Initial checkin of gRPC to third_party/

third_party/grpc/src/core/tsi/ssl_transport_security.c

Index: third_party/grpc/src/core/tsi/ssl_transport_security.c
diff --git a/third_party/grpc/src/core/tsi/ssl_transport_security.c b/third_party/grpc/src/core/tsi/ssl_transport_security.c
new file mode 100644
index 0000000000000000000000000000000000000000..6adcaac9edefd28cb6cc3cdf71bf525609d4904e
--- /dev/null
+++ b/third_party/grpc/src/core/tsi/ssl_transport_security.c
@@ -0,0 +1,1469 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/tsi/ssl_transport_security.h"
+
+#include <limits.h>
+#include <string.h>
+
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/thd.h>
+#include <grpc/support/useful.h>
+
+#include <openssl/bio.h>
+#include <openssl/crypto.h> /* For OPENSSL_free */
+#include <openssl/err.h>
+#include <openssl/ssl.h>
+#include <openssl/x509.h>
+#include <openssl/x509v3.h>
+
+#include "src/core/tsi/ssl_types.h"
+#include "src/core/tsi/transport_security.h"
+
+/* --- Constants. ---*/
+
+#define TSI_SSL_MAX_PROTECTED_FRAME_SIZE_UPPER_BOUND 16384
+#define TSI_SSL_MAX_PROTECTED_FRAME_SIZE_LOWER_BOUND 1024
+
+/* Putting a macro like this and littering the source file with #if is really
+   bad practice.
+   TODO(jboeuf): refactor all the #if / #endif in a separate module. */
+#ifndef TSI_OPENSSL_ALPN_SUPPORT
+#define TSI_OPENSSL_ALPN_SUPPORT 1
+#endif
+
+/* TODO(jboeuf): I have not found a way to get this number dynamically from the
+   SSL structure. This is what we would ultimately want though... */
+#define TSI_SSL_MAX_PROTECTION_OVERHEAD 100
+
+/* --- Structure definitions. ---*/
+
+struct tsi_ssl_handshaker_factory {
+  tsi_result (*create_handshaker)(tsi_ssl_handshaker_factory *self,
+                                  const char *server_name_indication,
+                                  tsi_handshaker **handshaker);
+  void (*destroy)(tsi_ssl_handshaker_factory *self);
+};
+
+typedef struct {
+  tsi_ssl_handshaker_factory base;
+  SSL_CTX *ssl_context;
+  unsigned char *alpn_protocol_list;
+  size_t alpn_protocol_list_length;
+} tsi_ssl_client_handshaker_factory;
+
+typedef struct {
+  tsi_ssl_handshaker_factory base;
+
+  /* Several contexts to support SNI.
+     The tsi_peer array contains the subject names of the server certificates
+     associated with the contexts at the same index.  */
+  SSL_CTX **ssl_contexts;
+  tsi_peer *ssl_context_x509_subject_names;
+  size_t ssl_context_count;
+  unsigned char *alpn_protocol_list;
+  size_t alpn_protocol_list_length;
+} tsi_ssl_server_handshaker_factory;
+
+typedef struct {
+  tsi_handshaker base;
+  SSL *ssl;
+  BIO *into_ssl;
+  BIO *from_ssl;
+  tsi_result result;
+} tsi_ssl_handshaker;
+
+typedef struct {
+  tsi_frame_protector base;
+  SSL *ssl;
+  BIO *into_ssl;
+  BIO *from_ssl;
+  unsigned char *buffer;
+  size_t buffer_size;
+  size_t buffer_offset;
+} tsi_ssl_frame_protector;
+
+/* --- Library Initialization. ---*/
+
+static gpr_once init_openssl_once = GPR_ONCE_INIT;
+static gpr_mu *openssl_mutexes = NULL;
+
+static void openssl_locking_cb(int mode, int type, const char *file, int line) {
+  if (mode & CRYPTO_LOCK) {
+    gpr_mu_lock(&openssl_mutexes[type]);
+  } else {
+    gpr_mu_unlock(&openssl_mutexes[type]);
+  }
+}
+
+static unsigned long openssl_thread_id_cb(void) {
+  return (unsigned long)gpr_thd_currentid();
+}
+
+static void init_openssl(void) {
+  int i;
+  int num_locks;
+  SSL_library_init();
+  SSL_load_error_strings();
+  OpenSSL_add_all_algorithms();
+  num_locks = CRYPTO_num_locks();
+  GPR_ASSERT(num_locks > 0);
+  openssl_mutexes = malloc((size_t)num_locks * sizeof(gpr_mu));
+  GPR_ASSERT(openssl_mutexes != NULL);
+  for (i = 0; i < CRYPTO_num_locks(); i++) {
+    gpr_mu_init(&openssl_mutexes[i]);
+  }
+  CRYPTO_set_locking_callback(openssl_locking_cb);
+  CRYPTO_set_id_callback(openssl_thread_id_cb);
+}
+
+/* --- Ssl utils. ---*/
+
+static const char *ssl_error_string(int error) {
+  switch (error) {
+    case SSL_ERROR_NONE:
+      return "SSL_ERROR_NONE";
+    case SSL_ERROR_ZERO_RETURN:
+      return "SSL_ERROR_ZERO_RETURN";
+    case SSL_ERROR_WANT_READ:
+      return "SSL_ERROR_WANT_READ";
+    case SSL_ERROR_WANT_WRITE:
+      return "SSL_ERROR_WANT_WRITE";
+    case SSL_ERROR_WANT_CONNECT:
+      return "SSL_ERROR_WANT_CONNECT";
+    case SSL_ERROR_WANT_ACCEPT:
+      return "SSL_ERROR_WANT_ACCEPT";
+    case SSL_ERROR_WANT_X509_LOOKUP:
+      return "SSL_ERROR_WANT_X509_LOOKUP";
+    case SSL_ERROR_SYSCALL:
+      return "SSL_ERROR_SYSCALL";
+    case SSL_ERROR_SSL:
+      return "SSL_ERROR_SSL";
+    default:
+      return "Unknown error";
+  }
+}
+
+/* TODO(jboeuf): Remove when we are past the debugging phase with this code. */
+static void ssl_log_where_info(const SSL *ssl, int where, int flag,
+                               const char *msg) {
+  if ((where & flag) && tsi_tracing_enabled) {
+    gpr_log(GPR_INFO, "%20.20s - %30.30s  - %5.10s", msg,
+            SSL_state_string_long(ssl), SSL_state_string(ssl));
+  }
+}
+
+/* Used for debugging. TODO(jboeuf): Remove when code is mature enough. */
+static void ssl_info_callback(const SSL *ssl, int where, int ret) {
+  if (ret == 0) {
+    gpr_log(GPR_ERROR, "ssl_info_callback: error occured.\n");
+    return;
+  }
+
+  ssl_log_where_info(ssl, where, SSL_CB_LOOP, "LOOP");
+  ssl_log_where_info(ssl, where, SSL_CB_HANDSHAKE_START, "HANDSHAKE START");
+  ssl_log_where_info(ssl, where, SSL_CB_HANDSHAKE_DONE, "HANDSHAKE DONE");
+}
+
+/* Returns 1 if name looks like an IP address, 0 otherwise.
+   This is a very rough heuristic as it does not handle IPV6 or things like:
+   0300.0250.00.01, 0xC0.0Xa8.0x0.0x1, 000030052000001, 0xc0.052000001 */
+static int looks_like_ip_address(const char *name) {
+  size_t i;
+  size_t dot_count = 0;
+  size_t num_size = 0;
+  for (i = 0; i < strlen(name); i++) {
+    if (name[i] >= '0' && name[i] <= '9') {
+      if (num_size > 3) return 0;
+      num_size++;
+    } else if (name[i] == '.') {
+      if (dot_count > 3 || num_size == 0) return 0;
+      dot_count++;
+      num_size = 0;
+    } else {
+      return 0;
+    }
+  }
+  if (dot_count < 3 || num_size == 0) return 0;
+  return 1;
+}
+
+/* Gets the subject CN from an X509 cert. */
+static tsi_result ssl_get_x509_common_name(X509 *cert, unsigned char **utf8,
+                                           size_t *utf8_size) {
+  int common_name_index = -1;
+  X509_NAME_ENTRY *common_name_entry = NULL;
+  ASN1_STRING *common_name_asn1 = NULL;
+  X509_NAME *subject_name = X509_get_subject_name(cert);
+  int utf8_returned_size = 0;
+  if (subject_name == NULL) {
+    gpr_log(GPR_ERROR, "Could not get subject name from certificate.");
+    return TSI_NOT_FOUND;
+  }
+  common_name_index =
+      X509_NAME_get_index_by_NID(subject_name, NID_commonName, -1);
+  if (common_name_index == -1) {
+    gpr_log(GPR_ERROR,
+            "Could not get common name of subject from certificate.");
+    return TSI_NOT_FOUND;
+  }
+  common_name_entry = X509_NAME_get_entry(subject_name, common_name_index);
+  if (common_name_entry == NULL) {
+    gpr_log(GPR_ERROR, "Could not get common name entry from certificate.");
+    return TSI_INTERNAL_ERROR;
+  }
+  common_name_asn1 = X509_NAME_ENTRY_get_data(common_name_entry);
+  if (common_name_asn1 == NULL) {
+    gpr_log(GPR_ERROR,
+            "Could not get common name entry asn1 from certificate.");
+    return TSI_INTERNAL_ERROR;
+  }
+  utf8_returned_size = ASN1_STRING_to_UTF8(utf8, common_name_asn1);
+  if (utf8_returned_size < 0) {
+    gpr_log(GPR_ERROR, "Could not extract utf8 from asn1 string.");
+    return TSI_OUT_OF_RESOURCES;
+  }
+  *utf8_size = (size_t)utf8_returned_size;
+  return TSI_OK;
+}
+
+/* Gets the subject CN of an X509 cert as a tsi_peer_property. */
+static tsi_result peer_property_from_x509_common_name(
+    X509 *cert, tsi_peer_property *property) {
+  unsigned char *common_name;
+  size_t common_name_size;
+  tsi_result result =
+      ssl_get_x509_common_name(cert, &common_name, &common_name_size);
+  if (result != TSI_OK) {
+    if (result == TSI_NOT_FOUND) {
+      common_name = NULL;
+      common_name_size = 0;
+    } else {
+      return result;
+    }
+  }
+  result = tsi_construct_string_peer_property(
+      TSI_X509_SUBJECT_COMMON_NAME_PEER_PROPERTY,
+      common_name == NULL ? "" : (const char *)common_name, common_name_size,
+      property);
+  OPENSSL_free(common_name);
+  return result;
+}
+
+/* Gets the subject SANs from an X509 cert as a tsi_peer_property. */
+static tsi_result add_subject_alt_names_properties_to_peer(
+    tsi_peer *peer, GENERAL_NAMES *subject_alt_names,
+    size_t subject_alt_name_count) {
+  size_t i;
+  tsi_result result = TSI_OK;
+
+  /* Reset for DNS entries filtering. */
+  peer->property_count -= subject_alt_name_count;
+
+  for (i = 0; i < subject_alt_name_count; i++) {
+    GENERAL_NAME *subject_alt_name =
+        sk_GENERAL_NAME_value(subject_alt_names, TSI_SIZE_AS_SIZE(i));
+    /* Filter out the non-dns entries names. */
+    if (subject_alt_name->type == GEN_DNS) {
+      unsigned char *dns_name = NULL;
+      int dns_name_size =
+          ASN1_STRING_to_UTF8(&dns_name, subject_alt_name->d.dNSName);
+      if (dns_name_size < 0) {
+        gpr_log(GPR_ERROR, "Could not get utf8 from asn1 string.");
+        result = TSI_INTERNAL_ERROR;
+        break;
+      }
+      result = tsi_construct_string_peer_property(
+          TSI_X509_SUBJECT_ALTERNATIVE_NAME_PEER_PROPERTY,
+          (const char *)dns_name, (size_t)dns_name_size,
+          &peer->properties[peer->property_count++]);
+      OPENSSL_free(dns_name);
+      if (result != TSI_OK) break;
+    }
+  }
+  return result;
+}
+
+/* Gets information about the peer's X509 cert as a tsi_peer object. */
+static tsi_result peer_from_x509(X509 *cert, int include_certificate_type,
+                                 tsi_peer *peer) {
+  /* TODO(jboeuf): Maybe add more properties. */
+  GENERAL_NAMES *subject_alt_names =
+      X509_get_ext_d2i(cert, NID_subject_alt_name, 0, 0);
+  int subject_alt_name_count = (subject_alt_names != NULL)
+                                   ? (int)sk_GENERAL_NAME_num(subject_alt_names)
+                                   : 0;
+  size_t property_count;
+  tsi_result result;
+  GPR_ASSERT(subject_alt_name_count >= 0);
+  property_count = (include_certificate_type ? (size_t)1 : 0) +
+                   1 /* common name */ + (size_t)subject_alt_name_count;
+  result = tsi_construct_peer(property_count, peer);
+  if (result != TSI_OK) return result;
+  do {
+    if (include_certificate_type) {
+      result = tsi_construct_string_peer_property_from_cstring(
+          TSI_CERTIFICATE_TYPE_PEER_PROPERTY, TSI_X509_CERTIFICATE_TYPE,
+          &peer->properties[0]);
+      if (result != TSI_OK) break;
+    }
+    result = peer_property_from_x509_common_name(
+        cert, &peer->properties[include_certificate_type ? 1 : 0]);
+    if (result != TSI_OK) break;
+
+    if (subject_alt_name_count != 0) {
+      result = add_subject_alt_names_properties_to_peer(
+          peer, subject_alt_names, (size_t)subject_alt_name_count);
+      if (result != TSI_OK) break;
+    }
+  } while (0);
+
+  if (subject_alt_names != NULL) {
+    sk_GENERAL_NAME_pop_free(subject_alt_names, GENERAL_NAME_free);
+  }
+  if (result != TSI_OK) tsi_peer_destruct(peer);
+  return result;
+}
+
+/* Logs the SSL error stack. */
+static void log_ssl_error_stack(void) {
+  unsigned long err;
+  while ((err = ERR_get_error()) != 0) {
+    char details[256];
+    ERR_error_string_n((uint32_t)err, details, sizeof(details));
+    gpr_log(GPR_ERROR, "%s", details);
+  }
+}
+
+/* Performs an SSL_read and handle errors. */
+static tsi_result do_ssl_read(SSL *ssl, unsigned char *unprotected_bytes,
+                              size_t *unprotected_bytes_size) {
+  int read_from_ssl;
+  GPR_ASSERT(*unprotected_bytes_size <= INT_MAX);
+  read_from_ssl =
+      SSL_read(ssl, unprotected_bytes, (int)*unprotected_bytes_size);
+  if (read_from_ssl == 0) {
+    gpr_log(GPR_ERROR, "SSL_read returned 0 unexpectedly.");
+    return TSI_INTERNAL_ERROR;
+  }
+  if (read_from_ssl < 0) {
+    read_from_ssl = SSL_get_error(ssl, read_from_ssl);
+    switch (read_from_ssl) {
+      case SSL_ERROR_WANT_READ:
+        /* We need more data to finish the frame. */
+        *unprotected_bytes_size = 0;
+        return TSI_OK;
+      case SSL_ERROR_WANT_WRITE:
+        gpr_log(
+            GPR_ERROR,
+            "Peer tried to renegotiate SSL connection. This is unsupported.");
+        return TSI_UNIMPLEMENTED;
+      case SSL_ERROR_SSL:
+        gpr_log(GPR_ERROR, "Corruption detected.");
+        log_ssl_error_stack();
+        return TSI_DATA_CORRUPTED;
+      default:
+        gpr_log(GPR_ERROR, "SSL_read failed with error %s.",
+                ssl_error_string(read_from_ssl));
+        return TSI_PROTOCOL_FAILURE;
+    }
+  }
+  *unprotected_bytes_size = (size_t)read_from_ssl;
+  return TSI_OK;
+}
+
+/* Performs an SSL_write and handle errors. */
+static tsi_result do_ssl_write(SSL *ssl, unsigned char *unprotected_bytes,
+                               size_t unprotected_bytes_size) {
+  int ssl_write_result;
+  GPR_ASSERT(unprotected_bytes_size <= INT_MAX);
+  ssl_write_result =
+      SSL_write(ssl, unprotected_bytes, (int)unprotected_bytes_size);
+  if (ssl_write_result < 0) {
+    ssl_write_result = SSL_get_error(ssl, ssl_write_result);
+    if (ssl_write_result == SSL_ERROR_WANT_READ) {
+      gpr_log(GPR_ERROR,
+              "Peer tried to renegotiate SSL connection. This is unsupported.");
+      return TSI_UNIMPLEMENTED;
+    } else {
+      gpr_log(GPR_ERROR, "SSL_write failed with error %s.",
+              ssl_error_string(ssl_write_result));
+      return TSI_INTERNAL_ERROR;
+    }
+  }
+  return TSI_OK;
+}
+
+/* Loads an in-memory PEM certificate chain into the SSL context. */
+static tsi_result ssl_ctx_use_certificate_chain(
+    SSL_CTX *context, const unsigned char *pem_cert_chain,
+    size_t pem_cert_chain_size) {
+  tsi_result result = TSI_OK;
+  X509 *certificate = NULL;
+  BIO *pem;
+  GPR_ASSERT(pem_cert_chain_size <= INT_MAX);
+  pem = BIO_new_mem_buf((void *)pem_cert_chain, (int)pem_cert_chain_size);
+  if (pem == NULL) return TSI_OUT_OF_RESOURCES;
+
+  do {
+    certificate = PEM_read_bio_X509_AUX(pem, NULL, NULL, "");
+    if (certificate == NULL) {
+      result = TSI_INVALID_ARGUMENT;
+      break;
+    }
+    if (!SSL_CTX_use_certificate(context, certificate)) {
+      result = TSI_INVALID_ARGUMENT;
+      break;
+    }
+    while (1) {
+      X509 *certificate_authority = PEM_read_bio_X509(pem, NULL, NULL, "");
+      if (certificate_authority == NULL) {
+        ERR_clear_error();
+        break; /* Done reading. */
+      }
+      if (!SSL_CTX_add_extra_chain_cert(context, certificate_authority)) {
+        X509_free(certificate_authority);
+        result = TSI_INVALID_ARGUMENT;
+        break;
+      }
+      /* We don't need to free certificate_authority as its ownership has been
+         transfered to the context. That is not the case for certificate though.
+       */
+    }
+  } while (0);
+
+  if (certificate != NULL) X509_free(certificate);
+  BIO_free(pem);
+  return result;
+}
+
+/* Loads an in-memory PEM private key into the SSL context. */
+static tsi_result ssl_ctx_use_private_key(SSL_CTX *context,
+                                          const unsigned char *pem_key,
+                                          size_t pem_key_size) {
+  tsi_result result = TSI_OK;
+  EVP_PKEY *private_key = NULL;
+  BIO *pem;
+  GPR_ASSERT(pem_key_size <= INT_MAX);
+  pem = BIO_new_mem_buf((void *)pem_key, (int)pem_key_size);
+  if (pem == NULL) return TSI_OUT_OF_RESOURCES;
+  do {
+    private_key = PEM_read_bio_PrivateKey(pem, NULL, NULL, "");
+    if (private_key == NULL) {
+      result = TSI_INVALID_ARGUMENT;
+      break;
+    }
+    if (!SSL_CTX_use_PrivateKey(context, private_key)) {
+      result = TSI_INVALID_ARGUMENT;
+      break;
+    }
+  } while (0);
+  if (private_key != NULL) EVP_PKEY_free(private_key);
+  BIO_free(pem);
+  return result;
+}
+
+/* Loads in-memory PEM verification certs into the SSL context and optionally
+   returns the verification cert names (root_names can be NULL). */
+static tsi_result ssl_ctx_load_verification_certs(
+    SSL_CTX *context, const unsigned char *pem_roots, size_t pem_roots_size,
+    STACK_OF(X509_NAME) * *root_names) {
+  tsi_result result = TSI_OK;
+  size_t num_roots = 0;
+  X509 *root = NULL;
+  X509_NAME *root_name = NULL;
+  BIO *pem;
+  X509_STORE *root_store;
+  GPR_ASSERT(pem_roots_size <= INT_MAX);
+  pem = BIO_new_mem_buf((void *)pem_roots, (int)pem_roots_size);
+  root_store = SSL_CTX_get_cert_store(context);
+  if (root_store == NULL) return TSI_INVALID_ARGUMENT;
+  if (pem == NULL) return TSI_OUT_OF_RESOURCES;
+  if (root_names != NULL) {
+    *root_names = sk_X509_NAME_new_null();
+    if (*root_names == NULL) return TSI_OUT_OF_RESOURCES;
+  }
+
+  while (1) {
+    root = PEM_read_bio_X509_AUX(pem, NULL, NULL, "");
+    if (root == NULL) {
+      ERR_clear_error();
+      break; /* We're at the end of stream. */
+    }
+    if (root_names != NULL) {
+      root_name = X509_get_subject_name(root);
+      if (root_name == NULL) {
+        gpr_log(GPR_ERROR, "Could not get name from root certificate.");
+        result = TSI_INVALID_ARGUMENT;
+        break;
+      }
+      root_name = X509_NAME_dup(root_name);
+      if (root_name == NULL) {
+        result = TSI_OUT_OF_RESOURCES;
+        break;
+      }
+      sk_X509_NAME_push(*root_names, root_name);
+      root_name = NULL;
+    }
+    if (!X509_STORE_add_cert(root_store, root)) {
+      gpr_log(GPR_ERROR, "Could not add root certificate to ssl context.");
+      result = TSI_INTERNAL_ERROR;
+      break;
+    }
+    X509_free(root);
+    num_roots++;
+  }
+
+  if (num_roots == 0) {
+    gpr_log(GPR_ERROR, "Could not load any root certificate.");
+    result = TSI_INVALID_ARGUMENT;
+  }
+
+  if (result != TSI_OK) {
+    if (root != NULL) X509_free(root);
+    if (root_names != NULL) {
+      sk_X509_NAME_pop_free(*root_names, X509_NAME_free);
+      *root_names = NULL;
+      if (root_name != NULL) X509_NAME_free(root_name);
+    }
+  }
+  BIO_free(pem);
+  return result;
+}
+
+/* Populates the SSL context with a private key and a cert chain, and sets the
+   cipher list and the ephemeral ECDH key. */
+static tsi_result populate_ssl_context(
+    SSL_CTX *context, const unsigned char *pem_private_key,
+    size_t pem_private_key_size, const unsigned char *pem_certificate_chain,
+    size_t pem_certificate_chain_size, const char *cipher_list) {
+  tsi_result result = TSI_OK;
+  if (pem_certificate_chain != NULL) {
+    result = ssl_ctx_use_certificate_chain(context, pem_certificate_chain,
+                                           pem_certificate_chain_size);
+    if (result != TSI_OK) {
+      gpr_log(GPR_ERROR, "Invalid cert chain file.");
+      return result;
+    }
+  }
+  if (pem_private_key != NULL) {
+    result =
+        ssl_ctx_use_private_key(context, pem_private_key, pem_private_key_size);
+    if (result != TSI_OK || !SSL_CTX_check_private_key(context)) {
+      gpr_log(GPR_ERROR, "Invalid private key.");
+      return result != TSI_OK ? result : TSI_INVALID_ARGUMENT;
+    }
+  }
+  if ((cipher_list != NULL) && !SSL_CTX_set_cipher_list(context, cipher_list)) {
+    gpr_log(GPR_ERROR, "Invalid cipher list: %s.", cipher_list);
+    return TSI_INVALID_ARGUMENT;
+  }
+  {
+    EC_KEY *ecdh = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
+    if (!SSL_CTX_set_tmp_ecdh(context, ecdh)) {
+      gpr_log(GPR_ERROR, "Could not set ephemeral ECDH key.");
+      EC_KEY_free(ecdh);
+      return TSI_INTERNAL_ERROR;
+    }
+    SSL_CTX_set_options(context, SSL_OP_SINGLE_ECDH_USE);
+    EC_KEY_free(ecdh);
+  }
+  return TSI_OK;
+}
+
+/* Extracts the CN and the SANs from an X509 cert as a peer object. */
+static tsi_result extract_x509_subject_names_from_pem_cert(
+    const unsigned char *pem_cert, size_t pem_cert_size, tsi_peer *peer) {
+  tsi_result result = TSI_OK;
+  X509 *cert = NULL;
+  BIO *pem;
+  GPR_ASSERT(pem_cert_size <= INT_MAX);
+  pem = BIO_new_mem_buf((void *)pem_cert, (int)pem_cert_size);
+  if (pem == NULL) return TSI_OUT_OF_RESOURCES;
+
+  cert = PEM_read_bio_X509(pem, NULL, NULL, "");
+  if (cert == NULL) {
+    gpr_log(GPR_ERROR, "Invalid certificate");
+    result = TSI_INVALID_ARGUMENT;
+  } else {
+    result = peer_from_x509(cert, 0, peer);
+  }
+  if (cert != NULL) X509_free(cert);
+  BIO_free(pem);
+  return result;
+}
+
+/* Builds the alpn protocol name list according to rfc 7301. */
+static tsi_result build_alpn_protocol_name_list(
+    const unsigned char **alpn_protocols,
+    const unsigned char *alpn_protocols_lengths, uint16_t num_alpn_protocols,
+    unsigned char **protocol_name_list, size_t *protocol_name_list_length) {
+  uint16_t i;
+  unsigned char *current;
+  *protocol_name_list = NULL;
+  *protocol_name_list_length = 0;
+  if (num_alpn_protocols == 0) return TSI_INVALID_ARGUMENT;
+  for (i = 0; i < num_alpn_protocols; i++) {
+    if (alpn_protocols_lengths[i] == 0) {
+      gpr_log(GPR_ERROR, "Invalid 0-length protocol name.");
+      return TSI_INVALID_ARGUMENT;
+    }
+    *protocol_name_list_length += (size_t)alpn_protocols_lengths[i] + 1;
+  }
+  *protocol_name_list = malloc(*protocol_name_list_length);
+  if (*protocol_name_list == NULL) return TSI_OUT_OF_RESOURCES;
+  current = *protocol_name_list;
+  for (i = 0; i < num_alpn_protocols; i++) {
+    *(current++) = alpn_protocols_lengths[i];
+    memcpy(current, alpn_protocols[i], alpn_protocols_lengths[i]);
+    current += alpn_protocols_lengths[i];
+  }
+  /* Safety check. */
+  if ((current < *protocol_name_list) ||
+      ((uintptr_t)(current - *protocol_name_list) !=
+       *protocol_name_list_length)) {
+    return TSI_INTERNAL_ERROR;
+  }
+  return TSI_OK;
+}
+
+/* --- tsi_frame_protector methods implementation. ---*/
+
+static tsi_result ssl_protector_protect(tsi_frame_protector *self,
+                                        const unsigned char *unprotected_bytes,
+                                        size_t *unprotected_bytes_size,
+                                        unsigned char *protected_output_frames,
+                                        size_t *protected_output_frames_size) {
+  tsi_ssl_frame_protector *impl = (tsi_ssl_frame_protector *)self;
+  int read_from_ssl;
+  size_t available;
+  tsi_result result = TSI_OK;
+
+  /* First see if we have some pending data in the SSL BIO. */
+  int pending_in_ssl = (int)BIO_pending(impl->from_ssl);
+  if (pending_in_ssl > 0) {
+    *unprotected_bytes_size = 0;
+    GPR_ASSERT(*protected_output_frames_size <= INT_MAX);
+    read_from_ssl = BIO_read(impl->from_ssl, protected_output_frames,
+                             (int)*protected_output_frames_size);
+    if (read_from_ssl < 0) {
+      gpr_log(GPR_ERROR,
+              "Could not read from BIO even though some data is pending");
+      return TSI_INTERNAL_ERROR;
+    }
+    *protected_output_frames_size = (size_t)read_from_ssl;
+    return TSI_OK;
+  }
+
+  /* Now see if we can send a complete frame. */
+  available = impl->buffer_size - impl->buffer_offset;
+  if (available > *unprotected_bytes_size) {
+    /* If we cannot, just copy the data in our internal buffer. */
+    memcpy(impl->buffer + impl->buffer_offset, unprotected_bytes,
+           *unprotected_bytes_size);
+    impl->buffer_offset += *unprotected_bytes_size;
+    *protected_output_frames_size = 0;
+    return TSI_OK;
+  }
+
+  /* If we can, prepare the buffer, send it to SSL_write and read. */
+  memcpy(impl->buffer + impl->buffer_offset, unprotected_bytes, available);
+  result = do_ssl_write(impl->ssl, impl->buffer, impl->buffer_size);
+  if (result != TSI_OK) return result;
+
+  GPR_ASSERT(*protected_output_frames_size <= INT_MAX);
+  read_from_ssl = BIO_read(impl->from_ssl, protected_output_frames,
+                           (int)*protected_output_frames_size);
+  if (read_from_ssl < 0) {
+    gpr_log(GPR_ERROR, "Could not read from BIO after SSL_write.");
+    return TSI_INTERNAL_ERROR;
+  }
+  *protected_output_frames_size = (size_t)read_from_ssl;
+  *unprotected_bytes_size = available;
+  impl->buffer_offset = 0;
+  return TSI_OK;
+}
+
+static tsi_result ssl_protector_protect_flush(
+    tsi_frame_protector *self, unsigned char *protected_output_frames,
+    size_t *protected_output_frames_size, size_t *still_pending_size) {
+  tsi_result result = TSI_OK;
+  tsi_ssl_frame_protector *impl = (tsi_ssl_frame_protector *)self;
+  int read_from_ssl = 0;
+  int pending;
+
+  if (impl->buffer_offset != 0) {
+    result = do_ssl_write(impl->ssl, impl->buffer, impl->buffer_offset);
+    if (result != TSI_OK) return result;
+    impl->buffer_offset = 0;
+  }
+
+  pending = (int)BIO_pending(impl->from_ssl);
+  GPR_ASSERT(pending >= 0);
+  *still_pending_size = (size_t)pending;
+  if (*still_pending_size == 0) return TSI_OK;
+
+  GPR_ASSERT(*protected_output_frames_size <= INT_MAX);
+  read_from_ssl = BIO_read(impl->from_ssl, protected_output_frames,
+                           (int)*protected_output_frames_size);
+  if (read_from_ssl <= 0) {
+    gpr_log(GPR_ERROR, "Could not read from BIO after SSL_write.");
+    return TSI_INTERNAL_ERROR;
+  }
+  *protected_output_frames_size = (size_t)read_from_ssl;
+  pending = (int)BIO_pending(impl->from_ssl);
+  GPR_ASSERT(pending >= 0);
+  *still_pending_size = (size_t)pending;
+  return TSI_OK;
+}
+
+static tsi_result ssl_protector_unprotect(
+    tsi_frame_protector *self, const unsigned char *protected_frames_bytes,
+    size_t *protected_frames_bytes_size, unsigned char *unprotected_bytes,
+    size_t *unprotected_bytes_size) {
+  tsi_result result = TSI_OK;
+  int written_into_ssl = 0;
+  size_t output_bytes_size = *unprotected_bytes_size;
+  size_t output_bytes_offset = 0;
+  tsi_ssl_frame_protector *impl = (tsi_ssl_frame_protector *)self;
+
+  /* First, try to read remaining data from ssl. */
+  result = do_ssl_read(impl->ssl, unprotected_bytes, unprotected_bytes_size);
+  if (result != TSI_OK) return result;
+  if (*unprotected_bytes_size == output_bytes_size) {
+    /* We have read everything we could and cannot process any more input. */
+    *protected_frames_bytes_size = 0;
+    return TSI_OK;
+  }
+  output_bytes_offset = *unprotected_bytes_size;
+  unprotected_bytes += output_bytes_offset;
+  *unprotected_bytes_size = output_bytes_size - output_bytes_offset;
+
+  /* Then, try to write some data to ssl. */
+  GPR_ASSERT(*protected_frames_bytes_size <= INT_MAX);
+  written_into_ssl = BIO_write(impl->into_ssl, protected_frames_bytes,
+                               (int)*protected_frames_bytes_size);
+  if (written_into_ssl < 0) {
+    gpr_log(GPR_ERROR, "Sending protected frame to ssl failed with %d",
+            written_into_ssl);
+    return TSI_INTERNAL_ERROR;
+  }
+  *protected_frames_bytes_size = (size_t)written_into_ssl;
+
+  /* Now try to read some data again. */
+  result = do_ssl_read(impl->ssl, unprotected_bytes, unprotected_bytes_size);
+  if (result == TSI_OK) {
+    /* Don't forget to output the total number of bytes read. */
+    *unprotected_bytes_size += output_bytes_offset;
+  }
+  return result;
+}
+
+static void ssl_protector_destroy(tsi_frame_protector *self) {
+  tsi_ssl_frame_protector *impl = (tsi_ssl_frame_protector *)self;
+  if (impl->buffer != NULL) free(impl->buffer);
+  if (impl->ssl != NULL) SSL_free(impl->ssl);
+  free(self);
+}
+
+static const tsi_frame_protector_vtable frame_protector_vtable = {
+    ssl_protector_protect, ssl_protector_protect_flush, ssl_protector_unprotect,
+    ssl_protector_destroy,
+};
+
+/* --- tsi_handshaker methods implementation. ---*/
+
+static tsi_result ssl_handshaker_get_bytes_to_send_to_peer(tsi_handshaker *self,
+                                                           unsigned char *bytes,
+                                                           size_t *bytes_size) {
+  tsi_ssl_handshaker *impl = (tsi_ssl_handshaker *)self;
+  int bytes_read_from_ssl = 0;
+  if (bytes == NULL || bytes_size == NULL || *bytes_size == 0 ||
+      *bytes_size > INT_MAX) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  GPR_ASSERT(*bytes_size <= INT_MAX);
+  bytes_read_from_ssl = BIO_read(impl->from_ssl, bytes, (int)*bytes_size);
+  if (bytes_read_from_ssl < 0) {
+    *bytes_size = 0;
+    if (!BIO_should_retry(impl->from_ssl)) {
+      impl->result = TSI_INTERNAL_ERROR;
+      return impl->result;
+    } else {
+      return TSI_OK;
+    }
+  }
+  *bytes_size = (size_t)bytes_read_from_ssl;
+  return BIO_pending(impl->from_ssl) == 0 ? TSI_OK : TSI_INCOMPLETE_DATA;
+}
+
+static tsi_result ssl_handshaker_get_result(tsi_handshaker *self) {
+  tsi_ssl_handshaker *impl = (tsi_ssl_handshaker *)self;
+  if ((impl->result == TSI_HANDSHAKE_IN_PROGRESS) &&
+      SSL_is_init_finished(impl->ssl)) {
+    impl->result = TSI_OK;
+  }
+  return impl->result;
+}
+
+static tsi_result ssl_handshaker_process_bytes_from_peer(
+    tsi_handshaker *self, const unsigned char *bytes, size_t *bytes_size) {
+  tsi_ssl_handshaker *impl = (tsi_ssl_handshaker *)self;
+  int bytes_written_into_ssl_size = 0;
+  if (bytes == NULL || bytes_size == 0 || *bytes_size > INT_MAX) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  GPR_ASSERT(*bytes_size <= INT_MAX);
+  bytes_written_into_ssl_size =
+      BIO_write(impl->into_ssl, bytes, (int)*bytes_size);
+  if (bytes_written_into_ssl_size < 0) {
+    gpr_log(GPR_ERROR, "Could not write to memory BIO.");
+    impl->result = TSI_INTERNAL_ERROR;
+    return impl->result;
+  }
+  *bytes_size = (size_t)bytes_written_into_ssl_size;
+
+  if (!tsi_handshaker_is_in_progress(self)) {
+    impl->result = TSI_OK;
+    return impl->result;
+  } else {
+    /* Get ready to get some bytes from SSL. */
+    int ssl_result = SSL_do_handshake(impl->ssl);
+    ssl_result = SSL_get_error(impl->ssl, ssl_result);
+    switch (ssl_result) {
+      case SSL_ERROR_WANT_READ:
+        if (BIO_pending(impl->from_ssl) == 0) {
+          /* We need more data. */
+          return TSI_INCOMPLETE_DATA;
+        } else {
+          return TSI_OK;
+        }
+      case SSL_ERROR_NONE:
+        return TSI_OK;
+      default: {
+        char err_str[256];
+        ERR_error_string_n(ERR_get_error(), err_str, sizeof(err_str));
+        gpr_log(GPR_ERROR, "Handshake failed with fatal error %s: %s.",
+                ssl_error_string(ssl_result), err_str);
+        impl->result = TSI_PROTOCOL_FAILURE;
+        return impl->result;
+      }
+    }
+  }
+}
+
+static tsi_result ssl_handshaker_extract_peer(tsi_handshaker *self,
+                                              tsi_peer *peer) {
+  tsi_result result = TSI_OK;
+  const unsigned char *alpn_selected = NULL;
+  unsigned int alpn_selected_len;
+  tsi_ssl_handshaker *impl = (tsi_ssl_handshaker *)self;
+  X509 *peer_cert = SSL_get_peer_certificate(impl->ssl);
+  if (peer_cert != NULL) {
+    result = peer_from_x509(peer_cert, 1, peer);
+    X509_free(peer_cert);
+    if (result != TSI_OK) return result;
+  }
+#if TSI_OPENSSL_ALPN_SUPPORT
+  SSL_get0_alpn_selected(impl->ssl, &alpn_selected, &alpn_selected_len);
+#endif /* TSI_OPENSSL_ALPN_SUPPORT */
+  if (alpn_selected == NULL) {
+    /* Try npn. */
+    SSL_get0_next_proto_negotiated(impl->ssl, &alpn_selected,
+                                   &alpn_selected_len);
+  }
+  if (alpn_selected != NULL) {
+    size_t i;
+    tsi_peer_property *new_properties =
+        calloc(1, sizeof(tsi_peer_property) * (peer->property_count + 1));
+    if (new_properties == NULL) return TSI_OUT_OF_RESOURCES;
+    for (i = 0; i < peer->property_count; i++) {
+      new_properties[i] = peer->properties[i];
+    }
+    result = tsi_construct_string_peer_property(
+        TSI_SSL_ALPN_SELECTED_PROTOCOL, (const char *)alpn_selected,
+        alpn_selected_len, &new_properties[peer->property_count]);
+    if (result != TSI_OK) {
+      free(new_properties);
+      return result;
+    }
+    if (peer->properties != NULL) free(peer->properties);
+    peer->property_count++;
+    peer->properties = new_properties;
+  }
+  return result;
+}
+
+static tsi_result ssl_handshaker_create_frame_protector(
+    tsi_handshaker *self, size_t *max_output_protected_frame_size,
+    tsi_frame_protector **protector) {
+  size_t actual_max_output_protected_frame_size =
+      TSI_SSL_MAX_PROTECTED_FRAME_SIZE_UPPER_BOUND;
+  tsi_ssl_handshaker *impl = (tsi_ssl_handshaker *)self;
+  tsi_ssl_frame_protector *protector_impl =
+      calloc(1, sizeof(tsi_ssl_frame_protector));
+  if (protector_impl == NULL) {
+    return TSI_OUT_OF_RESOURCES;
+  }
+
+  if (max_output_protected_frame_size != NULL) {
+    if (*max_output_protected_frame_size >
+        TSI_SSL_MAX_PROTECTED_FRAME_SIZE_UPPER_BOUND) {
+      *max_output_protected_frame_size =
+          TSI_SSL_MAX_PROTECTED_FRAME_SIZE_UPPER_BOUND;
+    } else if (*max_output_protected_frame_size <
+               TSI_SSL_MAX_PROTECTED_FRAME_SIZE_LOWER_BOUND) {
+      *max_output_protected_frame_size =
+          TSI_SSL_MAX_PROTECTED_FRAME_SIZE_LOWER_BOUND;
+    }
+    actual_max_output_protected_frame_size = *max_output_protected_frame_size;
+  }
+  protector_impl->buffer_size =
+      actual_max_output_protected_frame_size - TSI_SSL_MAX_PROTECTION_OVERHEAD;
+  protector_impl->buffer = malloc(protector_impl->buffer_size);
+  if (protector_impl->buffer == NULL) {
+    gpr_log(GPR_ERROR,
+            "Could not allocated buffer for tsi_ssl_frame_protector.");
+    free(protector_impl);
+    return TSI_INTERNAL_ERROR;
+  }
+
+  /* Transfer ownership of ssl to the frame protector. It is OK as the caller
+   * cannot call anything else but destroy on the handshaker after this call. */
+  protector_impl->ssl = impl->ssl;
+  impl->ssl = NULL;
+  protector_impl->into_ssl = impl->into_ssl;
+  protector_impl->from_ssl = impl->from_ssl;
+
+  protector_impl->base.vtable = &frame_protector_vtable;
+  *protector = &protector_impl->base;
+  return TSI_OK;
+}
+
+static void ssl_handshaker_destroy(tsi_handshaker *self) {
+  tsi_ssl_handshaker *impl = (tsi_ssl_handshaker *)self;
+  SSL_free(impl->ssl); /* The BIO objects are owned by ssl */
+  free(impl);
+}
+
+static const tsi_handshaker_vtable handshaker_vtable = {
+    ssl_handshaker_get_bytes_to_send_to_peer,
+    ssl_handshaker_process_bytes_from_peer, ssl_handshaker_get_result,
+    ssl_handshaker_extract_peer, ssl_handshaker_create_frame_protector,
+    ssl_handshaker_destroy,
+};
+
+/* --- tsi_ssl_handshaker_factory common methods. --- */
+
+tsi_result tsi_ssl_handshaker_factory_create_handshaker(
+    tsi_ssl_handshaker_factory *self, const char *server_name_indication,
+    tsi_handshaker **handshaker) {
+  if (self == NULL || handshaker == NULL) return TSI_INVALID_ARGUMENT;
+  return self->create_handshaker(self, server_name_indication, handshaker);
+}
+
+void tsi_ssl_handshaker_factory_destroy(tsi_ssl_handshaker_factory *self) {
+  if (self == NULL) return;
+  self->destroy(self);
+}
+
+static tsi_result create_tsi_ssl_handshaker(SSL_CTX *ctx, int is_client,
+                                            const char *server_name_indication,
+                                            tsi_handshaker **handshaker) {
+  SSL *ssl = SSL_new(ctx);
+  BIO *into_ssl = NULL;
+  BIO *from_ssl = NULL;
+  tsi_ssl_handshaker *impl = NULL;
+  *handshaker = NULL;
+  if (ctx == NULL) {
+    gpr_log(GPR_ERROR, "SSL Context is null. Should never happen.");
+    return TSI_INTERNAL_ERROR;
+  }
+  if (ssl == NULL) {
+    return TSI_OUT_OF_RESOURCES;
+  }
+  SSL_set_info_callback(ssl, ssl_info_callback);
+
+  into_ssl = BIO_new(BIO_s_mem());
+  from_ssl = BIO_new(BIO_s_mem());
+  if (into_ssl == NULL || from_ssl == NULL) {
+    gpr_log(GPR_ERROR, "BIO_new failed.");
+    SSL_free(ssl);
+    if (into_ssl != NULL) BIO_free(into_ssl);
+    if (from_ssl != NULL) BIO_free(into_ssl);
+    return TSI_OUT_OF_RESOURCES;
+  }
+  SSL_set_bio(ssl, into_ssl, from_ssl);
+  if (is_client) {
+    int ssl_result;
+    SSL_set_connect_state(ssl);
+    if (server_name_indication != NULL) {
+      if (!SSL_set_tlsext_host_name(ssl, server_name_indication)) {
+        gpr_log(GPR_ERROR, "Invalid server name indication %s.",
+                server_name_indication);
+        SSL_free(ssl);
+        return TSI_INTERNAL_ERROR;
+      }
+    }
+    ssl_result = SSL_do_handshake(ssl);
+    ssl_result = SSL_get_error(ssl, ssl_result);
+    if (ssl_result != SSL_ERROR_WANT_READ) {
+      gpr_log(GPR_ERROR,
+              "Unexpected error received from first SSL_do_handshake call: %s",
+              ssl_error_string(ssl_result));
+      SSL_free(ssl);
+      return TSI_INTERNAL_ERROR;
+    }
+  } else {
+    SSL_set_accept_state(ssl);
+  }
+
+  impl = calloc(1, sizeof(tsi_ssl_handshaker));
+  if (impl == NULL) {
+    SSL_free(ssl);
+    return TSI_OUT_OF_RESOURCES;
+  }
+  impl->ssl = ssl;
+  impl->into_ssl = into_ssl;
+  impl->from_ssl = from_ssl;
+  impl->result = TSI_HANDSHAKE_IN_PROGRESS;
+  impl->base.vtable = &handshaker_vtable;
+  *handshaker = &impl->base;
+  return TSI_OK;
+}
+
+static int select_protocol_list(const unsigned char **out,
+                                unsigned char *outlen,
+                                const unsigned char *client_list,
+                                size_t client_list_len,
+                                const unsigned char *server_list,
+                                size_t server_list_len) {
+  const unsigned char *client_current = client_list;
+  while ((unsigned int)(client_current - client_list) < client_list_len) {
+    unsigned char client_current_len = *(client_current++);
+    const unsigned char *server_current = server_list;
+    while ((server_current >= server_list) &&
+           (uintptr_t)(server_current - server_list) < server_list_len) {
+      unsigned char server_current_len = *(server_current++);
+      if ((client_current_len == server_current_len) &&
+          !memcmp(client_current, server_current, server_current_len)) {
+        *out = server_current;
+        *outlen = server_current_len;
+        return SSL_TLSEXT_ERR_OK;
+      }
+      server_current += server_current_len;
+    }
+    client_current += client_current_len;
+  }
+  return SSL_TLSEXT_ERR_NOACK;
+}
+
+/* --- tsi_ssl__client_handshaker_factory methods implementation. --- */
+
+static tsi_result ssl_client_handshaker_factory_create_handshaker(
+    tsi_ssl_handshaker_factory *self, const char *server_name_indication,
+    tsi_handshaker **handshaker) {
+  tsi_ssl_client_handshaker_factory *impl =
+      (tsi_ssl_client_handshaker_factory *)self;
+  return create_tsi_ssl_handshaker(impl->ssl_context, 1, server_name_indication,
+                                   handshaker);
+}
+
+static void ssl_client_handshaker_factory_destroy(
+    tsi_ssl_handshaker_factory *self) {
+  tsi_ssl_client_handshaker_factory *impl =
+      (tsi_ssl_client_handshaker_factory *)self;
+  if (impl->ssl_context != NULL) SSL_CTX_free(impl->ssl_context);
+  if (impl->alpn_protocol_list != NULL) free(impl->alpn_protocol_list);
+  free(impl);
+}
+
+static int client_handshaker_factory_npn_callback(SSL *ssl, unsigned char **out,
+                                                  unsigned char *outlen,
+                                                  const unsigned char *in,
+                                                  unsigned int inlen,
+                                                  void *arg) {
+  tsi_ssl_client_handshaker_factory *factory =
+      (tsi_ssl_client_handshaker_factory *)arg;
+  return select_protocol_list((const unsigned char **)out, outlen,
+                              factory->alpn_protocol_list,
+                              factory->alpn_protocol_list_length, in, inlen);
+}
+
+/* --- tsi_ssl_server_handshaker_factory methods implementation. --- */
+
+static tsi_result ssl_server_handshaker_factory_create_handshaker(
+    tsi_ssl_handshaker_factory *self, const char *server_name_indication,
+    tsi_handshaker **handshaker) {
+  tsi_ssl_server_handshaker_factory *impl =
+      (tsi_ssl_server_handshaker_factory *)self;
+  if (impl->ssl_context_count == 0 || server_name_indication != NULL) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  /* Create the handshaker with the first context. We will switch if needed
+     because of SNI in ssl_server_handshaker_factory_servername_callback.  */
+  return create_tsi_ssl_handshaker(impl->ssl_contexts[0], 0, NULL, handshaker);
+}
+
+static void ssl_server_handshaker_factory_destroy(
+    tsi_ssl_handshaker_factory *self) {
+  tsi_ssl_server_handshaker_factory *impl =
+      (tsi_ssl_server_handshaker_factory *)self;
+  size_t i;
+  for (i = 0; i < impl->ssl_context_count; i++) {
+    if (impl->ssl_contexts[i] != NULL) {
+      SSL_CTX_free(impl->ssl_contexts[i]);
+      tsi_peer_destruct(&impl->ssl_context_x509_subject_names[i]);
+    }
+  }
+  if (impl->ssl_contexts != NULL) free(impl->ssl_contexts);
+  if (impl->ssl_context_x509_subject_names != NULL) {
+    free(impl->ssl_context_x509_subject_names);
+  }
+  if (impl->alpn_protocol_list != NULL) free(impl->alpn_protocol_list);
+  free(impl);
+}
+
+static int does_entry_match_name(const char *entry, size_t entry_length,
+                                 const char *name) {
+  const char *dot;
+  const char *name_subdomain = NULL;
+  size_t name_length = strlen(name);
+  size_t name_subdomain_length;
+  if (entry_length == 0) return 0;
+
+  /* Take care of '.' terminations. */
+  if (name[name_length - 1] == '.') {
+    name_length--;
+  }
+  if (entry[entry_length - 1] == '.') {
+    entry_length--;
+    if (entry_length == 0) return 0;
+  }
+
+  if ((name_length == entry_length) &&
+      strncmp(name, entry, entry_length) == 0) {
+    return 1; /* Perfect match. */
+  }
+  if (entry[0] != '*') return 0;
+
+  /* Wildchar subdomain matching. */
+  if (entry_length < 3 || entry[1] != '.') { /* At least *.x */
+    gpr_log(GPR_ERROR, "Invalid wildchar entry.");
+    return 0;
+  }
+  name_subdomain = strchr(name, '.');
+  if (name_subdomain == NULL) return 0;
+  name_subdomain_length = strlen(name_subdomain);
+  if (name_subdomain_length < 2) return 0;
+  name_subdomain++; /* Starts after the dot. */
+  name_subdomain_length--;
+  entry += 2; /* Remove *. */
+  entry_length -= 2;
+  dot = strchr(name_subdomain, '.');
+  if ((dot == NULL) || (dot == &name_subdomain[name_subdomain_length - 1])) {
+    gpr_log(GPR_ERROR, "Invalid toplevel subdomain: %s", name_subdomain);
+    return 0;
+  }
+  if (name_subdomain[name_subdomain_length - 1] == '.') {
+    name_subdomain_length--;
+  }
+  return ((entry_length > 0) && (name_subdomain_length == entry_length) &&
+          strncmp(entry, name_subdomain, entry_length) == 0);
+}
+
+static int ssl_server_handshaker_factory_servername_callback(SSL *ssl, int *ap,
+                                                             void *arg) {
+  tsi_ssl_server_handshaker_factory *impl =
+      (tsi_ssl_server_handshaker_factory *)arg;
+  size_t i = 0;
+  const char *servername = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+  if (servername == NULL || strlen(servername) == 0) {
+    return SSL_TLSEXT_ERR_NOACK;
+  }
+
+  for (i = 0; i < impl->ssl_context_count; i++) {
+    if (tsi_ssl_peer_matches_name(&impl->ssl_context_x509_subject_names[i],
+                                  servername)) {
+      SSL_set_SSL_CTX(ssl, impl->ssl_contexts[i]);
+      return SSL_TLSEXT_ERR_OK;
+    }
+  }
+  gpr_log(GPR_ERROR, "No match found for server name: %s.", servername);
+  return SSL_TLSEXT_ERR_ALERT_WARNING;
+}
+
+#if TSI_OPENSSL_ALPN_SUPPORT
+static int server_handshaker_factory_alpn_callback(
+    SSL *ssl, const unsigned char **out, unsigned char *outlen,
+    const unsigned char *in, unsigned int inlen, void *arg) {
+  tsi_ssl_server_handshaker_factory *factory =
+      (tsi_ssl_server_handshaker_factory *)arg;
+  return select_protocol_list(out, outlen, in, inlen,
+                              factory->alpn_protocol_list,
+                              factory->alpn_protocol_list_length);
+}
+#endif /* TSI_OPENSSL_ALPN_SUPPORT */
+
+static int server_handshaker_factory_npn_advertised_callback(
+    SSL *ssl, const unsigned char **out, unsigned int *outlen, void *arg) {
+  tsi_ssl_server_handshaker_factory *factory =
+      (tsi_ssl_server_handshaker_factory *)arg;
+  *out = factory->alpn_protocol_list;
+  GPR_ASSERT(factory->alpn_protocol_list_length <= UINT_MAX);
+  *outlen = (unsigned int)factory->alpn_protocol_list_length;
+  return SSL_TLSEXT_ERR_OK;
+}
+
+/* --- tsi_ssl_handshaker_factory constructors. --- */
+
+tsi_result tsi_create_ssl_client_handshaker_factory(
+    const unsigned char *pem_private_key, size_t pem_private_key_size,
+    const unsigned char *pem_cert_chain, size_t pem_cert_chain_size,
+    const unsigned char *pem_root_certs, size_t pem_root_certs_size,
+    const char *cipher_list, const unsigned char **alpn_protocols,
+    const unsigned char *alpn_protocols_lengths, uint16_t num_alpn_protocols,
+    tsi_ssl_handshaker_factory **factory) {
+  SSL_CTX *ssl_context = NULL;
+  tsi_ssl_client_handshaker_factory *impl = NULL;
+  tsi_result result = TSI_OK;
+
+  gpr_once_init(&init_openssl_once, init_openssl);
+
+  if (factory == NULL) return TSI_INVALID_ARGUMENT;
+  *factory = NULL;
+  if (pem_root_certs == NULL) return TSI_INVALID_ARGUMENT;
+
+  ssl_context = SSL_CTX_new(TLSv1_2_method());
+  if (ssl_context == NULL) {
+    gpr_log(GPR_ERROR, "Could not create ssl context.");
+    return TSI_INVALID_ARGUMENT;
+  }
+
+  impl = calloc(1, sizeof(tsi_ssl_client_handshaker_factory));
+  if (impl == NULL) {
+    SSL_CTX_free(ssl_context);
+    return TSI_OUT_OF_RESOURCES;
+  }
+  impl->ssl_context = ssl_context;
+
+  do {
+    result =
+        populate_ssl_context(ssl_context, pem_private_key, pem_private_key_size,
+                             pem_cert_chain, pem_cert_chain_size, cipher_list);
+    if (result != TSI_OK) break;
+    result = ssl_ctx_load_verification_certs(ssl_context, pem_root_certs,
+                                             pem_root_certs_size, NULL);
+    if (result != TSI_OK) {
+      gpr_log(GPR_ERROR, "Cannot load server root certificates.");
+      break;
+    }
+
+    if (num_alpn_protocols != 0) {
+      result = build_alpn_protocol_name_list(
+          alpn_protocols, alpn_protocols_lengths, num_alpn_protocols,
+          &impl->alpn_protocol_list, &impl->alpn_protocol_list_length);
+      if (result != TSI_OK) {
+        gpr_log(GPR_ERROR, "Building alpn list failed with error %s.",
+                tsi_result_to_string(result));
+        break;
+      }
+#if TSI_OPENSSL_ALPN_SUPPORT
+      GPR_ASSERT(impl->alpn_protocol_list_length < UINT_MAX);
+      if (SSL_CTX_set_alpn_protos(
+              ssl_context, impl->alpn_protocol_list,
+              (unsigned int)impl->alpn_protocol_list_length)) {
+        gpr_log(GPR_ERROR, "Could not set alpn protocol list to context.");
+        result = TSI_INVALID_ARGUMENT;
+        break;
+      }
+#endif /* TSI_OPENSSL_ALPN_SUPPORT */
+      SSL_CTX_set_next_proto_select_cb(
+          ssl_context, client_handshaker_factory_npn_callback, impl);
+    }
+  } while (0);
+  if (result != TSI_OK) {
+    ssl_client_handshaker_factory_destroy(&impl->base);
+    return result;
+  }
+  SSL_CTX_set_verify(ssl_context, SSL_VERIFY_PEER, NULL);
+  /* TODO(jboeuf): Add revocation verification. */
+
+  impl->base.create_handshaker =
+      ssl_client_handshaker_factory_create_handshaker;
+  impl->base.destroy = ssl_client_handshaker_factory_destroy;
+  *factory = &impl->base;
+  return TSI_OK;
+}
+
+tsi_result tsi_create_ssl_server_handshaker_factory(
+    const unsigned char **pem_private_keys,
+    const size_t *pem_private_keys_sizes, const unsigned char **pem_cert_chains,
+    const size_t *pem_cert_chains_sizes, size_t key_cert_pair_count,
+    const unsigned char *pem_client_root_certs,
+    size_t pem_client_root_certs_size, int force_client_auth,
+    const char *cipher_list, const unsigned char **alpn_protocols,
+    const unsigned char *alpn_protocols_lengths, uint16_t num_alpn_protocols,
+    tsi_ssl_handshaker_factory **factory) {
+  tsi_ssl_server_handshaker_factory *impl = NULL;
+  tsi_result result = TSI_OK;
+  size_t i = 0;
+
+  gpr_once_init(&init_openssl_once, init_openssl);
+
+  if (factory == NULL) return TSI_INVALID_ARGUMENT;
+  *factory = NULL;
+  if (key_cert_pair_count == 0 || pem_private_keys == NULL ||
+      pem_cert_chains == NULL) {
+    return TSI_INVALID_ARGUMENT;
+  }
+
+  impl = calloc(1, sizeof(tsi_ssl_server_handshaker_factory));
+  if (impl == NULL) return TSI_OUT_OF_RESOURCES;
+  impl->base.create_handshaker =
+      ssl_server_handshaker_factory_create_handshaker;
+  impl->base.destroy = ssl_server_handshaker_factory_destroy;
+  impl->ssl_contexts = calloc(key_cert_pair_count, sizeof(SSL_CTX *));
+  impl->ssl_context_x509_subject_names =
+      calloc(key_cert_pair_count, sizeof(tsi_peer));
+  if (impl->ssl_contexts == NULL ||
+      impl->ssl_context_x509_subject_names == NULL) {
+    tsi_ssl_handshaker_factory_destroy(&impl->base);
+    return TSI_OUT_OF_RESOURCES;
+  }
+  impl->ssl_context_count = key_cert_pair_count;
+
+  if (num_alpn_protocols > 0) {
+    result = build_alpn_protocol_name_list(
+        alpn_protocols, alpn_protocols_lengths, num_alpn_protocols,
+        &impl->alpn_protocol_list, &impl->alpn_protocol_list_length);
+    if (result != TSI_OK) {
+      tsi_ssl_handshaker_factory_destroy(&impl->base);
+      return result;
+    }
+  }
+
+  for (i = 0; i < key_cert_pair_count; i++) {
+    do {
+      impl->ssl_contexts[i] = SSL_CTX_new(TLSv1_2_method());
+      if (impl->ssl_contexts[i] == NULL) {
+        gpr_log(GPR_ERROR, "Could not create ssl context.");
+        result = TSI_OUT_OF_RESOURCES;
+        break;
+      }
+      result = populate_ssl_context(
+          impl->ssl_contexts[i], pem_private_keys[i], pem_private_keys_sizes[i],
+          pem_cert_chains[i], pem_cert_chains_sizes[i], cipher_list);
+      if (result != TSI_OK) break;
+
+      if (pem_client_root_certs != NULL) {
+        int flags = SSL_VERIFY_PEER;
+        STACK_OF(X509_NAME) *root_names = NULL;
+        result = ssl_ctx_load_verification_certs(
+            impl->ssl_contexts[i], pem_client_root_certs,
+            pem_client_root_certs_size, &root_names);
+        if (result != TSI_OK) {
+          gpr_log(GPR_ERROR, "Invalid verification certs.");
+          break;
+        }
+        SSL_CTX_set_client_CA_list(impl->ssl_contexts[i], root_names);
+        if (force_client_auth) flags |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
+        SSL_CTX_set_verify(impl->ssl_contexts[i], flags, NULL);
+        /* TODO(jboeuf): Add revocation verification. */
+      }
+
+      result = extract_x509_subject_names_from_pem_cert(
+          pem_cert_chains[i], pem_cert_chains_sizes[i],
+          &impl->ssl_context_x509_subject_names[i]);
+      if (result != TSI_OK) break;
+
+      SSL_CTX_set_tlsext_servername_callback(
+          impl->ssl_contexts[i],
+          ssl_server_handshaker_factory_servername_callback);
+      SSL_CTX_set_tlsext_servername_arg(impl->ssl_contexts[i], impl);
+#if TSI_OPENSSL_ALPN_SUPPORT
+      SSL_CTX_set_alpn_select_cb(impl->ssl_contexts[i],
+                                 server_handshaker_factory_alpn_callback, impl);
+#endif /* TSI_OPENSSL_ALPN_SUPPORT */
+      SSL_CTX_set_next_protos_advertised_cb(
+          impl->ssl_contexts[i],
+          server_handshaker_factory_npn_advertised_callback, impl);
+    } while (0);
+
+    if (result != TSI_OK) {
+      tsi_ssl_handshaker_factory_destroy(&impl->base);
+      return result;
+    }
+  }
+  *factory = &impl->base;
+  return TSI_OK;
+}
+
+/* --- tsi_ssl utils. --- */
+
+int tsi_ssl_peer_matches_name(const tsi_peer *peer, const char *name) {
+  size_t i = 0;
+  size_t san_count = 0;
+  const tsi_peer_property *cn_property = NULL;
+
+  /* For now reject what looks like an IP address. */
+  if (looks_like_ip_address(name)) return 0;
+
+  /* Check the SAN first. */
+  for (i = 0; i < peer->property_count; i++) {
+    const tsi_peer_property *property = &peer->properties[i];
+    if (property->name == NULL) continue;
+    if (strcmp(property->name,
+               TSI_X509_SUBJECT_ALTERNATIVE_NAME_PEER_PROPERTY) == 0) {
+      san_count++;
+      if (does_entry_match_name(property->value.data, property->value.length,
+                                name)) {
+        return 1;
+      }
+    } else if (strcmp(property->name,
+                      TSI_X509_SUBJECT_COMMON_NAME_PEER_PROPERTY) == 0) {
+      cn_property = property;
+    }
+  }
+
+  /* If there's no SAN, try the CN. */
+  if (san_count == 0 && cn_property != NULL) {
+    if (does_entry_match_name(cn_property->value.data,
+                              cn_property->value.length, name)) {
+      return 1;
+    }
+  }
+
+  return 0; /* Not found. */
+}