1 files changed, 187 insertions, 0 deletions
diff --git a/src/common/crypto_pwbox.c b/src/common/crypto_pwbox.c
new file mode 100644
index 0000000000..b866c7ef39
--- /dev/null
+++ b/src/common/crypto_pwbox.c
@@ -0,0 +1,187 @@
+
+#include "crypto.h"
+#include "crypto_s2k.h"
+#include "crypto_pwbox.h"
+#include "di_ops.h"
+#include "util.h"
+#include "pwbox.h"
+
+/* 8 bytes "TORBOX00"
+   1 byte: header len (H)
+   H bytes: header, denoting secret key algorithm.
+   16 bytes: IV
+   Round up to multiple of 128 bytes, then encrypt:
+      4 bytes: data len
+      data
+      zeros
+   32 bytes: HMAC-SHA256 of all previous bytes.
+*/
+
+#define MAX_OVERHEAD (S2K_MAXLEN + 8 + 1 + 32 + CIPHER_IV_LEN)
+
+/**
+ * Make an authenticated passphrase-encrypted blob to encode the
+ * <b>input_len</b> bytes in <b>input</b> using the passphrase
+ * <b>secret</b> of <b>secret_len</b> bytes.  Allocate a new chunk of memory
+ * to hold the encrypted data, and store a pointer to that memory in
+ * *<b>out</b>, and its size in <b>outlen_out</b>.  Use <b>s2k_flags</b> as an
+ * argument to the passphrase-hashing function.
+ */
+int
+crypto_pwbox(uint8_t **out, size_t *outlen_out,
+             const uint8_t *input, size_t input_len,
+             const char *secret, size_t secret_len,
+             unsigned s2k_flags)
+{
+  uint8_t *result = NULL, *encrypted_portion;
+  size_t encrypted_len = 128 * CEIL_DIV(input_len+4, 128);
+  ssize_t result_len;
+  int spec_len;
+  uint8_t keys[CIPHER_KEY_LEN + DIGEST256_LEN];
+  pwbox_encoded_t *enc = NULL;
+  ssize_t enc_len;
+
+  crypto_cipher_t *cipher;
+  int rv;
+
+  enc = pwbox_encoded_new();
+
+  pwbox_encoded_setlen_skey_header(enc, S2K_MAXLEN);
+
+  spec_len = secret_to_key_make_specifier(
+                                      pwbox_encoded_getarray_skey_header(enc),
+                                      S2K_MAXLEN,
+                                      s2k_flags);
+  if (spec_len < 0 || spec_len > S2K_MAXLEN)
+    goto err;
+  pwbox_encoded_setlen_skey_header(enc, spec_len);
+  enc->header_len = spec_len;
+
+  crypto_rand((char*)enc->iv, sizeof(enc->iv));
+
+  pwbox_encoded_setlen_data(enc, encrypted_len);
+  encrypted_portion = pwbox_encoded_getarray_data(enc);
+
+  set_uint32(encrypted_portion, htonl((uint32_t)input_len));
+  memcpy(encrypted_portion+4, input, input_len);
+
+  /* Now that all the data is in position, derive some keys, encrypt, and
+   * digest */
+  if (secret_to_key_derivekey(keys, sizeof(keys),
+                              pwbox_encoded_getarray_skey_header(enc),
+                              spec_len,
+                              secret, secret_len) < 0)
+    goto err;
+
+  cipher = crypto_cipher_new_with_iv((char*)keys, (char*)enc->iv);
+  crypto_cipher_crypt_inplace(cipher, (char*)encrypted_portion, encrypted_len);
+  crypto_cipher_free(cipher);
+
+  result_len = pwbox_encoded_encoded_len(enc);
+  if (result_len < 0)
+    goto err;
+  result = tor_malloc(result_len);
+  enc_len = pwbox_encoded_encode(result, result_len, enc);
+  if (enc_len < 0)
+    goto err;
+  tor_assert(enc_len == result_len);
+
+  crypto_hmac_sha256((char*) result + result_len - 32,
+                     (const char*)keys + CIPHER_KEY_LEN,
+                     DIGEST256_LEN,
+                     (const char*)result,
+                     result_len - 32);
+
+  *out = result;
+  *outlen_out = result_len;
+  rv = 0;
+  goto out;
+
+ err:
+  tor_free(result);
+  rv = -1;
+
+ out:
+  pwbox_encoded_free(enc);
+  memwipe(keys, 0, sizeof(keys));
+  return rv;
+}
+
+/**
+ * Try to decrypt the passphrase-encrypted blob of <b>input_len</b> bytes in
+ * <b>input</b> using the passphrase <b>secret</b> of <b>secret_len</b> bytes.
+ * On success, return 0 and allocate a new chunk of memory to hold the
+ * decrypted data, and store a pointer to that memory in *<b>out</b>, and its
+ * size in <b>outlen_out</b>.  On failure, return UNPWBOX_BAD_SECRET if
+ * the passphrase might have been wrong, and UNPWBOX_CORRUPT if the object is
+ * definitely corrupt.
+ */
+int
+crypto_unpwbox(uint8_t **out, size_t *outlen_out,
+               const uint8_t *inp, size_t input_len,
+               const char *secret, size_t secret_len)
+{
+  uint8_t *result = NULL;
+  const uint8_t *encrypted;
+  uint8_t keys[CIPHER_KEY_LEN + DIGEST256_LEN];
+  uint8_t hmac[DIGEST256_LEN];
+  uint32_t result_len;
+  size_t encrypted_len;
+  crypto_cipher_t *cipher = NULL;
+  int rv = UNPWBOX_CORRUPTED;
+  ssize_t got_len;
+
+  pwbox_encoded_t *enc = NULL;
+
+  got_len = pwbox_encoded_parse(&enc, inp, input_len);
+  if (got_len < 0 || (size_t)got_len != input_len)
+    goto err;
+
+  /* Now derive the keys and check the hmac. */
+  if (secret_to_key_derivekey(keys, sizeof(keys),
+                              pwbox_encoded_getarray_skey_header(enc),
+                              pwbox_encoded_getlen_skey_header(enc),
+                              secret, secret_len) < 0)
+    goto err;
+
+  crypto_hmac_sha256((char *)hmac,
+                     (const char*)keys + CIPHER_KEY_LEN, DIGEST256_LEN,
+                     (const char*)inp, input_len - DIGEST256_LEN);
+
+  if (tor_memneq(hmac, enc->hmac, DIGEST256_LEN)) {
+    rv = UNPWBOX_BAD_SECRET;
+    goto err;
+  }
+
+  /* How long is the plaintext? */
+  encrypted = pwbox_encoded_getarray_data(enc);
+  encrypted_len = pwbox_encoded_getlen_data(enc);
+  if (encrypted_len < 4)
+    goto err;
+
+  cipher = crypto_cipher_new_with_iv((char*)keys, (char*)enc->iv);
+  crypto_cipher_decrypt(cipher, (char*)&result_len, (char*)encrypted, 4);
+  result_len = ntohl(result_len);
+  if (encrypted_len < result_len + 4)
+    goto err;
+
+  /* Allocate a buffer and decrypt */
+  result = tor_malloc_zero(result_len);
+  crypto_cipher_decrypt(cipher, (char*)result, (char*)encrypted+4, result_len);
+
+  *out = result;
+  *outlen_out = result_len;
+
+  rv = UNPWBOX_OKAY;
+  goto out;
+
+ err:
+  tor_free(result);
+
+ out:
+  crypto_cipher_free(cipher);
+  pwbox_encoded_free(enc);
+  memwipe(keys, 0, sizeof(keys));
+  return rv;
+}
+