Add sodium_increment()

ChangeLog

@@ -8,6 +8,8 @@ crypto_aead_chacha20poly1305_ietf_npubbytes(),
 crypto_aead_chacha20poly1305_ietf_encrypt() and
 crypto_aead_chacha20poly1305_ietf_decrypt().
  - Sodium can now be used in Windows Store apps.
+ - The sodium_increment() helper function has been added, to increment
+an arbitrary long number (such as a nonce).
 
 * Version 1.0.3
  - In addition to sodium_bin2hex(), sodium_hex2bin() is now a

src/libsodium/include/sodium/utils.h

@@ -95,6 +95,9 @@ int sodium_mprotect_readonly(void *ptr);
 SODIUM_EXPORT
 int sodium_mprotect_readwrite(void *ptr);
 
+SODIUM_EXPORT
+void sodium_increment(unsigned char *n, const size_t nlen);
+
 /* -------- */
 
 int _sodium_alloc_init(void);

src/libsodium/sodium/utils.c

@@ -510,3 +510,16 @@ sodium_mprotect_readwrite(void *ptr)
 {
     return _sodium_mprotect(ptr, _mprotect_readwrite);
 }
+
+void
+sodium_increment(unsigned char *n, const size_t nlen)
+{
+    size_t       i;
+    unsigned int c = 1U;
+
+    for (i = (size_t) 0U; i < nlen; i++) {
+        c += n[i];
+        n[i] = (unsigned char) c;
+        c >>= 8;
+    }
+}

test/default/sodium_utils.c

@@ -8,6 +8,8 @@ int main(void)
     unsigned char buf2[1000];
     char buf3[33];
     unsigned char buf4[4];
+    unsigned char nonce[24];
+    char          nonce_hex[49];
     const char *hex;
     const char *hex_end;
     size_t bin_len;
@@ -60,5 +62,26 @@ int main(void)
     }
     printf("dt5: %ld\n", (long) (hex_end - hex));
 
+    memset(nonce, 0, sizeof nonce);
+    sodium_increment(nonce, sizeof nonce);
+    printf("%s\n", sodium_bin2hex(nonce_hex, sizeof nonce_hex,
+                                  nonce, sizeof nonce));
+    memset(nonce, 255, sizeof nonce);
+    sodium_increment(nonce, sizeof nonce);
+    printf("%s\n", sodium_bin2hex(nonce_hex, sizeof nonce_hex,
+                                  nonce, sizeof nonce));
+    nonce[1] = 1U;
+    sodium_increment(nonce, sizeof nonce);
+    printf("%s\n", sodium_bin2hex(nonce_hex, sizeof nonce_hex,
+                                  nonce, sizeof nonce));
+    nonce[1] = 0U;
+    sodium_increment(nonce, sizeof nonce);
+    printf("%s\n", sodium_bin2hex(nonce_hex, sizeof nonce_hex,
+                                  nonce, sizeof nonce));
+    nonce[0] = 255U;
+    nonce[2] = 255U;
+    sodium_increment(nonce, sizeof nonce);
+    printf("%s\n", sodium_bin2hex(nonce_hex, sizeof nonce_hex,
+                                  nonce, sizeof nonce));
     return 0;
 }

test/default/sodium_utils.exp

@@ -11,3 +11,8 @@ dt2: 2
 dt3: 11
 dt4: 11
 dt5: 11
+010000000000000000000000000000000000000000000000
+000000000000000000000000000000000000000000000000
+010100000000000000000000000000000000000000000000
+020000000000000000000000000000000000000000000000
+0001ff000000000000000000000000000000000000000000