Uni/CSI-ES-2324
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[c] Improved readability of cfich_chacha20.c and fixed bugs on encryption

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This commit is contained in:
Afonso Franco 2024-02-22 02:45:34 +00:00
parent c05daa0f53
commit 53ba1d56ba
Signed by: afonso
SSH key fingerprint: SHA256:JiuxZNdA5bRWXPMUJChI0AQ75yC+cXY4xM0IaVwEVys
1 changed files with 75 additions and 100 deletions
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175
TPs/TP02/c/src/cfich_chacha20.c
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@ -28,35 +28,25 @@ close:
int encrypt(char *input_file, char *key_file) {
FILE *fkey = fopen(key_file, "rb");
FILE *finput = fopen(input_file, "rb");
// Create output file
char *output_file = malloc(strlen(input_file) + 5);
output_file = strcpy(output_file, input_file);
output_file = strcat(output_file, ".enc");
FILE *foutput = fopen(output_file, "wb");
if (fkey == NULL) {
printf("Error opening key file\n");
return 1;
}
if (finput == NULL) {
printf("Error opening input file\n");
return 1;
}
if (foutput == NULL) {
printf("Error opening output file\n");
return 1;
}
unsigned char key_bytes[32];
if (fread(key_bytes, 1, 32, fkey) != 32) {
printf("Error reading key from file\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
return 1;
}
fclose(fkey);
FILE *finput = fopen(input_file, "rb");
if (finput == NULL) {
printf("Error opening input file\n");
return 1;
}
// Determining file size
fseek(finput, 0, SEEK_END);
unsigned long fsize = ftell(finput);
@ -65,27 +55,21 @@ int encrypt(char *input_file, char *key_file) {
unsigned char *plaintext = malloc(fsize * sizeof(unsigned char));
if (plaintext == NULL) {
printf("Error allocating memory\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
return 1;
}
if (fread(plaintext, 1, fsize, finput) != fsize) {
printf("Error reading file\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(plaintext);
return 1;
}
fclose(finput);
unsigned char nonce[16];
if (RAND_bytes(nonce, 16) != 1) {
printf("Error generating nonce\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(plaintext);
return 1;
}
@ -95,176 +79,167 @@ int encrypt(char *input_file, char *key_file) {
EVP_CIPHER_CTX *ctx;
if (!(ctx = EVP_CIPHER_CTX_new())) {
printf("Error creating context\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(plaintext);
return 1;
}
if (EVP_EncryptInit_ex(ctx, EVP_chacha20(), NULL, key_bytes, nonce) != 1) {
printf("Error initializing encryption\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(plaintext);
EVP_CIPHER_CTX_free(ctx);
return 1;
}
int len;
if (EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, sizeof(plaintext)) != 1) {
printf("Error encrypting\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(plaintext);
return 1;
}
if (EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, fsize) != 1) {
printf("Error encrypting\n");
EVP_CIPHER_CTX_free(ctx);
free(plaintext);
return 1;
}
if (EVP_EncryptFinal_ex(ctx, ciphertext + len, &len) != 1) {
printf("Error finalizing encryption\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
EVP_CIPHER_CTX_free(ctx);
free(plaintext);
return 1;
}
// Add the nonce to the beginning of the file
char *nonce_and_ciphertext = malloc(16 + fsize);
nonce_and_ciphertext = memcpy(nonce_and_ciphertext, nonce, 16);
nonce_and_ciphertext = memcpy(nonce_and_ciphertext + 16, ciphertext, fsize);
char *nonce_and_ciphertext = malloc(16 + (fsize * sizeof(unsigned char)));
memcpy(nonce_and_ciphertext, nonce, 16);
memcpy(nonce_and_ciphertext + 16, ciphertext, fsize);
if (fwrite(nonce_and_ciphertext, 1, 16 + fsize, foutput) != (16 + fsize)) {
printf("Error writing to output file\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(plaintext);
free(nonce_and_ciphertext);
// Create output file
char *output_file = malloc(strlen(input_file) + 5);
strcpy(output_file, input_file);
strcat(output_file, ".enc");
FILE *foutput = fopen(output_file, "wb");
if (foutput == NULL) {
printf("Error opening output file\n");
EVP_CIPHER_CTX_free(ctx);
return 1;
}
if (fwrite(nonce_and_ciphertext, 1, 16 + fsize, foutput) != (16 + fsize)) {
printf("Error writing to output file\n");
fclose(foutput);
free(plaintext);
free(nonce_and_ciphertext);
free(output_file);
EVP_CIPHER_CTX_free(ctx);
return 1;
}
fclose(fkey);
fclose(finput);
fclose(foutput);
free(plaintext);
free(nonce_and_ciphertext);
free(output_file);
EVP_CIPHER_CTX_free(ctx);
return 0;
}
int decrypt(char *input_file, char *key_file) {
FILE *fkey = fopen(key_file, "rb");
FILE *finput = fopen(input_file, "rb");
// Create output file
char *output_file = malloc(strlen(input_file) + 5);
output_file = strcpy(output_file, input_file);
output_file = strcat(output_file, ".dec");
FILE *foutput = fopen(output_file, "wb");
if (fkey == NULL) {
printf("Error opening key file\n");
return 1;
}
if (finput == NULL) {
printf("Error opening input file\n");
return 1;
}
if (foutput == NULL) {
printf("Error opening output file\n");
return 1;
}
unsigned char key_bytes[32];
if (fread(key_bytes, 1, 32, fkey) != 32) {
printf("Error reading key from file\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
return 1;
}
fclose(fkey);
FILE *finput = fopen(input_file, "rb");
if (finput == NULL) {
printf("Error opening input file\n");
return 1;
}
// Determining file size
fseek(finput, 0, SEEK_END);
unsigned long fsize = ftell(finput);
rewind(finput);
unsigned char *nounce_and_ciphertext = malloc(fsize * sizeof(unsigned char));
if (nounce_and_ciphertext == NULL) {
unsigned char *nonce_and_ciphertext = malloc(fsize * sizeof(unsigned char));
if (nonce_and_ciphertext == NULL) {
printf("Error allocating memory\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
return 1;
}
if (fread(nounce_and_ciphertext, 1, fsize, finput) != fsize) {
if (fread(nonce_and_ciphertext, 1, fsize, finput) != fsize) {
printf("Error reading file\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(nounce_and_ciphertext);
free(nonce_and_ciphertext);
return 1;
}
fclose(finput);
unsigned char nonce[16];
memcpy(nonce, nounce_and_ciphertext, 16);
memcpy(nonce, nonce_and_ciphertext, 16);
unsigned char *ciphertext = malloc((fsize * sizeof(unsigned char)) - 16);
memcpy(ciphertext, nounce_and_ciphertext + 16, fsize - 16);
memcpy(ciphertext, nonce_and_ciphertext + 16, fsize - 16);
// Decrypt the ciphertext using chacha20
unsigned char plaintext[fsize - 16];
EVP_CIPHER_CTX *ctx;
if (!(ctx = EVP_CIPHER_CTX_new())) {
printf("Error creating context\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(nounce_and_ciphertext);
free(nonce_and_ciphertext);
free(ciphertext);
return 1;
}
if (EVP_DecryptInit_ex(ctx, EVP_chacha20(), NULL, key_bytes, nonce) != 1) {
printf("Error initializing decryption\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(nounce_and_ciphertext);
free(nonce_and_ciphertext);
free(ciphertext);
return 1;
}
int len;
if (EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, fsize - 16) != 1) {
printf("Error decrypting\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(nounce_and_ciphertext);
free(nonce_and_ciphertext);
free(ciphertext);
return 1;
}
if (EVP_DecryptFinal_ex(ctx, plaintext + len, &len) != 1) {
printf("Error finalizing decryption\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(nounce_and_ciphertext);
free(nonce_and_ciphertext);
free(ciphertext);
return 1;
}
free(ciphertext);
// Create output file
char *output_file = malloc(strlen(input_file) + 5);
strcpy(output_file, input_file);
strcat(output_file, ".dec");
FILE *foutput = fopen(output_file, "wb");
if (foutput == NULL) {
printf("Error opening output file\n");
return 1;
}
if (fwrite(plaintext, 1, fsize - 16, foutput) != (fsize - 16)) {
printf("Error writing to output file\n");
fclose(fkey);
fclose(finput);
fclose(foutput);
free(nounce_and_ciphertext);
free(nonce_and_ciphertext);
free(output_file);
return 1;
}
fclose(fkey);
fclose(finput);
fclose(foutput);
free(nounce_and_ciphertext);
free(nonce_and_ciphertext);
free(output_file);
return 0;
}