/*
sptps.c -- Simple Peer-to-Peer Security
- Copyright (C) 2011 Guus Sliepen <guus@tinc-vpn.org>,
+ Copyright (C) 2011-2021 Guus Sliepen <guus@tinc-vpn.org>,
+ 2010 Brandon L. Black <blblack@gmail.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include "system.h"
-#include "cipher.h"
-#include "crypto.h"
-#include "digest.h"
+#include "chacha-poly1305/chachapoly.h"
#include "ecdh.h"
#include "ecdsa.h"
#include "prf.h"
#include "sptps.h"
+#include "random.h"
+#include "xalloc.h"
-char *logfilename;
-#include "utils.c"
+#ifdef HAVE_OPENSSL
+#include <openssl/evp.h>
+#endif
+
+#define CIPHER_KEYLEN 64
+
+unsigned int sptps_replaywin = 16;
+
+/*
+ Nonce MUST be exchanged first (done)
+ Signatures MUST be done over both nonces, to guarantee the signature is fresh
+ Otherwise: if ECDHE key of one side is compromised, it can be reused!
+
+ Add explicit tag to beginning of structure to distinguish the client and server when signing. (done)
+
+ Sign all handshake messages up to ECDHE kex with long-term public keys. (done)
+
+ HMACed KEX finished message to prevent downgrade attacks and prove you have the right key material (done by virtue of Ed25519 over the whole ECDHE exchange?)
+
+ Explicit close message needs to be added.
+
+ Maybe do add some alert messages to give helpful error messages? Not more than TLS sends.
+
+ Use counter mode instead of OFB. (done)
+
+ Make sure ECC operations are fixed time (aka prevent side-channel attacks).
+*/
+
+void sptps_log_quiet(sptps_t *s, int s_errno, const char *format, va_list ap) {
+ (void)s;
+ (void)s_errno;
+ (void)format;
+ (void)ap;
+}
+
+void sptps_log_stderr(sptps_t *s, int s_errno, const char *format, va_list ap) {
+ (void)s;
+ (void)s_errno;
+
+ vfprintf(stderr, format, ap);
+ fputc('\n', stderr);
+}
+
+void (*sptps_log)(sptps_t *s, int s_errno, const char *format, va_list ap) = sptps_log_stderr;
+
+// Log an error message.
+static bool error(sptps_t *s, int s_errno, const char *format, ...) ATTR_FORMAT(printf, 3, 4);
+static bool error(sptps_t *s, int s_errno, const char *format, ...) {
+ (void)s;
+ (void)s_errno;
+
+ if(format) {
+ va_list ap;
+ va_start(ap, format);
+ sptps_log(s, s_errno, format, ap);
+ va_end(ap);
+ }
-static bool error(sptps_t *s, int s_errno, const char *msg) {
- fprintf(stderr, "SPTPS error: %s\n", msg);
errno = s_errno;
return false;
}
-static bool send_record_priv(sptps_t *s, uint8_t type, const char *data, uint16_t len) {
- char plaintext[len + 23];
- char ciphertext[len + 19];
+static void warning(sptps_t *s, const char *format, ...) ATTR_FORMAT(printf, 2, 3);
+static void warning(sptps_t *s, const char *format, ...) {
+ va_list ap;
+ va_start(ap, format);
+ sptps_log(s, 0, format, ap);
+ va_end(ap);
+}
- // Create header with sequence number, length and record type
- uint32_t seqno = htonl(s->outseqno++);
- uint16_t netlen = htons(len);
+static sptps_kex_t *new_sptps_kex(void) {
+ return xzalloc(sizeof(sptps_kex_t));
+}
- memcpy(plaintext, &seqno, 4);
- memcpy(plaintext + 4, &netlen, 2);
- plaintext[6] = type;
+static void free_sptps_kex(sptps_kex_t *kex) {
+ xzfree(kex, sizeof(sptps_kex_t));
+}
- // Add plaintext (TODO: avoid unnecessary copy)
- memcpy(plaintext + 7, data, len);
+static sptps_key_t *new_sptps_key(void) {
+ return xzalloc(sizeof(sptps_key_t));
+}
- if(s->state) {
- // If first handshake has finished, encrypt and HMAC
- if(!digest_create(&s->outdigest, plaintext, len + 7, plaintext + 7 + len))
+static void free_sptps_key(sptps_key_t *key) {
+ xzfree(key, sizeof(sptps_key_t));
+}
+
+static bool cipher_init(uint8_t suite, void **ctx, const sptps_key_t *keys, bool key_half) {
+ const uint8_t *key = key_half ? keys->key1 : keys->key0;
+
+ switch(suite) {
+#ifndef HAVE_OPENSSL
+
+ case SPTPS_CHACHA_POLY1305:
+ *ctx = malloc(sizeof(struct chachapoly_ctx));
+ return *ctx && chachapoly_init(*ctx, key, 256) == CHACHAPOLY_OK;
+
+#else
+
+ case SPTPS_CHACHA_POLY1305:
+#ifdef EVP_F_EVP_AEAD_CTX_INIT
+ *ctx = malloc(sizeof(EVP_AEAD_CTX));
+
+ return *ctx && EVP_AEAD_CTX_init(*ctx, EVP_aead_chacha20_poly1305(), key + (key_half ? CIPHER_KEYLEN : 0), 32, 16, NULL);
+#else
+ *ctx = EVP_CIPHER_CTX_new();
+
+ return *ctx
+ && EVP_EncryptInit_ex(*ctx, EVP_chacha20_poly1305(), NULL, NULL, NULL)
+ && EVP_CIPHER_CTX_ctrl(*ctx, EVP_CTRL_GCM_SET_IVLEN, 12, NULL)
+ && EVP_EncryptInit_ex(*ctx, NULL, NULL, key, key + 32);
+#endif
+
+ case SPTPS_AES256_GCM:
+ *ctx = EVP_CIPHER_CTX_new();
+
+ return *ctx
+ && EVP_EncryptInit_ex(*ctx, EVP_aes_256_gcm(), NULL, NULL, NULL)
+ && EVP_CIPHER_CTX_ctrl(*ctx, EVP_CTRL_GCM_SET_IVLEN, 12, NULL)
+ && EVP_EncryptInit_ex(*ctx, NULL, NULL, key, key + 32);
+#endif
+
+ default:
+ return false;
+ }
+}
+
+static void cipher_exit(uint8_t suite, void *ctx) {
+ switch(suite) {
+#ifndef HAVE_OPENSSL
+
+ case SPTPS_CHACHA_POLY1305:
+ free(ctx);
+ break;
+
+#else
+
+ case SPTPS_CHACHA_POLY1305:
+#ifdef EVP_F_EVP_AEAD_CTX_INIT
+ EVP_AEAD_CTX_cleanup(ctx);
+ free(ctx);
+ break;
+#endif
+
+ case SPTPS_AES256_GCM:
+ EVP_CIPHER_CTX_free(ctx);
+ break;
+#endif
+
+ default:
+ break;
+ }
+}
+
+static bool cipher_encrypt(uint8_t suite, void *ctx, uint32_t seqno, const uint8_t *in, size_t inlen, uint8_t *out, size_t *outlen) {
+ switch(suite) {
+#ifndef HAVE_OPENSSL
+
+ case SPTPS_CHACHA_POLY1305: {
+ if(chachapoly_crypt(ctx, nonce, (void *)in, inlen, out, out + inlen, 16, 1) != CHACHAPOLY_OK) {
+ return false;
+ }
+
+ if(outlen) {
+ *outlen = inlen + 16;
+ }
+
+ return true;
+ }
+
+#else
+
+ case SPTPS_CHACHA_POLY1305:
+#ifdef EVP_F_EVP_AEAD_CTX_INIT
+ {
+ size_t outlen1;
+
+ if(!EVP_AEAD_CTX_seal(ctx, out, &outlen1, inlen + 16, nonce, sizeof(nonce), in, inlen, NULL, 0)) {
+ return false;
+ }
+
+ if(outlen) {
+ *outlen = outlen1;
+ }
+
+ return true;
+ }
+
+#endif
+
+ case SPTPS_AES256_GCM: {
+ uint8_t nonce[12] = {seqno, seqno >> 8, seqno >> 16, seqno >> 24};
+
+ if(!EVP_EncryptInit_ex(ctx, NULL, NULL, NULL, nonce)) {
+ return false;
+ }
+
+ int outlen1 = 0, outlen2 = 0;
+
+ if(!EVP_EncryptUpdate(ctx, out, &outlen1, in, (int)inlen)) {
+ return false;
+ }
+
+ if(!EVP_EncryptFinal_ex(ctx, out + outlen1, &outlen2)) {
+ return false;
+ }
+
+ outlen1 += outlen2;
+
+ if(!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, 16, out + outlen1)) {
+ return false;
+ }
+
+ outlen1 += 16;
+
+ if(outlen) {
+ *outlen = outlen1;
+ }
+
+ return true;
+ }
+
+#endif
+
+ default:
+ return false;
+ }
+}
+
+static bool cipher_decrypt(uint8_t suite, void *ctx, uint32_t seqno, const uint8_t *in, size_t inlen, uint8_t *out, size_t *outlen) {
+ if(inlen < 16) {
+ return false;
+ }
+
+ inlen -= 16;
+
+ switch(suite) {
+#ifndef HAVE_OPENSSL
+
+ case SPTPS_CHACHA_POLY1305:
+ if(chachapoly_crypt(ctx, nonce, (void *)in, inlen, out, (void *)(in + inlen), 16, 0) != CHACHAPOLY_OK) {
+ return false;
+ }
+
+ if(outlen) {
+ *outlen = inlen;
+ }
+
+ return true;
+
+#else
+
+ case SPTPS_CHACHA_POLY1305:
+#ifdef EVP_F_EVP_AEAD_CTX_INIT
+ {
+ size_t outlen1;
+
+ if(!EVP_AEAD_CTX_open(ctx, out, &outlen1, inlen, nonce, sizeof(nonce), in, inlen + 16, NULL, 0)) {
+ return false;
+ }
+
+ if(outlen) {
+ *outlen = outlen1;
+ }
+
+ return true;
+ }
+
+#endif
+
+ case SPTPS_AES256_GCM: {
+ uint8_t nonce[12] = {seqno, seqno >> 8, seqno >> 16, seqno >> 24};
+
+ if(!EVP_DecryptInit_ex(ctx, NULL, NULL, NULL, nonce)) {
+ return false;
+ }
+
+ int outlen1 = 0, outlen2 = 0;
+
+ if(!EVP_DecryptUpdate(ctx, out, &outlen1, in, (int)inlen)) {
+ return false;
+ }
+
+ if(!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, 16, (void *)(in + inlen))) {
return false;
+ }
- if(!cipher_encrypt(&s->outcipher, plaintext + 4, sizeof ciphertext, ciphertext, NULL, false))
+ if(!EVP_DecryptFinal_ex(ctx, out + outlen1, &outlen2)) {
return false;
+ }
+
+ if(outlen) {
+ *outlen = outlen1 + outlen2;
+ }
+
+ return true;
+ }
+
+#endif
- return s->send_data(s->handle, ciphertext, len + 19);
+ default:
+ return false;
+ }
+}
+
+// Send a record (datagram version, accepts all record types, handles encryption and authentication).
+static bool send_record_priv_datagram(sptps_t *s, uint8_t type, const void *data, uint16_t len) {
+ uint8_t *buffer = alloca(len + SPTPS_DATAGRAM_OVERHEAD);
+ // Create header with sequence number, length and record type
+ uint32_t seqno = s->outseqno++;
+
+ memcpy(buffer, &seqno, 4);
+ buffer[4] = type;
+ memcpy(buffer + 5, data, len);
+
+ if(s->outstate) {
+ // If first handshake has finished, encrypt and HMAC
+ if(!cipher_encrypt(s->cipher_suite, s->outcipher, seqno, buffer + 4, len + 1, buffer + 4, NULL)) {
+ return error(s, EINVAL, "Failed to encrypt message");
+ }
+
+ return s->send_data(s->handle, type, buffer, len + SPTPS_DATAGRAM_OVERHEAD);
} else {
// Otherwise send as plaintext
- return s->send_data(s->handle, plaintext + 4, len + 3);
+ return s->send_data(s->handle, type, buffer, len + SPTPS_DATAGRAM_HEADER);
}
}
+// Send a record (private version, accepts all record types, handles encryption and authentication).
+static bool send_record_priv(sptps_t *s, uint8_t type, const void *data, uint16_t len) {
+ if(s->datagram) {
+ return send_record_priv_datagram(s, type, data, len);
+ }
+
+ uint8_t *buffer = alloca(len + SPTPS_OVERHEAD);
-bool send_record(sptps_t *s, uint8_t type, const char *data, uint16_t len) {
+ // Create header with sequence number, length and record type
+ uint32_t seqno = s->outseqno++;
+ uint16_t netlen = len;
+
+ memcpy(buffer, &netlen, 2);
+ buffer[2] = type;
+ memcpy(buffer + 3, data, len);
+
+ if(s->outstate) {
+ // If first handshake has finished, encrypt and HMAC
+ if(!cipher_encrypt(s->cipher_suite, s->outcipher, seqno, buffer + 2, len + 1, buffer + 2, NULL)) {
+ return error(s, EINVAL, "Failed to encrypt message");
+ }
+
+ return s->send_data(s->handle, type, buffer, len + SPTPS_OVERHEAD);
+ } else {
+ // Otherwise send as plaintext
+ return s->send_data(s->handle, type, buffer, len + SPTPS_HEADER);
+ }
+}
+
+// Send an application record.
+bool sptps_send_record(sptps_t *s, uint8_t type, const void *data, uint16_t len) {
// Sanity checks: application cannot send data before handshake is finished,
// and only record types 0..127 are allowed.
- if(!s->state)
+ if(!s->outstate) {
return error(s, EINVAL, "Handshake phase not finished yet");
+ }
- if(type & 128)
+ if(type >= SPTPS_HANDSHAKE) {
return error(s, EINVAL, "Invalid application record type");
+ }
return send_record_priv(s, type, data, len);
}
+// Send a Key EXchange record, containing a random nonce and an ECDHE public key.
static bool send_kex(sptps_t *s) {
- size_t keylen = ECDH_SIZE;
- size_t siglen = ecdsa_size(&s->mykey);
- char data[32 + keylen + siglen];
+ // Make room for our KEX message, which we will keep around since send_sig() needs it.
+ if(s->mykex) {
+ return false;
+ }
- // Create a random nonce.
- s->myrandom = realloc(s->myrandom, 32);
- if(!s->myrandom)
- return error(s, errno, strerror(errno));
+ s->mykex = new_sptps_kex();
+
+ // Set version byte to zero.
+ s->mykex->version = SPTPS_VERSION;
+ s->mykex->preferred_suite = s->preferred_suite;
+ s->mykex->cipher_suites = s->cipher_suites;
- randomize(s->myrandom, 32);
- memcpy(data, s->myrandom, 32);
+ // Create a random nonce.
+ randomize(s->mykex->nonce, ECDH_SIZE);
// Create a new ECDH public key.
- if(!ecdh_generate_public(&s->ecdh, data + 32))
- return false;
+ if(!(s->ecdh = ecdh_generate_public(s->mykex->pubkey))) {
+ return error(s, EINVAL, "Failed to generate ECDH public key");
+ }
- // Sign the former.
- if(!ecdsa_sign(&s->mykey, data, 32 + keylen, data + 32 + keylen))
- return false;
+ return send_record_priv(s, SPTPS_HANDSHAKE, s->mykex, sizeof(sptps_kex_t));
+}
- // Send the handshake record.
- return send_record_priv(s, 128, data, sizeof data);
+static size_t sigmsg_len(size_t labellen) {
+ return 1 + 2 * sizeof(sptps_kex_t) + labellen;
}
-static bool generate_key_material(sptps_t *s, const char *shared, size_t len, const char *hisrandom) {
- // Initialise cipher and digest structures if necessary
- if(!s->state) {
- bool result
- = cipher_open_by_name(&s->incipher, "aes-256-ofb")
- && cipher_open_by_name(&s->outcipher, "aes-256-ofb")
- && digest_open_by_name(&s->indigest, "sha256", 16)
- && digest_open_by_name(&s->outdigest, "sha256", 16);
- if(!result)
- return false;
+static void fill_msg(uint8_t *msg, bool initiator, const sptps_kex_t *kex0, const sptps_kex_t *kex1, const sptps_t *s) {
+ *msg = initiator, msg++;
+ memcpy(msg, kex0, sizeof(*kex0)), msg += sizeof(*kex0);
+ memcpy(msg, kex1, sizeof(*kex1)), msg += sizeof(*kex1);
+ memcpy(msg, s->label, s->labellen);
+}
+
+// Send a SIGnature record, containing an Ed25519 signature over both KEX records.
+static bool send_sig(sptps_t *s) {
+ // Concatenate both KEX messages, plus tag indicating if it is from the connection originator, plus label
+ size_t msglen = sigmsg_len(s->labellen);
+ uint8_t *msg = alloca(msglen);
+ fill_msg(msg, s->initiator, s->mykex, s->hiskex, s);
+
+ // Sign the result.
+ size_t siglen = ecdsa_size(s->mykey);
+ uint8_t *sig = alloca(siglen);
+
+ if(!ecdsa_sign(s->mykey, msg, msglen, sig)) {
+ return error(s, EINVAL, "Failed to sign SIG record");
}
- // Allocate memory for key material
- size_t keylen = digest_keylength(&s->indigest) + digest_keylength(&s->outdigest) + cipher_keylength(&s->incipher) + cipher_keylength(&s->outcipher);
+ // Send the SIG exchange record.
+ return send_record_priv(s, SPTPS_HANDSHAKE, sig, siglen);
+}
- s->key = realloc(s->key, keylen);
- if(!s->key)
- return error(s, errno, strerror(errno));
+// Generate key material from the shared secret created from the ECDHE key exchange.
+static bool generate_key_material(sptps_t *s, const uint8_t *shared, size_t len) {
+ // Allocate memory for key material
+ s->key = new_sptps_key();
// Create the HMAC seed, which is "key expansion" + session label + server nonce + client nonce
- char seed[s->labellen + 64 + 13];
- strcpy(seed, "key expansion");
- if(s->initiator) {
- memcpy(seed + 13, hisrandom, 32);
- memcpy(seed + 45, s->myrandom, 32);
- } else {
- memcpy(seed + 13, s->myrandom, 32);
- memcpy(seed + 45, hisrandom, 32);
- }
- memcpy(seed + 78, s->label, s->labellen);
+ const size_t msglen = sizeof("key expansion") - 1;
+ const size_t seedlen = msglen + s->labellen + ECDH_SIZE * 2;
+ uint8_t *seed = alloca(seedlen);
+
+ uint8_t *ptr = seed;
+ memcpy(ptr, "key expansion", msglen);
+ ptr += msglen;
+
+ memcpy(ptr, (s->initiator ? s->mykex : s->hiskex)->nonce, ECDH_SIZE);
+ ptr += ECDH_SIZE;
+
+ memcpy(ptr, (s->initiator ? s->hiskex : s->mykex)->nonce, ECDH_SIZE);
+ ptr += ECDH_SIZE;
+
+ memcpy(ptr, s->label, s->labellen);
// Use PRF to generate the key material
- if(!prf(shared, len, seed, s->labellen + 64 + 13, s->key, keylen))
- return false;
+ if(!prf(shared, len, seed, seedlen, s->key->both, sizeof(sptps_key_t))) {
+ return error(s, EINVAL, "Failed to generate key material");
+ }
return true;
}
+// Send an ACKnowledgement record.
static bool send_ack(sptps_t *s) {
- return send_record_priv(s, 128, "", 0);
+ return send_record_priv(s, SPTPS_HANDSHAKE, "", 0);
}
-static bool receive_ack(sptps_t *s, const char *data, uint16_t len) {
- if(len)
- return false;
+// Receive an ACKnowledgement record.
+static bool receive_ack(sptps_t *s, const uint8_t *data, uint16_t len) {
+ (void)data;
+
+ if(len) {
+ return error(s, EIO, "Invalid ACK record length");
+ }
+
+ if(!cipher_init(s->cipher_suite, &s->incipher, s->key, s->initiator)) {
+ return error(s, EINVAL, "Failed to initialize cipher");
+ }
+
+ free_sptps_key(s->key);
+ s->key = NULL;
+ s->instate = true;
+
+ return true;
+}
+
+static uint8_t select_cipher_suite(uint16_t mask, uint8_t pref1, uint8_t pref2) {
+ // Check if there is a viable preference, if so select the lowest one
+ uint8_t selection = 255;
+
+ if(mask & (1U << pref1)) {
+ selection = pref1;
+ }
+
+ if(pref2 < selection && (mask & (1U << pref2))) {
+ selection = pref2;
+ }
+
+ // Otherwise, select the lowest cipher suite both sides support
+ if(selection == 255) {
+ selection = 0;
+
+ while(!(mask & 1U)) {
+ selection++;
+ mask >>= 1;
+ }
+ }
- // TODO: set cipher/digest keys
- return error(s, ENOSYS, "receive_ack() not completely implemented yet");
+ return selection;
}
-static bool receive_kex(sptps_t *s, const char *data, uint16_t len) {
- size_t keylen = ECDH_SIZE;
- size_t siglen = ecdsa_size(&s->hiskey);
+// Receive a Key EXchange record, respond by sending a SIG record.
+static bool receive_kex(sptps_t *s, const uint8_t *data, uint16_t len) {
+ // Verify length of the HELLO record
+
+ if(len != sizeof(sptps_kex_t)) {
+ return error(s, EIO, "Invalid KEX record length");
+ }
+
+ if(*data != SPTPS_VERSION) {
+ return error(s, EINVAL, "Received incorrect version %d", *data);
+ }
+
+ uint16_t suites;
+ memcpy(&suites, data + 2, 2);
+ suites &= s->cipher_suites;
+
+ if(!suites) {
+ return error(s, EIO, "No matching cipher suites");
+ }
+
+ s->cipher_suite = select_cipher_suite(suites, s->preferred_suite, data[1] & 0xf);
+
+ // Make a copy of the KEX message, send_sig() and receive_sig() need it
+ if(s->hiskex) {
+ return error(s, EINVAL, "Received a second KEX message before first has been processed");
+ }
+
+ s->hiskex = new_sptps_kex();
+ memcpy(s->hiskex, data, sizeof(sptps_kex_t));
+
+ if(s->initiator) {
+ return send_sig(s);
+ } else {
+ return true;
+ }
+}
+// Receive a SIGnature record, verify it, if it passed, compute the shared secret and calculate the session keys.
+static bool receive_sig(sptps_t *s, const uint8_t *data, uint16_t len) {
// Verify length of KEX record.
- if(len != 32 + keylen + siglen)
+ if(len != ecdsa_size(s->hiskey)) {
return error(s, EIO, "Invalid KEX record length");
+ }
+
+ // Concatenate both KEX messages, plus tag indicating if it is from the connection originator
+ const size_t msglen = sigmsg_len(s->labellen);
+ uint8_t *msg = alloca(msglen);
+ fill_msg(msg, !s->initiator, s->hiskex, s->mykex, s);
// Verify signature.
- if(!ecdsa_verify(&s->hiskey, data, 32 + keylen, data + 32 + keylen))
- return false;
+ if(!ecdsa_verify(s->hiskey, msg, msglen, data)) {
+ return error(s, EIO, "Failed to verify SIG record");
+ }
// Compute shared secret.
- char shared[ECDH_SHARED_SIZE];
- if(!ecdh_compute_shared(&s->ecdh, data + 32, shared))
- return false;
+ uint8_t shared[ECDH_SHARED_SIZE];
+
+ if(!ecdh_compute_shared(s->ecdh, s->hiskex->pubkey, shared)) {
+ memzero(shared, sizeof(shared));
+ return error(s, EINVAL, "Failed to compute ECDH shared secret");
+ }
+
+ s->ecdh = NULL;
// Generate key material from shared secret.
- if(!generate_key_material(s, shared, sizeof shared, data))
+ bool generated = generate_key_material(s, shared, sizeof(shared));
+ memzero(shared, sizeof(shared));
+
+ if(!generated) {
return false;
+ }
- // Send cipher change record if necessary
- if(s->state)
- if(!send_ack(s))
- return false;
+ if(!s->initiator && !send_sig(s)) {
+ return false;
+ }
- // TODO: set cipher/digest keys
- if(s->initiator) {
- bool result
- = cipher_set_key(&s->incipher, s->key, false)
- && digest_set_key(&s->indigest, s->key + cipher_keylength(&s->incipher), digest_keylength(&s->indigest))
- && cipher_set_key(&s->outcipher, s->key + cipher_keylength(&s->incipher) + digest_keylength(&s->indigest), true)
- && digest_set_key(&s->outdigest, s->key + cipher_keylength(&s->incipher) + digest_keylength(&s->indigest) + cipher_keylength(&s->outcipher), digest_keylength(&s->outdigest));
- if(!result)
- return false;
- } else {
- bool result
- = cipher_set_key(&s->outcipher, s->key, true)
- && digest_set_key(&s->outdigest, s->key + cipher_keylength(&s->outcipher), digest_keylength(&s->outdigest))
- && cipher_set_key(&s->incipher, s->key + cipher_keylength(&s->outcipher) + digest_keylength(&s->outdigest), false)
- && digest_set_key(&s->indigest, s->key + cipher_keylength(&s->outcipher) + digest_keylength(&s->outdigest) + cipher_keylength(&s->incipher), digest_keylength(&s->indigest));
- if(!result)
- return false;
+ free_sptps_kex(s->mykex);
+ s->mykex = NULL;
+
+ free_sptps_kex(s->hiskex);
+ s->hiskex = NULL;
+
+ // Send cipher change record
+ if(s->outstate && !send_ack(s)) {
+ return false;
+ }
+
+ if(!cipher_init(s->cipher_suite, &s->outcipher, s->key, !s->initiator)) {
+ return error(s, EINVAL, "Failed to initialize cipher");
}
return true;
}
-static bool receive_handshake(sptps_t *s, const char *data, uint16_t len) {
+// Force another Key EXchange (for testing purposes).
+bool sptps_force_kex(sptps_t *s) {
+ if(!s->outstate || s->state != SPTPS_SECONDARY_KEX) {
+ return error(s, EINVAL, "Cannot force KEX in current state");
+ }
+
+ s->state = SPTPS_KEX;
+ return send_kex(s);
+}
+
+// Receive a handshake record.
+static bool receive_handshake(sptps_t *s, const uint8_t *data, uint16_t len) {
// Only a few states to deal with handshaking.
switch(s->state) {
- case 0:
- // We have sent our public ECDH key, we expect our peer to sent one as well.
- if(!receive_kex(s, data, len))
- return false;
- s->state = 1;
- return true;
- case 1:
- // We receive a secondary key exchange request, first respond by sending our own public ECDH key.
- if(!send_kex(s))
- return false;
- case 2:
- // If we already sent our secondary public ECDH key, we expect the peer to send his.
- if(!receive_kex(s, data, len))
- return false;
- s->state = 3;
- return true;
- case 3:
- // We expect an empty handshake message to indicate transition to the new keys.
- if(!receive_ack(s, data, len))
+ case SPTPS_SECONDARY_KEX:
+
+ // We receive a secondary KEX request, first respond by sending our own.
+ if(!send_kex(s)) {
+ return false;
+ }
+
+ // Fall through
+ case SPTPS_KEX:
+
+ // We have sent our KEX request, we expect our peer to sent one as well.
+ if(!receive_kex(s, data, len)) {
+ return false;
+ }
+
+ s->state = SPTPS_SIG;
+ return true;
+
+ case SPTPS_SIG:
+
+ // If we already sent our secondary public ECDH key, we expect the peer to send his.
+ if(!receive_sig(s, data, len)) {
+ return false;
+ }
+
+ if(s->outstate) {
+ s->state = SPTPS_ACK;
+ } else {
+ s->outstate = true;
+
+ if(!receive_ack(s, NULL, 0)) {
return false;
- s->state = 1;
- return true;
- default:
- return error(s, EIO, "Invalid session state");
+ }
+
+ s->receive_record(s->handle, SPTPS_HANDSHAKE, NULL, 0);
+ s->state = SPTPS_SECONDARY_KEX;
+ }
+
+ return true;
+
+ case SPTPS_ACK:
+
+ // We expect a handshake message to indicate transition to the new keys.
+ if(!receive_ack(s, data, len)) {
+ return false;
+ }
+
+ s->receive_record(s->handle, SPTPS_HANDSHAKE, NULL, 0);
+ s->state = SPTPS_SECONDARY_KEX;
+ return true;
+
+ // TODO: split ACK into a VERify and ACK?
+ default:
+ return error(s, EIO, "Invalid session state %d", s->state);
}
}
-bool receive_data(sptps_t *s, const char *data, size_t len) {
- while(len) {
- // First read the 2 length bytes.
- if(s->buflen < 6) {
- size_t toread = 6 - s->buflen;
- if(toread > len)
- toread = len;
-
- if(s->state) {
- if(!cipher_decrypt(&s->incipher, data, toread, s->inbuf + s->buflen, NULL, false))
- return false;
- } else {
- memcpy(s->inbuf + s->buflen, data, toread);
+static bool sptps_check_seqno(sptps_t *s, uint32_t seqno, bool update_state) {
+ // Replay protection using a sliding window of configurable size.
+ // s->inseqno is expected sequence number
+ // seqno is received sequence number
+ // s->late[] is a circular buffer, a 1 bit means a packet has not been received yet
+ // The circular buffer contains bits for sequence numbers from s->inseqno - s->replaywin * 8 to (but excluding) s->inseqno.
+ if(s->replaywin) {
+ if(seqno != s->inseqno) {
+ if(seqno >= s->inseqno + s->replaywin * 8) {
+ // Prevent packets that jump far ahead of the queue from causing many others to be dropped.
+ bool farfuture = s->farfuture < s->replaywin >> 2;
+
+ if(update_state) {
+ s->farfuture++;
+ }
+
+ if(farfuture) {
+ return update_state ? error(s, EIO, "Packet is %d seqs in the future, dropped (%u)\n", seqno - s->inseqno, s->farfuture) : false;
+ }
+
+ // Unless we have seen lots of them, in which case we consider the others lost.
+ if(update_state) {
+ warning(s, "Lost %d packets\n", seqno - s->inseqno);
+ }
+
+ if(update_state) {
+ // Mark all packets in the replay window as being late.
+ memset(s->late, 255, s->replaywin);
+ }
+ } else if(seqno < s->inseqno) {
+ // If the sequence number is farther in the past than the bitmap goes, or if the packet was already received, drop it.
+ if((s->inseqno >= s->replaywin * 8 && seqno < s->inseqno - s->replaywin * 8) || !(s->late[(seqno / 8) % s->replaywin] & (1 << seqno % 8))) {
+ return update_state ? error(s, EIO, "Received late or replayed packet, seqno %d, last received %d\n", seqno, s->inseqno) : false;
+ }
+ } else if(update_state) {
+ // We missed some packets. Mark them in the bitmap as being late.
+ for(uint32_t i = s->inseqno; i < seqno; i++) {
+ s->late[(i / 8) % s->replaywin] |= 1 << i % 8;
+ }
}
+ }
- s->buflen += toread;
- len -= toread;
- data += toread;
-
- // Exit early if we don't have the full length.
- if(s->buflen < 6)
- return true;
-
- // If we have the length bytes, ensure our buffer can hold the whole request.
- uint16_t reclen;
- memcpy(&reclen, s->inbuf + 4, 2);
- reclen = htons(reclen);
- s->inbuf = realloc(s->inbuf, reclen + 23UL);
- if(!s->inbuf)
- return error(s, errno, strerror(errno));
-
- // Add sequence number.
- uint32_t seqno = htonl(s->inseqno++);
- memcpy(s->inbuf, &seqno, 4);
-
- // Exit early if we have no more data to process.
- if(!len)
- return true;
- }
-
- // Read up to the end of the record.
- uint16_t reclen;
- memcpy(&reclen, s->inbuf + 4, 2);
- reclen = htons(reclen);
- size_t toread = reclen + (s->state ? 23UL : 7UL) - s->buflen;
- if(toread > len)
- toread = len;
+ if(update_state) {
+ // Mark the current packet as not being late.
+ s->late[(seqno / 8) % s->replaywin] &= ~(1 << seqno % 8);
+ s->farfuture = 0;
+ }
+ }
- if(s->state) {
- if(!cipher_decrypt(&s->incipher, data, toread, s->inbuf + s->buflen, NULL, false))
- return false;
+ if(update_state) {
+ if(seqno >= s->inseqno) {
+ s->inseqno = seqno + 1;
+ }
+
+ if(!s->inseqno) {
+ s->received = 0;
} else {
- memcpy(s->inbuf + s->buflen, data, toread);
+ s->received++;
+ }
+ }
+
+ return true;
+}
+
+// Check datagram for valid HMAC
+bool sptps_verify_datagram(sptps_t *s, const void *vdata, size_t len) {
+ if(!s->instate || len < 21) {
+ return error(s, EIO, "Received short packet");
+ }
+
+ const uint8_t *data = vdata;
+ uint32_t seqno;
+ memcpy(&seqno, data, 4);
+
+ if(!sptps_check_seqno(s, seqno, false)) {
+ return false;
+ }
+
+ uint8_t *buffer = alloca(len);
+ return cipher_decrypt(s->cipher_suite, s->incipher, seqno, data + 4, len - 4, buffer, NULL);
+}
+
+// Receive incoming data, datagram version.
+static bool sptps_receive_data_datagram(sptps_t *s, const uint8_t *data, size_t len) {
+ if(len < (s->instate ? 21 : 5)) {
+ return error(s, EIO, "Received short packet");
+ }
+
+ uint32_t seqno;
+ memcpy(&seqno, data, 4);
+ data += 4;
+ len -= 4;
+
+ if(!s->instate) {
+ if(seqno != s->inseqno) {
+ return error(s, EIO, "Invalid packet seqno: %d != %d", seqno, s->inseqno);
+ }
+
+ s->inseqno = seqno + 1;
+
+ uint8_t type = *(data++);
+ len--;
+
+ if(type != SPTPS_HANDSHAKE) {
+ return error(s, EIO, "Application record received before handshake finished");
+ }
+
+ return receive_handshake(s, data, len);
+ }
+
+ // Decrypt
+
+ uint8_t *buffer = alloca(len);
+ size_t outlen;
+
+ if(!cipher_decrypt(s->cipher_suite, s->incipher, seqno, data, len, buffer, &outlen)) {
+ return error(s, EIO, "Failed to decrypt and verify packet");
+ }
+
+ if(!sptps_check_seqno(s, seqno, true)) {
+ return false;
+ }
+
+ // Append a NULL byte for safety.
+ buffer[outlen] = 0;
+
+ data = buffer;
+ len = outlen;
+
+ uint8_t type = *(data++);
+ len--;
+
+ if(type < SPTPS_HANDSHAKE) {
+ if(!s->instate) {
+ return error(s, EIO, "Application record received before handshake finished");
+ }
+
+ if(!s->receive_record(s->handle, type, data, len)) {
+ return false;
+ }
+ } else if(type == SPTPS_HANDSHAKE) {
+ if(!receive_handshake(s, data, len)) {
+ return false;
}
+ } else {
+ return error(s, EIO, "Invalid record type %d", type);
+ }
+
+ return true;
+}
+
+// Receive incoming data. Check if it contains a complete record, if so, handle it.
+size_t sptps_receive_data(sptps_t *s, const void *vdata, size_t len) {
+ const uint8_t *data = vdata;
+ size_t total_read = 0;
+
+ if(!s->state) {
+ return error(s, EIO, "Invalid session state zero");
+ }
+ if(s->datagram) {
+ return sptps_receive_data_datagram(s, data, len) ? len : false;
+ }
+
+ // First read the 2 length bytes.
+ if(s->buflen < 2) {
+ size_t toread = 2 - s->buflen;
+
+ if(toread > len) {
+ toread = len;
+ }
+
+ memcpy(s->inbuf + s->buflen, data, toread);
+
+ total_read += toread;
s->buflen += toread;
len -= toread;
data += toread;
- // If we don't have a whole record, exit.
- if(s->buflen < reclen + (s->state ? 23UL : 7UL))
- return true;
+ // Exit early if we don't have the full length.
+ if(s->buflen < 2) {
+ return total_read;
+ }
- // Check HMAC.
- if(s->state)
- if(!digest_verify(&s->indigest, s->inbuf, reclen + 7UL, s->inbuf + reclen + 7UL))
- error(s, EIO, "Invalid HMAC");
+ // Get the length bytes
- uint8_t type = s->inbuf[6];
+ memcpy(&s->reclen, s->inbuf, 2);
- // Handle record.
- if(type < 128) {
- if(!s->receive_record(s->handle, type, s->inbuf + 7, reclen))
- return false;
- } else if(type == 128) {
- if(!receive_handshake(s, s->inbuf + 7, reclen))
- return false;
- } else {
- return error(s, EIO, "Invalid record type");
+ // If we have the length bytes, ensure our buffer can hold the whole request.
+ s->inbuf = realloc(s->inbuf, s->reclen + SPTPS_OVERHEAD);
+
+ if(!s->inbuf) {
+ return error(s, errno, "%s", strerror(errno));
}
- s->buflen = 4;
+ // Exit early if we have no more data to process.
+ if(!len) {
+ return total_read;
+ }
}
- return true;
+ // Read up to the end of the record.
+ size_t toread = s->reclen + (s->instate ? SPTPS_OVERHEAD : SPTPS_HEADER) - s->buflen;
+
+ if(toread > len) {
+ toread = len;
+ }
+
+ memcpy(s->inbuf + s->buflen, data, toread);
+ total_read += toread;
+ s->buflen += toread;
+
+ // If we don't have a whole record, exit.
+ if(s->buflen < s->reclen + (s->instate ? SPTPS_OVERHEAD : SPTPS_HEADER)) {
+ return total_read;
+ }
+
+ // Update sequence number.
+
+ uint32_t seqno = s->inseqno++;
+
+ // Check HMAC and decrypt.
+ if(s->instate) {
+ if(!cipher_decrypt(s->cipher_suite, s->incipher, seqno, s->inbuf + 2UL, s->reclen + 17UL, s->inbuf + 2UL, NULL)) {
+ return error(s, EINVAL, "Failed to decrypt and verify record");
+ }
+ }
+
+ // Append a NULL byte for safety.
+ s->inbuf[s->reclen + SPTPS_HEADER] = 0;
+
+ uint8_t type = s->inbuf[2];
+
+ if(type < SPTPS_HANDSHAKE) {
+ if(!s->instate) {
+ return error(s, EIO, "Application record received before handshake finished");
+ }
+
+ if(!s->receive_record(s->handle, type, s->inbuf + 3, s->reclen)) {
+ return false;
+ }
+ } else if(type == SPTPS_HANDSHAKE) {
+ if(!receive_handshake(s, s->inbuf + 3, s->reclen)) {
+ return false;
+ }
+ } else {
+ return error(s, EIO, "Invalid record type %d", type);
+ }
+
+ s->buflen = 0;
+
+ return total_read;
}
-bool start_sptps(sptps_t *s, void *handle, bool initiator, ecdsa_t mykey, ecdsa_t hiskey, const char *label, size_t labellen, send_data_t send_data, receive_record_t receive_record) {
+// Start a SPTPS session.
+bool sptps_start(sptps_t *s, const sptps_params_t *params) {
// Initialise struct sptps
- memset(s, 0, sizeof *s);
+ memset(s, 0, sizeof(*s));
+
+ s->handle = params->handle;
+ s->initiator = params->initiator;
+ s->datagram = params->datagram;
+ s->mykey = params->mykey;
+ s->hiskey = params->hiskey;
+ s->replaywin = sptps_replaywin;
+ s->cipher_suites = params->cipher_suites ? params->cipher_suites & SPTPS_ALL_CIPHER_SUITES : SPTPS_ALL_CIPHER_SUITES;
+ s->preferred_suite = params->preferred_suite;
+
+ if(s->replaywin) {
+ s->late = malloc(s->replaywin);
+
+ if(!s->late) {
+ return error(s, errno, "%s", strerror(errno));
+ }
- s->handle = handle;
- s->initiator = initiator;
- s->mykey = mykey;
- s->hiskey = hiskey;
+ memset(s->late, 0, s->replaywin);
+ }
+
+ s->labellen = params->labellen ? params->labellen : strlen(params->label);
+ s->label = malloc(s->labellen);
- s->label = malloc(labellen);
- if(!s->label)
- return error(s, errno, strerror(errno));
+ if(!s->label) {
+ return error(s, errno, "%s", strerror(errno));
+ }
- s->inbuf = malloc(7);
- if(!s->inbuf)
- return error(s, errno, strerror(errno));
- s->buflen = 4;
- memset(s->inbuf, 0, 4);
+ memcpy(s->label, params->label, s->labellen);
+
+ if(!s->datagram) {
+ s->inbuf = malloc(7);
+
+ if(!s->inbuf) {
+ return error(s, errno, "%s", strerror(errno));
+ }
+
+ s->buflen = 0;
+ }
- memcpy(s->label, label, labellen);
- s->labellen = labellen;
- s->send_data = send_data;
- s->receive_record = receive_record;
+ s->send_data = params->send_data;
+ s->receive_record = params->receive_record;
// Do first KEX immediately
+ s->state = SPTPS_KEX;
return send_kex(s);
}
-bool stop_sptps(sptps_t *s) {
+// Stop a SPTPS session.
+bool sptps_stop(sptps_t *s) {
// Clean up any resources.
- ecdh_free(&s->ecdh);
+ cipher_exit(s->cipher_suite, s->incipher);
+ cipher_exit(s->cipher_suite, s->outcipher);
+ ecdh_free(s->ecdh);
free(s->inbuf);
- free(s->myrandom);
- free(s->key);
+ free_sptps_kex(s->mykex);
+ free_sptps_kex(s->hiskex);
+ free_sptps_key(s->key);
free(s->label);
+ free(s->late);
+ memset(s, 0, sizeof(*s));
return true;
}