Split crypto and tls libraries into directories

I am calling the crypto library "crypt_ops", since I want
higher-level crypto things to be separated from lower-level ones.
This library will hold only the low-level ones, once we have it
refactored.

1 files changed, 817 insertions, 0 deletions

diff --git a/src/lib/crypt_ops/crypto_ed25519.c b/src/lib/crypt_ops/crypto_ed25519.c
new file mode 100644
index 0000000000..b0b954796c
--- /dev/null
+++ b/src/lib/crypt_ops/crypto_ed25519.c
@@ -0,0 +1,817 @@
+/* Copyright (c) 2013-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file crypto_ed25519.c
+ *
+ * \brief Wrapper code for an ed25519 implementation.
+ *
+ * Ed25519 is a Schnorr signature on a Twisted Edwards curve, defined
+ * by Dan Bernstein. For more information, see https://ed25519.cr.yp.to/
+ *
+ * This module wraps our choice of Ed25519 backend, and provides a few
+ * convenience functions for checking and generating signatures.  It also
+ * provides Tor-specific tools for key blinding and for converting Ed25519
+ * keys to and from the corresponding Curve25519 keys.
+ */
+
+#define CRYPTO_ED25519_PRIVATE
+#include "orconfig.h"
+#ifdef HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
+
+#include "common/crypto_curve25519.h"
+#include "common/crypto_digest.h"
+#include "common/crypto_ed25519.h"
+#include "common/crypto_format.h"
+#include "common/crypto_rand.h"
+#include "common/crypto_util.h"
+#include "common/torlog.h"
+#include "common/util.h"
+#include "common/util_format.h"
+
+#include "ed25519/ref10/ed25519_ref10.h"
+#include "ed25519/donna/ed25519_donna_tor.h"
+
+static void pick_ed25519_impl(void);
+
+/** An Ed25519 implementation, as a set of function pointers. */
+typedef struct {
+  int (*selftest)(void);
+
+  int (*seckey)(unsigned char *);
+  int (*seckey_expand)(unsigned char *, const unsigned char *);
+  int (*pubkey)(unsigned char *, const unsigned char *);
+  int (*keygen)(unsigned char *, unsigned char *);
+
+  int (*open)(const unsigned char *, const unsigned char *, size_t, const
+              unsigned char *);
+  int (*sign)(unsigned char *, const unsigned char *, size_t,
+              const unsigned char *, const unsigned char *);
+  int (*open_batch)(const unsigned char **, size_t *, const unsigned char **,
+                    const unsigned char **, size_t, int *);
+
+  int (*blind_secret_key)(unsigned char *, const unsigned char *,
+                          const unsigned char *);
+  int (*blind_public_key)(unsigned char *, const unsigned char *,
+                          const unsigned char *);
+
+  int (*pubkey_from_curve25519_pubkey)(unsigned char *, const unsigned char *,
+                                       int);
+
+  int (*ed25519_scalarmult_with_group_order)(unsigned char *,
+                                             const unsigned char *);
+} ed25519_impl_t;
+
+/** The Ref10 Ed25519 implementation. This one is pure C and lightly
+ * optimized. */
+static const ed25519_impl_t impl_ref10 = {
+  NULL,
+
+  ed25519_ref10_seckey,
+  ed25519_ref10_seckey_expand,
+  ed25519_ref10_pubkey,
+  ed25519_ref10_keygen,
+
+  ed25519_ref10_open,
+  ed25519_ref10_sign,
+  NULL,
+
+  ed25519_ref10_blind_secret_key,
+  ed25519_ref10_blind_public_key,
+
+  ed25519_ref10_pubkey_from_curve25519_pubkey,
+  ed25519_ref10_scalarmult_with_group_order,
+};
+
+/** The Ref10 Ed25519 implementation. This one is heavily optimized, but still
+ * mostly C. The C still tends to be heavily platform-specific. */
+static const ed25519_impl_t impl_donna = {
+  ed25519_donna_selftest,
+
+  ed25519_donna_seckey,
+  ed25519_donna_seckey_expand,
+  ed25519_donna_pubkey,
+  ed25519_donna_keygen,
+
+  ed25519_donna_open,
+  ed25519_donna_sign,
+  ed25519_sign_open_batch_donna,
+
+  ed25519_donna_blind_secret_key,
+  ed25519_donna_blind_public_key,
+
+  ed25519_donna_pubkey_from_curve25519_pubkey,
+  ed25519_donna_scalarmult_with_group_order,
+};
+
+/** Which Ed25519 implementation are we using?  NULL if we haven't decided
+ * yet. */
+static const ed25519_impl_t *ed25519_impl = NULL;
+
+/** Helper: Return our chosen Ed25519 implementation.
+ *
+ * This should only be called after we've picked an implementation, but
+ * it _does_ recover if you forget this.
+ **/
+static inline const ed25519_impl_t *
+get_ed_impl(void)
+{
+  if (BUG(ed25519_impl == NULL)) {
+    pick_ed25519_impl(); // LCOV_EXCL_LINE - We always call ed25519_init().
+  }
+  return ed25519_impl;
+}
+
+#ifdef TOR_UNIT_TESTS
+/** For testing: used to remember our actual choice of Ed25519
+ * implementation */
+static const ed25519_impl_t *saved_ed25519_impl = NULL;
+/** For testing: Use the Ed25519 implementation called <b>name</b> until
+ * crypto_ed25519_testing_restore_impl is called.  Recognized names are
+ * "donna" and "ref10". */
+void
+crypto_ed25519_testing_force_impl(const char *name)
+{
+  tor_assert(saved_ed25519_impl == NULL);
+  saved_ed25519_impl = ed25519_impl;
+  if (! strcmp(name, "donna")) {
+    ed25519_impl = &impl_donna;
+  } else {
+    tor_assert(!strcmp(name, "ref10"));
+    ed25519_impl = &impl_ref10;
+  }
+}
+/** For testing: go back to whatever Ed25519 implementation we had picked
+ * before crypto_ed25519_testing_force_impl was called.
+ */
+void
+crypto_ed25519_testing_restore_impl(void)
+{
+  ed25519_impl = saved_ed25519_impl;
+  saved_ed25519_impl = NULL;
+}
+#endif /* defined(TOR_UNIT_TESTS) */
+
+/**
+ * Initialize a new ed25519 secret key in <b>seckey_out</b>.  If
+ * <b>extra_strong</b>, take the RNG inputs directly from the operating
+ * system.  Return 0 on success, -1 on failure.
+ */
+int
+ed25519_secret_key_generate(ed25519_secret_key_t *seckey_out,
+                        int extra_strong)
+{
+  int r;
+  uint8_t seed[32];
+  if (extra_strong)
+    crypto_strongest_rand(seed, sizeof(seed));
+ else
+    crypto_rand((char*)seed, sizeof(seed));
+
+  r = get_ed_impl()->seckey_expand(seckey_out->seckey, seed);
+  memwipe(seed, 0, sizeof(seed));
+
+  return r < 0 ? -1 : 0;
+}
+
+/**
+ * Given a 32-byte random seed in <b>seed</b>, expand it into an ed25519
+ * secret key in <b>seckey_out</b>.  Return 0 on success, -1 on failure.
+ */
+int
+ed25519_secret_key_from_seed(ed25519_secret_key_t *seckey_out,
+                             const uint8_t *seed)
+{
+  if (get_ed_impl()->seckey_expand(seckey_out->seckey, seed) < 0)
+     return -1;
+  return 0;
+}
+
+/**
+ * Given a secret key in <b>seckey</b>, expand it into an
+ * ed25519 public key.  Return 0 on success, -1 on failure.
+ */
+int
+ed25519_public_key_generate(ed25519_public_key_t *pubkey_out,
+                        const ed25519_secret_key_t *seckey)
+{
+  if (get_ed_impl()->pubkey(pubkey_out->pubkey, seckey->seckey) < 0)
+    return -1;
+  return 0;
+}
+
+/** Generate a new ed25519 keypair in <b>keypair_out</b>.  If
+ * <b>extra_strong</b> is set, try to mix some system entropy into the key
+ * generation process. Return 0 on success, -1 on failure. */
+int
+ed25519_keypair_generate(ed25519_keypair_t *keypair_out, int extra_strong)
+{
+  if (ed25519_secret_key_generate(&keypair_out->seckey, extra_strong) < 0)
+    return -1;
+  if (ed25519_public_key_generate(&keypair_out->pubkey,
+                                  &keypair_out->seckey)<0)
+    return -1;
+  return 0;
+}
+
+/** Return true iff 'pubkey' is set to zero (eg to indicate that it is not
+ * set). */
+int
+ed25519_public_key_is_zero(const ed25519_public_key_t *pubkey)
+{
+  return tor_mem_is_zero((char*)pubkey->pubkey, ED25519_PUBKEY_LEN);
+}
+
+/* Return a heap-allocated array that contains <b>msg</b> prefixed by the
+ * string <b>prefix_str</b>. Set <b>final_msg_len_out</b> to the size of the
+ * final array. If an error occurred, return NULL. It's the responsibility of
+ * the caller to free the returned array. */
+static uint8_t *
+get_prefixed_msg(const uint8_t *msg, size_t msg_len,
+                 const char *prefix_str,
+                 size_t *final_msg_len_out)
+{
+  size_t prefixed_msg_len, prefix_len;
+  uint8_t *prefixed_msg;
+
+  tor_assert(prefix_str);
+  tor_assert(final_msg_len_out);
+
+  prefix_len = strlen(prefix_str);
+
+  /* msg_len + strlen(prefix_str) must not overflow. */
+  if (msg_len > SIZE_T_CEILING - prefix_len) {
+    return NULL;
+  }
+
+  prefixed_msg_len = msg_len + prefix_len;
+  prefixed_msg = tor_malloc_zero(prefixed_msg_len);
+
+  memcpy(prefixed_msg, prefix_str, prefix_len);
+  memcpy(prefixed_msg + prefix_len, msg, msg_len);
+
+  *final_msg_len_out = prefixed_msg_len;
+  return prefixed_msg;
+}
+
+/**
+ * Set <b>signature_out</b> to a signature of the <b>len</b>-byte message
+ * <b>msg</b>, using the secret and public key in <b>keypair</b>.
+ *
+ * Return 0 if we successfully signed the message, otherwise return -1.
+ */
+int
+ed25519_sign(ed25519_signature_t *signature_out,
+             const uint8_t *msg, size_t len,
+             const ed25519_keypair_t *keypair)
+{
+  if (get_ed_impl()->sign(signature_out->sig, msg, len,
+                          keypair->seckey.seckey,
+                          keypair->pubkey.pubkey) < 0) {
+    return -1;
+  }
+
+  return 0;
+}
+
+/**
+ * Like ed25519_sign(), but also prefix <b>msg</b> with <b>prefix_str</b>
+ * before signing. <b>prefix_str</b> must be a NUL-terminated string.
+ */
+MOCK_IMPL(int,
+ed25519_sign_prefixed,(ed25519_signature_t *signature_out,
+                       const uint8_t *msg, size_t msg_len,
+                       const char *prefix_str,
+                       const ed25519_keypair_t *keypair))
+{
+  int retval;
+  size_t prefixed_msg_len;
+  uint8_t *prefixed_msg;
+
+  tor_assert(prefix_str);
+
+  prefixed_msg = get_prefixed_msg(msg, msg_len, prefix_str,
+                                  &prefixed_msg_len);
+  if (BUG(!prefixed_msg)) {
+    /* LCOV_EXCL_START -- only possible when the message and prefix are
+     * ridiculously huge */
+    log_warn(LD_GENERAL, "Failed to get prefixed msg.");
+    return -1;
+    /* LCOV_EXCL_STOP */
+  }
+
+  retval = ed25519_sign(signature_out,
+                        prefixed_msg, prefixed_msg_len,
+                        keypair);
+  tor_free(prefixed_msg);
+
+  return retval;
+}
+
+/**
+ * Check whether if <b>signature</b> is a valid signature for the
+ * <b>len</b>-byte message in <b>msg</b> made with the key <b>pubkey</b>.
+ *
+ * Return 0 if the signature is valid; -1 if it isn't.
+ */
+MOCK_IMPL(int,
+ed25519_checksig,(const ed25519_signature_t *signature,
+                  const uint8_t *msg, size_t len,
+                  const ed25519_public_key_t *pubkey))
+{
+  return
+    get_ed_impl()->open(signature->sig, msg, len, pubkey->pubkey) < 0 ? -1 : 0;
+}
+
+/**
+ * Like ed2519_checksig(), but also prefix <b>msg</b> with <b>prefix_str</b>
+ * before verifying signature. <b>prefix_str</b> must be a NUL-terminated
+ * string.
+ */
+int
+ed25519_checksig_prefixed(const ed25519_signature_t *signature,
+                          const uint8_t *msg, size_t msg_len,
+                          const char *prefix_str,
+                          const ed25519_public_key_t *pubkey)
+{
+  int retval;
+  size_t prefixed_msg_len;
+  uint8_t *prefixed_msg;
+
+  prefixed_msg = get_prefixed_msg(msg, msg_len, prefix_str,
+                                  &prefixed_msg_len);
+  if (BUG(!prefixed_msg)) {
+    /* LCOV_EXCL_START -- only possible when the message and prefix are
+     * ridiculously huge */
+    log_warn(LD_GENERAL, "Failed to get prefixed msg.");
+    return -1;
+    /* LCOV_EXCL_STOP */
+  }
+
+  retval = ed25519_checksig(signature,
+                            prefixed_msg, prefixed_msg_len,
+                            pubkey);
+  tor_free(prefixed_msg);
+
+  return retval;
+}
+
+/** Validate every signature among those in <b>checkable</b>, which contains
+ * exactly <b>n_checkable</b> elements.  If <b>okay_out</b> is non-NULL, set
+ * the i'th element of <b>okay_out</b> to 1 if the i'th element of
+ * <b>checkable</b> is valid, and to 0 otherwise.  Return 0 if every signature
+ * was valid. Otherwise return -N, where N is the number of invalid
+ * signatures.
+ */
+MOCK_IMPL(int,
+ed25519_checksig_batch,(int *okay_out,
+                        const ed25519_checkable_t *checkable,
+                        int n_checkable))
+{
+  int i, res;
+  const ed25519_impl_t *impl = get_ed_impl();
+
+  if (impl->open_batch == NULL) {
+    /* No batch verification implementation available, fake it by checking the
+     * each signature individually.
+     */
+    res = 0;
+    for (i = 0; i < n_checkable; ++i) {
+      const ed25519_checkable_t *ch = &checkable[i];
+      int r = ed25519_checksig(&ch->signature, ch->msg, ch->len, ch->pubkey);
+      if (r < 0)
+        --res;
+      if (okay_out)
+        okay_out[i] = (r == 0);
+    }
+  } else {
+    /* ed25519-donna style batch verification available.
+     *
+     * Theoretically, this should only be called if n_checkable >= 3, since
+     * that's the threshold where the batch verification actually kicks in,
+     * but the only difference is a few mallocs/frees.
+     */
+    const uint8_t **ms;
+    size_t *lens;
+    const uint8_t **pks;
+    const uint8_t **sigs;
+    int *oks;
+    int all_ok;
+
+    ms = tor_calloc(n_checkable, sizeof(uint8_t*));
+    lens = tor_calloc(n_checkable, sizeof(size_t));
+    pks = tor_calloc(n_checkable, sizeof(uint8_t*));
+    sigs = tor_calloc(n_checkable, sizeof(uint8_t*));
+    oks = okay_out ? okay_out : tor_calloc(n_checkable, sizeof(int));
+
+    for (i = 0; i < n_checkable; ++i) {
+      ms[i] = checkable[i].msg;
+      lens[i] = checkable[i].len;
+      pks[i] = checkable[i].pubkey->pubkey;
+      sigs[i] = checkable[i].signature.sig;
+      oks[i] = 0;
+    }
+
+    res = 0;
+    all_ok = impl->open_batch(ms, lens, pks, sigs, n_checkable, oks);
+    for (i = 0; i < n_checkable; ++i) {
+      if (!oks[i])
+        --res;
+    }
+    /* XXX: For now sanity check oks with the return value.  Once we have
+     * more confidence in the code, if `all_ok == 0` we can skip iterating
+     * over oks since all the signatures were found to be valid.
+     */
+    tor_assert(((res == 0) && !all_ok) || ((res < 0) && all_ok));
+
+    tor_free(ms);
+    tor_free(lens);
+    tor_free(pks);
+    tor_free(sigs);
+    if (! okay_out)
+      tor_free(oks);
+  }
+
+  return res;
+}
+
+/**
+ * Given a curve25519 keypair in <b>inp</b>, generate a corresponding
+ * ed25519 keypair in <b>out</b>, and set <b>signbit_out</b> to the
+ * sign bit of the X coordinate of the ed25519 key.
+ *
+ * NOTE THAT IT IS PROBABLY NOT SAFE TO USE THE GENERATED KEY FOR ANYTHING
+ * OUTSIDE OF WHAT'S PRESENTED IN PROPOSAL 228.  In particular, it's probably
+ * not a great idea to use it to sign attacker-supplied anything.
+ */
+int
+ed25519_keypair_from_curve25519_keypair(ed25519_keypair_t *out,
+                                        int *signbit_out,
+                                        const curve25519_keypair_t *inp)
+{
+  const char string[] = "Derive high part of ed25519 key from curve25519 key";
+  ed25519_public_key_t pubkey_check;
+  crypto_digest_t *ctx;
+  uint8_t sha512_output[DIGEST512_LEN];
+
+  memcpy(out->seckey.seckey, inp->seckey.secret_key, 32);
+
+  ctx = crypto_digest512_new(DIGEST_SHA512);
+  crypto_digest_add_bytes(ctx, (const char*)out->seckey.seckey, 32);
+  crypto_digest_add_bytes(ctx, (const char*)string, sizeof(string));
+  crypto_digest_get_digest(ctx, (char *)sha512_output, sizeof(sha512_output));
+  crypto_digest_free(ctx);
+  memcpy(out->seckey.seckey + 32, sha512_output, 32);
+
+  ed25519_public_key_generate(&out->pubkey, &out->seckey);
+
+  *signbit_out = out->pubkey.pubkey[31] >> 7;
+
+  ed25519_public_key_from_curve25519_public_key(&pubkey_check, &inp->pubkey,
+                                                *signbit_out);
+
+  tor_assert(fast_memeq(pubkey_check.pubkey, out->pubkey.pubkey, 32));
+
+  memwipe(&pubkey_check, 0, sizeof(pubkey_check));
+  memwipe(sha512_output, 0, sizeof(sha512_output));
+
+  return 0;
+}
+
+/**
+ * Given a curve25519 public key and sign bit of X coordinate of the ed25519
+ * public key, generate the corresponding ed25519 public key.
+ */
+int
+ed25519_public_key_from_curve25519_public_key(ed25519_public_key_t *pubkey,
+                                     const curve25519_public_key_t *pubkey_in,
+                                     int signbit)
+{
+  return get_ed_impl()->pubkey_from_curve25519_pubkey(pubkey->pubkey,
+                                                      pubkey_in->public_key,
+                                                      signbit);
+}
+
+/**
+ * Given an ed25519 keypair in <b>inp</b>, generate a corresponding
+ * ed25519 keypair in <b>out</b>, blinded by the corresponding 32-byte input
+ * in 'param'.
+ *
+ * Tor uses key blinding for the "next-generation" hidden services design:
+ * service descriptors are encrypted with a key derived from the service's
+ * long-term public key, and then signed with (and stored at a position
+ * indexed by) a short-term key derived by blinding the long-term keys.
+ *
+ * Return 0 if blinding was successful, else return -1. */
+int
+ed25519_keypair_blind(ed25519_keypair_t *out,
+                      const ed25519_keypair_t *inp,
+                      const uint8_t *param)
+{
+  ed25519_public_key_t pubkey_check;
+
+  get_ed_impl()->blind_secret_key(out->seckey.seckey,
+                                  inp->seckey.seckey, param);
+
+  if (ed25519_public_blind(&pubkey_check, &inp->pubkey, param) < 0) {
+    return -1;
+  }
+  ed25519_public_key_generate(&out->pubkey, &out->seckey);
+
+  tor_assert(fast_memeq(pubkey_check.pubkey, out->pubkey.pubkey, 32));
+
+  memwipe(&pubkey_check, 0, sizeof(pubkey_check));
+
+  return 0;
+}
+
+/**
+ * Given an ed25519 public key in <b>inp</b>, generate a corresponding blinded
+ * public key in <b>out</b>, blinded with the 32-byte parameter in
+ * <b>param</b>.  Return 0 on success, -1 on railure.
+ */
+int
+ed25519_public_blind(ed25519_public_key_t *out,
+                     const ed25519_public_key_t *inp,
+                     const uint8_t *param)
+{
+  return get_ed_impl()->blind_public_key(out->pubkey, inp->pubkey, param);
+}
+
+/**
+ * Store seckey unencrypted to <b>filename</b>, marking it with <b>tag</b>.
+ * Return 0 on success, -1 on failure.
+ */
+int
+ed25519_seckey_write_to_file(const ed25519_secret_key_t *seckey,
+                             const char *filename,
+                             const char *tag)
+{
+  return crypto_write_tagged_contents_to_file(filename,
+                                              "ed25519v1-secret",
+                                              tag,
+                                              seckey->seckey,
+                                              sizeof(seckey->seckey));
+}
+
+/**
+ * Read seckey unencrypted from <b>filename</b>, storing it into
+ * <b>seckey_out</b>.  Set *<b>tag_out</b> to the tag it was marked with.
+ * Return 0 on success, -1 on failure.
+ */
+int
+ed25519_seckey_read_from_file(ed25519_secret_key_t *seckey_out,
+                              char **tag_out,
+                              const char *filename)
+{
+  ssize_t len;
+
+  len = crypto_read_tagged_contents_from_file(filename, "ed25519v1-secret",
+                                              tag_out, seckey_out->seckey,
+                                              sizeof(seckey_out->seckey));
+  if (len == sizeof(seckey_out->seckey)) {
+    return 0;
+  } else if (len >= 0) {
+    errno = EINVAL;
+  }
+
+  tor_free(*tag_out);
+  return -1;
+}
+
+/**
+ * Store pubkey unencrypted to <b>filename</b>, marking it with <b>tag</b>.
+ * Return 0 on success, -1 on failure.
+ */
+int
+ed25519_pubkey_write_to_file(const ed25519_public_key_t *pubkey,
+                             const char *filename,
+                             const char *tag)
+{
+  return crypto_write_tagged_contents_to_file(filename,
+                                              "ed25519v1-public",
+                                              tag,
+                                              pubkey->pubkey,
+                                              sizeof(pubkey->pubkey));
+}
+
+/**
+ * Store pubkey unencrypted to <b>filename</b>, marking it with <b>tag</b>.
+ * Return 0 on success, -1 on failure.
+ */
+int
+ed25519_pubkey_read_from_file(ed25519_public_key_t *pubkey_out,
+                              char **tag_out,
+                              const char *filename)
+{
+  ssize_t len;
+
+  len = crypto_read_tagged_contents_from_file(filename, "ed25519v1-public",
+                                              tag_out, pubkey_out->pubkey,
+                                              sizeof(pubkey_out->pubkey));
+  if (len == sizeof(pubkey_out->pubkey)) {
+    return 0;
+  } else if (len >= 0) {
+    errno = EINVAL;
+  }
+
+  tor_free(*tag_out);
+  return -1;
+}
+
+/** Release all storage held for <b>kp</b>. */
+void
+ed25519_keypair_free_(ed25519_keypair_t *kp)
+{
+  if (! kp)
+    return;
+
+  memwipe(kp, 0, sizeof(*kp));
+  tor_free(kp);
+}
+
+/** Return true iff <b>key1</b> and <b>key2</b> are the same public key. */
+int
+ed25519_pubkey_eq(const ed25519_public_key_t *key1,
+                  const ed25519_public_key_t *key2)
+{
+  tor_assert(key1);
+  tor_assert(key2);
+  return tor_memeq(key1->pubkey, key2->pubkey, ED25519_PUBKEY_LEN);
+}
+
+/**
+ * Set <b>dest</b> to contain the same key as <b>src</b>.
+ */
+void
+ed25519_pubkey_copy(ed25519_public_key_t *dest,
+                    const ed25519_public_key_t *src)
+{
+  tor_assert(dest);
+  tor_assert(src);
+  memcpy(dest, src, sizeof(ed25519_public_key_t));
+}
+
+/** Check whether the given Ed25519 implementation seems to be working.
+ * If so, return 0; otherwise return -1. */
+MOCK_IMPL(STATIC int,
+ed25519_impl_spot_check,(void))
+{
+  static const uint8_t alicesk[32] = {
+    0xc5,0xaa,0x8d,0xf4,0x3f,0x9f,0x83,0x7b,
+    0xed,0xb7,0x44,0x2f,0x31,0xdc,0xb7,0xb1,
+    0x66,0xd3,0x85,0x35,0x07,0x6f,0x09,0x4b,
+    0x85,0xce,0x3a,0x2e,0x0b,0x44,0x58,0xf7
+  };
+  static const uint8_t alicepk[32] = {
+    0xfc,0x51,0xcd,0x8e,0x62,0x18,0xa1,0xa3,
+    0x8d,0xa4,0x7e,0xd0,0x02,0x30,0xf0,0x58,
+    0x08,0x16,0xed,0x13,0xba,0x33,0x03,0xac,
+    0x5d,0xeb,0x91,0x15,0x48,0x90,0x80,0x25
+  };
+  static const uint8_t alicemsg[2] = { 0xaf, 0x82 };
+  static const uint8_t alicesig[64] = {
+    0x62,0x91,0xd6,0x57,0xde,0xec,0x24,0x02,
+    0x48,0x27,0xe6,0x9c,0x3a,0xbe,0x01,0xa3,
+    0x0c,0xe5,0x48,0xa2,0x84,0x74,0x3a,0x44,
+    0x5e,0x36,0x80,0xd7,0xdb,0x5a,0xc3,0xac,
+    0x18,0xff,0x9b,0x53,0x8d,0x16,0xf2,0x90,
+    0xae,0x67,0xf7,0x60,0x98,0x4d,0xc6,0x59,
+    0x4a,0x7c,0x15,0xe9,0x71,0x6e,0xd2,0x8d,
+    0xc0,0x27,0xbe,0xce,0xea,0x1e,0xc4,0x0a
+  };
+  const ed25519_impl_t *impl = get_ed_impl();
+  uint8_t sk[ED25519_SECKEY_LEN];
+  uint8_t pk[ED25519_PUBKEY_LEN];
+  uint8_t sig[ED25519_SIG_LEN];
+  int r = 0;
+
+  /* Some implementations (eg: The modified Ed25519-donna) have handy self-test
+   * code that sanity-checks the internals.  If present, use that to screen out
+   * catastrophic errors like massive compiler failure.
+   */
+  if (impl->selftest && impl->selftest() != 0)
+    goto fail;
+
+  /* Validate results versus known answer tests.  People really should be
+   * running "make test" instead of relying on this, but it's better than
+   * nothing.
+   *
+   * Test vectors taken from "EdDSA & Ed25519 - 6. Test Vectors for Ed25519
+   * (TEST3)" (draft-josefsson-eddsa-ed25519-03).
+   */
+
+  /* Key expansion, public key derivation. */
+  if (impl->seckey_expand(sk, alicesk) < 0)
+    goto fail;
+  if (impl->pubkey(pk, sk) < 0)
+    goto fail;
+  if (fast_memneq(pk, alicepk, ED25519_PUBKEY_LEN))
+    goto fail;
+
+  /* Signing, verification. */
+  if (impl->sign(sig, alicemsg, sizeof(alicemsg), sk, pk) < 0)
+    return -1;
+  if (fast_memneq(sig, alicesig, ED25519_SIG_LEN))
+    return -1;
+  if (impl->open(sig, alicemsg, sizeof(alicemsg), pk) < 0)
+    return -1;
+
+  /* XXX/yawning: Someone that's more paranoid than I am, can write "Assume
+   * ref0 is canonical, and fuzz impl against it" if they want, but I doubt
+   * that will catch anything that the known answer tests won't.
+   */
+  goto end;
+
+ // LCOV_EXCL_START -- We can only reach this if our ed25519 implementation is
+ // broken.
+ fail:
+  r = -1;
+ // LCOV_EXCL_STOP
+ end:
+  return r;
+}
+
+/** Force the Ed25519 implementation to a given one, without sanity checking
+ * the output.  Used for testing.
+ */
+void
+ed25519_set_impl_params(int use_donna)
+{
+  if (use_donna)
+    ed25519_impl = &impl_donna;
+  else
+    ed25519_impl = &impl_ref10;
+}
+
+/** Choose whether to use the Ed25519-donna implementation. */
+static void
+pick_ed25519_impl(void)
+{
+  ed25519_impl = &impl_donna;
+
+  if (ed25519_impl_spot_check() == 0)
+    return;
+
+  /* LCOV_EXCL_START
+   * unreachable unless ed25519_donna is broken */
+  log_warn(LD_CRYPTO, "The Ed25519-donna implementation seems broken; using "
+           "the ref10 implementation.");
+  ed25519_impl = &impl_ref10;
+  /* LCOV_EXCL_STOP */
+}
+
+/* Initialize the Ed25519 implementation. This is necessary if you're
+ * going to use them in a multithreaded setting, and not otherwise. */
+void
+ed25519_init(void)
+{
+  pick_ed25519_impl();
+}
+
+/* Return true if <b>point</b> is the identity element of the ed25519 group. */
+static int
+ed25519_point_is_identity_element(const uint8_t *point)
+{
+  /* The identity element in ed25159 is the point with coordinates (0,1). */
+  static const uint8_t ed25519_identity[32] = {
+    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
+  tor_assert(sizeof(ed25519_identity) == ED25519_PUBKEY_LEN);
+  return tor_memeq(point, ed25519_identity, sizeof(ed25519_identity));
+}
+
+/** Validate <b>pubkey</b> to ensure that it has no torsion component.
+ *  Return 0 if <b>pubkey</b> is valid, else return -1. */
+int
+ed25519_validate_pubkey(const ed25519_public_key_t *pubkey)
+{
+  uint8_t result[32] = {9};
+
+  /* First check that we were not given the identity element */
+  if (ed25519_point_is_identity_element(pubkey->pubkey)) {
+    log_warn(LD_CRYPTO, "ed25519 pubkey is the identity");
+    return -1;
+  }
+
+  /* For any point on the curve, doing l*point should give the identity element
+   * (where l is the group order). Do the computation and check that the
+   * identity element is returned. */
+  if (get_ed_impl()->ed25519_scalarmult_with_group_order(result,
+                                                         pubkey->pubkey) < 0) {
+    log_warn(LD_CRYPTO, "ed25519 group order scalarmult failed");
+    return -1;
+  }
+
+  if (!ed25519_point_is_identity_element(result)) {
+    log_warn(LD_CRYPTO, "ed25519 validation failed");
+    return -1;
+  }
+
+  return 0;
+}
+