CTFs and solutions

openssl-enc/enc1.c

@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include <string.h>
+
+#include <openssl/evp.h>
+
+
+#define ENCRYPT 1
+#define DECRYPT 0
+
+int main()
+{
+    
+
+    unsigned char key[] = "0123456789ABCDEF";
+    unsigned char iv[]  = "1111111111111111";
+
+    EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
+    EVP_CipherInit(ctx,EVP_aes_128_cbc(), key, iv, ENCRYPT);
+    //This disable the padding
+    EVP_CIPHER_CTX_set_padding(ctx, 0);
+
+    unsigned char plaintext[] = "This is the plaintext to encrypt."; //len 33
+    unsigned char ciphertext[48];
+
+    int update_len, final_len;
+    int ciphertext_len=0;
+
+    EVP_CipherUpdate(ctx,ciphertext,&update_len,plaintext,strlen(plaintext));
+    ciphertext_len+=update_len;
+    printf("update size: %d\n",ciphertext_len);
+
+    EVP_CipherFinal_ex(ctx,ciphertext+ciphertext_len,&final_len);
+    ciphertext_len+=final_len;
+
+    EVP_CIPHER_CTX_free(ctx);
+
+    printf("Ciphertext lenght = %d\n", ciphertext_len);
+    for(int i = 0; i < ciphertext_len; i++)
+        printf("%02x", ciphertext[i]);
+    printf("\n");
+
+    return 0;
+}
+