Added signer/checker using ed25519 and libsodium I wrote for fun.

other/fun/sign.c

@@ -0,0 +1,134 @@
+/* Binary signer/checker using ed25519
+ * 
+ * Compile with:
+ *  gcc -o sign sign.c -lsodium
+ *
+ * Generate a keypair:
+ *  ./sign g
+ *
+ * Sign a file:
+ *  ./sign s PRIVATEKEY file.bin signedfile.bin
+ *
+ * Check a file:
+ *
+ * ./sign c PUBKEY signedfile.bin
+ *
+ * NOTE: The signature is appended to the end of the file.
+ */
+#include <sodium.h>
+#include <string.h>
+
+unsigned char *hex_string_to_bin(char hex_string[])
+{
+    size_t len = strlen(hex_string);
+    unsigned char *val = malloc(len);
+    char *pos = hex_string;
+    int i;
+
+    for (i = 0; i < len; ++i, pos += 2)
+        sscanf(pos, "%2hhx", &val[i]);
+
+    return val;
+}
+
+int load_file(char *filename, char **result)
+{
+    int size = 0;
+    FILE *f = fopen(filename, "rb");
+
+    if (f == NULL) {
+        *result = NULL;
+        return -1; // -1 means file opening fail
+    }
+
+    fseek(f, 0, SEEK_END);
+    size = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    *result = (char *)malloc(size + 1);
+
+    if (size != fread(*result, sizeof(char), size, f)) {
+        free(*result);
+        return -2; // -2 means file reading fail
+    }
+
+    fclose(f);
+    (*result)[size] = 0;
+    return size;
+}
+
+int main(int argc, char *argv[])
+{
+    unsigned char pk[crypto_sign_ed25519_PUBLICKEYBYTES];
+    unsigned char sk[crypto_sign_ed25519_SECRETKEYBYTES];
+    if (argc == 2 && argv[1][0] == 'g') {
+        crypto_sign_ed25519_keypair(pk, sk);
+        printf("Public key:\n");
+        int i;
+
+        for (i = 0; i < crypto_sign_ed25519_PUBLICKEYBYTES; i++) {
+            printf("%02hhX", pk[i]);
+        }
+
+        printf("\nSecret key:\n");
+
+        for (i = 0; i < crypto_sign_ed25519_SECRETKEYBYTES; i++) {
+            printf("%02hhX", sk[i]);
+        }
+
+        printf("\n");
+    }
+
+    if (argc == 5 && argv[1][0] == 's') {
+        unsigned char *secret_key = hex_string_to_bin(argv[2]);
+        char *data;
+        int size = load_file(argv[3], &data);
+
+        if (size < 0)
+            goto fail;
+
+        unsigned long long smlen;
+        char *sm = malloc(size + crypto_sign_ed25519_BYTES * 2);
+        crypto_sign_ed25519(sm, &smlen, data, size, secret_key);
+        if (smlen - size != crypto_sign_ed25519_BYTES)
+            goto fail;
+        FILE *f = fopen(argv[4], "wb");
+
+        if (f == NULL)
+            goto fail;
+        memcpy(sm + smlen, sm, crypto_sign_ed25519_BYTES); //Move signature from beginning to end of file.
+
+        if (fwrite(sm + (smlen - size), 1, smlen, f) != smlen)
+            goto fail;
+
+        fclose(f);
+        printf("Signed successfully\n");
+    }
+
+    if (argc == 4 && argv[1][0] == 'c') {
+        unsigned char *public_key = hex_string_to_bin(argv[2]);
+        char *data;
+        int size = load_file(argv[3], &data);
+
+        if (size < 0)
+            goto fail;
+
+        char *signe = malloc(size + crypto_sign_ed25519_BYTES);
+        memcpy(signe, data + size - crypto_sign_ed25519_BYTES, crypto_sign_ed25519_BYTES);//Move signature from end to beginning of file.
+        memcpy(signe + crypto_sign_ed25519_BYTES, data, size - crypto_sign_ed25519_BYTES);
+        unsigned long long smlen;
+        char *m = malloc(size);
+        unsigned long long mlen;
+
+        if (crypto_sign_ed25519_open(m, &mlen, signe, size, public_key) == -1) {
+            printf("Failed checking sig\n");
+            goto fail;
+        }
+        printf("Checked successfully\n");
+    }
+
+    return 0;
+    
+    fail:
+        printf("FAIL\n");
+        return 1;
+}