nss.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

/*
 * Source file for all NSS-specific code for the TLS/SSL layer. No code
 * but vtls.c should ever call or use these functions.
 */

#include "curl_setup.h"

#ifdef USE_NSS

#include "urldata.h"
#include "sendf.h"
#include "formdata.h" /* for the boundary function */
#include "url.h" /* for the ssl config check function */
#include "connect.h"
#include "strequal.h"
#include "select.h"
#include "vtls.h"
#include "llist.h"
#include "curl_printf.h"
#include "nssg.h"
#include <nspr.h>
#include <nss.h>
#include <ssl.h>
#include <sslerr.h>
#include <secerr.h>
#include <secmod.h>
#include <sslproto.h>
#include <prtypes.h>
#include <pk11pub.h>
#include <prio.h>
#include <secitem.h>
#include <secport.h>
#include <certdb.h>
#include <base64.h>
#include <cert.h>
#include <prerror.h>

#define NSSVERNUM ((NSS_VMAJOR<<16)|(NSS_VMINOR<<8)|NSS_VPATCH)

#if NSSVERNUM >= 0x030f00 /* 3.15.0 */
#include <ocsp.h>
#endif

#include "rawstr.h"
#include "warnless.h"
#include "x509asn1.h"

/* The last #include files should be: */
#include "curl_memory.h"
#include "memdebug.h"

#define SSL_DIR "/etc/pki/nssdb"

/* enough to fit the string "PEM Token #[0|1]" */
#define SLOTSIZE 13

PRFileDesc *PR_ImportTCPSocket(PRInt32 osfd);

PRLock * nss_initlock = NULL;
PRLock * nss_crllock = NULL;
struct curl_llist *nss_crl_list = NULL;
NSSInitContext * nss_context = NULL;

volatile int initialized = 0;

typedef struct {
  const char *name;
  int num;
} cipher_s;

#define PK11_SETATTRS(_attr, _idx, _type, _val, _len) do {  \
  CK_ATTRIBUTE *ptr = (_attr) + ((_idx)++);                 \
  ptr->type = (_type);                                      \
  ptr->pValue = (_val);                                     \
  ptr->ulValueLen = (_len);                                 \
} WHILE_FALSE

#define CERT_NewTempCertificate __CERT_NewTempCertificate

#define NUM_OF_CIPHERS sizeof(cipherlist)/sizeof(cipherlist[0])
static const cipher_s cipherlist[] = {
  /* SSL2 cipher suites */
  {"rc4",                        SSL_EN_RC4_128_WITH_MD5},
  {"rc4-md5",                    SSL_EN_RC4_128_WITH_MD5},
  {"rc4export",                  SSL_EN_RC4_128_EXPORT40_WITH_MD5},
  {"rc2",                        SSL_EN_RC2_128_CBC_WITH_MD5},
  {"rc2export",                  SSL_EN_RC2_128_CBC_EXPORT40_WITH_MD5},
  {"des",                        SSL_EN_DES_64_CBC_WITH_MD5},
  {"desede3",                    SSL_EN_DES_192_EDE3_CBC_WITH_MD5},
  /* SSL3/TLS cipher suites */
  {"rsa_rc4_128_md5",            SSL_RSA_WITH_RC4_128_MD5},
  {"rsa_rc4_128_sha",            SSL_RSA_WITH_RC4_128_SHA},
  {"rsa_3des_sha",               SSL_RSA_WITH_3DES_EDE_CBC_SHA},
  {"rsa_des_sha",                SSL_RSA_WITH_DES_CBC_SHA},
  {"rsa_rc4_40_md5",             SSL_RSA_EXPORT_WITH_RC4_40_MD5},
  {"rsa_rc2_40_md5",             SSL_RSA_EXPORT_WITH_RC2_CBC_40_MD5},
  {"rsa_null_md5",               SSL_RSA_WITH_NULL_MD5},
  {"rsa_null_sha",               SSL_RSA_WITH_NULL_SHA},
  {"fips_3des_sha",              SSL_RSA_FIPS_WITH_3DES_EDE_CBC_SHA},
  {"fips_des_sha",               SSL_RSA_FIPS_WITH_DES_CBC_SHA},
  {"fortezza",                   SSL_FORTEZZA_DMS_WITH_FORTEZZA_CBC_SHA},
  {"fortezza_rc4_128_sha",       SSL_FORTEZZA_DMS_WITH_RC4_128_SHA},
  {"fortezza_null",              SSL_FORTEZZA_DMS_WITH_NULL_SHA},
  /* TLS 1.0: Exportable 56-bit Cipher Suites. */
  {"rsa_des_56_sha",             TLS_RSA_EXPORT1024_WITH_DES_CBC_SHA},
  {"rsa_rc4_56_sha",             TLS_RSA_EXPORT1024_WITH_RC4_56_SHA},
  /* AES ciphers. */
  {"dhe_dss_aes_128_cbc_sha",    TLS_DHE_DSS_WITH_AES_128_CBC_SHA},
  {"dhe_dss_aes_256_cbc_sha",    TLS_DHE_DSS_WITH_AES_256_CBC_SHA},
  {"dhe_rsa_aes_128_cbc_sha",    TLS_DHE_RSA_WITH_AES_128_CBC_SHA},
  {"dhe_rsa_aes_256_cbc_sha",    TLS_DHE_RSA_WITH_AES_256_CBC_SHA},
  {"rsa_aes_128_sha",            TLS_RSA_WITH_AES_128_CBC_SHA},
  {"rsa_aes_256_sha",            TLS_RSA_WITH_AES_256_CBC_SHA},
  /* ECC ciphers. */
  {"ecdh_ecdsa_null_sha",        TLS_ECDH_ECDSA_WITH_NULL_SHA},
  {"ecdh_ecdsa_rc4_128_sha",     TLS_ECDH_ECDSA_WITH_RC4_128_SHA},
  {"ecdh_ecdsa_3des_sha",        TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA},
  {"ecdh_ecdsa_aes_128_sha",     TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA},
  {"ecdh_ecdsa_aes_256_sha",     TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA},
  {"ecdhe_ecdsa_null_sha",       TLS_ECDHE_ECDSA_WITH_NULL_SHA},
  {"ecdhe_ecdsa_rc4_128_sha",    TLS_ECDHE_ECDSA_WITH_RC4_128_SHA},
  {"ecdhe_ecdsa_3des_sha",       TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA},
  {"ecdhe_ecdsa_aes_128_sha",    TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA},
  {"ecdhe_ecdsa_aes_256_sha",    TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA},
  {"ecdh_rsa_null_sha",          TLS_ECDH_RSA_WITH_NULL_SHA},
  {"ecdh_rsa_128_sha",           TLS_ECDH_RSA_WITH_RC4_128_SHA},
  {"ecdh_rsa_3des_sha",          TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA},
  {"ecdh_rsa_aes_128_sha",       TLS_ECDH_RSA_WITH_AES_128_CBC_SHA},
  {"ecdh_rsa_aes_256_sha",       TLS_ECDH_RSA_WITH_AES_256_CBC_SHA},
  {"echde_rsa_null",             TLS_ECDHE_RSA_WITH_NULL_SHA},
  {"ecdhe_rsa_rc4_128_sha",      TLS_ECDHE_RSA_WITH_RC4_128_SHA},
  {"ecdhe_rsa_3des_sha",         TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA},
  {"ecdhe_rsa_aes_128_sha",      TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA},
  {"ecdhe_rsa_aes_256_sha",      TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA},
  {"ecdh_anon_null_sha",         TLS_ECDH_anon_WITH_NULL_SHA},
  {"ecdh_anon_rc4_128sha",       TLS_ECDH_anon_WITH_RC4_128_SHA},
  {"ecdh_anon_3des_sha",         TLS_ECDH_anon_WITH_3DES_EDE_CBC_SHA},
  {"ecdh_anon_aes_128_sha",      TLS_ECDH_anon_WITH_AES_128_CBC_SHA},
  {"ecdh_anon_aes_256_sha",      TLS_ECDH_anon_WITH_AES_256_CBC_SHA},
#ifdef TLS_RSA_WITH_NULL_SHA256
  /* new HMAC-SHA256 cipher suites specified in RFC */
  {"rsa_null_sha_256",                TLS_RSA_WITH_NULL_SHA256},
  {"rsa_aes_128_cbc_sha_256",         TLS_RSA_WITH_AES_128_CBC_SHA256},
  {"rsa_aes_256_cbc_sha_256",         TLS_RSA_WITH_AES_256_CBC_SHA256},
  {"dhe_rsa_aes_128_cbc_sha_256",     TLS_DHE_RSA_WITH_AES_128_CBC_SHA256},
  {"dhe_rsa_aes_256_cbc_sha_256",     TLS_DHE_RSA_WITH_AES_256_CBC_SHA256},
  {"ecdhe_ecdsa_aes_128_cbc_sha_256", TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256},
  {"ecdhe_rsa_aes_128_cbc_sha_256",   TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256},
#endif
#ifdef TLS_RSA_WITH_AES_128_GCM_SHA256
  /* AES GCM cipher suites in RFC 5288 and RFC 5289 */
  {"rsa_aes_128_gcm_sha_256",         TLS_RSA_WITH_AES_128_GCM_SHA256},
  {"dhe_rsa_aes_128_gcm_sha_256",     TLS_DHE_RSA_WITH_AES_128_GCM_SHA256},
  {"dhe_dss_aes_128_gcm_sha_256",     TLS_DHE_DSS_WITH_AES_128_GCM_SHA256},
  {"ecdhe_ecdsa_aes_128_gcm_sha_256", TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256},
  {"ecdh_ecdsa_aes_128_gcm_sha_256",  TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256},
  {"ecdhe_rsa_aes_128_gcm_sha_256",   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256},
  {"ecdh_rsa_aes_128_gcm_sha_256",    TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256},
#endif
};

static const char* pem_library = "libnsspem.so";
SECMODModule* mod = NULL;

/* NSPR I/O layer we use to detect blocking direction during SSL handshake */
static PRDescIdentity nspr_io_identity = PR_INVALID_IO_LAYER;
static PRIOMethods nspr_io_methods;

static const char* nss_error_to_name(PRErrorCode code)
{
  const char *name = PR_ErrorToName(code);
  if(name)
    return name;

  return "unknown error";
}

static void nss_print_error_message(struct SessionHandle *data, PRUint32 err)
{
  failf(data, "%s", PR_ErrorToString(err, PR_LANGUAGE_I_DEFAULT));
}

static SECStatus set_ciphers(struct SessionHandle *data, PRFileDesc * model,
                             char *cipher_list)
{
  unsigned int i;
  PRBool cipher_state[NUM_OF_CIPHERS];
  PRBool found;
  char *cipher;

  /* First disable all ciphers. This uses a different max value in case
   * NSS adds more ciphers later we don't want them available by
   * accident
   */
  for(i=0; i<SSL_NumImplementedCiphers; i++) {
    SSL_CipherPrefSet(model, SSL_ImplementedCiphers[i], PR_FALSE);
  }

  /* Set every entry in our list to false */
  for(i=0; i<NUM_OF_CIPHERS; i++) {
    cipher_state[i] = PR_FALSE;
  }

  cipher = cipher_list;

  while(cipher_list && (cipher_list[0])) {
    while((*cipher) && (ISSPACE(*cipher)))
      ++cipher;

    if((cipher_list = strchr(cipher, ','))) {
      *cipher_list++ = '\0';
    }

    found = PR_FALSE;

    for(i=0; i<NUM_OF_CIPHERS; i++) {
      if(Curl_raw_equal(cipher, cipherlist[i].name)) {
        cipher_state[i] = PR_TRUE;
        found = PR_TRUE;
        break;
      }
    }

    if(found == PR_FALSE) {
      failf(data, "Unknown cipher in list: %s", cipher);
      return SECFailure;
    }

    if(cipher_list) {
      cipher = cipher_list;
    }
  }

  /* Finally actually enable the selected ciphers */
  for(i=0; i<NUM_OF_CIPHERS; i++) {
    if(!cipher_state[i])
      continue;

    if(SSL_CipherPrefSet(model, cipherlist[i].num, PR_TRUE) != SECSuccess) {
      failf(data, "cipher-suite not supported by NSS: %s", cipherlist[i].name);
      return SECFailure;
    }
  }

  return SECSuccess;
}

/*
 * Get the number of ciphers that are enabled. We use this to determine
 * if we need to call NSS_SetDomesticPolicy() to enable the default ciphers.
 */
static int num_enabled_ciphers(void)
{
  PRInt32 policy = 0;
  int count = 0;
  unsigned int i;

  for(i=0; i<NUM_OF_CIPHERS; i++) {
    SSL_CipherPolicyGet(cipherlist[i].num, &policy);
    if(policy)
      count++;
  }
  return count;
}

/*
 * Determine whether the nickname passed in is a filename that needs to
 * be loaded as a PEM or a regular NSS nickname.
 *
 * returns 1 for a file
 * returns 0 for not a file (NSS nickname)
 */
static int is_file(const char *filename)
{
  struct_stat st;

  if(filename == NULL)
    return 0;

  if(stat(filename, &st) == 0)
    if(S_ISREG(st.st_mode))
      return 1;

  return 0;
}

/* Check if the given string is filename or nickname of a certificate.  If the
 * given string is recognized as filename, return NULL.  If the given string is
 * recognized as nickname, return a duplicated string.  The returned string
 * should be later deallocated using free().  If the OOM failure occurs, we
 * return NULL, too.
 */
static char* dup_nickname(struct SessionHandle *data, enum dupstring cert_kind)
{
  const char *str = data->set.str[cert_kind];
  const char *n;

  if(!is_file(str))
    /* no such file exists, use the string as nickname */
    return strdup(str);

  /* search the last slash; we require at least one slash in a file name */
  n = strrchr(str, '/');
  if(!n) {
    infof(data, "warning: certificate file name \"%s\" handled as nickname; "
          "please use \"./%s\" to force file name\n", str, str);
    return strdup(str);
  }

  /* we'll use the PEM reader to read the certificate from file */
  return NULL;
}

/* Call PK11_CreateGenericObject() with the given obj_class and filename.  If
 * the call succeeds, append the object handle to the list of objects so that
 * the object can be destroyed in Curl_nss_close(). */
static CURLcode nss_create_object(struct ssl_connect_data *ssl,
                                  CK_OBJECT_CLASS obj_class,
                                  const char *filename, bool cacert)
{
  PK11SlotInfo *slot;
  PK11GenericObject *obj;
  CK_BBOOL cktrue = CK_TRUE;
  CK_BBOOL ckfalse = CK_FALSE;
  CK_ATTRIBUTE attrs[/* max count of attributes */ 4];
  int attr_cnt = 0;
  CURLcode result = (cacert)
    ? CURLE_SSL_CACERT_BADFILE
    : CURLE_SSL_CERTPROBLEM;

  const int slot_id = (cacert) ? 0 : 1;
  char *slot_name = aprintf("PEM Token #%d", slot_id);
  if(!slot_name)
    return CURLE_OUT_OF_MEMORY;

  slot = PK11_FindSlotByName(slot_name);
  free(slot_name);
  if(!slot)
    return result;

  PK11_SETATTRS(attrs, attr_cnt, CKA_CLASS, &obj_class, sizeof(obj_class));
  PK11_SETATTRS(attrs, attr_cnt, CKA_TOKEN, &cktrue, sizeof(CK_BBOOL));
  PK11_SETATTRS(attrs, attr_cnt, CKA_LABEL, (unsigned char *)filename,
                strlen(filename) + 1);

  if(CKO_CERTIFICATE == obj_class) {
    CK_BBOOL *pval = (cacert) ? (&cktrue) : (&ckfalse);
    PK11_SETATTRS(attrs, attr_cnt, CKA_TRUST, pval, sizeof(*pval));
  }

  obj = PK11_CreateGenericObject(slot, attrs, attr_cnt, PR_FALSE);
  PK11_FreeSlot(slot);
  if(!obj)
    return result;

  if(!Curl_llist_insert_next(ssl->obj_list, ssl->obj_list->tail, obj)) {
    PK11_DestroyGenericObject(obj);
    return CURLE_OUT_OF_MEMORY;
  }

  if(!cacert && CKO_CERTIFICATE == obj_class)
    /* store reference to a client certificate */
    ssl->obj_clicert = obj;

  return CURLE_OK;
}

/* Destroy the NSS object whose handle is given by ptr.  This function is
 * a callback of Curl_llist_alloc() used by Curl_llist_destroy() to destroy
 * NSS objects in Curl_nss_close() */
static void nss_destroy_object(void *user, void *ptr)
{
  PK11GenericObject *obj = (PK11GenericObject *)ptr;
  (void) user;
  PK11_DestroyGenericObject(obj);
}

/* same as nss_destroy_object() but for CRL items */
static void nss_destroy_crl_item(void *user, void *ptr)
{
  SECItem *crl_der = (SECItem *)ptr;
  (void) user;
  SECITEM_FreeItem(crl_der, PR_TRUE);
}

static CURLcode nss_load_cert(struct ssl_connect_data *ssl,
                              const char *filename, PRBool cacert)
{
  CURLcode result = (cacert)
    ? CURLE_SSL_CACERT_BADFILE
    : CURLE_SSL_CERTPROBLEM;

  /* libnsspem.so leaks memory if the requested file does not exist.  For more
   * details, go to <https://bugzilla.redhat.com/734760>. */
  if(is_file(filename))
    result = nss_create_object(ssl, CKO_CERTIFICATE, filename, cacert);

  if(!result && !cacert) {
    /* we have successfully loaded a client certificate */
    CERTCertificate *cert;
    char *nickname = NULL;
    char *n = strrchr(filename, '/');
    if(n)
      n++;

    /* The following undocumented magic helps to avoid a SIGSEGV on call
     * of PK11_ReadRawAttribute() from SelectClientCert() when using an
     * immature version of libnsspem.so.  For more details, go to
     * <https://bugzilla.redhat.com/733685>. */
    nickname = aprintf("PEM Token #1:%s", n);
    if(nickname) {
      cert = PK11_FindCertFromNickname(nickname, NULL);
      if(cert)
        CERT_DestroyCertificate(cert);

      free(nickname);
    }
  }

  return result;
}

/* add given CRL to cache if it is not already there */
static CURLcode nss_cache_crl(SECItem *crl_der)
{
  CERTCertDBHandle *db = CERT_GetDefaultCertDB();
  CERTSignedCrl *crl = SEC_FindCrlByDERCert(db, crl_der, 0);
  if(crl) {
    /* CRL already cached */
    SEC_DestroyCrl(crl);
    SECITEM_FreeItem(crl_der, PR_TRUE);
    return CURLE_OK;
  }

  /* acquire lock before call of CERT_CacheCRL() and accessing nss_crl_list */
  PR_Lock(nss_crllock);

  /* store the CRL item so that we can free it in Curl_nss_cleanup() */
  if(!Curl_llist_insert_next(nss_crl_list, nss_crl_list->tail, crl_der)) {
    SECITEM_FreeItem(crl_der, PR_TRUE);
    PR_Unlock(nss_crllock);
    return CURLE_OUT_OF_MEMORY;
  }

  if(SECSuccess != CERT_CacheCRL(db, crl_der)) {
    /* unable to cache CRL */
    PR_Unlock(nss_crllock);
    return CURLE_SSL_CRL_BADFILE;
  }

  /* we need to clear session cache, so that the CRL could take effect */
  SSL_ClearSessionCache();
  PR_Unlock(nss_crllock);
  return CURLE_OK;
}

static CURLcode nss_load_crl(const char* crlfilename)
{
  PRFileDesc *infile;
  PRFileInfo  info;
  SECItem filedata = { 0, NULL, 0 };
  SECItem *crl_der = NULL;
  char *body;

  infile = PR_Open(crlfilename, PR_RDONLY, 0);
  if(!infile)
    return CURLE_SSL_CRL_BADFILE;

  if(PR_SUCCESS != PR_GetOpenFileInfo(infile, &info))
    goto fail;

  if(!SECITEM_AllocItem(NULL, &filedata, info.size + /* zero ended */ 1))
    goto fail;

  if(info.size != PR_Read(infile, filedata.data, info.size))
    goto fail;

  crl_der = SECITEM_AllocItem(NULL, NULL, 0U);
  if(!crl_der)
    goto fail;

  /* place a trailing zero right after the visible data */
  body = (char*)filedata.data;
  body[--filedata.len] = '\0';

  body = strstr(body, "-----BEGIN");
  if(body) {
    /* assume ASCII */
    char *trailer;
    char *begin = PORT_Strchr(body, '\n');
    if(!begin)
      begin = PORT_Strchr(body, '\r');
    if(!begin)
      goto fail;

    trailer = strstr(++begin, "-----END");
    if(!trailer)
      goto fail;

    /* retrieve DER from ASCII */
    *trailer = '\0';
    if(ATOB_ConvertAsciiToItem(crl_der, begin))
      goto fail;

    SECITEM_FreeItem(&filedata, PR_FALSE);
  }
  else
    /* assume DER */
    *crl_der = filedata;

  PR_Close(infile);
  return nss_cache_crl(crl_der);

fail:
  PR_Close(infile);
  SECITEM_FreeItem(crl_der, PR_TRUE);
  SECITEM_FreeItem(&filedata, PR_FALSE);
  return CURLE_SSL_CRL_BADFILE;
}

static CURLcode nss_load_key(struct connectdata *conn, int sockindex,
                             char *key_file)
{
  PK11SlotInfo *slot;
  SECStatus status;
  CURLcode result;
  struct ssl_connect_data *ssl = conn->ssl;

  (void)sockindex; /* unused */

  result = nss_create_object(ssl, CKO_PRIVATE_KEY, key_file, FALSE);
  if(result) {
    PR_SetError(SEC_ERROR_BAD_KEY, 0);
    return result;
  }

  slot = PK11_FindSlotByName("PEM Token #1");
  if(!slot)
    return CURLE_SSL_CERTPROBLEM;

  /* This will force the token to be seen as re-inserted */
  SECMOD_WaitForAnyTokenEvent(mod, 0, 0);
  PK11_IsPresent(slot);

  status = PK11_Authenticate(slot, PR_TRUE,
                             conn->data->set.str[STRING_KEY_PASSWD]);
  PK11_FreeSlot(slot);

  return (SECSuccess == status) ? CURLE_OK : CURLE_SSL_CERTPROBLEM;
}

static int display_error(struct connectdata *conn, PRInt32 err,
                         const char *filename)
{
  switch(err) {
  case SEC_ERROR_BAD_PASSWORD:
    failf(conn->data, "Unable to load client key: Incorrect password");
    return 1;
  case SEC_ERROR_UNKNOWN_CERT:
    failf(conn->data, "Unable to load certificate %s", filename);
    return 1;
  default:
    break;
  }
  return 0; /* The caller will print a generic error */
}

static CURLcode cert_stuff(struct connectdata *conn, int sockindex,
                           char *cert_file, char *key_file)
{
  struct SessionHandle *data = conn->data;
  CURLcode result;

  if(cert_file) {
    result = nss_load_cert(&conn->ssl[sockindex], cert_file, PR_FALSE);
    if(result) {
      const PRErrorCode err = PR_GetError();
      if(!display_error(conn, err, cert_file)) {
        const char *err_name = nss_error_to_name(err);
        failf(data, "unable to load client cert: %d (%s)", err, err_name);
      }

      return result;
    }
  }

  if(key_file || (is_file(cert_file))) {
    if(key_file)
      result = nss_load_key(conn, sockindex, key_file);
    else
      /* In case the cert file also has the key */
      result = nss_load_key(conn, sockindex, cert_file);
    if(result) {
      const PRErrorCode err = PR_GetError();
      if(!display_error(conn, err, key_file)) {
        const char *err_name = nss_error_to_name(err);
        failf(data, "unable to load client key: %d (%s)", err, err_name);
      }

      return result;
    }
  }

  return CURLE_OK;
}

static char * nss_get_password(PK11SlotInfo * slot, PRBool retry, void *arg)
{
  (void)slot; /* unused */

  if(retry || NULL == arg)
    return NULL;
  else
    return (char *)PORT_Strdup((char *)arg);
}

/* bypass the default SSL_AuthCertificate() hook in case we do not want to
 * verify peer */
static SECStatus nss_auth_cert_hook(void *arg, PRFileDesc *fd, PRBool checksig,
                                    PRBool isServer)
{
  struct connectdata *conn = (struct connectdata *)arg;

#ifdef SSL_ENABLE_OCSP_STAPLING
  if(conn->data->set.ssl.verifystatus) {
    SECStatus cacheResult;

    const SECItemArray *csa = SSL_PeerStapledOCSPResponses(fd);
    if(!csa) {
      failf(conn->data, "Invalid OCSP response");
      return SECFailure;
    }

    if(csa->len == 0) {
      failf(conn->data, "No OCSP response received");
      return SECFailure;
    }

    cacheResult = CERT_CacheOCSPResponseFromSideChannel(
      CERT_GetDefaultCertDB(), SSL_PeerCertificate(fd),
      PR_Now(), &csa->items[0], arg
    );

    if(cacheResult != SECSuccess) {
      failf(conn->data, "Invalid OCSP response");
      return cacheResult;
    }
  }
#endif

  if(!conn->data->set.ssl.verifypeer) {
    infof(conn->data, "skipping SSL peer certificate verification\n");
    return SECSuccess;
  }

  return SSL_AuthCertificate(CERT_GetDefaultCertDB(), fd, checksig, isServer);
}

/**
 * Inform the application that the handshake is complete.
 */
static void HandshakeCallback(PRFileDesc *sock, void *arg)
{
  struct connectdata *conn = (struct connectdata*) arg;
  unsigned int buflenmax = 50;
  unsigned char buf[50];
  unsigned int buflen;
  SSLNextProtoState state;

  if(!conn->data->set.ssl_enable_npn && !conn->data->set.ssl_enable_alpn) {
    return;
  }

  if(SSL_GetNextProto(sock, &state, buf, &buflen, buflenmax) == SECSuccess) {

    switch(state) {
    case SSL_NEXT_PROTO_NO_SUPPORT:
    case SSL_NEXT_PROTO_NO_OVERLAP:
      infof(conn->data, "ALPN/NPN, server did not agree to a protocol\n");
      return;
#ifdef SSL_ENABLE_ALPN
    case SSL_NEXT_PROTO_SELECTED:
      infof(conn->data, "ALPN, server accepted to use %.*s\n", buflen, buf);
      break;
#endif
    case SSL_NEXT_PROTO_NEGOTIATED:
      infof(conn->data, "NPN, server accepted to use %.*s\n", buflen, buf);
      break;
    }

#ifdef USE_NGHTTP2
    if(buflen == NGHTTP2_PROTO_VERSION_ID_LEN &&
       !memcmp(NGHTTP2_PROTO_VERSION_ID, buf, NGHTTP2_PROTO_VERSION_ID_LEN)) {
      conn->negnpn = CURL_HTTP_VERSION_2_0;
    }
    else
#endif
    if(buflen == ALPN_HTTP_1_1_LENGTH &&
       !memcmp(ALPN_HTTP_1_1, buf, ALPN_HTTP_1_1_LENGTH)) {
      conn->negnpn = CURL_HTTP_VERSION_1_1;
    }
  }
}

static SECStatus CanFalseStartCallback(PRFileDesc *sock, void *client_data,
                                       PRBool *canFalseStart)
{
  struct connectdata *conn = client_data;
  struct SessionHandle *data = conn->data;

  SSLChannelInfo channelInfo;
  SSLCipherSuiteInfo cipherInfo;

  SECStatus rv;
  PRBool negotiatedExtension;

  *canFalseStart = PR_FALSE;

  if(SSL_GetChannelInfo(sock, &channelInfo, sizeof(channelInfo)) != SECSuccess)
    return SECFailure;

  if(SSL_GetCipherSuiteInfo(channelInfo.cipherSuite, &cipherInfo,
                            sizeof(cipherInfo)) != SECSuccess)
    return SECFailure;

  /* Prevent version downgrade attacks from TLS 1.2, and avoid False Start for
   * TLS 1.3 and later. See https://bugzilla.mozilla.org/show_bug.cgi?id=861310
   */
  if(channelInfo.protocolVersion != SSL_LIBRARY_VERSION_TLS_1_2)
    goto end;

  /* Only allow ECDHE key exchange algorithm.
   * See https://bugzilla.mozilla.org/show_bug.cgi?id=952863 */
  if(cipherInfo.keaType != ssl_kea_ecdh)
    goto end;

  /* Prevent downgrade attacks on the symmetric cipher. We do not allow CBC
   * mode due to BEAST, POODLE, and other attacks on the MAC-then-Encrypt
   * design. See https://bugzilla.mozilla.org/show_bug.cgi?id=1109766 */
  if(cipherInfo.symCipher != ssl_calg_aes_gcm)
    goto end;

  /* Enforce ALPN or NPN to do False Start, as an indicator of server
   * compatibility. */
  rv = SSL_HandshakeNegotiatedExtension(sock, ssl_app_layer_protocol_xtn,
                                        &negotiatedExtension);
  if(rv != SECSuccess || !negotiatedExtension) {
    rv = SSL_HandshakeNegotiatedExtension(sock, ssl_next_proto_nego_xtn,
                                          &negotiatedExtension);
  }

  if(rv != SECSuccess || !negotiatedExtension)
    goto end;

  *canFalseStart = PR_TRUE;

  infof(data, "Trying TLS False Start\n");

end:
  return SECSuccess;
}

static void display_cert_info(struct SessionHandle *data,
                              CERTCertificate *cert)
{
  char *subject, *issuer, *common_name;
  PRExplodedTime printableTime;
  char timeString[256];
  PRTime notBefore, notAfter;

  subject = CERT_NameToAscii(&cert->subject);
  issuer = CERT_NameToAscii(&cert->issuer);
  common_name = CERT_GetCommonName(&cert->subject);
  infof(data, "\tsubject: %s\n", subject);

  CERT_GetCertTimes(cert, &notBefore, &notAfter);
  PR_ExplodeTime(notBefore, PR_GMTParameters, &printableTime);
  PR_FormatTime(timeString, 256, "%b %d %H:%M:%S %Y GMT", &printableTime);
  infof(data, "\tstart date: %s\n", timeString);
  PR_ExplodeTime(notAfter, PR_GMTParameters, &printableTime);
  PR_FormatTime(timeString, 256, "%b %d %H:%M:%S %Y GMT", &printableTime);
  infof(data, "\texpire date: %s\n", timeString);
  infof(data, "\tcommon name: %s\n", common_name);
  infof(data, "\tissuer: %s\n", issuer);

  PR_Free(subject);
  PR_Free(issuer);
  PR_Free(common_name);
}

static CURLcode display_conn_info(struct connectdata *conn, PRFileDesc *sock)
{
  CURLcode result = CURLE_OK;
  SSLChannelInfo channel;
  SSLCipherSuiteInfo suite;
  CERTCertificate *cert;
  CERTCertificate *cert2;
  CERTCertificate *cert3;
  PRTime now;
  int i;

  if(SSL_GetChannelInfo(sock, &channel, sizeof channel) ==
     SECSuccess && channel.length == sizeof channel &&
     channel.cipherSuite) {
    if(SSL_GetCipherSuiteInfo(channel.cipherSuite,
                              &suite, sizeof suite) == SECSuccess) {
      infof(conn->data, "SSL connection using %s\n", suite.cipherSuiteName);
    }
  }

  cert = SSL_PeerCertificate(sock);
  if(cert) {
    infof(conn->data, "Server certificate:\n");

    if(!conn->data->set.ssl.certinfo) {
      display_cert_info(conn->data, cert);
      CERT_DestroyCertificate(cert);
    }
    else {
      /* Count certificates in chain. */
      now = PR_Now();
      i = 1;
      if(!cert->isRoot) {
        cert2 = CERT_FindCertIssuer(cert, now, certUsageSSLCA);
        while(cert2) {
          i++;
          if(cert2->isRoot) {
            CERT_DestroyCertificate(cert2);
            break;
          }
          cert3 = CERT_FindCertIssuer(cert2, now, certUsageSSLCA);
          CERT_DestroyCertificate(cert2);
          cert2 = cert3;
        }
      }

      result = Curl_ssl_init_certinfo(conn->data, i);
      if(!result) {
        for(i = 0; cert; cert = cert2) {
          result = Curl_extract_certinfo(conn, i++, (char *)cert->derCert.data,
                                         (char *)cert->derCert.data +
                                                 cert->derCert.len);
          if(result)
            break;

          if(cert->isRoot) {
            CERT_DestroyCertificate(cert);
            break;
          }

          cert2 = CERT_FindCertIssuer(cert, now, certUsageSSLCA);
          CERT_DestroyCertificate(cert);
        }
      }
    }
  }

  return result;
}

static SECStatus BadCertHandler(void *arg, PRFileDesc *sock)
{
  struct connectdata *conn = (struct connectdata *)arg;
  struct SessionHandle *data = conn->data;
  PRErrorCode err = PR_GetError();
  CERTCertificate *cert;

  /* remember the cert verification result */
  data->set.ssl.certverifyresult = err;

  if(err == SSL_ERROR_BAD_CERT_DOMAIN && !data->set.ssl.verifyhost)
    /* we are asked not to verify the host name */
    return SECSuccess;

  /* print only info about the cert, the error is printed off the callback */
  cert = SSL_PeerCertificate(sock);
  if(cert) {
    infof(data, "Server certificate:\n");
    display_cert_info(data, cert);
    CERT_DestroyCertificate(cert);
  }

  return SECFailure;
}

/**
 *
 * Check that the Peer certificate's issuer certificate matches the one found
 * by issuer_nickname.  This is not exactly the way OpenSSL and GNU TLS do the
 * issuer check, so we provide comments that mimic the OpenSSL
 * X509_check_issued function (in x509v3/v3_purp.c)
 */
static SECStatus check_issuer_cert(PRFileDesc *sock,
                                   char *issuer_nickname)
{
  CERTCertificate *cert, *cert_issuer, *issuer;
  SECStatus res=SECSuccess;
  void *proto_win = NULL;

  /*
    PRArenaPool   *tmpArena = NULL;
    CERTAuthKeyID *authorityKeyID = NULL;
    SECITEM       *caname = NULL;
  */

  cert = SSL_PeerCertificate(sock);
  cert_issuer = CERT_FindCertIssuer(cert, PR_Now(), certUsageObjectSigner);

  proto_win = SSL_RevealPinArg(sock);
  issuer = PK11_FindCertFromNickname(issuer_nickname, proto_win);

  if((!cert_issuer) || (!issuer))
    res = SECFailure;
  else if(SECITEM_CompareItem(&cert_issuer->derCert,
                              &issuer->derCert)!=SECEqual)
    res = SECFailure;

  CERT_DestroyCertificate(cert);
  CERT_DestroyCertificate(issuer);
  CERT_DestroyCertificate(cert_issuer);
  return res;
}

/**
 *
 * Callback to pick the SSL client certificate.
 */
static SECStatus SelectClientCert(void *arg, PRFileDesc *sock,
                                  struct CERTDistNamesStr *caNames,
                                  struct CERTCertificateStr **pRetCert,
                                  struct SECKEYPrivateKeyStr **pRetKey)
{
  struct ssl_connect_data *connssl = (struct ssl_connect_data *)arg;
  struct SessionHandle *data = connssl->data;
  const char *nickname = connssl->client_nickname;

  if(connssl->obj_clicert) {
    /* use the cert/key provided by PEM reader */
    static const char pem_slotname[] = "PEM Token #1";
    SECItem cert_der = { 0, NULL, 0 };
    void *proto_win = SSL_RevealPinArg(sock);
    struct CERTCertificateStr *cert;
    struct SECKEYPrivateKeyStr *key;

    PK11SlotInfo *slot = PK11_FindSlotByName(pem_slotname);
    if(NULL == slot) {
      failf(data, "NSS: PK11 slot not found: %s", pem_slotname);
      return SECFailure;
    }

    if(PK11_ReadRawAttribute(PK11_TypeGeneric, connssl->obj_clicert, CKA_VALUE,
                             &cert_der) != SECSuccess) {
      failf(data, "NSS: CKA_VALUE not found in PK11 generic object");
      PK11_FreeSlot(slot);
      return SECFailure;
    }

    cert = PK11_FindCertFromDERCertItem(slot, &cert_der, proto_win);
    SECITEM_FreeItem(&cert_der, PR_FALSE);
    if(NULL == cert) {
      failf(data, "NSS: client certificate from file not found");
      PK11_FreeSlot(slot);
      return SECFailure;
    }

    key = PK11_FindPrivateKeyFromCert(slot, cert, NULL);
    PK11_FreeSlot(slot);
    if(NULL == key) {
      failf(data, "NSS: private key from file not found");
      CERT_DestroyCertificate(cert);
      return SECFailure;
    }

    infof(data, "NSS: client certificate from file\n");
    display_cert_info(data, cert);

    *pRetCert = cert;
    *pRetKey = key;