static bool
tls_crypt_v2_wrap_client_key(struct buffer *wkc,
const struct key2 *src_key,
const struct buffer *src_metadata,
struct key_ctx *server_key, struct gc_arena *gc)
{
cipher_ctx_t *cipher_ctx = server_key->cipher;
struct buffer work = alloc_buf_gc(TLS_CRYPT_V2_MAX_WKC_LEN
+ cipher_ctx_block_size(cipher_ctx), gc);
/* Calculate auth tag and synthetic IV */
uint8_t *tag = buf_write_alloc(&work, TLS_CRYPT_TAG_SIZE);
if (!tag)
{
msg(M_WARN, "ERROR: could not write tag");
return false;
}
uint16_t net_len = htons(sizeof(src_key->keys) + BLEN(src_metadata)
+ TLS_CRYPT_V2_TAG_SIZE + sizeof(uint16_t));
hmac_ctx_t *hmac_ctx = server_key->hmac;
hmac_ctx_reset(hmac_ctx);
hmac_ctx_update(hmac_ctx, (void *)&net_len, sizeof(net_len));
hmac_ctx_update(hmac_ctx, (void *)src_key->keys, sizeof(src_key->keys));
hmac_ctx_update(hmac_ctx, BPTR(src_metadata), BLEN(src_metadata));
hmac_ctx_final(hmac_ctx, tag);
dmsg(D_CRYPTO_DEBUG, "TLS-CRYPT WRAP TAG: %s",
format_hex(tag, TLS_CRYPT_TAG_SIZE, 0, gc));
/* Use the 128 most significant bits of the tag as IV */
ASSERT(cipher_ctx_reset(cipher_ctx, tag));
/* Overflow check (OpenSSL requires an extra block in the dst buffer) */
if (buf_forward_capacity(&work) < (sizeof(src_key->keys)
+ BLEN(src_metadata)
+ sizeof(net_len)
+ cipher_ctx_block_size(cipher_ctx)))
{
msg(M_WARN, "ERROR: could not crypt: insufficient space in dst");
return false;
}
/* Encrypt */
int outlen = 0;
ASSERT(cipher_ctx_update(cipher_ctx, BEND(&work), &outlen,
(void *)src_key->keys, sizeof(src_key->keys)));
ASSERT(buf_inc_len(&work, outlen));
ASSERT(cipher_ctx_update(cipher_ctx, BEND(&work), &outlen,
BPTR(src_metadata), BLEN(src_metadata)));
ASSERT(buf_inc_len(&work, outlen));
ASSERT(cipher_ctx_final(cipher_ctx, BEND(&work), &outlen));
ASSERT(buf_inc_len(&work, outlen));
ASSERT(buf_write(&work, &net_len, sizeof(net_len)));
return buf_copy(wkc, &work);
}
void
openvpn_encrypt (struct buffer *buf, struct buffer work,
const struct crypto_options *opt,
const struct frame* frame)
{
struct gc_arena gc;
gc_init (&gc);
if (buf->len > 0 && opt->key_ctx_bi)
{
struct key_ctx *ctx = &opt->key_ctx_bi->encrypt;
/* Do Encrypt from buf -> work */
if (ctx->cipher)
{
uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH];
const int iv_size = cipher_ctx_iv_length (ctx->cipher);
const cipher_kt_t *cipher_kt = cipher_ctx_get_cipher_kt (ctx->cipher);
int outlen;
if (cipher_kt_mode_cbc(cipher_kt))
{
CLEAR (iv_buf);
/* generate pseudo-random IV */
if (opt->flags & CO_USE_IV)
prng_bytes (iv_buf, iv_size);
/* Put packet ID in plaintext buffer or IV, depending on cipher mode */
if (opt->packet_id)
{
struct packet_id_net pin;
packet_id_alloc_outgoing (&opt->packet_id->send, &pin, BOOL_CAST (opt->flags & CO_PACKET_ID_LONG_FORM));
ASSERT (packet_id_write (&pin, buf, BOOL_CAST (opt->flags & CO_PACKET_ID_LONG_FORM), true));
}
}
else if (cipher_kt_mode_ofb_cfb(cipher_kt))
{
struct packet_id_net pin;
struct buffer b;
ASSERT (opt->flags & CO_USE_IV); /* IV and packet-ID required */
ASSERT (opt->packet_id); /* for this mode. */
packet_id_alloc_outgoing (&opt->packet_id->send, &pin, true);
memset (iv_buf, 0, iv_size);
buf_set_write (&b, iv_buf, iv_size);
ASSERT (packet_id_write (&pin, &b, true, false));
}
else /* We only support CBC, CFB, or OFB modes right now */
{
ASSERT (0);
}
/* initialize work buffer with FRAME_HEADROOM bytes of prepend capacity */
ASSERT (buf_init (&work, FRAME_HEADROOM (frame)));
/* set the IV pseudo-randomly */
if (opt->flags & CO_USE_IV)
dmsg (D_PACKET_CONTENT, "ENCRYPT IV: %s", format_hex (iv_buf, iv_size, 0, &gc));
dmsg (D_PACKET_CONTENT, "ENCRYPT FROM: %s",
format_hex (BPTR (buf), BLEN (buf), 80, &gc));
/* cipher_ctx was already initialized with key & keylen */
ASSERT (cipher_ctx_reset(ctx->cipher, iv_buf));
/* Buffer overflow check */
if (!buf_safe (&work, buf->len + cipher_ctx_block_size(ctx->cipher)))
{
msg (D_CRYPT_ERRORS, "ENCRYPT: buffer size error, bc=%d bo=%d bl=%d wc=%d wo=%d wl=%d cbs=%d",
buf->capacity,
buf->offset,
buf->len,
work.capacity,
work.offset,
work.len,
cipher_ctx_block_size (ctx->cipher));
goto err;
}
/* Encrypt packet ID, payload */
ASSERT (cipher_ctx_update (ctx->cipher, BPTR (&work), &outlen, BPTR (buf), BLEN (buf)));
ASSERT (buf_inc_len(&work, outlen));
/* Flush the encryption buffer */
ASSERT (cipher_ctx_final(ctx->cipher, BPTR (&work) + outlen, &outlen));
ASSERT (buf_inc_len(&work, outlen));
/* For all CBC mode ciphers, check the last block is complete */
ASSERT (cipher_kt_mode (cipher_kt) != OPENVPN_MODE_CBC ||
outlen == iv_size);
/* prepend the IV to the ciphertext */
if (opt->flags & CO_USE_IV)
{
uint8_t *output = buf_prepend (&work, iv_size);
ASSERT (output);
memcpy (output, iv_buf, iv_size);
}
dmsg (D_PACKET_CONTENT, "ENCRYPT TO: %s",
format_hex (BPTR (&work), BLEN (&work), 80, &gc));
}
else /* No Encryption */
{
if (opt->packet_id)
{
struct packet_id_net pin;
packet_id_alloc_outgoing (&opt->packet_id->send, &pin, BOOL_CAST (opt->flags & CO_PACKET_ID_LONG_FORM));
ASSERT (packet_id_write (&pin, buf, BOOL_CAST (opt->flags & CO_PACKET_ID_LONG_FORM), true));
}
work = *buf;
}
/* HMAC the ciphertext (or plaintext if !cipher) */
if (ctx->hmac)
{
uint8_t *output = NULL;
hmac_ctx_reset (ctx->hmac);
hmac_ctx_update (ctx->hmac, BPTR(&work), BLEN(&work));
output = buf_prepend (&work, hmac_ctx_size(ctx->hmac));
ASSERT (output);
hmac_ctx_final (ctx->hmac, output);
}
*buf = work;
}
gc_free (&gc);
return;
err:
crypto_clear_error();
buf->len = 0;
gc_free (&gc);
return;
}
/*
* If (opt->flags & CO_USE_IV) is not NULL, we will read an IV from the packet.
*
* Set buf->len to 0 and return false on decrypt error.
*
* On success, buf is set to point to plaintext, true
* is returned.
*/
bool
openvpn_decrypt (struct buffer *buf, struct buffer work,
const struct crypto_options *opt,
const struct frame* frame)
{
static const char error_prefix[] = "Authenticate/Decrypt packet error";
struct gc_arena gc;
gc_init (&gc);
if (buf->len > 0 && opt->key_ctx_bi)
{
struct key_ctx *ctx = &opt->key_ctx_bi->decrypt;
struct packet_id_net pin;
bool have_pin = false;
/* Verify the HMAC */
if (ctx->hmac)
{
int hmac_len;
uint8_t local_hmac[MAX_HMAC_KEY_LENGTH]; /* HMAC of ciphertext computed locally */
hmac_ctx_reset(ctx->hmac);
/* Assume the length of the input HMAC */
hmac_len = hmac_ctx_size (ctx->hmac);
/* Authentication fails if insufficient data in packet for HMAC */
if (buf->len < hmac_len)
CRYPT_ERROR ("missing authentication info");
hmac_ctx_update (ctx->hmac, BPTR (buf) + hmac_len, BLEN (buf) - hmac_len);
hmac_ctx_final (ctx->hmac, local_hmac);
/* Compare locally computed HMAC with packet HMAC */
if (memcmp_constant_time (local_hmac, BPTR (buf), hmac_len))
CRYPT_ERROR ("packet HMAC authentication failed");
ASSERT (buf_advance (buf, hmac_len));
}
/* Decrypt packet ID + payload */
if (ctx->cipher)
{
const int iv_size = cipher_ctx_iv_length (ctx->cipher);
const cipher_kt_t *cipher_kt = cipher_ctx_get_cipher_kt (ctx->cipher);
uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH];
int outlen;
/* initialize work buffer with FRAME_HEADROOM bytes of prepend capacity */
ASSERT (buf_init (&work, FRAME_HEADROOM_ADJ (frame, FRAME_HEADROOM_MARKER_DECRYPT)));
/* use IV if user requested it */
CLEAR (iv_buf);
if (opt->flags & CO_USE_IV)
{
if (buf->len < iv_size)
CRYPT_ERROR ("missing IV info");
memcpy (iv_buf, BPTR (buf), iv_size);
ASSERT (buf_advance (buf, iv_size));
}
/* show the IV's initial state */
if (opt->flags & CO_USE_IV)
dmsg (D_PACKET_CONTENT, "DECRYPT IV: %s", format_hex (iv_buf, iv_size, 0, &gc));
if (buf->len < 1)
CRYPT_ERROR ("missing payload");
/* ctx->cipher was already initialized with key & keylen */
if (!cipher_ctx_reset (ctx->cipher, iv_buf))
CRYPT_ERROR ("cipher init failed");
/* Buffer overflow check (should never happen) */
if (!buf_safe (&work, buf->len + cipher_ctx_block_size(ctx->cipher)))
CRYPT_ERROR ("potential buffer overflow");
/* Decrypt packet ID, payload */
if (!cipher_ctx_update (ctx->cipher, BPTR (&work), &outlen, BPTR (buf), BLEN (buf)))
CRYPT_ERROR ("cipher update failed");
ASSERT (buf_inc_len(&work, outlen));
/* Flush the decryption buffer */
if (!cipher_ctx_final (ctx->cipher, BPTR (&work) + outlen, &outlen))
CRYPT_ERROR ("cipher final failed");
ASSERT (buf_inc_len(&work, outlen));
dmsg (D_PACKET_CONTENT, "DECRYPT TO: %s",
format_hex (BPTR (&work), BLEN (&work), 80, &gc));
/* Get packet ID from plaintext buffer or IV, depending on cipher mode */
{
if (cipher_kt_mode_cbc(cipher_kt))
{
if (opt->packet_id)
{
if (!packet_id_read (&pin, &work, BOOL_CAST (opt->flags & CO_PACKET_ID_LONG_FORM)))
CRYPT_ERROR ("error reading CBC packet-id");
have_pin = true;
}
}
else if (cipher_kt_mode_ofb_cfb(cipher_kt))
{
struct buffer b;
ASSERT (opt->flags & CO_USE_IV); /* IV and packet-ID required */
ASSERT (opt->packet_id); /* for this mode. */
buf_set_read (&b, iv_buf, iv_size);
if (!packet_id_read (&pin, &b, true))
CRYPT_ERROR ("error reading CFB/OFB packet-id");
have_pin = true;
}
else /* We only support CBC, CFB, or OFB modes right now */
{
ASSERT (0);
}
}
}
else
{
work = *buf;
if (opt->packet_id)
{
if (!packet_id_read (&pin, &work, BOOL_CAST (opt->flags & CO_PACKET_ID_LONG_FORM)))
CRYPT_ERROR ("error reading packet-id");
have_pin = !BOOL_CAST (opt->flags & CO_IGNORE_PACKET_ID);
}
}
if (have_pin)
{
packet_id_reap_test (&opt->packet_id->rec);
if (packet_id_test (&opt->packet_id->rec, &pin))
{
packet_id_add (&opt->packet_id->rec, &pin);
if (opt->pid_persist && (opt->flags & CO_PACKET_ID_LONG_FORM))
packet_id_persist_save_obj (opt->pid_persist, opt->packet_id);
}
else
{
if (!(opt->flags & CO_MUTE_REPLAY_WARNINGS))
msg (D_REPLAY_ERRORS, "%s: bad packet ID (may be a replay): %s -- see the man page entry for --no-replay and --replay-window for more info or silence this warning with --mute-replay-warnings",
error_prefix, packet_id_net_print (&pin, true, &gc));
goto error_exit;
}
}
*buf = work;
}
gc_free (&gc);
return true;
error_exit:
crypto_clear_error();
buf->len = 0;
gc_free (&gc);
return false;
}
