1 files changed, 136 insertions, 42 deletions

diff --git a/src/common/crypto_curve25519.c b/src/common/crypto_curve25519.c
index 9e83440e16..5bb14b0d95 100644
--- a/src/common/crypto_curve25519.c
+++ b/src/common/crypto_curve25519.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2012-2013, The Tor Project, Inc. */
+/* Copyright (c) 2012-2015, The Tor Project, Inc. */
 /* See LICENSE for licensing information */
 
 /* Wrapper code for a curve25519 implementation. */
@@ -8,6 +8,7 @@
 #ifdef HAVE_SYS_STAT_H
 #include <sys/stat.h>
 #endif
+#include "container.h"
 #include "crypto.h"
 #include "crypto_curve25519.h"
 #include "util.h"
@@ -63,26 +64,44 @@ curve25519_public_key_is_ok(const curve25519_public_key_t *key)
   return !safe_mem_is_zero(key->public_key, CURVE25519_PUBKEY_LEN);
 }
 
-/** Generate a new keypair and return the secret key.  If <b>extra_strong</b>
- * is true, this key is possibly going to get used more than once, so
- * use a better-than-usual RNG. Return 0 on success, -1 on failure. */
+/**
+ * Generate CURVE25519_SECKEY_LEN random bytes in <b>out</b>. If
+ * <b>extra_strong</b> is true, this key is possibly going to get used more
+ * than once, so use a better-than-usual RNG. Return 0 on success, -1 on
+ * failure.
+ *
+ * This function does not adjust the output of the RNG at all; the will caller
+ * will need to clear or set the appropriate bits to make curve25519 work.
+ */
 int
-curve25519_secret_key_generate(curve25519_secret_key_t *key_out,
-                               int extra_strong)
+curve25519_rand_seckey_bytes(uint8_t *out, int extra_strong)
 {
   uint8_t k_tmp[CURVE25519_SECKEY_LEN];
 
-  if (crypto_rand((char*)key_out->secret_key, CURVE25519_SECKEY_LEN) < 0)
+  if (crypto_rand((char*)out, CURVE25519_SECKEY_LEN) < 0)
     return -1;
   if (extra_strong && !crypto_strongest_rand(k_tmp, CURVE25519_SECKEY_LEN)) {
     /* If they asked for extra-strong entropy and we have some, use it as an
      * HMAC key to improve not-so-good entropy rather than using it directly,
      * just in case the extra-strong entropy is less amazing than we hoped. */
-    crypto_hmac_sha256((char *)key_out->secret_key,
-                    (const char *)k_tmp, sizeof(k_tmp),
-                    (const char *)key_out->secret_key, CURVE25519_SECKEY_LEN);
+    crypto_hmac_sha256((char*) out,
+                       (const char *)k_tmp, sizeof(k_tmp),
+                       (const char *)out, CURVE25519_SECKEY_LEN);
   }
   memwipe(k_tmp, 0, sizeof(k_tmp));
+  return 0;
+}
+
+/** Generate a new keypair and return the secret key.  If <b>extra_strong</b>
+ * is true, this key is possibly going to get used more than once, so
+ * use a better-than-usual RNG. Return 0 on success, -1 on failure. */
+int
+curve25519_secret_key_generate(curve25519_secret_key_t *key_out,
+                               int extra_strong)
+{
+  if (curve25519_rand_seckey_bytes(key_out->secret_key, extra_strong) < 0)
+    return -1;
+
   key_out->secret_key[0] &= 248;
   key_out->secret_key[31] &= 127;
   key_out->secret_key[31] |= 64;
@@ -109,69 +128,144 @@ curve25519_keypair_generate(curve25519_keypair_t *keypair_out,
   return 0;
 }
 
+/** Write the <b>datalen</b> bytes from <b>data</b> to the file named
+ * <b>fname</b> in the tagged-data format.  This format contains a
+ * 32-byte header, followed by the data itself.  The header is the
+ * NUL-padded string "== <b>typestring</b>: <b>tag</b> ==".  The length
+ * of <b>typestring</b> and <b>tag</b> must therefore be no more than
+ * 24.
+ **/
 int
-curve25519_keypair_write_to_file(const curve25519_keypair_t *keypair,
-                                 const char *fname,
-                                 const char *tag)
+crypto_write_tagged_contents_to_file(const char *fname,
+                                     const char *typestring,
+                                     const char *tag,
+                                     const uint8_t *data,
+                                     size_t datalen)
 {
-  char contents[32 + CURVE25519_SECKEY_LEN + CURVE25519_PUBKEY_LEN];
-  int r;
+  char header[32];
+  smartlist_t *chunks = smartlist_new();
+  sized_chunk_t ch0, ch1;
+  int r = -1;
 
-  memset(contents, 0, sizeof(contents));
-  tor_snprintf(contents, sizeof(contents), "== c25519v1: %s ==", tag);
-  tor_assert(strlen(contents) <= 32);
-  memcpy(contents+32, keypair->seckey.secret_key, CURVE25519_SECKEY_LEN);
-  memcpy(contents+32+CURVE25519_SECKEY_LEN,
-         keypair->pubkey.public_key, CURVE25519_PUBKEY_LEN);
+  memset(header, 0, sizeof(header));
+  if (tor_snprintf(header, sizeof(header),
+                   "== %s: %s ==", typestring, tag) < 0)
+    goto end;
+  ch0.bytes = header;
+  ch0.len = 32;
+  ch1.bytes = (const char*) data;
+  ch1.len = datalen;
+  smartlist_add(chunks, &ch0);
+  smartlist_add(chunks, &ch1);
 
-  r = write_bytes_to_file(fname, contents, sizeof(contents), 1);
+  r = write_chunks_to_file(fname, chunks, 1, 0);
 
-  memwipe(contents, 0, sizeof(contents));
+ end:
+  smartlist_free(chunks);
   return r;
 }
 
-int
-curve25519_keypair_read_from_file(curve25519_keypair_t *keypair_out,
-                                  char **tag_out,
-                                  const char *fname)
+/** Read a tagged-data file from <b>fname</b> into the
+ * <b>data_out_len</b>-byte buffer in <b>data_out</b>. Check that the
+ * typestring matches <b>typestring</b>; store the tag into a newly allocated
+ * string in <b>tag_out</b>. Return -1 on failure, and the number of bytes of
+ * data on success. */
+ssize_t
+crypto_read_tagged_contents_from_file(const char *fname,
+                                      const char *typestring,
+                                      char **tag_out,
+                                      uint8_t *data_out,
+                                      ssize_t data_out_len)
 {
   char prefix[33];
-  char *content;
+  char *content = NULL;
   struct stat st;
-  int r = -1;
+  ssize_t r = -1;
+  size_t st_size = 0;
 
   *tag_out = NULL;
-
   st.st_size = 0;
   content = read_file_to_str(fname, RFTS_BIN|RFTS_IGNORE_MISSING, &st);
   if (! content)
     goto end;
-  if (st.st_size != 32 + CURVE25519_SECKEY_LEN + CURVE25519_PUBKEY_LEN)
+  if (st.st_size < 32 || st.st_size > 32 + data_out_len)
     goto end;
+  st_size = (size_t)st.st_size;
 
   memcpy(prefix, content, 32);
-  prefix[32] = '\0';
-  if (strcmpstart(prefix, "== c25519v1: ") ||
-      strcmpend(prefix, " =="))
+  prefix[32] = 0;
+  /* Check type, extract tag. */
+  if (strcmpstart(prefix, "== ") || strcmpend(prefix, " ==") ||
+      ! tor_mem_is_zero(prefix+strlen(prefix), 32-strlen(prefix)))
+    goto end;
+
+  if (strcmpstart(prefix+3, typestring) ||
+      3+strlen(typestring) >= 32 ||
+      strcmpstart(prefix+3+strlen(typestring), ": "))
     goto end;
 
-  *tag_out = tor_strndup(prefix+strlen("== c25519v1: "),
-                         strlen(prefix) - strlen("== c25519v1:  =="));
+  *tag_out = tor_strndup(prefix+5+strlen(typestring),
+                         strlen(prefix)-8-strlen(typestring));
+
+  memcpy(data_out, content+32, st_size-32);
+  r = st_size - 32;
+
+ end:
+  if (content)
+    memwipe(content, 0, st_size);
+  tor_free(content);
+  return r;
+}
+
+/** DOCDOC */
+int
+curve25519_keypair_write_to_file(const curve25519_keypair_t *keypair,
+                                 const char *fname,
+                                 const char *tag)
+{
+  uint8_t contents[CURVE25519_SECKEY_LEN + CURVE25519_PUBKEY_LEN];
+  int r;
+
+  memcpy(contents, keypair->seckey.secret_key, CURVE25519_SECKEY_LEN);
+  memcpy(contents+CURVE25519_SECKEY_LEN,
+         keypair->pubkey.public_key, CURVE25519_PUBKEY_LEN);
+
+  r = crypto_write_tagged_contents_to_file(fname,
+                                           "c25519v1",
+                                           tag,
+                                           contents,
+                                           sizeof(contents));
+
+  memwipe(contents, 0, sizeof(contents));
+  return r;
+}
+
+/** DOCDOC */
+int
+curve25519_keypair_read_from_file(curve25519_keypair_t *keypair_out,
+                                  char **tag_out,
+                                  const char *fname)
+{
+  uint8_t content[CURVE25519_SECKEY_LEN + CURVE25519_PUBKEY_LEN];
+  ssize_t len;
+  int r = -1;
+
+  len = crypto_read_tagged_contents_from_file(fname, "c25519v1", tag_out,
+                                              content, sizeof(content));
+  if (len != sizeof(content))
+    goto end;
 
-  memcpy(keypair_out->seckey.secret_key, content+32, CURVE25519_SECKEY_LEN);
+  memcpy(keypair_out->seckey.secret_key, content, CURVE25519_SECKEY_LEN);
   curve25519_public_key_generate(&keypair_out->pubkey, &keypair_out->seckey);
   if (tor_memneq(keypair_out->pubkey.public_key,
-                 content + 32 + CURVE25519_SECKEY_LEN,
+                 content + CURVE25519_SECKEY_LEN,
                  CURVE25519_PUBKEY_LEN))
     goto end;
 
   r = 0;
 
  end:
-  if (content) {
-    memwipe(content, 0, (size_t) st.st_size);
-    tor_free(content);
-  }
+  memwipe(content, 0, sizeof(content));
   if (r != 0) {
     memset(keypair_out, 0, sizeof(*keypair_out));
     tor_free(*tag_out);