libsxmp/sxt/ppkp_ops.c

/*
 * Secure eXtended Message Passing framework
 * Secure eXtended Transport layer implementation: (libsxt)
 * - very similar to SSH2/TLS
 * - using already proven and tested crypto algos
 * - better than TLS for message passing
 *
 * PublicPrivateKeyPairs operation API
 *
 * (c) Alexander Vdolainen 2016 <avdolainen@zoho.com>
 *
 * libsxmp is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * libsxmp is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.";
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <stdarg.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <fcntl.h>

#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/engine.h>

#include <sxt/errno.h>
#include <sxt/safebuf.h>
#include <sxt/rdb.h>
#include <sxt/crypt.h>
#include <sxt/sxtkey.h>
#include <sxt/ed25519.h>
#include <sxt/ciphers.h>
#include <sxt/base64.h>

#if 0
#define blub(a)  printf("%s:%d -> %d\n", __FUNCTION__, __LINE__, (a))
#endif

/* locals */
static int sxtkey_export_priv_ed25519(const sxtkey_t *key, const char *pass, sxtsafebuffer_t **bin);
static int sxt_public_ed25519_2sb(const sxtkey_t *key, sxtsafebuffer_t **buf);
static int sxt_public_ed25519_2rdb(const sxtkey_t *key, sxtrdb_t **out);
static int _sxtkey_check_fmtrawbuf(const char *buffer);
static int _sxtkey_privkey_decrypt(sxtrdb_t *privkey, sxtrdb_t *kdfopt, const char *passkey);

int sxtkey_generate(sxtkey_t *key, int type, int opt)
{
  int r = 0;

  if(!key) return SXT_EINVAL;

  /* set defaults */
  key->type = type;
  key->flags = SXT_PPKP_PRIVATE | SXT_PPKP_PUBLIC;

  switch(type) {
  case PPKP_ED25519:
    key->pubkey = malloc(sizeof(ed25519_pubkey));
    if(!key->pubkey) {
      r = SXT_ENOMEM;
      goto __fall;
    }
    key->privkey = malloc(sizeof(ed25519_privkey));
    if(!key->privkey) {
      r = SXT_ENOMEM;
      goto __safefall0;
    }

    r = crypto_sign_ed25519_keypair(*key->pubkey, *key->privkey);
    if(r) {
      r = SXT_ECRYPTO;
      goto __safefall0;
    }
    break;
  default:
    return SXT_EINVAL;
  }

  if(!r) return SXT_SUCCESS;

 __safefall0:
  if(key->pubkey) free(key->pubkey);
  if(key->privkey) free(key->privkey);

 __fall:
  return r;
}

sxtkey_t *sxtkey_alloc(void)
{
  sxtkey_t *key = malloc(sizeof(sxtkey_t));

  if(!key) return NULL;
  else memset(key, 0, sizeof(sxtkey_t));

  return key;
}

void sxtkey_burn(sxtkey_t *key)
{
  if(!key) return;

  key->priv = NULL;

  switch(key->type) {
  case PPKP_ED25519:
    if(key->pubkey) memset(key->pubkey, 0, sizeof(ed25519_pubkey));
    if(key->privkey) memset(key->privkey, 0, sizeof(ed25519_privkey));
    break;
  default:
    return;
  }

  key->type = 0;
  key->flags = 0;

  return;
}

void sxtkey_free(sxtkey_t *key)
{
  if(!key) return;

  switch(key->type) {
  case PPKP_ED25519:
    if(key->pubkey) free(key->pubkey);
    if(key->privkey) free(key->privkey);
    break;
  default: return; /* cannot free unrecognized key due to the
                    * potential memleak
                    */
  }

  free(key);
  return;
}

const char *sxtkey_name(int type)
{
  switch(type) {
  case PPKP_ED25519:
    return "ppkp-ed25519";
  default: return NULL;
  }

  return NULL;
}

uint8_t sxtkey_type_fname(const char *name)
{
  if(!name) return 0;

  if(!strcmp(name, "ppkp-ed25519")) return PPKP_ED25519;
  else return 0;
}

int sxtkey_public(const sxtkey_t *key)
{
  if(!key) return 0;

  return (key->flags & SXT_PPKP_PUBLIC) == SXT_PPKP_PUBLIC;
}

int sxtkey_private(const sxtkey_t *key)
{
  if(!key) return 0;

  return (key->flags & SXT_PPKP_PRIVATE) == SXT_PPKP_PRIVATE;
}

int sxtkey_assign_hash(sxtkey_t *key, uint64_t hash)
{
  if(!key) return SXT_EINVAL;

  //  if(!sxtkey_private(key)) return SXT_EINVAL;

  //if(key->hash) return SXT_EKEY;
  key->hash = hash;

  return SXT_SUCCESS;
}

uint64_t sxtkey_hash(const sxtkey_t *key)
{
  if(!key) return 0;

  return key->hash;
}

/* will duplicate a key depends on it's kind */
int sxtkey_dup(const sxtkey_t *key, sxtkey_t **dest)
{
  int r = SXT_EKEY;

  if(!key) return SXT_EINVAL;

  if(sxtkey_public(key)) return sxtkey_dup_public(key, dest);
  else if(sxtkey_private(key)) return sxtkey_dup_private(key, dest);
  else return sxtkey_dup_private(key, dest);

  /* never riched */
  return r;
}

/* will duplicate public key, if key was private or pair - it becomes public */
int sxtkey_dup_public(const sxtkey_t *key, sxtkey_t **dest)
{
  sxtkey_t *nkey = NULL;
  int r = SXT_SUCCESS;

  if(!key) return SXT_EINVAL;

  if(!sxtkey_private(key)) return SXT_EKEY;

  if(!(nkey = sxtkey_alloc())) return SXT_ENOMEM;
  else nkey->flags = 0;

  switch(key->type) {
  case PPKP_ED25519: /* actually the same still, but in case of other key types will differ */
    /* check first */
    if(!key->pubkey || !key->privkey) {
      r = SXT_EKEY;
      goto __failed;
    }

    /* allocate new values */
    if(!(nkey->pubkey = malloc(ED25519_PK_LEN))) {
      r = SXT_ENOMEM;
      goto __failed;
    }
    if(!(nkey->privkey = malloc(ED25519_SK_LEN))) {
      free(nkey->pubkey);
      r = SXT_ENOMEM;
      goto __failed;
    }

    /* copy that */
    memcpy(nkey->pubkey, key->pubkey, ED25519_PK_LEN);
    memcpy(nkey->privkey, key->privkey, ED25519_SK_LEN);
    break;
  default: /* don't now about it */
    sxtkey_free(nkey);
    return SXT_EKEY;
  }

  /* copy other values */
  nkey->flags |= SXT_PPKP_PUBLIC;
  nkey->type = key->type;
  nkey->hash = key->hash;
  nkey->priv = key->priv;

  *dest = nkey;

  return r;

 __failed:
  sxtkey_free(nkey);
  return r;
}

/* will duplicate private key, if key public error will returns */
int sxtkey_dup_private(const sxtkey_t *key, sxtkey_t **dest)
{
  sxtkey_t *nkey = NULL;
  int r = SXT_SUCCESS;

  if(!key) return SXT_EINVAL;
  //if(sxt_key_public(key)) return SXT_EKEY; /* cannot duplicate private key from public */

  if(!(nkey = sxtkey_alloc())) return SXT_ENOMEM;
  else nkey->flags = 0;

  switch(key->type) {
  case PPKP_ED25519:
    /* check first */
    if(!key->pubkey || !key->privkey) {
      r = SXT_EKEY;
      goto __failed;
    }

    /* allocate new values */
    if(!(nkey->pubkey = malloc(ED25519_PK_LEN))) {
      r = SXT_ENOMEM;
      goto __failed;
    }
    if(!(nkey->privkey = malloc(ED25519_SK_LEN))) {
      free(nkey->pubkey);
      r = SXT_ENOMEM;
      goto __failed;
    }

    /* copy that */
    memcpy(nkey->pubkey, key->pubkey, ED25519_PK_LEN);
    memcpy(nkey->privkey, key->privkey, ED25519_SK_LEN);
    break;
  default: /* don't now about it */
    sxtkey_free(nkey);
    return SXT_EKEY;
  }

  /* copy other values */
  nkey->flags = SXT_PPKP_PRIVATE;
  nkey->type = key->type;
  nkey->hash = key->hash;
  nkey->priv = key->priv;

  *dest = nkey;

  return r;

 __failed:
  sxtkey_free(nkey);
  return r;
}

int sxtkey_import_priv_file(const char *file, const char *passkey,
                            int (*ask_passkey)(char *pkbuf, size_t length, int confirm, void *priv),
                            void *priv, sxtkey_t **ik)
{
  FILE *stream = NULL;
  char *rawfbuf = NULL, *tbuf, *tebuf, *tuple = NULL, *b64pk = NULL;
  struct stat stbuf;
  uint8_t keytype = 0;
  int r = SXT_SUCCESS, tcc = 0, len;

  *ik = NULL;

  /* check input file */
  if(!file) return SXT_EINVAL;
  if(stat(file, &stbuf) != 0) return SXT_EIO;
  else if(!S_ISREG(stbuf.st_mode)) return SXT_EINVAL;
  if(stbuf.st_size >= SXT_PPKP_MAXCSIZE) return SXT_EINVAL;

  if((stream = fopen(file, "r")) == NULL) return SXT_EIO;

  if(!(rawfbuf = malloc(stbuf.st_size + sizeof(char)))) goto __failed;
  else rawfbuf[stbuf.st_size] = '\0';

  if(fread(rawfbuf, stbuf.st_size, 1, stream) != 1) {
    r = SXT_EIO;
    goto __failed;
  }

  /* check general format */
  r = _sxtkey_check_fmtrawbuf(rawfbuf);
  if(r != SXT_SUCCESS) goto __failed;

  /* now we need to get a keytype and decode b64blob */
  for(tbuf = rawfbuf, tcc = 0, tebuf = NULL; *tbuf != '\0'; tbuf++) {
    switch(tcc) {
    case 0: /* just entering */
      if(*tbuf == '(') tcc++;
      break;
    case 1: /* first e.g. key type plain text description */
      if(!tebuf) tebuf = tbuf;
      else if(tebuf && *tbuf == ' ') {
        len = (tbuf - tebuf) + sizeof(char);
        if(!(tuple = malloc(len))) {
          r = SXT_ENOMEM;
          goto __failed;
        } else memset(tuple, 0, len);

        /* check keytype */
        memcpy(tuple, tebuf, len - sizeof(char));
        keytype = sxtkey_type_fname(tuple);
        free(tuple);

        if(keytype == 0) {
          r = SXT_EKEY; /* unsupported key type */
          goto __failed;
        }
        /* going further */
        tebuf = NULL;
        tcc++;
      }
      break;
    case 2: /* private key contents */
      if(!tebuf && *tbuf != ' ') tebuf = tbuf;
      else if(tebuf && *tbuf == '"') {
        tebuf++;
        len = (tbuf - tebuf) + sizeof(char);
        if(len <= 1) {
          r = SXT_EKEYFMT;
          goto __failed;
        }

        if(!(tuple = malloc(len))) { r = SXT_ENOMEM; goto __failed; }
        else memset(tuple, 0, len);

        memcpy(tuple, tebuf, len - sizeof(char));
        b64pk = tuple;
        tuple = tebuf = NULL;
        tcc++;
      }
      break;
    case 3:
      if(*tbuf == ')') tcc++;
      else if(*tbuf != ' ') {
        r = SXT_EKEYFMT;
        goto __failed;
      }
      break;
    default: break;
    }
  }

  if(tcc < 3) {
    r = SXT_EKEYFMT;
    goto __failed;
  }

  r = sxtkey_privkey_import_fbase64blob(b64pk, keytype, ask_passkey, priv, ik);

 __failed:
  if(stream) fclose(stream);
  if(rawfbuf) free(rawfbuf);
  if(b64pk) free(b64pk);

  return r;
}

int sxtkey_privkey_import_rdbuf(sxtrdb_t *buf, uint8_t keytype,
                                int (*ask_passkey)(char *pkbuf, size_t length,
                                                   int confirm, void *priv),
                                void *priv, sxtkey_t **ik)
{
  uint8_t flags = 0, chk = 0;
  char *passkey = NULL;
  sxtrdb_t *kdfopt = NULL, *ctrl_pubkey = NULL, *privkey = NULL;
  sxtrdb_t *ed25519_pubbuf = NULL, *ed25519_privbuf = NULL;
  sxtkey_t *key = NULL;
  char *keyname = NULL, *ciphername = NULL, *kdfname = NULL, *magic = NULL;
  uint64_t hash = 0;
  uint32_t r1 = 0, r2 = 0, ctrl_pklen = 0;
  int r = SXT_SUCCESS, decrypt = 0;

  if(!buf) return SXT_EINVAL;
  if(!sxtrdb_length(buf)) return SXT_EINVAL;
  if(keytype == 0) return SXT_EKEY;

  r = sxtrdb_escan(buf, "sbsssRdRR", &magic, &flags, &keyname, &ciphername, &kdfname,
                   &kdfopt, &ctrl_pklen, &ctrl_pubkey, &privkey);
  if(r != SXT_SUCCESS) goto __failed;

  if(strcmp(PPKP_MAGIC, magic)) { /* magic should be right */
  __eekey:
    r = SXT_EKEY;
    goto __failed;
  }

  if(strcmp(sxtkey_name(keytype), keyname)) goto __eekey;

  /* check for auth function */
  if(flags & SXT_PPKP_ENCRYPT) decrypt++;
  if(decrypt && !ask_passkey) {
    r = SXT_EAUTH;
    goto __failed;
  }

  switch(keytype) {
  case PPKP_ED25519:
    /* check public key length first */
    if(ctrl_pklen != ED25519_PK_LEN + sizeof(uint32_t)) {
      r = SXT_EKEY;
      goto __failed;
    }
    /* check for encryption details */
    if(decrypt) {
      if(strcmp(ciphername, "aes128-cbc") || strcmp(kdfname, "bcrypt")) {
        r = SXT_EKEY;
        goto __failed;
      }
      /* get passkey */
      passkey = malloc(64*sizeof(char));
      if(!passkey) {
        r = SXT_ENOMEM;
        goto __failed;
      }
      r = ask_passkey(passkey, 63, 0, priv);
      if(r != SXT_SUCCESS) { /* FIXME: might be return SXT_EAUTH here ? */
        goto __failed;
      }
      /* decrypt it */
      r = _sxtkey_privkey_decrypt(privkey, kdfopt, passkey);
      if(r != SXT_SUCCESS) goto __failed;
    } else {
      /* nil expected */
      if(strcmp(ciphername, "nil") || strcmp(kdfname, "nil")) {
        r = SXT_EKEY;
        goto __failed;
      }
    }
    /* here we have privkey decrypted */
    r = sxtrdb_escan(privkey, "ddRRqb", &r1, &r2, &ed25519_pubbuf, &ed25519_privbuf, &hash, &chk);
    if(r != SXT_SUCCESS) {
      hash = 0;
      chk = 0;
      r = SXT_EKEY;
      goto __failed;
    }
    /* control check for random numbers */
    if(r1 != r2)       goto __invalid;

    /* control check of public keys */
    if(sxtrdb_cmp(ctrl_pubkey, ed25519_pubbuf)) {
    __invalid:
      sxtrdb_free(ed25519_pubbuf);
      sxtrdb_free(ed25519_privbuf);
      r = SXT_EKEY;
      goto __failed;
    }

    /* alloc a key and copy data */
    if(!(key = sxtkey_alloc())) {
    __enomem:
      sxtrdb_free(ed25519_pubbuf);
      sxtrdb_free(ed25519_privbuf);
      r = SXT_ENOMEM;
      goto __failed;
    }

    /* allocate space */
    if(!(key->pubkey = malloc(ED25519_PK_LEN)) ||
       !(key->privkey = malloc(ED25519_SK_LEN))) {
      if(key->pubkey) free(key->pubkey);
      if(key->privkey) free(key->privkey);
      sxtkey_free(key);
      goto __enomem;
    }
    /* copy and set all required data */
    memcpy(key->pubkey, sxtrdb_rdata(ed25519_pubbuf), ED25519_PK_LEN);
    memcpy(key->privkey, sxtrdb_rdata(ed25519_privbuf), ED25519_SK_LEN);
    /* free it */
    sxtrdb_free(ed25519_pubbuf);
    sxtrdb_free(ed25519_privbuf);
    key->type = keytype;
    key->hash = hash;
    key->flags = SXT_PPKP_PRIVATE;

    /* and the rest */
    *ik = key;
    r = SXT_SUCCESS;
    break;
  default: /* unsupported key type ... */
    r = SXT_EKEY;
    goto __failed;
    break;
  }

 __failed:
  /* free temproary stuff */
  if(magic) free(magic);
  if(keyname) free(keyname);
  if(ciphername) free(ciphername);
  if(kdfname) free(kdfname);
  if(passkey) {
    memset(passkey, 0, 64);
    free(passkey);
  }
  if(kdfopt) sxtrdb_free(kdfopt);
  if(ctrl_pubkey) sxtrdb_free(ctrl_pubkey);
  if(privkey) sxtrdb_free(privkey);

  return r;
}

int sxtkey_privkey_import_fbase64blob(const char *b64pk, uint8_t keytype,
                                      int (*ask_passkey)(char *pkbuf, size_t length,
                                                         int confirm, void *priv),
                                      void *priv, sxtkey_t **ik)
{
  sxtrdb_t *fullkeybuf = NULL;
  char *decoded = NULL;
  int len, r = SXT_SUCCESS;

  if(!b64pk) return SXT_EINVAL;
  else len = strlen(b64pk);
  if(keytype == 0) return SXT_EKEY;
  if(!len) return SXT_EINVAL;

  if(!(decoded = malloc(len + sizeof(char)))) return SXT_ENOMEM;

  /* decode */
  len = sxt_b64decode_in(b64pk, len, decoded, len);
  if(!len) {
    r = SXT_EKEYFMT;
    goto __failed;
  }

  /* allocate a buffer and insert raw data */
  if(!(fullkeybuf = sxtrdb_new())) {
    r = SXT_ENOMEM;
    goto __failed;
  } else sxtrdb_setflags(fullkeybuf, SXTRDB_BURN);
  sxtrdb_write_raw_head(fullkeybuf, decoded, len);

  r = sxtkey_privkey_import_rdbuf(fullkeybuf, keytype, ask_passkey, priv, ik);

 __failed:
  if(decoded) {
    memset(decoded, 0, len);
    free(decoded);
  }
  if(fullkeybuf) sxtrdb_free(fullkeybuf);

  return r;
}

int sxtkey_pubkey_import_fbase64blob(const char *b64b, uint8_t keytype,
                                     uint64_t ctrl_hash, sxtkey_t **ik)
{
  sxtkey_t *key = NULL;
  sxtrdb_t *keybuf = NULL;
  char *blob = NULL, *ed25519pk = NULL;
  uint64_t hash;
  uint32_t klen = 0;
  int len, r = SXT_SUCCESS;

  if(!b64b) return SXT_EINVAL;
  if(!sxtkey_name(keytype)) return SXT_EKEY;

  /* ok, first decode */
  len = strlen(b64b) + sizeof(char);
  if(!(blob = malloc(len))) return SXT_ENOMEM;
  else memset(blob, 0, len);
  len = sxt_b64decode_in(b64b, len - 1, blob, len);

  if(!(keybuf = sxtrdb_new())) {
    r = SXT_ENOMEM;
    goto __failed;
  }

  switch(keytype) {
  case PPKP_ED25519:
    if(!(ed25519pk = malloc(ED25519_PK_LEN))) {
      r = SXT_ENOMEM;
      goto __failed;
    }
    /* <pubkey><hash> */
    sxtrdb_write_raw(keybuf, blob, len);
    sxtrdb_resetcur(keybuf);
    sxtrdb_escan(keybuf, "dpq", &klen, ED25519_PK_LEN, ed25519pk, &hash);

    if(klen != ED25519_PK_LEN) {
      r = SXT_EKEY;
      goto __failed;
    }

    if(hash != ctrl_hash) {
      r = SXT_EKEY;
      goto __failed;
    }

    if(!(key = sxtkey_alloc())) {
      r = SXT_ENOMEM; goto __failed;
    }
    key->type = keytype;
    if(!(key->pubkey = malloc(ED25519_PK_LEN))) {
      sxtkey_free(key);
      r = SXT_ENOMEM; goto __failed;
    }
    key->hash = hash;
    key->flags = SXT_PPKP_PUBLIC;
    memcpy(key->pubkey, ed25519pk, ED25519_PK_LEN);

    r = SXT_SUCCESS;
    *ik = key;
    break;
  default: r = SXT_EKEYFMT; break;
  }

 __failed:
  if(blob) free(blob);
  if(keybuf) sxtrdb_free(keybuf);
  if(ed25519pk) free(ed25519pk);

  return r;
}

int sxtkey_import_public_file(const char *file, sxtkey_t **ik)
{
  FILE *stream = NULL;
  char *rawfbuf = NULL, *tbuf, *tebuf, *tuple = NULL, *b64pk = NULL;
  sxtrdb_t *chbuf = NULL;
  int tc = 0, tcc = 0, len;
  struct stat stbuf;
  int r = SXT_ENOMEM;
  uint64_t ctrl_hash;
  uint8_t keytype = 0;

  *ik = NULL;

  if(!file) return SXT_EINVAL;

  if(stat(file, &stbuf) != 0) return SXT_EIO;
  else if(!S_ISREG(stbuf.st_mode)) return SXT_EINVAL;

  if(stbuf.st_size >= SXT_PPKP_MAXCSIZE) return SXT_EINVAL;

  if((stream = fopen(file, "r")) == NULL) return SXT_EIO;

  if(!(rawfbuf = malloc(stbuf.st_size + sizeof(char)))) goto __failed;
  else rawfbuf[stbuf.st_size] = '\0';

  if(fread(rawfbuf, stbuf.st_size, 1, stream) != 1) {
    r = SXT_EIO;
    goto __failed;
  }

  /* check general format */
  r = _sxtkey_check_fmtrawbuf(rawfbuf);
  if(r != SXT_SUCCESS) goto __failed;

  /* ok, now we can parse it, avoid to use libsexpr here,
   * to make sxt inpedendent as possible */
  for(tbuf = rawfbuf, tc = 0, tcc = 0, tebuf = NULL; *tbuf != '\0'; tbuf++) {
    switch(tcc) {
    case 0: /* just entering */
      if(*tbuf == '(') tcc++;
      break;
    case 1: /* first e.g. key type plain text description */
      if(!tebuf) tebuf = tbuf;
      else if(tebuf && *tbuf == ' ') {
        if(!tebuf) goto __failed;
        len = (tbuf - tebuf) + sizeof(char);
        if(!(tuple = malloc(len))) {
          r = SXT_ENOMEM;
          goto __failed;
        } else memset(tuple, 0, len);

        /* check keytype */
        memcpy(tuple, tebuf, len - sizeof(char));
        keytype = sxtkey_type_fname(tuple);
        free(tuple);

        if(keytype == 0) {
          r = SXT_EKEY; /* unsupported key type */
          goto __failed;
        }
        /* going further */
        tebuf = NULL;
        tcc++;
      }
      break;
    case 2: /* public sign keyword */
      if(!tebuf && *tbuf != ' ') tebuf = tbuf;
      else if(tebuf && *tbuf == ' ') {
        if(*tebuf != '\'') { /* invalid format */
          r = SXT_EKEYFMT;
          goto __failed;
        }

        /* get tuple */
        len = (tbuf - tebuf) + sizeof(char);
        if(!(tuple = malloc(len))) {
          r = SXT_ENOMEM;
          goto __failed;
        } else memset(tuple, 0, len);
        memcpy(tuple, tebuf, len - sizeof(char));

        if(strcmp(tuple, "'public")) tc = SXT_EKEYFMT;
        else tc = 0;

        free(tuple);
        if(tc) {
          r = tc;
          goto __failed;
        }
        tebuf = NULL;
        tcc++;
      }
      break;
    case 3: /* key contents */
      if(!tebuf && *tbuf != ' ') tebuf = tbuf;
      else if(tebuf && *tbuf == ' ') {
        len = (tbuf - tebuf) + sizeof(char);
        /* check format */
        if(*tebuf != '"') tc = SXT_EKEYFMT;
        if(!tc && tebuf[len - 2] != '"') tc = SXT_EKEYFMT;
        len -= 2;
        if(tc || len <= 0) {          r = tc; goto __failed;        }
        tebuf++;

        if(!(tuple = malloc(len))) { r = SXT_ENOMEM; goto __failed; }
        else memset(tuple, 0, len);

        memcpy(tuple, tebuf, len - sizeof(char));
        b64pk = tuple;
        tuple = tebuf = NULL;
        tcc++;
      }
      break;
    case 4: /* base64 encoded hash to verify contents */
      if(!tebuf && *tbuf == '"') tebuf = tbuf;
      else if(tebuf && *tbuf == '"') {
        tebuf++;
        len = (tbuf - tebuf) + sizeof(char);
        if(len <= 1) tc = SXT_EKEYFMT;

        if(tc) {r = tc; goto __failed;}
        if(!(tuple = malloc(len))) { r = SXT_ENOMEM; goto __failed; }
        else memset(tuple, 0, len);
        memcpy(tuple, tebuf, len - 1);

        /* decode hash */
        tebuf = NULL;
        if(!(tebuf = malloc(len))) {
          free(tuple);
          r = SXT_ENOMEM; goto __failed;
        } else memset(tebuf, 0, len);
        len = sxt_b64decode_in(tuple, strlen(tuple), tebuf, len);

        free(tuple);
        if(!(chbuf = sxtrdb_new())) {
          free(tebuf);
          r = SXT_ENOMEM; goto __failed;
        }
        sxtrdb_write_raw(chbuf, tebuf, len);
        sxtrdb_resetcur(chbuf);
        sxtrdb_read_u64(chbuf, &ctrl_hash);
        sxtrdb_free(chbuf);
        free(tebuf);
        tebuf = tuple = NULL;
        tcc++;
      }
      break;
    case 5:
      if(*tbuf == ')') tcc++;
      else if(*tbuf != ' ') {
        r = SXT_EKEYFMT;
        goto __failed;
      }
      break;
    default: break;
    }
  }

  /* ok check fmt last time */
  if(tcc < 6) {
    r = SXT_EKEYFMT; goto __failed;
  }

  /* import from base64 encoded blob */
  r = sxtkey_pubkey_import_fbase64blob(b64pk, keytype, ctrl_hash, ik);

 __failed:
  if(stream) fclose(stream);
  if(rawfbuf) free(rawfbuf);
  if(b64pk) free(b64pk);

  return r;
}

int sxtkey_export_priv_file(const sxtkey_t *key, const char *file, const char *passkey,
                            int (*ask_passkey)(char *pkbuf, size_t length, int confirm, void *priv),
                            void *priv)
{
  FILE *out = NULL;
  char *pass = NULL;
  sxtsafebuffer_t *bin = NULL;
  int r = 0;

  if(!key) return SXT_EINVAL;
  if(!sxtkey_private(key)) return SXT_EKEY;

  if((out = fopen(file, "wb")) == NULL) return SXT_EIO;

  /* passkey challenge */
  if(passkey) pass = (char *)passkey;
  else if(ask_passkey) {
    if((pass = malloc(sizeof(char)*64)) == NULL) {
      r = SXT_ENOMEM;
      goto __failed;
    }
    r = ask_passkey(pass, 64, 1, priv);
    if(r != SXT_SUCCESS)      goto __failed;
  }

  /* ok, get the base64 encoded data for the key */
  switch(key->type) {
  case PPKP_ED25519:
    r = sxtkey_export_priv_ed25519(key, pass, &bin);
    if(!bin) goto __failed;
    break;
  default:
    r = SXT_EKEY;
    goto __failed;
  }

  /* sxt key container as follows: (<key-type> "<base64 encoded content of the key>")\n */
  fprintf(out, "(%s \"%s\")\n", sxtkey_name(key->type), (char *)sxtsafebuffer_getdata(bin));

  sxtsafebuffer_destroy(bin);

 __failed:
  if(pass && pass != passkey) {
    memset(pass, 0, sizeof(char)*64); /* clean to disallow passkeys found in coredumps */
    free(pass);
  }
  fclose(out);

  return r;
}

static int sxtkey_publickey2blob_whash(const sxtkey_t *key, sxtsafebuffer_t **o)
{
  sxtsafebuffer_t *buf = NULL, *pk = NULL;
  sxtrdb_t *b = NULL;
  int r = SXT_SUCCESS;

  if(!key) return SXT_EINVAL;

  /* get a public key blob without hash */
  switch(key->type) {
  case PPKP_ED25519:
    if((r = sxt_public_ed25519_2sb(key, &pk)) != SXT_SUCCESS)
      return r;
    break;
  default: return SXT_EKEY;
  }

  if(!(b = sxtrdb_new())) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  sxtrdb_print(b, "pq", sxtsafebuffer_length(pk), sxtsafebuffer_getdata(pk),
               key->hash);
  if(!(buf = sxtsafebuffer_new(sxtrdb_length(b)))) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  memcpy(sxtsafebuffer_getdata(buf), sxtrdb_rdata(b), sxtrdb_length(b));

  *o = buf;

 __failed:
  if(pk) sxtsafebuffer_destroy(pk);
  if(b) sxtrdb_free(b);

  return r;
}

static int sxtkey_hash2blob(const sxtkey_t *key, sxtsafebuffer_t **o)
{
  sxtsafebuffer_t *buf = NULL;
  sxtrdb_t *b = NULL;
  int r = SXT_SUCCESS;

  if(!key) return SXT_EINVAL;

  if(!(b = sxtrdb_new())) return SXT_ENOMEM;

  sxtrdb_print(b, "q", key->hash);
  if(!(buf = sxtsafebuffer_new(sxtrdb_length(b)))) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  memcpy(sxtsafebuffer_getdata(buf), sxtrdb_rdata(b), sxtrdb_length(b));

  *o = buf;

 __failed:
  if(b) sxtrdb_free(b);

  return r;
}

int sxtkey_export_public_file(const sxtkey_t *key, const char *file)
{
  FILE *out = NULL;
  sxtsafebuffer_t *hashbuf = NULL, *pubkeybuf = NULL;
  sxtsafebuffer_t *pubkey_sb = NULL, *hash_sb = NULL;
  char *pckey = NULL, *pchash = NULL;
  int r = SXT_SUCCESS;

  if(!key) return SXT_EINVAL;
  if(!sxtkey_public(key)) return SXT_EKEY;

  if((out = fopen(file, "wb")) == NULL) return SXT_EIO;

  /*
   * format described as follows:
   * (<key-type> 'public "<pubkey><hash>" "<hash>")\n
   * all scoped values are base64 encoded
   */

  /* get a public key with hash blob */
  if((r = sxtkey_publickey2blob_whash(key, &pubkey_sb)) != SXT_SUCCESS) goto __failed;

  /* get key hash blob */
  if((r = sxtkey_hash2blob(key, &hash_sb)) != SXT_SUCCESS) goto __failed;

  /* allocate buffers for base64 encoded data */
  if(!(pubkeybuf = sxtsafebuffer_new(sxt_rawlen2b64len(sxtsafebuffer_length(pubkey_sb))))) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  if(!(hashbuf = sxtsafebuffer_new(sxt_rawlen2b64len(sxtsafebuffer_length(hash_sb))))) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  /* do base64 encode */
  sxt_b64encode_in(sxtsafebuffer_getdata(pubkey_sb), sxtsafebuffer_getdata(pubkeybuf),
                   sxtsafebuffer_length(pubkey_sb)); /* pubkey */
  sxt_b64encode_in(sxtsafebuffer_getdata(hash_sb), sxtsafebuffer_getdata(hashbuf),
                   sxtsafebuffer_length(hash_sb)); /* hash */

  /* get cstring to output */
  if(!(pckey = sxtsafebuffer_getcstr(pubkeybuf))) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  if(!(pchash = sxtsafebuffer_getcstr(hashbuf))) {
    r = SXT_ENOMEM;
    sxtsafebuffer_freecstr(pckey);
    goto __failed;
  }

  /* output this */
  fprintf(out, "(%s 'public \"%s\" \"%s\")\n", sxtkey_name(key->type), pckey, pchash);

  /* free all stuff */
  sxtsafebuffer_freecstr(pckey);
  sxtsafebuffer_freecstr(pchash);

 __failed:
  if(pubkey_sb) sxtsafebuffer_destroy(pubkey_sb);
  if(hash_sb) sxtsafebuffer_destroy(hash_sb);
  if(hashbuf) sxtsafebuffer_destroy(hashbuf);
  if(pubkeybuf) sxtsafebuffer_destroy(pubkeybuf);
  fclose(out);

  return r;
}

static int sxtkey_export_priv_ed25519(const sxtkey_t *key, const char *pass, sxtsafebuffer_t **bin)
{
  int r = 0;
  sxtsafebuffer_t *b64 = NULL, *pubkey_sb = NULL;
  sxtrdb_t *keybuf = NULL, *privbuf = NULL;
  sxtrdb_t *kdfopts = NULL;
  uint32_t urand;
  uint8_t flags = 0;

  if(!key) return SXT_EINVAL;
  if(key->type != PPKP_ED25519) return SXT_EKEY;

  /* allocate a buffer for the key at all */
  if(!(keybuf = sxtrdb_new())) return SXT_ENOMEM;
  else sxtrdb_setflags(keybuf, SXTRDB_BURN);

  /* ok firstly get private-key-data according to SXT key container doc */
  if((r = sxt_public_ed25519_2sb(key, &pubkey_sb)) != SXT_SUCCESS) goto __failed;

  /* now we need random number */
  sxt_get_random(&urand, sizeof(uint32_t), 1);

  if(!(privbuf = sxtrdb_new())) {
    r = SXT_ENOMEM;
    goto __failed;
  } else sxtrdb_setflags(privbuf, SXTRDB_BURN);

  /* two random numbers */
  if(!sxtrdb_print(privbuf, "dd", urand, urand)) {
    r = SXT_ENOMEM;
    goto __failed;
  }

  /* pub, priv, hash, zero padding */
  if(!sxtrdb_print(privbuf, "dpdpqb", (uint32_t)ED25519_PK_LEN, (size_t)ED25519_PK_LEN,
                   key->pubkey, (uint32_t)ED25519_SK_LEN, (size_t)ED25519_SK_LEN,
                   key->privkey, key->hash, (uint8_t)'\0')) {
    r = SXT_ENOMEM;
    goto __failed;
  }

  /* if hash is non-zero - include it i.e. set flag */
  if(key->hash) flags |= SXT_PPKP_IHASH;

  if(pass) { /* we need to encrypt the key i.e. privbuf *must* be encrypted */
    /* to avoid yet another wheel invention,
     * the following was taken from ssh implementation, i mean
     * kdf and crypto in use to encrypt the key
     */
    uint8_t pad = 1;
    size_t keystub_len;
    sxtsafebuffer_t *salt;
    sxt_cipher_t *cipher = sxt_cipher_get("aes128-cbc");
    uint8_t keystub[128];

    /* set flags */
    flags |= SXT_PPKP_ENCRYPT;

    if(!cipher) {
      /* it might be in case of forgotten initialization function */
      r = SXT_EKEY;
      goto __failed;
    }

    /* get the salt */
    if(!(salt = sxtsafebuffer_new(16))) {
    __enomem1:
      sxt_cipher_free(cipher);
      r = SXT_ENOMEM;
      goto __failed;
    } else sxt_get_random(sxtsafebuffer_getdata(salt), 16, 1);

    /* generate kdf description <salt><rounds> */
    if(!(kdfopts = sxtrdb_new())) {
      sxtsafebuffer_destroy(salt);
      goto __enomem1;
    }
    sxtrdb_print(kdfopts, "Pd", 16, sxtsafebuffer_getdata(salt), (uint32_t)32);

    /* ok, now we need to get a padding, just to be sure to be aligned for the
       cipher block size */
    while(sxtrdb_length(privbuf) % cipher->blksize != 0) {
      if(sxtrdb_write_u8(privbuf, pad) != sizeof(uint8_t)) {
        sxt_cipher_free(cipher);
        r = SXT_ENOMEM;
        goto __failed;
      }
      pad++;
    }

    /* key stub */
    keystub_len = cipher->keysize/8 + cipher->blksize;
    if(keystub_len > sizeof(keystub)) {
      r = SXT_EKEY;
      sxt_cipher_free(cipher);
      goto __failed;
    }

    /* bcrypt those stuff */
    if(bcrypt_pbkdf(pass, strlen(pass), sxtsafebuffer_getdata(salt),
                    sxtsafebuffer_length(salt), keystub, keystub_len, 32)) {
      r = SXT_ERROR;
      sxt_cipher_free(cipher);
      goto __failed;
    }

    /* encrypt with cipher */
    sxt_cipher_set_encrypt_key(cipher, keystub, keystub + cipher->keysize/8);
    sxt_cipher_encrypt(cipher, sxtrdb_rdata(privbuf), sxtrdb_rdata(privbuf), sxtrdb_length(privbuf));

    /* clean up all */
    memset(keystub, 0, sizeof(keystub));
    sxt_cipher_free(cipher);
    sxtsafebuffer_destroy(salt);
  }

  /* in case of non-crypted key we anyways should include encrypt options */
  if(!kdfopts) {
    if(!(kdfopts = sxtrdb_new())) {
      r = SXT_ENOMEM;
      goto __failed;
    }
    sxtrdb_print(kdfopts, "Pd", 3, "nil", (uint32_t)0);
  }

  /* there are a time to print all required content to the buffer */
  /* <MAGIC VERSION SIGN><8bit flags><key-type>
   * <cipher-name><kdf-name><kdf-opts>
   * <public-key>
   * <private-key-data>
   * according to the documentation
   */
  sxtrdb_print(keybuf, "sbsssPPP", PPKP_MAGIC, flags, "ppkp-ed25519",
               pass ? "aes128-cbc" : "nil", pass ? "bcrypt" : "nil",
               sxtrdb_length(kdfopts), sxtrdb_rdata(kdfopts),
               sxtsafebuffer_length(pubkey_sb), sxtsafebuffer_getdata(pubkey_sb),
               sxtrdb_length(privbuf), sxtrdb_rdata(privbuf));

  /* as described - encode all with base64 */
  b64 = sxtsafebuffer_new(sxt_rawlen2b64len(sxtrdb_length(keybuf)));
  if(!b64) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  /* encode buffer */
  sxt_b64encode_in((const char *)sxtrdb_rdata(keybuf), (char *)sxtsafebuffer_getdata(b64),
                   sxtrdb_length(keybuf));

  /* the last ... */
  *bin = b64;
  r = SXT_SUCCESS;

 __failed:
  if(keybuf) sxtrdb_free(keybuf); /* container free */
  if(pubkey_sb) sxtsafebuffer_destroy(pubkey_sb); /* public key bin free */
  if(privbuf) sxtrdb_free(privbuf); /* private key buffer free */

  return r;
}

static int sxt_public_ed25519_2sb(const sxtkey_t *key, sxtsafebuffer_t **buf)
{
  sxtrdb_t *rbuf = NULL;
  sxtsafebuffer_t *o = NULL;
  int r = SXT_SUCCESS;

  if(!key->pubkey) return SXT_EKEY;

  r = sxt_public_ed25519_2rdb(key, &rbuf);
  if(!rbuf) return r;

  if(!(o = sxtsafebuffer_new((size_t)sxtrdb_length(rbuf)))) {
    r = SXT_ENOMEM;
    goto __failed;
  }
  sxtsafebuffer_setdata(o, sxtrdb_rdata(rbuf), (size_t)sxtrdb_length(rbuf));
  *buf = o;

 __failed:
  sxtrdb_free(rbuf);

  return r;
}

static int sxt_public_ed25519_2rdb(const sxtkey_t *key, sxtrdb_t **out)
{
  sxtrdb_t *buf = NULL;

  if(!key->pubkey) return SXT_EKEY;

  if(!(buf = sxtrdb_new())) return SXT_ENOMEM;
  else sxtrdb_setflags(buf, SXTRDB_BURN);

  if(!sxtrdb_print(buf, "dp", (uint32_t)ED25519_PK_LEN, (size_t)ED25519_PK_LEN,
                   key->pubkey)) {
    sxtrdb_free(buf);
    return SXT_EKEY;
  }

  *out = buf;

  return SXT_SUCCESS;
}

static int _sxtkey_check_fmtrawbuf(const char *buffer)
{
  char *tbuf;
  int r = SXT_SUCCESS, tc = 0, tcc = 0;

  /* currently only own container supported,
   * let's checkout format:
   * = () and ""
   */
  for(tbuf = (char *)buffer; *tbuf != '\0'; tbuf++) {
    switch(*tbuf) {
    case '(': tc++; break;
    case ')': tc--; break;
    case '"':
      if(!tc) {
        r = SXT_EKEYFMT;
        goto __failed;
      } else tcc++;
      break;
    default: break; /* just ignore */
    }
  }

  r = SXT_EKEYFMT;
  if(tc) goto __failed;
  if(tcc%2) goto __failed;

  r = SXT_SUCCESS;

 __failed:
  return r;
}

static int _sxtkey_privkey_decrypt(sxtrdb_t *privkey, sxtrdb_t *kdfopt,
                                   const char *passkey)
{
  int r = SXT_SUCCESS;
  sxtrdb_t *salt = NULL;
  sxt_cipher_t *cipher = sxt_cipher_get("aes128-cbc");
  uint32_t rounds, keystub_len;
  uint8_t keystub[128];

  /* default check */
  if(!privkey || !kdfopt) return SXT_EINVAL;
  if(!passkey) return SXT_EAUTH;

  /* cipher */
  if(!(cipher = sxt_cipher_get("aes128-cbc"))) return SXT_EKEY;

  /* get salt and rounds */
  if((r = sxtrdb_escan(kdfopt, "Rd", &salt, &rounds)) != SXT_SUCCESS)
    goto __failed;

  /* check blob length and cipher block size */
  if(sxtrdb_length(privkey) % cipher->blksize != 0) {
    r = SXT_EKEY;
    goto __failed;
  }

  /* bcrypt */
  keystub_len = cipher->keysize/8 + cipher->blksize;
  if(keystub_len > sizeof(keystub)) {
    r = SXT_EKEY;
    goto __failed;
  }
  if(bcrypt_pbkdf(passkey, strlen(passkey), sxtrdb_rdata(salt), sxtrdb_length(salt),
                  keystub, keystub_len, rounds) < 0) {
    memset(keystub, 0, keystub_len);
    r = SXT_EAUTH;
    goto __failed;
  }

  /* set decrypt key and decrypt */
  cipher->f->set_decrypt_key(cipher, keystub, keystub + cipher->keysize/8);
  cipher->f->decrypt(cipher, sxtrdb_rdata(privkey), sxtrdb_rdata(privkey),
                     sxtrdb_length(privkey));

  /* free/burn unused data */
  memset(keystub, 0, keystub_len);

 __failed:
  if(cipher) sxt_cipher_free(cipher);
  if(salt) sxtrdb_free(salt);

  return r;
}