padlen = 0; unsigned char bits[8]; index = (context->count[0] >> 3) & 0x3F; padlen = (index < 56) ? (56 - index) : (120 - index); MD5Encode(bits, context->count, 8); MD5Update(context, PADDING, padlen); MD5Update(context, bits, 8); MD5Encode(digest, context->state, 16); } void MD5Encode(unsigned char *output, unsigned int *input, unsigned int len) { unsigned int i = 0; unsigned int j = 0; while (j < len) { output[j] = input[i] & 0xFF; output[j + 1] = (input[i] >> 8) & 0xFF; output[j + 2] = (input[i] >> 16) & 0xFF; output[j + 3] = (input[i] >> 24) & 0xFF; i++; j += 4; } } void MD5Decode(unsigned int *output, unsigned char *input, unsigned int len) { unsigned int i = 0; unsigned int j = 0; while (j < len) { output[i] = (input[j]) | (input[j + 1] << 8) | (input[j + 2] << 16) | (input[j + 3] << 24); i++; j += 4; } } void MD5Transform(unsigned int state[4], unsigned char block[64]) { unsigned int a = state[0]; unsigned int b = state[1]; unsigned int c = state[2]; unsigned int d = state[3]; unsigned int x[64]; MD5Decode(x, block, 64); FF(a, b, c, d, x[0], 7, 0xd76aa478); /* 1 */ FF(d, a, b, c, x[1], 12, 0xe8c7b756); /* 2 */ FF(c, d, a, b, x[2], 17, 0x242070db); /* 3 */ FF(b, c, d, a, x[3], 22, 0xc1bdceee); /* 4 */ FF(a, b, c, d, x[4], 7, 0xf57c0faf); /* 5 */ FF(d, a, b, c, x[5], 12, 0x4787c62a); /* 6 */ FF(c, d, a, b, x[6], 17, 0xa8304613); /* 7 */ FF(b, c, d, a, x[7], 22, 0xfd469501); /* 8 */ FF(a, b, c, d, x[8], 7, 0x698098d8); /* 9 */ FF(d, a, b, c, x[9], 12, 0x8b44f7af); /* 10 */ FF(c, d, a, b, x[10], 17, 0xffff5bb1); /* 11 */ FF(b, c, d, a, x[11], 22, 0x895cd7be); /* 12 */ FF(a, b, c, d, x[12], 7, 0x6b901122); /* 13 */ FF(d, a, b, c, x[13], 12, 0xfd987193); /* 14 */ FF(c, d, a, b, x[14], 17, 0xa679438e); /* 15 */ FF(b, c, d, a, x[15], 22, 0x49b40821); /* 16 */ /* Round 2 */ GG(a, b, c, d, x[1], 5, 0xf61e2562); /* 17 */ GG(d, a, b, c, x[6], 9, 0xc040b340); /* 18 */ GG(c, d, a, b, x[11], 14, 0x265e5a51); /* 19 */ GG(b, c, d, a, x[0], 20, 0xe9b6c7aa); /* 20 */ GG(a, b, c, d, x[5], 5, 0xd62f105d); /* 21 */ GG(d, a, b, c, x[10], 9, 0x2441453); /* 22 */ GG(c, d, a, b, x[15], 14, 0xd8a1e681); /* 23 */ GG(b, c, d, a, x[4], 20, 0xe7d3fbc8); /* 24 */ GG(a, b, c, d, x[9], 5, 0x21e1cde6); /* 25 */ GG(d, a, b, c, x[14], 9, 0xc33707d6); /* 26 */ GG(c, d, a, b, x[3], 14, 0xf4d50d87); /* 27 */ GG(b, c, d, a, x[8], 20, 0x455a14ed); /* 28 */ GG(a, b, c, d, x[13], 5, 0xa9e3e905); /* 29 */ GG(d, a, b, c, x[2], 9, 0xfcefa3f8); /* 30 */ GG(c, d, a, b, x[7], 14, 0x676f02d9); /* 31 */ GG(b, c, d, a, x[12], 20, 0x8d2a4c8a); /* 32 */ /* Round 3 */ HH(a, b, c, d, x[5], 4, 0xfffa3942); /* 33 */ HH(d, a, b, c, x[8], 11, 0x8771f681); /* 34 */ HH(c, d, a, b, x[11], 16, 0x6d9d6122); /* 35 */ HH(b, c, d, a, x[14], 23, 0xfde5380c); /* 36 */ HH(a, b, c, d, x[1], 4, 0xa4beea44); /* 37 */ HH(d, a, b, c, x[4], 11, 0x4bdecfa9); /* 38 */ HH(c, d, a, b, x[7], 16, 0xf6bb4b60); /* 39 */ HH(b, c, d, a, x[10], 23, 0xbebfbc70); /* 40 */ HH(a, b, c, d, x[13], 4, 0x289b7ec6); /* 41 */ HH(d, a, b, c, x[0], 11, 0xeaa127fa); /* 42 */ HH(c, d, a, b, x[3], 16, 0xd4ef3085); /* 43 */ HH(b, c, d, a, x[6], 23, 0x4881d05); /* 44 */ HH(a, b, c, d, x[9], 4, 0xd9d4d039); /* 45 */ HH(d, a, b, c, x[12], 11, 0xe6db99e5); /* 46 */ HH(c, d, a, b, x[15], 16, 0x1fa27cf8); /* 47 */ HH(b, c, d, a, x[2], 23, 0xc4ac5665); /* 48 */ /* Round 4 */ II(a, b, c, d, x[0], 6, 0xf4292244); /* 49 */ II(d, a, b, c, x[7], 10, 0x432aff97); /* 50 */ II(c, d, a, b, x[14], 15, 0xab9423a7); /* 51 */ II(b, c, d, a, x[5], 21, 0xfc93a039); /* 52 */ II(a, b, c, d, x[12], 6, 0x655b59c3); /* 53 */ II(d, a, b, c, x[3], 10, 0x8f0ccc92); /* 54 */ II(c, d, a, b, x[10], 15, 0xffeff47d); /* 55 */ II(b, c, d, a, x[1], 21, 0x85845dd1); /* 56 */ II(a, b, c, d, x[8], 6, 0x6fa87e4f); /* 57 */ II(d, a, b, c, x[15], 10, 0xfe2ce6e0); /* 58 */ II(c, d, a, b, x[6], 15, 0xa3014314); /* 59 */ II(b, c, d, a, x[13], 21, 0x4e0811a1); /* 60 */ II(a, b, c, d, x[4], 6, 0xf7537e82); /* 61 */ II(d, a, b, c, x[11], 10, 0xbd3af235); /* 62 */ II(c, d, a, b, x[2], 15, 0x2ad7d2bb); /* 63 */ II(b, c, d, a, x[9], 21, 0xeb86d391); /* 64 */ state[0] += a; state[1] += b; state[2] += c; state[3] += d; }
完整代码（md5.h）：
#ifndef MD5_H #define MD5_H typedef struct { unsigned int count[2]; unsigned int state[4]; unsigned char buffer[64]; } MD5_CTX; #define F(x,y,z) ((x & y) | (~x & z)) #define G(x,y,z) ((x & z) | (y & ~z)) #define H(x,y,z) (x^y^z) #define I(x,y,z) (y ^ (x | ~z)) #define ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n))) #define FF(a,b,c,d,x,s,ac) \ { \ a += F(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } #define GG(a,b,c,d,x,s,ac) \ { \ a += G(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } #define HH(a,b,c,d,x,s,ac) \ { \ a += H(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } #define II(a,b,c,d,x,s,ac) \ { \ a += I(b,c,d) + x + ac; \ a = ROTATE_LEFT(a,s); \ a += b; \ } void MD5Init(MD5_CTX *context); void MD5Update(MD5_CTX *context, unsigned char *input, unsigned int inputlen); void MD5Final(MD5_CTX *context, unsigned char digest[16]); void MD5Transform(unsigned int state[4], unsigned char block[64]); void MD5Encode(unsigned char *output, unsigned int *input, unsigned int len); void MD5Decode(unsigned int *output, unsigned char *input, unsigned int len); #endif
完整代码（setup.sh）：linux下的编译脚本。
#!/bin/bash # demo_aaa.c demo_bbb.c demo_ccc.c ... target=( encrypt_video ) # mod_aaa.c mod_bbb.c mod_ccc.c ... subsrc=( md5.c ) cflags=( -lpthread ) SUDO=sudo ext_cflags="" function check_permisson() { if [ ${UID} -eq 0 ];then SUDO="" else SUDO="sudo -E" fi } function setup_all() { # gcc ${target}.c ${subsrc}.c -o ${target}.run for(( i=0;i<${#target[@]};i++)) do echo "compile ${target[i]}.c ${subsrc[@]} ${cflags[@]} ${ext_cflags} ..." gcc ${target[i]}.c ${subsrc[@]} -o ${target[i]}.run ${cflags[@]} ${ext_cflags} if [ $? -ne 0 ];then echo "compile ${target[i]}.c ${subsrc[@]} failed"; exit 1; fi echo "compile ${target[i]}.c ${subsrc[@]} ${cflags[@]} ${ext_cflags} complete" done; } function setup_clean() { rm -rf ${target[@]}.run } function help() { echo "usage: $0 all --compile program or objects" echo "usage: $0 clean --clean program or objects" } function all() { check_permisson; ext_cflags="" setup_all; } function clean() { setup_clean; } if [ $# -lt 1 ];then help; exit 1; fi $@