First attempt at a simple xxtea en/de-crypter.

tools/crypto/Makefile

@@ -0,0 +1,18 @@
+CC = gcc
+LD = gcc
+LDFLAGS = -Wall -O2 -std=c99
+EXES = xxtea
+TESTFILE= test.out
+
+all: $(EXES)
+
+% : %.c
+	$(LD) $(LDFLAGS) -o $@ $<
+
+clean: 
+	rm -f $(EXES) $(TESTFILE)
+
+tests: all
+	./xxtea -o $(TESTFILE) test/in.1
+	cmp $(TESTFILE) test/out.1
+	$(RM) $(TESTFILE)

tools/crypto/test/out.1

@@ -0,0 +1 @@
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tools/crypto/xxtea.c

@@ -0,0 +1,194 @@
+/* simple XXTEA en/decrypt utility
+ * 
+ * BSD Licence
+ *
+ * btea function is from 
+ * <https://secure.wikimedia.org/wikipedia/en/wiki/XXTEA#Reference_code>
+ *
+ * (c) by Sec <sec@42.org> 6/2011
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <stdint.h>
+#include <getopt.h>
+
+// default block size
+
+void btea(uint32_t *v, int n, uint32_t const k[4]);
+
+int main(int argc, char *argv[]) {
+  FILE *fp;
+  FILE *ofp;
+
+  char *prog;
+  char c;			/* for getopt */
+  uint32_t k[4];    /* key */
+  uint32_t *buf;
+
+  /* Default values */
+  char verbose=0;	// be silent
+  k[0]=0; k[1]=0; k[2]=0; k[3]=0;
+  char block=16;
+  char *outfile=NULL; // outfile == infile
+
+  /* init section */
+  prog=argv[0];
+  if(!prog)prog="xxtea";
+  if(strrchr(prog,'/')){
+	  prog=strrchr(argv[0],'/');
+	  prog++;
+  }
+
+  /* The big getopt loop */
+  while ((c = getopt(argc, argv, "vhk:b:o:")) != EOF)
+	  switch (c) {
+		  case 'v':
+			  verbose++;
+			  break;
+
+		  case 'k':
+			  // XXX: get key
+			  break;
+
+		  case 'b':
+			  block=atoi(optarg);
+			  break;
+
+		  case 'o':
+			  outfile=optarg;
+			  break;
+
+		  case 'h':
+		  default:
+			  fprintf(stderr, "Usage: %s [options] filename\n\n"
+"This program en/decrypts a file with the XXTEA algorithm\n"
+"\n\n"
+"-v           Be verbose (-v -v = even more)\n"
+"-o file      Output to <file>. (Default: overwrite input file)\n"
+"-k key       128bit hex key. [Not yet implemented]\n"
+"-b block     Set blocksize. (Default: file size)\n"
+"-h           This help\n\n"
+"\n",prog);
+			  exit(255);
+
+	  }
+
+  argc -= optind; argv += optind;
+
+  if (argc !=1){
+	  fprintf(stderr,"Error: No filename given!\n");
+	  exit(254);
+  };
+
+  if(outfile){
+      if ((fp = fopen(argv[0],"rb")) == NULL){
+          fprintf(stderr,"Error: Can't open file %s\n",argv[0]);
+          exit(253);
+      }
+      if ((ofp = fopen(outfile,"wb")) == NULL){
+          fprintf(stderr,"Error: Can't open file %s\n",argv[0]);
+          exit(253);
+      }
+  }else{
+      if ((fp = fopen(argv[0],"r+b")) == NULL){
+          fprintf(stderr,"Error: Can't open file %s\n",argv[0]);
+          exit(253);
+      }
+      ofp=fp;
+  };
+
+  if(block==0){
+      fseek(fp, 0L, SEEK_END);
+      block = ftell(fp)/sizeof(*buf); // XXX: padding!
+      fseek(fp, 0L, SEEK_SET);
+  };
+  buf=malloc(sizeof(*buf)*block);
+
+  if(!buf){
+      fprintf(stderr,"Error: malloc() failed.\n");
+  };
+
+  int cnt;
+  if (verbose)
+      fprintf(stderr,"Encrypting: ");
+
+  do{
+	  cnt=fread(buf,sizeof(*buf),block,fp); // XXX: deal with non-block-sized?
+
+      if(cnt<0){
+		  fprintf(stderr, "Error: read failed\n");
+		  exit(253);
+      };
+
+      if(verbose)
+          fprintf(stderr,"cnt=%d:",cnt);
+/*      if(cnt%sizeof(*buf)!=0){
+          fprintf(stderr,"Whoops. needs padding: cnt=%d, mod=%d\n",cnt,cnt%sizeof(*buf));
+      }; */
+
+      btea(buf, cnt, k);
+
+      if(!outfile) // in-place crypting...
+          if (fseek(fp,-cnt*sizeof(*buf),SEEK_CUR) != 0){
+              fprintf(stderr, "Error: Seek failed\n");
+              exit(253);
+          }
+
+      if (fwrite(buf,sizeof(*buf),cnt,ofp) != cnt){
+          fprintf(stderr, "Error: CRC write failed\n");
+          exit(253);
+      }
+      if(verbose) fprintf(stderr,".\n");
+  }while(cnt==block);
+
+  if(verbose)
+      fprintf(stderr,"done\n");
+
+  fclose(fp);
+
+  if(outfile)
+      fclose(ofp);
+  
+  return 0;
+}
+
+#define DELTA 0x9e3779b9
+#define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (k[(p&3)^e] ^ z)))
+
+void btea(uint32_t *v, int n, uint32_t const k[4]) {
+    uint32_t y, z, sum;
+    unsigned p, rounds, e;
+    if (n > 1) {          /* Coding Part */
+        rounds = 6 + 52/n;
+        sum = 0;
+        z = v[n-1];
+        do {
+            sum += DELTA;
+            e = (sum >> 2) & 3;
+            for (p=0; p<n-1; p++) {
+                y = v[p+1]; 
+                z = v[p] += MX;
+            }
+            y = v[0];
+            z = v[n-1] += MX;
+        } while (--rounds);
+    } else if (n < -1) {  /* Decoding Part */
+        n = -n;
+        rounds = 6 + 52/n;
+        sum = rounds*DELTA;
+        y = v[0];
+        do {
+            e = (sum >> 2) & 3;
+            for (p=n-1; p>0; p--) {
+                z = v[p-1];
+                y = v[p] -= MX;
+            }
+            z = v[n-1];
+            y = v[0] -= MX;
+        } while ((sum -= DELTA) != 0);
+    }
+}