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-rw-r--r--src/lib/crypt.c490
1 files changed, 490 insertions, 0 deletions
diff --git a/src/lib/crypt.c b/src/lib/crypt.c
new file mode 100644
index 00000000..94f1b50e
--- /dev/null
+++ b/src/lib/crypt.c
@@ -0,0 +1,490 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2019
+ *
+ * Elliptic curve Diffie-Hellman key exchange and
+ * AES encryption for flows using OpenSSL
+ *
+ * Dimitri Staessens <dimitri@ouroboros.rocks>
+ * Sander Vrijders <sander@ouroboros.rocks>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifdef HAVE_OPENSSL
+
+#include <openssl/evp.h>
+#include <openssl/ec.h>
+#include <openssl/pem.h>
+
+#define MSGBUFSZ 2048
+#define IVSZ 16
+#define DH_TIMEO 2 /* seconds */
+/* SYMMKEYSZ defined in dev.c */
+
+/*
+ * Derive the common secret from
+ * your public key pair (kp)
+ * the remote public key (pub).
+ * Store it in a preallocated buffer (s).
+ */
+static int __openssl_ecdh_derive_secret(EVP_PKEY * kp,
+ EVP_PKEY * pub,
+ uint8_t * s)
+{
+ EVP_PKEY_CTX * ctx;
+ int ret;
+ uint8_t * secret;
+ size_t secret_len;
+
+ ctx = EVP_PKEY_CTX_new(kp, NULL);
+ if (ctx == NULL)
+ goto fail_new;
+
+ ret = EVP_PKEY_derive_init(ctx);
+ if (ret != 1)
+ goto fail_ctx;
+
+ ret = EVP_PKEY_derive_set_peer(ctx, pub);
+ if (ret != 1)
+ goto fail_ctx;
+
+ ret = EVP_PKEY_derive(ctx, NULL, &secret_len);
+ if (ret != 1)
+ goto fail_ctx;
+
+ if (secret_len < SYMMKEYSZ)
+ goto fail_ctx;
+
+ secret = OPENSSL_malloc(secret_len);
+ if (secret == NULL)
+ goto fail_ctx;
+
+ ret = EVP_PKEY_derive(ctx, secret, &secret_len);
+ if (ret != 1)
+ goto fail_derive;
+
+ /* Hash the secret for use as AES key. */
+ mem_hash(HASH_SHA3_256, s, secret, secret_len);
+
+ OPENSSL_free(secret);
+ EVP_PKEY_CTX_free(ctx);
+
+ return 0;
+
+ fail_derive:
+ OPENSSL_free(s);
+ fail_ctx:
+ EVP_PKEY_CTX_free(ctx);
+ fail_new:
+ return -ECRYPT;
+}
+
+static int __openssl_ecdh_gen_key(EVP_PKEY ** kp)
+{
+ EVP_PKEY_CTX * ctx = NULL;
+ EVP_PKEY_CTX * kctx = NULL;
+ EVP_PKEY * params = NULL;
+ int ret;
+
+ ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL);
+ if (ctx == NULL)
+ goto fail_new_id;
+
+ ret = EVP_PKEY_paramgen_init(ctx);
+ if (ret != 1)
+ goto fail_paramgen;
+
+ ret = EVP_PKEY_CTX_set_ec_paramgen_curve_nid(ctx, NID_X9_62_prime256v1);
+ if (ret != 1)
+ goto fail_paramgen;
+
+ ret = EVP_PKEY_paramgen(ctx, &params);
+ if (ret != 1)
+ goto fail_paramgen;
+
+ kctx = EVP_PKEY_CTX_new(params, NULL);
+ if (kctx == NULL)
+ goto fail_keygen_init;
+
+ ret = EVP_PKEY_keygen_init(kctx);
+ if (ret != 1)
+ goto fail_keygen;
+
+ ret = EVP_PKEY_keygen(kctx, kp);
+ if (ret != 1)
+ goto fail_keygen;
+
+ EVP_PKEY_free(params);
+ EVP_PKEY_CTX_free(kctx);
+ EVP_PKEY_CTX_free(ctx);
+
+ return 0;
+
+ fail_keygen:
+ EVP_PKEY_CTX_free(kctx);
+ fail_keygen_init:
+ EVP_PKEY_free(params);
+ fail_paramgen:
+ EVP_PKEY_CTX_free(ctx);
+ fail_new_id:
+ return -ECRYPT;
+}
+
+/* ECDH from the server side. */
+static int openssl_ecdh_srv(int fd,
+ uint8_t * s)
+{
+ EVP_PKEY * kp = NULL;
+ EVP_PKEY * pub = NULL;
+ uint8_t buf[MSGBUFSZ];
+ ssize_t len;
+ int buf_sz;
+ uint8_t * pos;
+ struct timespec timeo = {DH_TIMEO,0};
+
+ assert(s != NULL);
+
+ (void) fd;
+ (void) s;
+
+ if (__openssl_ecdh_gen_key(&kp) < 0)
+ goto fail_gen_key;
+
+ fccntl(fd, FLOWSRCVTIMEO, &timeo);
+
+ len = flow_read(fd, buf, MSGBUFSZ);
+ if (len < 0) {
+ fccntl(fd, FLOWSRCVTIMEO, NULL);
+ goto fail_get_key;
+ }
+
+ fccntl(fd, FLOWSRCVTIMEO, NULL);
+
+ pos = buf; /* i2d_PUBKEY increments the pointer, don't use buf! */
+ pub = d2i_PUBKEY(NULL, (const uint8_t **) &pos, (long) len);
+
+ pos = buf; /* i2d_PUBKEY increments the pointer, don't use buf! */
+ buf_sz = i2d_PUBKEY(kp, &pos);
+ if (buf_sz < 0)
+ goto fail_get_key;
+
+ if (flow_write(fd, buf, (size_t) buf_sz) < 0)
+ goto fail_get_key;
+
+ if (__openssl_ecdh_derive_secret(kp, pub, s) < 0)
+ goto fail_get_key;
+
+ EVP_PKEY_free(kp);
+ EVP_PKEY_free(pub);
+
+ return 0;
+
+ fail_get_key:
+ EVP_PKEY_free(kp);
+ fail_gen_key:
+ return -ECRYPT;
+}
+
+/* ECDH from the client side. */
+static int openssl_ecdh_clt(int fd,
+ uint8_t * s)
+{
+ EVP_PKEY * kp = NULL;
+ EVP_PKEY * pub = NULL;
+ uint8_t buf[MSGBUFSZ];
+ int buf_sz;
+ uint8_t * pos;
+ ssize_t len;
+ struct timespec timeo = {DH_TIMEO,0};
+
+ assert(s != NULL);
+
+ (void) fd;
+ (void) s;
+
+ if (__openssl_ecdh_gen_key(&kp) < 0)
+ goto fail_gen_key;
+
+ pos = buf; /* i2d_PUBKEY increments the pointer, don't use buf! */
+ buf_sz = i2d_PUBKEY(kp, &pos);
+ if (buf_sz < 0)
+ goto fail_get_key;
+
+ if (flow_write(fd, buf, (size_t) buf_sz) < 0)
+ goto fail_get_key;
+
+ fccntl(fd, FLOWSRCVTIMEO, &timeo);
+
+ len = flow_read(fd, buf, MSGBUFSZ);
+ if (len < 0) {
+ fccntl(fd, FLOWSRCVTIMEO, NULL);
+ goto fail_get_key;
+ }
+
+ fccntl(fd, FLOWSRCVTIMEO, NULL);
+
+ pos = buf; /* i2d_PUBKEY increments the pointer, don't use buf! */
+ pub = d2i_PUBKEY(NULL, (const uint8_t **) &pos, (long) len);
+
+ if (__openssl_ecdh_derive_secret(kp, pub, s) < 0)
+ goto fail_get_key;
+
+ EVP_PKEY_free(kp);
+ EVP_PKEY_free(pub);
+
+ return 0;
+
+ fail_get_key:
+ EVP_PKEY_free(kp);
+ fail_gen_key:
+ return -ECRYPT;
+}
+
+/*
+ * AES encryption calls. If FRCT is disabled, we should generate a
+ * 128-bit random IV and append it to the packet. If the flow is
+ * reliable, we could initialize the context once, and consider the
+ * stream a single encrypted message to avoid initializing the
+ * encryption context for each packet.
+ */
+
+static int openssl_encrypt(struct flow * f,
+ struct shm_du_buff * sdb)
+{
+ uint8_t * out;
+ uint8_t * in;
+ uint8_t * head;
+ uint8_t iv[IVSZ];
+ int in_sz;
+ int out_sz;
+ int tmp_sz;
+ int ret;
+
+ in = shm_du_buff_head(sdb);
+ in_sz = shm_du_buff_tail(sdb) - in;
+
+ if (random_buffer(iv, IVSZ) < 0)
+ goto fail_iv;
+
+ out = malloc(in_sz + EVP_MAX_BLOCK_LENGTH);
+ if (out == NULL)
+ goto fail_iv;
+
+ EVP_CIPHER_CTX_reset(f->ctx);
+
+ ret = EVP_EncryptInit_ex(f->ctx,
+ EVP_aes_256_cbc(),
+ NULL,
+ f->key,
+ iv);
+ if (ret != 1)
+ goto fail_encrypt_init;
+
+ ret = EVP_EncryptUpdate(f->ctx, out, &tmp_sz, in, in_sz);
+ if (ret != 1)
+ goto fail_encrypt;
+
+ out_sz = tmp_sz;
+ ret = EVP_EncryptFinal_ex(f->ctx, out + tmp_sz, &tmp_sz);
+ if (ret != 1)
+ goto fail_encrypt;
+
+ out_sz += tmp_sz;
+
+ EVP_CIPHER_CTX_cleanup(f->ctx);
+
+ assert(out_sz >= in_sz);
+
+ head = shm_du_buff_head_alloc(sdb, IVSZ);
+ if (head == NULL)
+ goto fail_encrypt;
+
+ if (shm_du_buff_tail_alloc(sdb, out_sz - in_sz) == NULL)
+ goto fail_tail_alloc;
+
+ memcpy(head, iv, IVSZ);
+ memcpy(in, out, out_sz);
+
+ free(out);
+
+ return 0;
+
+ fail_tail_alloc:
+ shm_du_buff_head_release(sdb, IVSZ);
+ fail_encrypt:
+ EVP_CIPHER_CTX_cleanup(f->ctx);
+ fail_encrypt_init:
+ free(out);
+ fail_iv:
+ return -ECRYPT;
+}
+
+static int openssl_decrypt(struct flow * f,
+ struct shm_du_buff * sdb)
+{
+ uint8_t * in;
+ uint8_t * out;
+ uint8_t iv[IVSZ];
+ int ret;
+ int out_sz;
+ int in_sz;
+ int tmp_sz;
+
+ in = shm_du_buff_head_release(sdb, IVSZ);
+
+ memcpy(iv, in, IVSZ);
+
+ in = shm_du_buff_head(sdb);
+
+ in_sz = shm_du_buff_tail(sdb) - shm_du_buff_head(sdb);
+
+ out = malloc(in_sz);
+ if (out == NULL)
+ goto fail_malloc;
+
+ EVP_CIPHER_CTX_reset(f->ctx);
+
+ ret = EVP_DecryptInit_ex(f->ctx,
+ EVP_aes_256_cbc(),
+ NULL,
+ f->key,
+ iv);
+ if (ret != 1)
+ goto fail_decrypt_init;
+
+ ret = EVP_DecryptUpdate(f->ctx, out, &tmp_sz, in, in_sz);
+ if (ret != 1)
+ goto fail_decrypt;
+
+ out_sz = tmp_sz;
+
+ ret = EVP_DecryptFinal_ex(f->ctx, out + tmp_sz, &tmp_sz);
+ if (ret != 1)
+ goto fail_decrypt;
+
+ out_sz += tmp_sz;
+
+ assert(out_sz <= in_sz);
+
+ shm_du_buff_tail_release(sdb, in_sz - out_sz);
+
+ memcpy(in, out, out_sz);
+
+ free(out);
+
+ return 0;
+
+ fail_decrypt:
+ EVP_CIPHER_CTX_cleanup(f->ctx);
+ fail_decrypt_init:
+ free(out);
+ fail_malloc:
+ return -ECRYPT;
+
+}
+
+static int openssl_crypt_init(struct flow * f)
+{
+ f->ctx = EVP_CIPHER_CTX_new();
+ if (f->ctx == NULL)
+ goto fail_new;
+
+ return 0;
+
+ fail_new:
+ return -ECRYPT;
+}
+
+static void openssl_crypt_fini(struct flow * f)
+{
+ EVP_CIPHER_CTX_free(f->ctx);
+ f->ctx = NULL;
+}
+
+#endif /* HAVE_OPENSSL */
+
+static int crypt_dh_srv(int fd,
+ uint8_t * s)
+{
+#ifdef HAVE_OPENSSL
+ return openssl_ecdh_clt(fd, s);
+#else
+ (void) fd;
+
+ memset(s, 0, SYMMKEYSZ);
+
+ return -ECRYPT;
+#endif
+}
+
+static int crypt_dh_clt(int fd,
+ uint8_t * s)
+{
+#ifdef HAVE_OPENSSL
+ return openssl_ecdh_srv(fd, s);
+#else
+ (void) fd;
+
+ memset(s, 0, SYMMKEYSZ);
+
+ return 0;
+#endif
+}
+
+static int crypt_encrypt(struct flow * f,
+ struct shm_du_buff * sdb)
+{
+#ifdef HAVE_OPENSSL
+ return openssl_encrypt(f, sdb);
+#else
+ (void) f;
+ (void) sdb;
+
+ return 0;
+#endif
+}
+
+static int crypt_decrypt(struct flow * f,
+ struct shm_du_buff * sdb)
+{
+#ifdef HAVE_OPENSSL
+ return openssl_decrypt(f, sdb);
+#else
+ (void) f;
+ (void) sdb;
+
+ return 0;
+#endif
+}
+
+
+static int crypt_init(struct flow * f)
+{
+#ifdef HAVE_OPENSSL
+ return openssl_crypt_init(f);
+#else
+ (void) f;
+
+ return 0;
+#endif
+}
+
+static void crypt_fini(struct flow * f)
+{
+#ifdef HAVE_OPENSSL
+ openssl_crypt_fini(f);
+#else
+ (void) f;
+#endif
+}
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