src/quic_tls.c

#include <string.h>

#include <openssl/ssl.h>

#if defined(OPENSSL_IS_BORINGSSL)
#include <openssl/hkdf.h>
#else
#include <openssl/evp.h>
#include <openssl/kdf.h>
#endif

#include <haproxy/buf.h>
#include <haproxy/chunk.h>
//#include <haproxy/quic_tls-t.h>
#include <haproxy/xprt_quic.h>


__attribute__((format (printf, 3, 4)))
void hexdump(const void *buf, size_t buflen, const char *title_fmt, ...);

/* Initial salt depending on QUIC version to derive client/server initial secrets.
 * This one is for draft-29 QUIC version.
 */
unsigned char initial_salt[20] = {
	0xaf, 0xbf, 0xec, 0x28, 0x99, 0x93, 0xd2, 0x4c,
	0x9e, 0x97, 0x86, 0xf1, 0x9c, 0x61, 0x11, 0xe0,
	0x43, 0x90, 0xa8, 0x99
};

/* Dump the RX/TX secrets of <secs> QUIC TLS secrets. */
void quic_tls_keys_hexdump(struct buffer *buf, struct quic_tls_secrets *secs)
{
	int i;
	size_t aead_keylen = (size_t)EVP_CIPHER_key_length(secs->aead);
	size_t aead_ivlen = (size_t)EVP_CIPHER_iv_length(secs->aead);
	size_t hp_len = (size_t)EVP_CIPHER_key_length(secs->hp);

	chunk_appendf(buf, "\n          key=");
	for (i = 0; i < aead_keylen; i++)
		chunk_appendf(buf, "%02x", secs->key[i]);
	chunk_appendf(buf, "\n          iv=");
	for (i = 0; i < aead_ivlen; i++)
		chunk_appendf(buf, "%02x", secs->iv[i]);
	chunk_appendf(buf, "\n          hp=");
	for (i = 0; i < hp_len; i++)
		chunk_appendf(buf, "%02x", secs->hp_key[i]);
}

/* Dump <secret> TLS secret. */
void quic_tls_secret_hexdump(struct buffer *buf,
                             const unsigned char *secret, size_t secret_len)
{
	int i;

	chunk_appendf(buf, " secret=");
	for (i = 0; i < secret_len; i++)
		chunk_appendf(buf, "%02x", secret[i]);
}

#if defined(OPENSSL_IS_BORINGSSL)
int quic_hkdf_extract(const EVP_MD *md,
                      unsigned char *buf, size_t *buflen,
                      const unsigned char *key, size_t keylen,
                      unsigned char *salt, size_t saltlen)
{
	return HKDF_extract(buf, buflen, md, key, keylen, salt, saltlen);
}

int quic_hkdf_expand(const EVP_MD *md,
                     unsigned char *buf, size_t buflen,
                     const unsigned char *key, size_t keylen,
                     const unsigned char *label, size_t labellen)
{
	return HKDF_expand(buf, buflen, md, key, keylen, label, labellen);
}
#else
int quic_hkdf_extract(const EVP_MD *md,
                      unsigned char *buf, size_t *buflen,
                      const unsigned char *key, size_t keylen,
                      unsigned char *salt, size_t saltlen)
{
    EVP_PKEY_CTX *ctx;

    ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
    if (!ctx)
        return 0;

    if (EVP_PKEY_derive_init(ctx) <= 0 ||
        EVP_PKEY_CTX_hkdf_mode(ctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY) <= 0 ||
        EVP_PKEY_CTX_set_hkdf_md(ctx, md) <= 0 ||
        EVP_PKEY_CTX_set1_hkdf_salt(ctx, salt, saltlen) <= 0 ||
        EVP_PKEY_CTX_set1_hkdf_key(ctx, key, keylen) <= 0 ||
        EVP_PKEY_derive(ctx, buf, buflen) <= 0)
        goto err;

    EVP_PKEY_CTX_free(ctx);
    return 1;

 err:
    EVP_PKEY_CTX_free(ctx);
    return 0;
}

int quic_hkdf_expand(const EVP_MD *md,
                     unsigned char *buf, size_t buflen,
                     const unsigned char *key, size_t keylen,
                     const unsigned char *label, size_t labellen)
{
    EVP_PKEY_CTX *ctx;

    ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
    if (!ctx)
        return 0;

    if (EVP_PKEY_derive_init(ctx) <= 0 ||
        EVP_PKEY_CTX_hkdf_mode(ctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY) <= 0 ||
        EVP_PKEY_CTX_set_hkdf_md(ctx, md) <= 0 ||
        EVP_PKEY_CTX_set1_hkdf_key(ctx, key, keylen) <= 0 ||
        EVP_PKEY_CTX_add1_hkdf_info(ctx, label, labellen) <= 0 ||
        EVP_PKEY_derive(ctx, buf, &buflen) <= 0)
        goto err;

    EVP_PKEY_CTX_free(ctx);
    return 1;

 err:
    EVP_PKEY_CTX_free(ctx);
    return 0;
}
#endif

/* https://quicwg.org/base-drafts/draft-ietf-quic-tls.html#protection-keys
 * refers to:
 *
 * https://tools.ietf.org/html/rfc8446#section-7.1:
 * 7.1.  Key Schedule
 *
 * The key derivation process makes use of the HKDF-Extract and
 * HKDF-Expand functions as defined for HKDF [RFC5869], as well as the
 * functions defined below:
 *
 *     HKDF-Expand-Label(Secret, Label, Context, Length) =
 *          HKDF-Expand(Secret, HkdfLabel, Length)
 *
 *     Where HkdfLabel is specified as:
 *
 *     struct {
 *         uint16 length = Length;
 *         opaque label<7..255> = "tls13 " + Label;
 *         opaque context<0..255> = Context;
 *     } HkdfLabel;
 *
 *     Derive-Secret(Secret, Label, Messages) =
 *          HKDF-Expand-Label(Secret, Label,
 *                            Transcript-Hash(Messages), Hash.length)
 *
 */
int quic_hkdf_expand_label(const EVP_MD *md,
                           unsigned char *buf, size_t buflen,
                           const unsigned char *key, size_t keylen,
                           const unsigned char *label, size_t labellen)
{
	unsigned char hdkf_label[256], *pos;
	const unsigned char hdkf_label_label[] = "tls13 ";
	size_t hdkf_label_label_sz = sizeof hdkf_label_label - 1;

	pos = hdkf_label;
	*pos++ = buflen >> 8;
	*pos++ = buflen & 0xff;
	*pos++ = hdkf_label_label_sz + labellen;
	memcpy(pos, hdkf_label_label, hdkf_label_label_sz);
	pos += hdkf_label_label_sz;
	memcpy(pos, label, labellen);
	pos += labellen;
	*pos++ = '\0';

	return quic_hkdf_expand(md, buf, buflen,
	                        key, keylen, hdkf_label, pos - hdkf_label);
}

/*
 * This function derives two keys from <secret> is <ctx> as TLS cryptographic context.
 * ->key is the TLS key to be derived to encrypt/decrypt data at TLS level.
 * ->iv is the initialization vector to be used with ->key.
 * ->hp_key is the key to be derived for header protection.
 * Obviouly these keys have the same size becaused derived with the same TLS cryptographic context.
 */
int quic_tls_derive_keys(const EVP_CIPHER *aead, const EVP_CIPHER *hp,
                         const EVP_MD *md,
                         unsigned char *key, size_t keylen,
                         unsigned char *iv, size_t ivlen,
                         unsigned char *hp_key, size_t hp_keylen,
                         const unsigned char *secret, size_t secretlen)
{
	size_t aead_keylen = (size_t)EVP_CIPHER_key_length(aead);
	size_t aead_ivlen = (size_t)EVP_CIPHER_iv_length(aead);
	size_t hp_len = (size_t)EVP_CIPHER_key_length(hp);
	const unsigned char    key_label[] = "quic key";
	const unsigned char     iv_label[] = "quic iv";
	const unsigned char hp_key_label[] = "quic hp";

	if (aead_keylen > keylen || aead_ivlen > ivlen || hp_len > hp_keylen)
		return 0;

	if (!quic_hkdf_expand_label(md, key, aead_keylen, secret, secretlen,
	                            key_label, sizeof key_label - 1) ||
	    !quic_hkdf_expand_label(md, iv, aead_ivlen, secret, secretlen,
	                            iv_label, sizeof iv_label - 1) ||
	    !quic_hkdf_expand_label(md, hp_key, hp_len, secret, secretlen,
	                            hp_key_label, sizeof hp_key_label - 1))
		return 0;

	return 1;
}

/*
 * Derive the initial secret from <secret> and QUIC version dependent salt.
 * Returns the size of the derived secret if succeeded, 0 if not.
 */
int quic_derive_initial_secret(const EVP_MD *md,
                               unsigned char *initial_secret, size_t initial_secret_sz,
                               const unsigned char *secret, size_t secret_sz)
{
	if (!quic_hkdf_extract(md, initial_secret, &initial_secret_sz, secret, secret_sz,
	                       initial_salt, sizeof initial_salt))
		return 0;

	return 1;
}

/*
 * Derive the client initial secret from the initial secret.
 * Returns the size of the derived secret if succeeded, 0 if not.
 */
int quic_tls_derive_initial_secrets(const EVP_MD *md,
                                    unsigned char *rx, size_t rx_sz,
                                    unsigned char *tx, size_t tx_sz,
                                    const unsigned char *secret, size_t secret_sz,
                                    int server)
{
	const unsigned char client_label[] = "client in";
	const unsigned char server_label[] = "server in";
	const unsigned char *tx_label, *rx_label;
	size_t rx_label_sz, tx_label_sz;

	if (server) {
		rx_label = client_label;
		rx_label_sz = sizeof client_label;
		tx_label = server_label;
		tx_label_sz = sizeof server_label;
	}
	else {
		rx_label = server_label;
		rx_label_sz = sizeof server_label;
		tx_label = client_label;
		tx_label_sz = sizeof client_label;
	}

	if (!quic_hkdf_expand_label(md, rx, rx_sz, secret, secret_sz,
	                            rx_label, rx_label_sz - 1) ||
	    !quic_hkdf_expand_label(md, tx, tx_sz, secret, secret_sz,
	                            tx_label, tx_label_sz - 1))
	    return 0;

	return 1;
}

/*
 * Build an IV into <iv> buffer with <ivlen> as size from <aead_iv> with
 * <aead_ivlen> as size depending on <pn> packet number.
 * This is the function which must be called to build an AEAD IV for the AEAD cryptographic algorithm
 * used to encrypt/decrypt the QUIC packet payloads depending on the packet number <pn>.
 * This function fails and return 0 only if the two buffer lengths are different, 1 if not.
 */
int quic_aead_iv_build(unsigned char *iv, size_t ivlen,
                       unsigned char *aead_iv, size_t aead_ivlen, uint64_t pn)
{
	int i;
	unsigned int shift;
	unsigned char *pos = iv;

	if (ivlen != aead_ivlen)
		return 0;

	for (i = 0; i < ivlen - sizeof pn; i++)
		*pos++ = *aead_iv++;

	/* Only the remaining (sizeof pn) bytes are XOR'ed. */
	shift = 56;
	for (i = aead_ivlen - sizeof pn; i < aead_ivlen ; i++, shift -= 8)
		*pos++ = *aead_iv++ ^ (pn >> shift);

	return 1;
}

/*
 * https://quicwg.org/base-drafts/draft-ietf-quic-tls.html#aead
 *
 * 5.3. AEAD Usage
 *
 * Packets are protected prior to applying header protection (Section 5.4).
 * The unprotected packet header is part of the associated data (A). When removing
 * packet protection, an endpoint first removes the header protection.
 * (...)
 * These ciphersuites have a 16-byte authentication tag and produce an output 16
 * bytes larger than their input.
 * The key and IV for the packet are computed as described in Section 5.1. The nonce,
 * N, is formed by combining the packet protection IV with the packet number. The 62
 * bits of the reconstructed QUIC packet number in network byte order are left-padded
 * with zeros to the size of the IV. The exclusive OR of the padded packet number and
 * the IV forms the AEAD nonce.
 *
 * The associated data, A, for the AEAD is the contents of the QUIC header, starting
 * from the flags byte in either the short or long header, up to and including the
 * unprotected packet number.
 *
 * The input plaintext, P, for the AEAD is the payload of the QUIC packet, as described
 * in [QUIC-TRANSPORT].
 *
 * The output ciphertext, C, of the AEAD is transmitted in place of P.
 *
 * Some AEAD functions have limits for how many packets can be encrypted under the same
 * key and IV (see for example [AEBounds]). This might be lower than the packet number limit.
 * An endpoint MUST initiate a key update (Section 6) prior to exceeding any limit set for
 * the AEAD that is in use.
 */

int quic_tls_encrypt(unsigned char *buf, size_t len,
                     const unsigned char *aad, size_t aad_len,
                     const EVP_CIPHER *aead, const unsigned char *key, const unsigned char *iv)
{
	EVP_CIPHER_CTX *ctx;
	int ret, outlen;

	ret = 0;
	ctx = EVP_CIPHER_CTX_new();
	if (!ctx)
		return 0;

	if (!EVP_EncryptInit_ex(ctx, aead, NULL, key, iv) ||
		!EVP_EncryptUpdate(ctx, NULL, &outlen, aad, aad_len) ||
		!EVP_EncryptUpdate(ctx, buf, &outlen, buf, len) ||
		!EVP_EncryptFinal_ex(ctx, buf + outlen, &outlen) ||
		!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, QUIC_TLS_TAG_LEN, buf + len))
		goto out;

	ret = 1;

 out:
	EVP_CIPHER_CTX_free(ctx);

	return ret;
}

int quic_tls_decrypt(unsigned char *buf, size_t len,
                     unsigned char *aad, size_t aad_len,
                     const EVP_CIPHER *aead, const unsigned char *key, const unsigned char *iv)
{
	int ret, outlen;
	size_t off;
	EVP_CIPHER_CTX *ctx;

	ret = 0;
	off = 0;
	ctx = EVP_CIPHER_CTX_new();
	if (!ctx)
		return 0;

	if (!EVP_DecryptInit_ex(ctx, aead, NULL, key, iv) ||
		!EVP_DecryptUpdate(ctx, NULL, &outlen, aad, aad_len) ||
		!EVP_DecryptUpdate(ctx, buf, &outlen, buf, len - QUIC_TLS_TAG_LEN))
		goto out;

	off += outlen;

	if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, QUIC_TLS_TAG_LEN,
	                         buf + len - QUIC_TLS_TAG_LEN) ||
	    !EVP_DecryptFinal_ex(ctx, buf + off, &outlen))
		goto out;

	off += outlen;

	ret = off;

 out:
	EVP_CIPHER_CTX_free(ctx);
	return ret;
}