[c] implemented cfich_chacha20.c
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SHA256:JiuxZNdA5bRWXPMUJChI0AQ75yC+cXY4xM0IaVwEVys
1 changed files with 308 additions and 0 deletions
308
TPs/TP02/c/src/cfich_chacha20.c
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308
TPs/TP02/c/src/cfich_chacha20.c
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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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goto close;
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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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goto close;
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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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goto close;
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}
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goto close;
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close:
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fclose(f);
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}
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int encrypt(char *input_file, char *key_file) {
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FILE *fkey = fopen(key_file, "rb");
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FILE *finput = fopen(input_file, "rb");
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// Create output file
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char *output_file = malloc(strlen(input_file) + 5);
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output_file = strcpy(output_file, input_file);
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output_file = strcat(output_file, ".enc");
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FILE *foutput = fopen(output_file, "wb");
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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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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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if (foutput == NULL) {
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printf("Error opening output 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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fclose(finput);
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fclose(foutput);
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return 1;
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}
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// Determining file size
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fseek(finput, 0, SEEK_END);
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unsigned long fsize = ftell(finput);
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rewind(finput);
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unsigned char *plaintext = malloc(fsize * sizeof(unsigned char));
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if (plaintext == NULL) {
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printf("Error allocating memory\n");
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fclose(fkey);
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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 (fread(plaintext, 1, fsize, finput) != fsize) {
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printf("Error reading file\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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return 1;
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}
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unsigned char nonce[16];
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if (RAND_bytes(nonce, 16) != 1) {
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printf("Error generating nonce\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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return 1;
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}
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// Encrypt the plaintext using chacha20
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unsigned char ciphertext[fsize];
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EVP_CIPHER_CTX *ctx;
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if (!(ctx = EVP_CIPHER_CTX_new())) {
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printf("Error creating context\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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return 1;
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}
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if (EVP_EncryptInit_ex(ctx, EVP_chacha20(), NULL, key_bytes, nonce) != 1) {
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printf("Error initializing encryption\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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return 1;
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}
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int len;
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if (EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, sizeof(plaintext)) != 1) {
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printf("Error encrypting\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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return 1;
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}
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if (EVP_EncryptFinal_ex(ctx, ciphertext + len, &len) != 1) {
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printf("Error finalizing encryption\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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return 1;
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}
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// Add the nonce to the beginning of the file
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char *nonce_and_ciphertext = malloc(16 + fsize);
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nonce_and_ciphertext = memcpy(nonce_and_ciphertext, nonce, 16);
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nonce_and_ciphertext = memcpy(nonce_and_ciphertext + 16, ciphertext, fsize);
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if (fwrite(nonce_and_ciphertext, 1, 16 + fsize, foutput) != (16 + fsize)) {
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printf("Error writing to output file\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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free(nonce_and_ciphertext);
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return 1;
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}
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(plaintext);
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free(nonce_and_ciphertext);
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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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FILE *fkey = fopen(key_file, "rb");
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FILE *finput = fopen(input_file, "rb");
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// Create output file
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char *output_file = malloc(strlen(input_file) + 5);
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output_file = strcpy(output_file, input_file);
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output_file = strcat(output_file, ".dec");
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FILE *foutput = fopen(output_file, "wb");
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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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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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if (foutput == NULL) {
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printf("Error opening output 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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fclose(finput);
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fclose(foutput);
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return 1;
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}
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// Determining file size
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fseek(finput, 0, SEEK_END);
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unsigned long fsize = ftell(finput);
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rewind(finput);
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unsigned char *nounce_and_ciphertext = malloc(fsize * sizeof(unsigned char));
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if (nounce_and_ciphertext == NULL) {
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printf("Error allocating memory\n");
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fclose(fkey);
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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 (fread(nounce_and_ciphertext, 1, fsize, finput) != fsize) {
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printf("Error reading file\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(nounce_and_ciphertext);
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return 1;
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}
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unsigned char nonce[16];
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memcpy(nonce, nounce_and_ciphertext, 16);
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unsigned char *ciphertext = malloc((fsize * sizeof(unsigned char)) - 16);
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memcpy(ciphertext, nounce_and_ciphertext + 16, fsize - 16);
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// Decrypt the ciphertext using chacha20
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unsigned char plaintext[fsize - 16];
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EVP_CIPHER_CTX *ctx;
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if (!(ctx = EVP_CIPHER_CTX_new())) {
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printf("Error creating context\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(nounce_and_ciphertext);
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return 1;
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}
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if (EVP_DecryptInit_ex(ctx, EVP_chacha20(), NULL, key_bytes, nonce) != 1) {
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printf("Error initializing decryption\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(nounce_and_ciphertext);
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return 1;
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}
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int len;
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if (EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, fsize - 16) != 1) {
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printf("Error decrypting\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(nounce_and_ciphertext);
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return 1;
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}
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if (EVP_DecryptFinal_ex(ctx, plaintext + len, &len) != 1) {
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printf("Error finalizing decryption\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(nounce_and_ciphertext);
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return 1;
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}
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if (fwrite(plaintext, 1, fsize - 16, foutput) != (fsize - 16)) {
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printf("Error writing to output file\n");
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(nounce_and_ciphertext);
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return 1;
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}
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fclose(fkey);
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fclose(finput);
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fclose(foutput);
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free(nounce_and_ciphertext);
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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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