CTFs and solutions

openssl-dgst/hash3.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <openssl/evp.h>
+#include <openssl/err.h>
+#include <string.h>
+
+#define MAXBUF 1024
+
+int main(int argc, char **argv){
+       
+      
+        if(argc != 2){
+            fprintf(stderr,"Invalid parameters. Usage: %s filename\n",argv[0]);
+            exit(1);
+        }
+
+
+        FILE *f_in;
+        if((f_in = fopen(argv[1],"r")) == NULL) {
+                fprintf(stderr,"Couldn't open the input file, try again\n");
+                exit(1);
+        }
+
+
+       //EVP_MD_CTX *EVP_MD_CTX_new(void);
+		EVP_MD_CTX *md = EVP_MD_CTX_new();
+
+        //int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
+        // int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
+        EVP_DigestInit(md, EVP_sha256());
+
+        int n;
+        unsigned char buffer[MAXBUF];
+        while((n = fread(buffer,1,MAXBUF,f_in)) > 0){
+            EVP_DigestUpdate(md, buffer, n);
+        }
+
+        unsigned char md_value[EVP_MD_size(EVP_sha256())];
+        int md_len;
+
+        //int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s);
+        EVP_DigestFinal_ex(md, md_value, &md_len);
+
+        // void EVP_MD_CTX_free(EVP_MD_CTX *ctx);
+		EVP_MD_CTX_free(md);
+
+        printf("The digest is: ");
+        for(int i = 0; i < md_len; i++)
+			     printf("%02x", md_value[i]);
+        printf("\n");
+
+	return 0;
+
+}