Add TEA encryption tool

packages/mcp/src/Makefile

@@ -1,6 +1,6 @@
 CFLAGS = -Wall -Werror
 TARGETS = claim.cgi puzzler.cgi puzzles.cgi
-TARGETS += pointscli arc4
+TARGETS += pointscli arc4 tea
 
 all: build
 

packages/mcp/src/tea.c

@@ -0,0 +1,130 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+
+static const char magic[4] = "tea.";
+
+#define min(a,b) (((a)<(b))?(a):(b))
+
+void 
+tea_encrypt(uint32_t *v, uint32_t *k) {
+    uint32_t v0=v[0], v1=v[1], sum=0, i;           /* set up */
+    uint32_t delta=0x9e3779b9;                     /* a key schedule constant */
+    uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3];   /* cache key */
+    for (i=0; i < 32; i++) {                       /* basic cycle start */
+        sum += delta;
+        v0 += ((v1<<4) + k0) ^ (v1 + sum) ^ ((v1>>5) + k1);
+        v1 += ((v0<<4) + k2) ^ (v0 + sum) ^ ((v0>>5) + k3);  
+    }                                              /* end cycle */
+    v[0]=v0; v[1]=v1;
+}
+
+/*
+ * Use TEA in CTR mode to create a stream cipher.
+ */
+static void
+tea_apply(FILE *out, FILE *in, uint32_t *k, uint32_t ivec)
+{
+    uint32_t count = 0;
+    uint32_t v[2];
+    size_t idx = sizeof v;
+    char *p    = (char *)v;
+
+    while (1) {
+        int c = fgetc(in);
+        
+        if (EOF == c) {
+            break;
+        }
+
+        if (sizeof v == idx) {
+            v[0] = ivec;
+            v[1] = count++;
+            tea_encrypt(v, k);
+            idx = 0;
+        }
+
+        fputc(c ^ p[idx++], out);
+    }
+}
+
+int
+tea_decrypt_stream(FILE *out, FILE *in, uint32_t *k)
+{
+    uint32_t ivec;
+
+   {
+        char m[4] = {0};
+
+        fread(m, sizeof m, 1, in);
+        if (memcmp(m, magic, 4)) {
+            return -1;
+        }
+    }
+
+    fread(&ivec, sizeof ivec, 1, in);
+    tea_apply(out, in, k, ivec);
+
+    return 0;
+}
+
+int
+tea_encrypt_stream(FILE *out, FILE *in, uint32_t *k)
+{
+    uint32_t ivec;
+
+    fwrite(magic, sizeof magic, 1, out);
+
+    {
+        FILE *r = fopen("/dev/urandom", "r");
+
+        if (! r) {
+            return -1;
+        }
+        fread(&ivec, sizeof ivec, 1, r);
+        fclose(r);
+    }
+    fwrite(&ivec, sizeof ivec, 1, out);
+
+    tea_apply(out, in, k, ivec);
+
+    return 0;
+}
+
+int
+usage(const char *prog)
+{
+  fprintf(stderr, "Usage: %s [-e] <PLAINTEXT\n", prog);
+  fprintf(stderr, "\n");
+  fprintf(stderr, "You must pass in a key on fd 3 or in the environment variable KEY.\n");
+  return EX_USAGE;
+}
+
+int
+main(int argc, char *argv[])
+{
+    uint32_t key[4] = {0};
+
+    {
+        char *ekey = getenv("KEY");
+
+        if (ekey) {
+            memcpy(key, ekey, min(strlen(ekey), sizeof(key)));
+        } else if (-1 == read(3, key, sizeof(key))) {
+            return usage(argv[0]);
+        }
+    }
+
+    if (! argv[1]) {
+        tea_decrypt_stream(stdout, stdin, key);
+    } else if (0 == strcmp(argv[1], "-e")) {
+        tea_encrypt_stream(stdout, stdin, key);
+    } else {
+        return usage(argv[0]);
+    }
+
+  return 0;
+}