[c] implemented cfich_aes_cbc.c
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1 changed files with 206 additions and 0 deletions
206
TPs/TP02/c/src/cfich_aes_cbc.c
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206
TPs/TP02/c/src/cfich_aes_cbc.c
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#include <openssl/err.h>
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#include <openssl/evp.h>
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#include <openssl/rand.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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void setup(char *key_file) {
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FILE *f = fopen(key_file, "wb");
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if (f == NULL) {
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printf("Error opening file\n");
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return;
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}
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unsigned char key_bytes[32];
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if (RAND_bytes(key_bytes, 32) != 1) {
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printf("Error generating random bytes\n");
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fclose(f);
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return;
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}
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if (fwrite(key_bytes, 1, 32, f) != 32) {
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printf("Error writing to file\n");
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}
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fclose(f);
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}
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int aes(const char *input_file, const char *output_file, const char *key_file, int enc) {
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int BUF_SIZE = 1024;
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int cipher_block_size = EVP_CIPHER_block_size(EVP_aes_256_cbc());
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int input_size = BUF_SIZE;
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int output_size = input_size + (cipher_block_size - 1);
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int u_len = 0,f_len = 0;
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unsigned char input_buf[input_size], output_buf[output_size];
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FILE *finput = fopen(input_file, "rb");
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if (finput == NULL) {
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printf("Error opening input file\n");
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return 1;
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}
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// Open output file
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FILE *foutput = fopen(output_file, "wb");
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if (foutput == NULL) {
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printf("Error opening output file\n");
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fclose(finput);
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return 1;
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}
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FILE *fkey = fopen(key_file, "rb");
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if (fkey == NULL) {
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printf("Error opening key file\n");
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return 1;
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}
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unsigned char key_bytes[32];
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if (fread(key_bytes, 1, 32, fkey) != 32) {
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printf("Error reading key from file\n");
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fclose(fkey);
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return 1;
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}
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fclose(fkey);
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EVP_CIPHER_CTX *ctx = NULL;
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if (!(ctx = EVP_CIPHER_CTX_new())) {
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printf("Error creating context\n");
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fclose(finput);
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fclose(foutput);
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return 1;
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}
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// If enc is 1, then we are encrypting, else we are decrypting
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// If we are encrypting, we need to generate an IV
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// If we are decrypting, we need to read the IV from the file
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unsigned char iv[16];
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if (enc) {
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if (RAND_bytes(iv, 16) != 1) {
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printf("Error generating IV\n");
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return 1;
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}
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if (fwrite(iv, 1, 16, foutput) != 16) {
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printf("Error writing IV to file\n");
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return 1;
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}
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} else {
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if (fread(iv, 1, 16, finput) != 16) {
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printf("Error reading IV from file\n");
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return 1;
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}
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}
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if (EVP_CipherInit_ex(ctx, EVP_aes_256_cbc(), NULL, key_bytes, iv, enc) != 1) {
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fprintf(stderr, "ERROR: EVP_CipherInit_ex failed. OpenSSL error: %s\n",
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ERR_error_string(ERR_get_error(), NULL));
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EVP_CIPHER_CTX_free(ctx);
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return 1;
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}
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int read_size, len;
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while ((read_size = fread(input_buf, 1, BUF_SIZE, finput)) > 0) {
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printf("Read %d bytes, passing through CipherUpdate...\n", read_size);
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if (EVP_CipherUpdate(ctx, output_buf, &len, input_buf, read_size) != 1) {
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fprintf(stderr, "ERROR: EVP_CipherUpdate failed. OpenSSL error: %s\n",
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ERR_error_string(ERR_get_error(), NULL));
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fclose(finput);
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fclose(foutput);
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return 1;
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}
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printf("\tGot back %d bytes from CipherUpdate...\n", len);
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printf("Writing %d bytes to %s...\n", len, output_file);
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if (fwrite(output_buf, 1, len, foutput) != len) {
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printf("Error writing to output file\n");
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return 1;
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}
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printf("\tWrote %d bytes\n", len);
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u_len += len;
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}
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if (read_size == -1) {
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fprintf(stderr, "ERROR: Reading from the file %s failed.\n", input_file);
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}
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if (EVP_CipherFinal_ex(ctx, output_buf, &f_len) != 1) {
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fprintf(stderr, "ERROR: EVP_CipherFinal_ex failed. OpenSSL error: %s\n",
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ERR_error_string(ERR_get_error(), NULL));
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fclose(finput);
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fclose(foutput);
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return 1;
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}
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printf("u_len: %d, f_len: %d\n", u_len, f_len);
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if (f_len) {
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printf("Writing final %d bytes to %s...\n", f_len, output_file);
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if (fwrite(output_buf, 1, f_len, foutput) != f_len) {
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printf("Error writing to output file\n");
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fclose(finput);
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fclose(foutput);
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return 1;
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}
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}
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printf("\tWrote last %d bytes\n", f_len);
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fclose(finput);
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fclose(foutput);
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return 0;
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}
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int encrypt(char *input_file, char *key_file) {
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char *output_file = malloc(strlen(input_file) + 5);
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strcpy(output_file, input_file);
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strcat(output_file, ".enc");
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aes(input_file, output_file, key_file,1);
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return 0;
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}
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int decrypt(char *input_file, char *key_file) {
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char *output_file = malloc(strlen(input_file) + 5);
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strcpy(output_file, input_file);
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strcat(output_file, ".dec");
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aes(input_file, output_file, key_file,0);
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return 0;
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}
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int main(int argc, char *argv[]) {
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if (argc < 3) {
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fprintf(stderr, "Usage: %s {setup|enc|dec} [file_path] [key_file_path]\n", argv[0]);
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return 1;
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}
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char *mode = argv[1];
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char *file_path = argv[2];
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char *key_file_path = NULL;
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if (strcmp(mode, "setup") == 0) {
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if (argc != 3) {
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fprintf(stderr, "Usage: %s setup [key_file_path]\n", argv[0]);
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return 1;
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}
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key_file_path = file_path;
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setup(key_file_path);
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} else if (strcmp(mode, "enc") == 0 || strcmp(mode, "dec") == 0) {
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if (argc != 4) {
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fprintf(stderr,
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"Usage: %s {enc|dec} [file_path] "
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"[key_file_path]\n",
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argv[0]);
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return 1;
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}
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file_path = argv[2];
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key_file_path = argv[3];
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if (strcmp(mode, "enc") == 0)
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encrypt(file_path, key_file_path);
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else
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decrypt(file_path, key_file_path);
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} else {
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fprintf(stderr, "Invalid mode. Use 'setup', 'enc', or 'dec'.\n");
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return 1;
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}
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return 0;
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}
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