src/ssl/ssl_hs_common.t0

\ Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
\
\ Permission is hereby granted, free of charge, to any person obtaining
\ a copy of this software and associated documentation files (the
\ "Software"), to deal in the Software without restriction, including
\ without limitation the rights to use, copy, modify, merge, publish,
\ distribute, sublicense, and/or sell copies of the Software, and to
\ permit persons to whom the Software is furnished to do so, subject to
\ the following conditions:
\
\ The above copyright notice and this permission notice shall be
\ included in all copies or substantial portions of the Software.
\
\ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
\ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
\ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
\ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
\ BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
\ ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
\ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
\ SOFTWARE.

\ ----------------------------------------------------------------------
\ This is the common T0 code for processing handshake messages (code that
\ is used by both client and server).

preamble {

#include <stddef.h>
#include <string.h>

#include "inner.h"

/*
 * This macro evaluates to a pointer to the current engine context.
 */
#define ENG  ((br_ssl_engine_context *)(void *)((unsigned char *)t0ctx - offsetof(br_ssl_engine_context, cpu)))

}

\ IMPLEMENTATION NOTES
\ ====================
\
\ This code handles all records except application data records.
\ Application data is accepted (incoming records, outgoing payload data)
\ only when the application_data flag is set, which is done at the end
\ of the handshake; and it is cleared whenever a renegotiation or a
\ closure takes place.
\
\ Incoming alerts are processed on the fly; fatal alerts terminate the
\ context, while warnings are ignored, except for close_notify, which
\ triggers the closure procedure. That procedure never returns (it ends
\ with an 'ERR_OK fail' call). We can thus make this processing right
\ into the read functions.
\
\ Specific actions from the caller (closure or renegotiation) may happen
\ only when jumping back into the T0 code, i.e. just after a 'co' call.
\ Similarly, incoming record type may change only while the caller has
\ control, so we need to check that type only when returning from a 'co'.
\
\ The handshake processor needs to defer back to the caller ('co') only
\ in one of the following situations:
\
\ -- Some handshake data is expected.
\
\ -- The handshake is finished, and application data may flow. There may
\    be some incoming handshake data (HelloRequest from the server). This
\    is the only situation where a renegotiation call won't be ignored.
\
\ -- Some change-cipher-spec data is expected.
\
\ -- An alert record is expected. Other types of incoming records will be
\    skipped.
\
\ -- Waiting for the currently accumulated record to be sent and the
\    output buffer to become free again for another record.

\ Placeholder for handling not yet implemented functionalities.
: NYI ( -- ! )
	"NOT YET IMPLEMENTED!" puts cr -1 fail ;

\ Debug function that prints a string (and a newline) on stderr.
cc: DBG ( addr -- ) {
	extern void *stderr;
	extern int fprintf(void *, const char *, ...);
	fprintf(stderr, "%s\n", &t0_datablock[T0_POPi()]);
}

\ Debug function that prints a string and an integer value (followed
\ by a newline) on stderr.
cc: DBG2 ( addr x -- ) {
	extern void *stderr;
	extern int fprintf(void *, const char *, ...);
	int32_t x = T0_POPi();
	fprintf(stderr, "%s: %ld (0x%08lX)\n",
		&t0_datablock[T0_POPi()], (long)x, (unsigned long)(uint32_t)x);
}

\ Mark the context as failed with a specific error code. This also
\ returns control to the caller.
cc: fail ( err -- ! ) {
	br_ssl_engine_fail(ENG, (int)T0_POPi());
	T0_CO();
}

\ Read a byte from the context (address is offset in context).
cc: get8 ( addr -- val ) {
	size_t addr = (size_t)T0_POP();
	T0_PUSH(*((unsigned char *)ENG + addr));
}

\ Read a 16-bit word from the context (address is offset in context).
cc: get16 ( addr -- val ) {
	size_t addr = (size_t)T0_POP();
	T0_PUSH(*(uint16_t *)(void *)((unsigned char *)ENG + addr));
}

\ Read a 32-bit word from the context (address is offset in context).
cc: get32 ( addr -- val ) {
	size_t addr = (size_t)T0_POP();
	T0_PUSH(*(uint32_t *)(void *)((unsigned char *)ENG + addr));
}

\ Set a byte in the context (address is offset in context).
cc: set8 ( val addr -- ) {
	size_t addr = (size_t)T0_POP();
	*((unsigned char *)ENG + addr) = (unsigned char)T0_POP();
}

\ Set a 16-bit word in the context (address is offset in context).
cc: set16 ( val addr -- ) {
	size_t addr = (size_t)T0_POP();
	*(uint16_t *)(void *)((unsigned char *)ENG + addr) = (uint16_t)T0_POP();
}

\ Set a 32-bit word in the context (address is offset in context).
cc: set32 ( val addr -- ) {
	size_t addr = (size_t)T0_POP();
	*(uint32_t *)(void *)((unsigned char *)ENG + addr) = (uint32_t)T0_POP();
}

\ Define a word that evaluates as an address of a field within the
\ engine context. The field name (C identifier) must follow in the
\ source. For field 'foo', the defined word is 'addr-foo'.
: addr-eng:
	next-word { field }
	"addr-" field + 0 1 define-word
	0 8191 "offsetof(br_ssl_engine_context, " field + ")" + make-CX
	postpone literal postpone ; ;

addr-eng: max_frag_len
addr-eng: log_max_frag_len
addr-eng: peer_log_max_frag_len
addr-eng: shutdown_recv
addr-eng: record_type_in
addr-eng: record_type_out
addr-eng: version_in
addr-eng: version_out
addr-eng: application_data
addr-eng: version_min
addr-eng: version_max
addr-eng: suites_buf
addr-eng: suites_num
addr-eng: server_name
addr-eng: client_random
addr-eng: server_random
addr-eng: ecdhe_curve
addr-eng: ecdhe_point
addr-eng: ecdhe_point_len
addr-eng: reneg
addr-eng: saved_finished
addr-eng: flags
addr-eng: pad
addr-eng: action
addr-eng: alert
addr-eng: close_received
addr-eng: protocol_names_num
addr-eng: selected_protocol

\ Similar to 'addr-eng:', for fields in the 'session' substructure.
: addr-session-field:
	next-word { field }
	"addr-" field + 0 1 define-word
	0 8191 "offsetof(br_ssl_engine_context, session) + offsetof(br_ssl_session_parameters, " field + ")" + make-CX
	postpone literal postpone ; ;

addr-session-field: session_id
addr-session-field: session_id_len
addr-session-field: version
addr-session-field: cipher_suite
addr-session-field: master_secret

\ Check a server flag by index.
: flag? ( index -- bool )
	addr-flags get32 swap >> 1 and neg ;

\ Define a word that evaluates to an error constant. This assumes that
\ all relevant error codes are in the 0..63 range.
: err:
	next-word { name }
	name 0 1 define-word
	0 63 "BR_" name + make-CX postpone literal postpone ; ;

err: ERR_OK
err: ERR_BAD_PARAM
err: ERR_BAD_STATE
err: ERR_UNSUPPORTED_VERSION
err: ERR_BAD_VERSION
err: ERR_BAD_LENGTH
err: ERR_TOO_LARGE
err: ERR_BAD_MAC
err: ERR_NO_RANDOM
err: ERR_UNKNOWN_TYPE
err: ERR_UNEXPECTED
err: ERR_BAD_CCS
err: ERR_BAD_ALERT
err: ERR_BAD_HANDSHAKE
err: ERR_OVERSIZED_ID
err: ERR_BAD_CIPHER_SUITE
err: ERR_BAD_COMPRESSION
err: ERR_BAD_FRAGLEN
err: ERR_BAD_SECRENEG
err: ERR_EXTRA_EXTENSION
err: ERR_BAD_SNI
err: ERR_BAD_HELLO_DONE
err: ERR_LIMIT_EXCEEDED
err: ERR_BAD_FINISHED
err: ERR_RESUME_MISMATCH
err: ERR_INVALID_ALGORITHM
err: ERR_BAD_SIGNATURE
err: ERR_WRONG_KEY_USAGE
err: ERR_NO_CLIENT_AUTH

\ Get supported curves (bit mask).
cc: supported-curves ( -- x ) {
	uint32_t x = ENG->iec == NULL ? 0 : ENG->iec->supported_curves;
	T0_PUSH(x);
}

\ Get supported hash functions (bit mask and number).
\ Note: this (on purpose) skips MD5.
cc: supported-hash-functions ( -- x num ) {
	int i;
	unsigned x, num;

	x = 0;
	num = 0;
	for (i = br_sha1_ID; i <= br_sha512_ID; i ++) {
		if (br_multihash_getimpl(&ENG->mhash, i)) {
			x |= 1U << i;
			num ++;
		}
	}
	T0_PUSH(x);
	T0_PUSH(num);
}

\ Test support for RSA signatures.
cc: supports-rsa-sign? ( -- bool ) {
	T0_PUSHi(-(ENG->irsavrfy != 0));
}

\ Test support for ECDSA signatures.
cc: supports-ecdsa? ( -- bool ) {
	T0_PUSHi(-(ENG->iecdsa != 0));
}

\ (Re)initialise the multihasher.
cc: multihash-init ( -- ) {
	br_multihash_init(&ENG->mhash);
}

\ Flush the current record: if some payload data has been accumulated,
\ close the record and schedule it for sending. If there is no such data,
\ this function does nothing.
cc: flush-record ( -- ) {
	br_ssl_engine_flush_record(ENG);
}

\ Yield control to the caller.
\ When the control is returned to us, react to the new context. Returned
\ value is a bitwise combination of the following:
\   0x01   handshake data is available
\   0x02   change-cipher-spec data is available
\   0x04   some data other than handshake or change-cipher-spec is available
\   0x08   output buffer is ready for a new outgoing record
\   0x10   renegotiation is requested and not to be ignored
\ Flags 0x01, 0x02 and 0x04 are mutually exclusive.
: wait-co ( -- state )
	co
	0
	addr-action get8 dup if
		case
			1 of 0 do-close endof
			2 of addr-application_data get8 1 = if
				0x10 or
			then endof
		endcase
	else
		drop
	then
	addr-close_received get8 ifnot
		has-input? if
			addr-record_type_in get8 case

				\ ChangeCipherSpec
				20 of 0x02 or endof

				\ Alert -- if close_notify received, trigger
				\ the closure sequence.
				21 of process-alerts if -1 do-close then endof

				\ Handshake
				22 of 0x01 or endof

				\ Not CCS, Alert or Handshake.
				drop 0x04 or 0
			endcase
		then
	then
	can-output? if 0x08 or then ;

\ Send an alert message. This shall be called only when there is room for
\ an outgoing record.
: send-alert ( level alert -- )
	21 addr-record_type_out set8
	swap write8-native drop write8-native drop
	flush-record ;

\ Send an alert message of level "warning". This shall be called only when
\ there is room for an outgoing record.
: send-warning ( alert -- )
	1 swap send-alert ;

\ Fail by sending a fatal alert.
: fail-alert ( alert -- ! )
	{ alert }
	flush-record
	begin can-output? not while wait-co drop repeat
	2 alert send-alert
	begin can-output? not while wait-co drop repeat
	alert 512 + fail ;

\ Perform the close operation:
\ -- Prevent new application data from the caller.
\ -- Incoming data is discarded (except alerts).
\ -- Outgoing data is flushed.
\ -- A close_notify alert is sent.
\ -- If 'cnr' is zero, then incoming data is discarded until a close_notify
\    is received.
\ -- At the end, the context is terminated.
\
\ cnr shall be either 0 or -1.
: do-close ( cnr -- ! )
	\ 'cnr' is set to non-zero when a close_notify is received from
	\ the peer.
	{ cnr }

	\ Get out of application data state. If we were accepting
	\ application data (flag is 1), and we still expect a close_notify
	\ from the peer (cnr is 0), then we should set the flag to 2.
	\ In all other cases, flag should be set to 0.
	addr-application_data get8 cnr not and 1 << addr-application_data set8

	\ Flush existing payload if any.
	flush-record

	\ Wait for room to send the close_notify. Since individual records
	\ can always hold at least 512 bytes, we know that when there is
	\ room, then there is room for a complete close_notify (two bytes).
	begin can-output? not while cnr wait-for-close >cnr repeat

	\ Write the close_notify and flush it.
	\ 21 addr-record_type_out set8
	\ 1 write8-native 0 write8-native 2drop
	\ flush-record
	0 send-warning

	\ Loop until our record has been sent (we know it's gone when
	\ writing is again possible) and a close_notify has been received.
	cnr
	begin
		dup can-output? and if ERR_OK fail then
		wait-for-close
	again ;

\ Yield control to the engine, with a possible flush. If 'cnr' is 0,
\ then input is analysed: all input is discarded, until a close_notify
\ is received.
: wait-for-close ( cnr -- cnr )
	co
	dup ifnot
		has-input? if
			addr-record_type_in get8 21 = if
				drop process-alerts
				\ If we received a close_notify then we
				\ no longer accept incoming application
				\ data records.
				0 addr-application_data set8
			else
				discard-input
			then
		then
	then ;

\ Test whether there is some accumulated payload that still needs to be
\ sent.
cc: payload-to-send? ( -- bool ) {
	T0_PUSHi(-br_ssl_engine_has_pld_to_send(ENG));
}

\ Test whether there is some available input data.
cc: has-input? ( -- bool ) {
	T0_PUSHi(-(ENG->hlen_in != 0));
}

\ Test whether some payload bytes may be written.
cc: can-output? ( -- bool ) {
	T0_PUSHi(-(ENG->hlen_out > 0));
}

\ Discard current input entirely.
cc: discard-input ( -- ) {
	ENG->hlen_in = 0;
}

\ Low-level read for one byte. If there is no available byte right
\ away, then -1 is returned. Otherwise, the byte value is returned.
\ If the current record type is "handshake" then the read byte is also
\ injected in the multi-hasher.
cc: read8-native ( -- x ) {
	if (ENG->hlen_in > 0) {
		unsigned char x;

		x = *ENG->hbuf_in ++;
		if (ENG->record_type_in == BR_SSL_HANDSHAKE) {
			br_multihash_update(&ENG->mhash, &x, 1);
		}
		T0_PUSH(x);
		ENG->hlen_in --;
	} else {
		T0_PUSHi(-1);
	}
}

\ Low-level read for several bytes. On entry, this expects an address
\ (offset in the engine context) and a length; these values designate
\ where the chunk should go. Upon exit, the new address and length
\ are pushed; that output length contains how many bytes could not be
\ read. If there is no available byte for reading, the address and
\ length are unchanged.
\ If the current record type is "handshake" then the read bytes are
\ injected in the multi-hasher.
cc: read-chunk-native ( addr len -- addr len ) {
	size_t clen = ENG->hlen_in;
	if (clen > 0) {
		uint32_t addr, len;

		len = T0_POP();
		addr = T0_POP();
		if ((size_t)len < clen) {
			clen = (size_t)len;
		}
		memcpy((unsigned char *)ENG + addr, ENG->hbuf_in, clen);
		if (ENG->record_type_in == BR_SSL_HANDSHAKE) {
			br_multihash_update(&ENG->mhash, ENG->hbuf_in, clen);
		}
		T0_PUSH(addr + (uint32_t)clen);
		T0_PUSH(len - (uint32_t)clen);
		ENG->hbuf_in += clen;
		ENG->hlen_in -= clen;
	}
}

\ Process available alert bytes. If a fatal alert is received, then the
\ context is terminated; otherwise, this returns either true (-1) if a
\ close_notify was received, false (0) otherwise.
: process-alerts ( -- bool )
	0
	begin has-input? while read8-native process-alert-byte or repeat
	dup if 1 addr-shutdown_recv set8 then ;

\ Process an alert byte. Returned value is non-zero if this is a close_notify,
\ zero otherwise.
: process-alert-byte ( x -- bool )
	addr-alert get8 case
		0 of
			\ 'alert' field is 0, so this byte shall be a level.
			\ Levels shall be 1 (warning) or 2 (fatal); we convert
			\ all other values to "fatal".
			dup 1 <> if drop 2 then
			addr-alert set8 0
		endof
		1 of
			0 addr-alert set8
			\ close_notify has value 0.
			\ no_renegotiation has value 100, and we treat it
			\ as a fatal alert.
			dup 100 = if 256 + fail then
			0=
		endof
		\ Fatal alert implies context termination.
		drop 256 + fail
	endcase ;

\ In general we only deal with handshake data here. Alerts are processed
\ in specific code right when they are received, and ChangeCipherSpec has
\ its own handling code. So we need to check that the data is "handshake"
\ only when returning from a coroutine call.

\ Yield control to the engine. Alerts are processed; if incoming data is
\ neither handshake or alert, then an error is triggered.
: wait-for-handshake ( -- )
	wait-co 0x07 and 0x01 > if ERR_UNEXPECTED fail then ;

\ Flush outgoing data (if any), then wait for the output buffer to be
\ clear; when this is done, set the output record type to the specified
\ value.
: wait-rectype-out ( rectype -- )
	{ rectype }
	flush-record
	begin
		can-output? if rectype addr-record_type_out set8 ret then
		wait-co drop
	again ;

\ Read one byte of handshake data. Block until that byte is available.
\ This does not check any length.
: read8-nc ( -- x )
	begin
		read8-native dup 0< ifnot ret then
		drop wait-for-handshake
	again ;

\ Test whether there are some more bytes in the current record. These
\ bytes have not necessarily been received yet (processing of unencrypted
\ records may begin before all bytes are received).
cc: more-incoming-bytes? ( -- bool ) {
	T0_PUSHi(ENG->hlen_in != 0 || !br_ssl_engine_recvrec_finished(ENG));
}

\ For reading functions, the TOS is supposed to contain the number of bytes
\ that can still be read (from encapsulating structure header), and it is
\ updated.

: check-len ( lim len -- lim )
	- dup 0< if ERR_BAD_PARAM fail then ;

\ Read one byte of handshake data. This pushes an integer in the 0..255 range.
: read8 ( lim -- lim x )
	1 check-len read8-nc ;

\ Read a 16-bit value (in the 0..65535 range)
: read16 ( lim -- lim n )
	2 check-len read8-nc 8 << read8-nc + ;

\ Read a 24-bit value (in the 0..16777215 range)
: read24 ( lim -- lim n )
	3 check-len read8-nc 8 << read8-nc + 8 << read8-nc + ;

\ Read some bytes. The "address" is an offset within the context
\ structure.
: read-blob ( lim addr len -- lim )
	{ addr len }
	len check-len
	addr len
	begin
		read-chunk-native
		dup 0 = if 2drop ret then
		wait-for-handshake
	again ;

\ Read some bytes and drop them.
: skip-blob ( lim len -- lim )
	swap over check-len swap
	begin dup while read8-nc drop 1- repeat
	drop ;

\ Read a 16-bit length, then skip exactly that many bytes.
: read-ignore-16 ( lim -- lim )
	read16 skip-blob ;

\ Open a substructure: the inner structure length is checked against,
\ and subtracted, from the output structure current limit.
: open-elt ( lim len -- lim-outer lim-inner )
	dup { len }
	- dup 0< if ERR_BAD_PARAM fail then
	len ;

\ Close the current structure. This checks that the limit is 0.
: close-elt ( lim -- )
	if ERR_BAD_PARAM fail then ;

\ Write one byte of handshake data.
: write8 ( n -- )
	begin
		dup write8-native if drop ret then
		wait-co drop
	again ;

\ Low-level write for one byte. On exit, it pushes either -1 (byte was
\ written) or 0 (no room in output buffer).
cc: write8-native ( x -- bool ) {
	unsigned char x;

	x = (unsigned char)T0_POP();
	if (ENG->hlen_out > 0) {
		if (ENG->record_type_out == BR_SSL_HANDSHAKE) {
			br_multihash_update(&ENG->mhash, &x, 1);
		}
		*ENG->hbuf_out ++ = x;
		ENG->hlen_out --;
		T0_PUSHi(-1);
	} else {
		T0_PUSHi(0);
	}
}

\ Write a 16-bit value.
: write16 ( n -- )
	dup 8 u>> write8 write8 ;

\ Write a 24-bit value.
: write24 ( n -- )
	dup 16 u>> write8 write16 ;

\ Write some bytes. The "address" is an offset within the context
\ structure.
: write-blob ( addr len -- )
	begin
		write-blob-chunk
		dup 0 = if 2drop ret then
		wait-co drop
	again ;

cc: write-blob-chunk ( addr len -- addr len ) {
	size_t clen = ENG->hlen_out;
	if (clen > 0) {
		uint32_t addr, len;

		len = T0_POP();
		addr = T0_POP();
		if ((size_t)len < clen) {
			clen = (size_t)len;
		}
		memcpy(ENG->hbuf_out, (unsigned char *)ENG + addr, clen);
		if (ENG->record_type_out == BR_SSL_HANDSHAKE) {
			br_multihash_update(&ENG->mhash, ENG->hbuf_out, clen);
		}
		T0_PUSH(addr + (uint32_t)clen);
		T0_PUSH(len - (uint32_t)clen);
		ENG->hbuf_out += clen;
		ENG->hlen_out -= clen;
	}
}

\ Write a blob with the length as header (over one byte)
: write-blob-head8 ( addr len -- )
	dup write8 write-blob ;

\ Write a blob with the length as header (over two bytes)
: write-blob-head16 ( addr len -- )
	dup write16 write-blob ;

\ Perform a byte-to-byte comparison between two blobs. Each blob is
\ provided as an "address" (offset in the context structure); the
\ length is common. Returned value is true (-1) if the two blobs are
\ equal, false (0) otherwise.
cc: memcmp ( addr1 addr2 len -- bool ) {
	size_t len = (size_t)T0_POP();
	void *addr2 = (unsigned char *)ENG + (size_t)T0_POP();
	void *addr1 = (unsigned char *)ENG + (size_t)T0_POP();
	int x = memcmp(addr1, addr2, len);
	T0_PUSH((uint32_t)-(x == 0));
}

\ Copy bytes between two areas, whose addresses are provided as
\ offsets in the context structure.
cc: memcpy ( dst src len -- ) {
	size_t len = (size_t)T0_POP();
	void *src = (unsigned char *)ENG + (size_t)T0_POP();
	void *dst = (unsigned char *)ENG + (size_t)T0_POP();
	memcpy(dst, src, len);
}

\ Get string length (zero-terminated). The string address is provided as
\ an offset relative to the context start. Returned length does not include
\ the terminated 0.
cc: strlen ( str -- len ) {
	void *str = (unsigned char *)ENG + (size_t)T0_POP();
	T0_PUSH((uint32_t)strlen(str));
}

\ Fill a buffer with zeros. The buffer address is an offset in the context.
cc: bzero ( addr len -- ) {
	size_t len = (size_t)T0_POP();
	void *addr = (unsigned char *)ENG + (size_t)T0_POP();
	memset(addr, 0, len);
}

\ Scan the list of supported cipher suites for a given value. If found,
\ then the list index at which it was found is returned; otherwise, -1
\ is returned.
: scan-suite ( suite -- index )
	{ suite }
	addr-suites_num get8 { num }
	0
	begin dup num < while
		dup 1 << addr-suites_buf + get16 suite = if ret then
		1+
	repeat
	drop -1 ;

\ =======================================================================

\ Generate random bytes into buffer (address is offset in context).
cc: mkrand ( addr len -- ) {
	size_t len = (size_t)T0_POP();
	void *addr = (unsigned char *)ENG + (size_t)T0_POP();
	br_hmac_drbg_generate(&ENG->rng, addr, len);
}

\ Read a handshake message header: type and length. These are returned
\ in reverse order (type is TOS, length is below it).
: read-handshake-header-core ( -- lim type )
	read8-nc 3 read24 swap drop swap ;

\ Read a handshake message header: type and length. If the header is for
\ a HelloRequest message, then it is discarded and a new header is read
\ (repeatedly if necessary).
: read-handshake-header ( -- lim type )
	begin
		read-handshake-header-core dup 0= while
		drop if ERR_BAD_HANDSHAKE fail then
	repeat ;

\ =======================================================================

\ Cipher suite processing.
\
\ Unfortunately, cipher suite identifiers are attributed mostly arbitrary,
\ so we have to map the cipher suite numbers we support into aggregate
\ words that encode the information we need. Table below is organized
\ as a sequence of pairs of 16-bit words, the first being the cipher suite
\ identifier, the second encoding the algorithm elements. The suites are
\ ordered by increasing cipher suite ID, so that fast lookups may be
\ performed with a binary search (not implemented for the moment, since it
\ does not appear to matter much in practice).
\
\ Algorithm elements are encoded over 4 bits each, in the following order
\ (most significant to least significant):
\
\ -- Server key type:
\       0  RSA           (RSA key exchange)
\       1  ECDHE-RSA     (ECDHE key exchange, RSA signature)
\       2  ECDHE-ECDSA   (ECDHE key exchange, ECDSA signature)
\       3  ECDH-RSA      (ECDH key exchange, certificate is RSA-signed)
\       4  ECDH-ECDSA    (ECDH key exchange, certificate is ECDSA-signed)
\ -- Encryption algorithm:
\       0  3DES/CBC
\       1  AES-128/CBC
\       2  AES-256/CBC
\       3  AES-128/GCM
\       4  AES-256/GCM
\       5  ChaCha20/Poly1305
\       6  AES-128/CCM
\       7  AES-256/CCM
\       8  AES-128/CCM8
\       9  AES-256/CCM8
\ -- MAC algorithm:
\       0  none         (for suites with AEAD encryption)
\       2  HMAC/SHA-1
\       4  HMAC/SHA-256
\       5  HMAC/SHA-384
\ -- PRF for TLS-1.2:
\       4  with SHA-256
\       5  with SHA-384
\
\ WARNING: if adding a new cipher suite that does not use SHA-256 for the
\ PRF (with TLS 1.2), be sure to check the suites_sha384[] array defined
\ in ssl/ssl_keyexport.c

data: cipher-suite-def

hexb| 000A 0024 | \ TLS_RSA_WITH_3DES_EDE_CBC_SHA
hexb| 002F 0124 | \ TLS_RSA_WITH_AES_128_CBC_SHA
hexb| 0035 0224 | \ TLS_RSA_WITH_AES_256_CBC_SHA
hexb| 003C 0144 | \ TLS_RSA_WITH_AES_128_CBC_SHA256
hexb| 003D 0244 | \ TLS_RSA_WITH_AES_256_CBC_SHA256

hexb| 009C 0304 | \ TLS_RSA_WITH_AES_128_GCM_SHA256
hexb| 009D 0405 | \ TLS_RSA_WITH_AES_256_GCM_SHA384

hexb| C003 4024 | \ TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA
hexb| C004 4124 | \ TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA
hexb| C005 4224 | \ TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA
hexb| C008 2024 | \ TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA
hexb| C009 2124 | \ TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
hexb| C00A 2224 | \ TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
hexb| C00D 3024 | \ TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA
hexb| C00E 3124 | \ TLS_ECDH_RSA_WITH_AES_128_CBC_SHA
hexb| C00F 3224 | \ TLS_ECDH_RSA_WITH_AES_256_CBC_SHA
hexb| C012 1024 | \ TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
hexb| C013 1124 | \ TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
hexb| C014 1224 | \ TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA

hexb| C023 2144 | \ TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
hexb| C024 2255 | \ TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
hexb| C025 4144 | \ TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256
hexb| C026 4255 | \ TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384
hexb| C027 1144 | \ TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
hexb| C028 1255 | \ TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
hexb| C029 3144 | \ TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256
hexb| C02A 3255 | \ TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384
hexb| C02B 2304 | \ TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
hexb| C02C 2405 | \ TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
hexb| C02D 4304 | \ TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256
hexb| C02E 4405 | \ TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384
hexb| C02F 1304 | \ TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
hexb| C030 1405 | \ TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
hexb| C031 3304 | \ TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256
hexb| C032 3405 | \ TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384

hexb| C09C 0604 | \ TLS_RSA_WITH_AES_128_CCM
hexb| C09D 0704 | \ TLS_RSA_WITH_AES_256_CCM
hexb| C0A0 0804 | \ TLS_RSA_WITH_AES_128_CCM_8
hexb| C0A1 0904 | \ TLS_RSA_WITH_AES_256_CCM_8
hexb| C0AC 2604 | \ TLS_ECDHE_ECDSA_WITH_AES_128_CCM
hexb| C0AD 2704 | \ TLS_ECDHE_ECDSA_WITH_AES_256_CCM
hexb| C0AE 2804 | \ TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
hexb| C0AF 2904 | \ TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8

hexb| CCA8 1504 | \ TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
hexb| CCA9 2504 | \ TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256

hexb| 0000 | \ List terminator.

\ Convert cipher suite identifier to element words. This returns 0 if
\ the cipher suite is not known.
: cipher-suite-to-elements ( suite -- elts )
	{ id }
	cipher-suite-def
	begin
		dup 2+ swap data-get16
		dup ifnot 2drop 0 ret then
		id = if data-get16 ret then
		2+
	again ;

\ Check that a given cipher suite is supported. Note that this also
\ returns true (-1) for the TLS_FALLBACK_SCSV pseudo-ciphersuite.
: suite-supported? ( suite -- bool )
	dup 0x5600 = if drop -1 ret then
	cipher-suite-to-elements 0<> ;

\ Get expected key type for cipher suite. The key type is one of
\ BR_KEYTYPE_RSA or BR_KEYTYPE_EC, combined with either BR_KEYTYPE_KEYX
\ (RSA encryption or static ECDH) or BR_KEYTYPE_SIGN (RSA or ECDSA
\ signature, for ECDHE cipher suites).
: expected-key-type ( suite -- key-type )
	cipher-suite-to-elements 12 >>
	case
		0 of CX 0 63 { BR_KEYTYPE_RSA | BR_KEYTYPE_KEYX } endof
		1 of CX 0 63 { BR_KEYTYPE_RSA | BR_KEYTYPE_SIGN } endof
		2 of CX 0 63 { BR_KEYTYPE_EC  | BR_KEYTYPE_SIGN } endof
		3 of CX 0 63 { BR_KEYTYPE_EC  | BR_KEYTYPE_KEYX } endof
		4 of CX 0 63 { BR_KEYTYPE_EC  | BR_KEYTYPE_KEYX } endof
		0 swap
	endcase ;

\ Test whether the cipher suite uses RSA key exchange.
: use-rsa-keyx? ( suite -- bool )
	cipher-suite-to-elements 12 >> 0= ;

\ Test whether the cipher suite uses ECDHE key exchange, signed with RSA.
: use-rsa-ecdhe? ( suite -- bool )
	cipher-suite-to-elements 12 >> 1 = ;

\ Test whether the cipher suite uses ECDHE key exchange, signed with ECDSA.
: use-ecdsa-ecdhe? ( suite -- bool )
	cipher-suite-to-elements 12 >> 2 = ;

\ Test whether the cipher suite uses ECDHE key exchange (with RSA or ECDSA).
: use-ecdhe? ( suite -- bool )
	cipher-suite-to-elements 12 >> dup 0> swap 3 < and ;

\ Test whether the cipher suite uses ECDH (static) key exchange.
: use-ecdh? ( suite -- bool )
	cipher-suite-to-elements 12 >> 2 > ;

\ Get identifier for the PRF (TLS 1.2).
: prf-id ( suite -- id )
	cipher-suite-to-elements 15 and ;

\ Test whether a cipher suite is only for TLS-1.2. Cipher suites that
\ can be used with TLS-1.0 or 1.1 use HMAC/SHA-1. RFC do not formally
\ forbid using a CBC-based TLS-1.2 cipher suite, e.g. based on HMAC/SHA-256,
\ with older protocol versions; however, servers should not do that, since
\ it may confuse clients. Since the server code does not try such games,
\ for consistency, the client should reject it as well (normal servers
\ don't do that, so any attempt is a sign of foul play).
: use-tls12? ( suite -- bool )
	cipher-suite-to-elements 0xF0 and 0x20 <> ;

\ Switch to negotiated security parameters for input or output.
: switch-encryption ( is-client for-input -- )
	{ for-input }
	addr-cipher_suite get16 cipher-suite-to-elements { elts }

	\ prf_id
	elts 15 and

	\ mac_id
	elts 4 >> 15 and

	\ cipher type and key length
	elts 8 >> 15 and case
		\ 3DES/CBC
		0 of 0 24
			for-input if
				switch-cbc-in
			else
				switch-cbc-out
			then
		endof

		\ AES-128/CBC
		1 of 1 16
			for-input if
				switch-cbc-in
			else
				switch-cbc-out
			then
		endof

		\ AES-256/CBC
		2 of 1 32
			for-input if
				switch-cbc-in
			else
				switch-cbc-out
			then
		endof

		\ AES-128/GCM
		3 of drop 16
			for-input if
				switch-aesgcm-in
			else
				switch-aesgcm-out
			then
		endof

		\ AES-256/GCM
		4 of drop 32
			for-input if
				switch-aesgcm-in
			else
				switch-aesgcm-out
			then
		endof

		\ ChaCha20+Poly1305
		5 of drop
			for-input if
				switch-chapol-in
			else
				switch-chapol-out
			then
		endof

		\ Now we only have AES/CCM suites (6 to 9). Since the
		\ input is between 0 and 15, and we checked values 0 to 5,
		\ we only need to reject values larger than 9.
		dup 9 > if
			ERR_BAD_PARAM fail
		then

		\ Stack: is_client prf_id mac_id cipher_id
		\ We want to remove the mac_id (it is zero for CCM suites)
		\ and replace the cipher_id with the key and tag lengths.
		\ The following table applies:
		\  id   key length   tag length
		\   6       16          16
		\   7       32          16
		\   8       16           8
		\   9       32           8
		swap drop
		dup 1 and 4 << 16 + swap
		8 and 16 swap -
		for-input if
			switch-aesccm-in
		else
			switch-aesccm-out
		then
		ret
	endcase
	;

cc: switch-cbc-out ( is_client prf_id mac_id aes cipher_key_len -- ) {
	int is_client, prf_id, mac_id, aes;
	unsigned cipher_key_len;

	cipher_key_len = T0_POP();
	aes = T0_POP();
	mac_id = T0_POP();
	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_cbc_out(ENG, is_client, prf_id, mac_id,
		aes ? ENG->iaes_cbcenc : ENG->ides_cbcenc, cipher_key_len);
}

cc: switch-cbc-in ( is_client prf_id mac_id aes cipher_key_len -- ) {
	int is_client, prf_id, mac_id, aes;
	unsigned cipher_key_len;

	cipher_key_len = T0_POP();
	aes = T0_POP();
	mac_id = T0_POP();
	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_cbc_in(ENG, is_client, prf_id, mac_id,
		aes ? ENG->iaes_cbcdec : ENG->ides_cbcdec, cipher_key_len);
}

cc: switch-aesgcm-out ( is_client prf_id cipher_key_len -- ) {
	int is_client, prf_id;
	unsigned cipher_key_len;

	cipher_key_len = T0_POP();
	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_gcm_out(ENG, is_client, prf_id,
		ENG->iaes_ctr, cipher_key_len);
}

cc: switch-aesgcm-in ( is_client prf_id cipher_key_len -- ) {
	int is_client, prf_id;
	unsigned cipher_key_len;

	cipher_key_len = T0_POP();
	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_gcm_in(ENG, is_client, prf_id,
		ENG->iaes_ctr, cipher_key_len);
}

cc: switch-chapol-out ( is_client prf_id -- ) {
	int is_client, prf_id;

	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_chapol_out(ENG, is_client, prf_id);
}

cc: switch-chapol-in ( is_client prf_id -- ) {
	int is_client, prf_id;

	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_chapol_in(ENG, is_client, prf_id);
}

cc: switch-aesccm-out ( is_client prf_id cipher_key_len tag_len -- ) {
	int is_client, prf_id;
	unsigned cipher_key_len, tag_len;

	tag_len = T0_POP();
	cipher_key_len = T0_POP();
	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_ccm_out(ENG, is_client, prf_id,
		ENG->iaes_ctrcbc, cipher_key_len, tag_len);
}

cc: switch-aesccm-in ( is_client prf_id cipher_key_len tag_len -- ) {
	int is_client, prf_id;
	unsigned cipher_key_len, tag_len;

	tag_len = T0_POP();
	cipher_key_len = T0_POP();
	prf_id = T0_POP();
	is_client = T0_POP();
	br_ssl_engine_switch_ccm_in(ENG, is_client, prf_id,
		ENG->iaes_ctrcbc, cipher_key_len, tag_len);
}

\ Write Finished message.
: write-Finished ( from_client -- )
	compute-Finished
	20 write8 12 write24 addr-pad 12 write-blob ;

\ Read Finished message.
: read-Finished ( from_client -- )
	compute-Finished
	read-handshake-header 20 <> if ERR_UNEXPECTED fail then
	addr-pad 12 + 12 read-blob
	close-elt
	addr-pad dup 12 + 12 memcmp ifnot ERR_BAD_FINISHED fail then ;

\ Compute the "Finished" contents (either the value to send, or the
\ expected value). The 12-byte string is written in the pad. The
\ "from_client" value is non-zero for the Finished sent by the client.
\ The computed value is also saved in the relevant buffer for handling
\ secure renegotiation.
: compute-Finished ( from_client -- )
	dup addr-saved_finished swap ifnot 12 + then swap
	addr-cipher_suite get16 prf-id compute-Finished-inner
	addr-pad 12 memcpy ;

cc: compute-Finished-inner ( from_client prf_id -- ) {
	int prf_id = T0_POP();
	int from_client = T0_POPi();
	unsigned char tmp[48];
	br_tls_prf_seed_chunk seed;

	br_tls_prf_impl prf = br_ssl_engine_get_PRF(ENG, prf_id);
	seed.data = tmp;
	if (ENG->session.version >= BR_TLS12) {
		seed.len = br_multihash_out(&ENG->mhash, prf_id, tmp);
	} else {
		br_multihash_out(&ENG->mhash, br_md5_ID, tmp);
		br_multihash_out(&ENG->mhash, br_sha1_ID, tmp + 16);
		seed.len = 36;
	}
	prf(ENG->pad, 12, ENG->session.master_secret,
		sizeof ENG->session.master_secret,
		from_client ? "client finished" : "server finished",
		1, &seed);
}

\ Receive ChangeCipherSpec and Finished from the peer.
: read-CCS-Finished ( is-client -- )
	has-input? if
		addr-record_type_in get8 20 <> if ERR_UNEXPECTED fail then
	else
		begin
			wait-co 0x07 and dup 0x02 <> while
			if ERR_UNEXPECTED fail then
		repeat
		drop
	then
	read8-nc 1 <> more-incoming-bytes? or if ERR_BAD_CCS fail then
	dup 1 switch-encryption

	\ Read and verify Finished from peer.
	not read-Finished ;

\ Send ChangeCipherSpec and Finished to the peer.
: write-CCS-Finished ( is-client -- )
	\ Flush and wait for output buffer to be clear, so that we may
	\ write our ChangeCipherSpec. We must switch immediately after
	\ triggering the flush.
	20 wait-rectype-out
	1 write8
	flush-record
	dup 0 switch-encryption
	22 wait-rectype-out
	write-Finished
	flush-record ;

\ Read and parse a list of supported signature algorithms (with hash
\ functions). The resulting bit field is returned.
: read-list-sign-algos ( lim -- lim value )
	0 { hashes }
	read16 open-elt
	begin dup while
		read8 { hash } read8 { sign }

		\ If hash is 0x08 then this is a "new algorithm" identifier,
		\ and we set the corresponding bit if it is in the 0..15
		\ range. Otherwise, we keep the value only if the signature
		\ is either 1 (RSA) or 3 (ECDSA), and the hash is one of the
		\ SHA-* functions (2 to 6). Note that we reject MD5.
		hash 8 = if
			sign 15 <= if
				1 sign 16 + << hashes or >hashes
			then
		else
			hash 2 >= hash 6 <= and
			sign 1 = sign 3 = or
			and if
				hashes 1 sign 1- 2 << hash + << or >hashes
			then
		then
	repeat
	close-elt
	hashes ;

\ =======================================================================

\ Compute total chain length. This includes the individual certificate
\ headers, but not the total chain header. This also sets the cert_cur,
\ cert_len and chain_len context fields.
cc: total-chain-length ( -- len ) {
	size_t u;
	uint32_t total;

	total = 0;
	for (u = 0; u < ENG->chain_len; u ++) {
		total += 3 + (uint32_t)ENG->chain[u].data_len;
	}
	T0_PUSH(total);
}

\ Get length for current certificate in the chain; if the chain end was
\ reached, then this returns -1.
cc: begin-cert ( -- len ) {
	if (ENG->chain_len == 0) {
		T0_PUSHi(-1);
	} else {
		ENG->cert_cur = ENG->chain->data;
		ENG->cert_len = ENG->chain->data_len;
		ENG->chain ++;
		ENG->chain_len --;
		T0_PUSH(ENG->cert_len);
	}
}

\ Copy a chunk of certificate data into the pad. Returned value is the
\ chunk length, or 0 if the certificate end is reached.
cc: copy-cert-chunk ( -- len ) {
	size_t clen;

	clen = ENG->cert_len;
	if (clen > sizeof ENG->pad) {
		clen = sizeof ENG->pad;
	}
	memcpy(ENG->pad, ENG->cert_cur, clen);
	ENG->cert_cur += clen;
	ENG->cert_len -= clen;
	T0_PUSH(clen);
}

\ Write a Certificate message. Total chain length (excluding the 3-byte
\ header) is returned; it is 0 if the chain is empty.
: write-Certificate ( -- total_chain_len )
	11 write8
	total-chain-length dup
	dup 3 + write24 write24
	begin
		begin-cert
		dup 0< if drop ret then write24
		begin copy-cert-chunk dup while
			addr-pad swap write-blob
		repeat
		drop
	again ;

cc: x509-start-chain ( by_client -- ) {
	const br_x509_class *xc;
	uint32_t bc;

	bc = T0_POP();
	xc = *(ENG->x509ctx);
	xc->start_chain(ENG->x509ctx, bc ? ENG->server_name : NULL);
}

cc: x509-start-cert ( length -- ) {
	const br_x509_class *xc;

	xc = *(ENG->x509ctx);
	xc->start_cert(ENG->x509ctx, T0_POP());
}

cc: x509-append ( length -- ) {
	const br_x509_class *xc;
	size_t len;

	xc = *(ENG->x509ctx);
	len = T0_POP();
	xc->append(ENG->x509ctx, ENG->pad, len);
}

cc: x509-end-cert ( -- ) {
	const br_x509_class *xc;

	xc = *(ENG->x509ctx);
	xc->end_cert(ENG->x509ctx);
}

cc: x509-end-chain ( -- err ) {
	const br_x509_class *xc;

	xc = *(ENG->x509ctx);
	T0_PUSH(xc->end_chain(ENG->x509ctx));
}

cc: get-key-type-usages ( -- key-type-usages ) {
	const br_x509_class *xc;
	const br_x509_pkey *pk;
	unsigned usages;

	xc = *(ENG->x509ctx);
	pk = xc->get_pkey(ENG->x509ctx, &usages);
	if (pk == NULL) {
		T0_PUSH(0);
	} else {
		T0_PUSH(pk->key_type | usages);
	}
}

\ Read a Certificate message.
\ Parameter: non-zero if this is a read by the client of a certificate
\ sent by the server; zero otherwise.
\ Returned value:
\   - Empty: 0
\   - Valid: combination of key type and allowed key usages.
\   - Invalid: negative (-x for error code x)
: read-Certificate ( by_client -- key-type-usages )
	\ Get header, and check message type.
	read-handshake-header 11 = ifnot ERR_UNEXPECTED fail then

	\ If the chain is empty, do some special processing.
	dup 3 = if
		read24 if ERR_BAD_PARAM fail then
		swap drop ret
	then

	\ Start processing the chain through the X.509 engine.
	swap x509-start-chain

	\ Total chain length is a 24-bit integer.
	read24 open-elt
	begin
		dup while
		read24 open-elt
		dup x509-start-cert

		\ We read the certificate by chunks through the pad, so
		\ as to use the existing reading function (read-blob)
		\ that also ensures proper hashing.
		begin
			dup while
			dup 256 > if 256 else dup then { len }
			addr-pad len read-blob
			len x509-append
		repeat
		close-elt
		x509-end-cert
	repeat

	\ We must close the chain AND the handshake message.
	close-elt
	close-elt

	\ Chain processing is finished; get the error code.
	x509-end-chain
	dup if neg ret then drop

	\ Return key type and usages.
	get-key-type-usages ;

\ =======================================================================

\ Copy a specific protocol name from the list to the pad. The byte
\ length is returned.
cc: copy-protocol-name ( idx -- len ) {
	size_t idx = T0_POP();
	size_t len = strlen(ENG->protocol_names[idx]);
	memcpy(ENG->pad, ENG->protocol_names[idx], len);
	T0_PUSH(len);
}

\ Compare name in pad with the configured list of protocol names.
\ If a match is found, then the index is returned; otherwise, -1
\ is returned.
cc: test-protocol-name ( len -- n ) {
	size_t len = T0_POP();
	size_t u;

	for (u = 0; u < ENG->protocol_names_num; u ++) {
		const char *name;

		name = ENG->protocol_names[u];
		if (len == strlen(name) && memcmp(ENG->pad, name, len) == 0) {
			T0_PUSH(u);
			T0_RET();
		}
	}
	T0_PUSHi(-1);
}