Add simple toy program for encrypting/decrypting files with AES.

aescrypt.c

@@ -0,0 +1,78 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "aes.h"
+
+#define BUFFER_SIZE 0x4000
+
+unsigned char inbuf[BUFFER_SIZE];
+unsigned char outbuf[BUFFER_SIZE];
+
+unsigned char iv[16] = "abcdefghijklmnop";
+
+int main(int argc, char **argv) {
+    FILE *infile, *outfile;
+    size_t count;
+    char *filename;
+    struct aes_context context;
+    int encrypt;
+    
+    if (argc != 4) {
+        fprintf(stderr, "wrong number of arguments\n");
+        exit(EXIT_FAILURE);
+    }
+    
+    if (strncmp(argv[1], "-d", 2) == 0) {
+        encrypt = 0;
+    } else if (strncmp(argv[1], "-e", 2) == 0) {
+        encrypt = 1;
+    }
+    
+    infile = fopen(argv[3], "rb");
+    if (infile == NULL) {
+        fprintf(stderr, "error opening input file\n");
+        return EXIT_FAILURE;
+    }
+
+    filename = malloc(strlen(argv[3]) + 5);
+    strcpy(filename, argv[3]);
+    if (encrypt) {
+        strcat(filename, ".aes");
+    } else {
+        strcat(filename, ".dec");
+    }
+    
+    outfile = fopen(filename, "wb");
+    if (filename == NULL) {
+        fprintf(stderr, "error opening output file\n");
+        return EXIT_FAILURE;
+    }
+    
+    memcpy(context.data, iv, 16);
+    strncpy(context.key, argv[2], 32);
+    
+    aes128_expandkey(&context);
+
+    do {
+        count = fread(inbuf, 1, BUFFER_SIZE, infile);
+        count = (count + 15) / 16;
+        if (encrypt) {
+            aes_cbc_encrypt(&context, inbuf, outbuf, count);
+        } else {
+            aes_cbc_decrypt(&context, inbuf, outbuf, count, iv);
+            if (count != 0)
+                memcpy(iv, inbuf + (count - 1) * 16, 16);
+        }
+        count *= 16;
+        if (fwrite(outbuf, 1, count, outfile) != count) {
+            fprintf(stderr, "error writing file\n");
+            goto finish;
+        }
+    } while (count != 0);
+
+finish:
+    fclose(infile);
+    fclose(outfile);
+    
+    free(filename);
+}