1 files changed, 98 insertions, 0 deletions
diff --git a/src/feature/dirparse/signing.c b/src/feature/dirparse/signing.c
new file mode 100644
index 0000000000..8d6a40605b
--- /dev/null
+++ b/src/feature/dirparse/signing.c
@@ -0,0 +1,98 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file signing.c
+ * \brief Code to sign directory objects.
+ **/
+
+#include "core/or/or.h"
+#include "feature/dirparse/signing.h"
+
+/** Helper: used to generate signatures for routers, directories and
+ * network-status objects.  Given a <b>digest_len</b>-byte digest in
+ * <b>digest</b> and a secret <b>private_key</b>, generate an PKCS1-padded
+ * signature, BASE64-encode it, surround it with -----BEGIN/END----- pairs,
+ * and return the new signature on success or NULL on failure.
+ */
+char *
+router_get_dirobj_signature(const char *digest,
+                            size_t digest_len,
+                            const crypto_pk_t *private_key)
+{
+  char *signature;
+  size_t i, keysize;
+  int siglen;
+  char *buf = NULL;
+  size_t buf_len;
+  /* overestimate of BEGIN/END lines total len. */
+#define BEGIN_END_OVERHEAD_LEN 64
+
+  keysize = crypto_pk_keysize(private_key);
+  signature = tor_malloc(keysize);
+  siglen = crypto_pk_private_sign(private_key, signature, keysize,
+                                  digest, digest_len);
+  if (siglen < 0) {
+    log_warn(LD_BUG,"Couldn't sign digest.");
+    goto err;
+  }
+
+  /* The *2 here is a ridiculous overestimate of base-64 overhead. */
+  buf_len = (siglen * 2) + BEGIN_END_OVERHEAD_LEN;
+  buf = tor_malloc(buf_len);
+
+  if (strlcpy(buf, "-----BEGIN SIGNATURE-----\n", buf_len) >= buf_len)
+    goto truncated;
+
+  i = strlen(buf);
+  if (base64_encode(buf+i, buf_len-i, signature, siglen,
+                    BASE64_ENCODE_MULTILINE) < 0) {
+    log_warn(LD_BUG,"couldn't base64-encode signature");
+    goto err;
+  }
+
+  if (strlcat(buf, "-----END SIGNATURE-----\n", buf_len) >= buf_len)
+    goto truncated;
+
+  tor_free(signature);
+  return buf;
+
+ truncated:
+  log_warn(LD_BUG,"tried to exceed string length.");
+ err:
+  tor_free(signature);
+  tor_free(buf);
+  return NULL;
+}
+
+/** Helper: used to generate signatures for routers, directories and
+ * network-status objects.  Given a digest in <b>digest</b> and a secret
+ * <b>private_key</b>, generate a PKCS1-padded signature, BASE64-encode it,
+ * surround it with -----BEGIN/END----- pairs, and write it to the
+ * <b>buf_len</b>-byte buffer at <b>buf</b>.  Return 0 on success, -1 on
+ * failure.
+ */
+int
+router_append_dirobj_signature(char *buf, size_t buf_len, const char *digest,
+                               size_t digest_len, crypto_pk_t *private_key)
+{
+  size_t sig_len, s_len;
+  char *sig = router_get_dirobj_signature(digest, digest_len, private_key);
+  if (!sig) {
+    log_warn(LD_BUG, "No signature generated");
+    return -1;
+  }
+  sig_len = strlen(sig);
+  s_len = strlen(buf);
+  if (sig_len + s_len + 1 > buf_len) {
+    log_warn(LD_BUG, "Not enough room for signature");
+    tor_free(sig);
+    return -1;
+  }
+  memcpy(buf+s_len, sig, sig_len+1);
+  tor_free(sig);
+  return 0;
+}