/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2026 OpenVPN Inc <sales@openvpn.net>
 *  Copyright (C) 2010-2026 Sentyron B.V. <openvpn@sentyron.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, see <https://www.gnu.org/licenses/>.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <inttypes.h>

#include "syshead.h"
#include <string.h>

#include "crypto.h"
#include "crypto_epoch.h"
#include "packet_id.h"
#include "error.h"
#include "integer.h"
#include "platform.h"

#include "memdbg.h"

/*
 * Encryption and Compression Routines.
 *
 * On entry, buf contains the input data and length.
 * On exit, it should be set to the output data and length.
 *
 * If buf->len is <= 0 we should return
 * If buf->len is set to 0 on exit it tells the caller to ignore the packet.
 *
 * work is a workspace buffer we are given of size BUF_SIZE.
 * work may be used to return output data, or the input buffer
 * may be modified and returned as output.  If output data is
 * returned in work, the data should start after buf.headroom bytes
 * of padding to leave room for downstream routines to prepend.
 *
 * Up to a total of buf.headroom bytes may be prepended to the input buf
 * by all routines (encryption, decryption, compression, and decompression).
 *
 * Note that the buf_prepend return will assert if we try to
 * make a header bigger than buf.headroom.  This should not
 * happen unless the frame parameters are wrong.
 */

static void
openvpn_encrypt_aead(struct buffer *buf, struct buffer work, struct crypto_options *opt)
{
    struct gc_arena gc;
    int outlen = 0;
    const bool use_epoch_data_format = opt->flags & CO_EPOCH_DATA_KEY_FORMAT;

    if (use_epoch_data_format)
    {
        epoch_check_send_iterate(opt);
    }

    const struct key_ctx *ctx = &opt->key_ctx_bi.encrypt;
    uint8_t *mac_out = NULL;
    const int mac_len = OPENVPN_AEAD_TAG_LENGTH;

    /* IV, packet-ID and implicit IV required for this mode. */
    ASSERT(ctx->cipher);
    ASSERT(packet_id_initialized(&opt->packet_id));

    gc_init(&gc);

    /* Prepare IV */
    {
        struct buffer iv_buffer;
        uint8_t iv[OPENVPN_MAX_IV_LENGTH] = { 0 };
        const unsigned int iv_len = cipher_ctx_iv_length(ctx->cipher);

        ASSERT(iv_len >= OPENVPN_AEAD_MIN_IV_LEN && iv_len <= OPENVPN_MAX_IV_LENGTH);

        buf_set_write(&iv_buffer, iv, iv_len);

        /* IV starts with packet id to make the IV unique for packet */
        if (use_epoch_data_format)
        {
            /* Note this does not check aead_usage_limit but can overstep it by
             * a few extra blocks in one extra write. This is not affecting the
             * security margin as these extra blocks are on a completely
             * different order of magnitude than the security margin.
             * The next iteration/call to epoch_check_send_iterate will
             * iterate the epoch
             */
            if (!packet_id_write_epoch(&opt->packet_id.send, ctx->epoch, &iv_buffer))
            {
                msg(D_CRYPT_ERRORS, "ENCRYPT ERROR: packet ID roll over");
                goto err;
            }
        }
        else
        {
            if (!packet_id_write(&opt->packet_id.send, &iv_buffer, false, false))
            {
                msg(D_CRYPT_ERRORS, "ENCRYPT ERROR: packet ID roll over");
                goto err;
            }
        }
        /* Write packet id part of IV to work buffer */
        ASSERT(buf_write(&work, iv, BLENZ(&iv_buffer)));

        /* This generates the IV by XORing the implicit part of the IV
         * with the packet id already written to the iv buffer */
        for (unsigned int i = 0; i < iv_len; i++)
        {
            iv[i] = iv[i] ^ ctx->implicit_iv[i];
        }

        dmsg(D_PACKET_CONTENT, "ENCRYPT IV: %s", format_hex(iv, iv_len, 0, &gc));

        /* Init cipher_ctx with IV.  key & keylen are already initialized */
        ASSERT(cipher_ctx_reset(ctx->cipher, iv));
    }

    dmsg(D_PACKET_CONTENT, "ENCRYPT FROM: %s", format_hex(BPTR(buf), BLEN(buf), 80, &gc));

    /* Buffer overflow check */
    if (!buf_safe(&work, buf->len + mac_len + cipher_ctx_block_size(ctx->cipher)))
    {
        msg(D_CRYPT_ERRORS, "ENCRYPT: buffer size error, bc=%d bo=%d bl=%d wc=%d wo=%d wl=%d",
            buf->capacity, buf->offset, buf->len, work.capacity, work.offset, work.len);
        goto err;
    }

    /* For AEAD ciphers, authenticate Additional Data, including opcode */
    ASSERT(cipher_ctx_update_ad(ctx->cipher, BPTR(&work), BLEN(&work)));
    dmsg(D_PACKET_CONTENT, "ENCRYPT AD: %s", format_hex(BPTR(&work), BLEN(&work), 0, &gc));

    if (!use_epoch_data_format)
    {
        /* Reserve space for authentication tag */
        mac_out = buf_write_alloc(&work, mac_len);
        ASSERT(mac_out);
    }

    /* Encrypt packet ID, payload */
    ASSERT(cipher_ctx_update(ctx->cipher, BEND(&work), &outlen, BPTR(buf), BLEN(buf)));
    ASSERT(buf_inc_len(&work, outlen));

    /* Flush the encryption buffer */
    ASSERT(cipher_ctx_final(ctx->cipher, BEND(&work), &outlen));
    ASSERT(buf_inc_len(&work, outlen));

    /* update number of plaintext blocks encrypted. Use the (x + (n-1))/n trick
     * to round up the result to the number of blocks used */
    const int blocksize = AEAD_LIMIT_BLOCKSIZE;
    opt->key_ctx_bi.encrypt.plaintext_blocks += (BLEN(&work) + (blocksize - 1)) / blocksize;

    /* if the tag is at end the end, allocate it now */
    if (use_epoch_data_format)
    {
        /* Reserve space for authentication tag */
        mac_out = buf_write_alloc(&work, mac_len);
        ASSERT(mac_out);
    }

    /* Write authentication tag */
    ASSERT(cipher_ctx_get_tag(ctx->cipher, mac_out, mac_len));

    *buf = work;

    dmsg(D_PACKET_CONTENT, "ENCRYPT TO: %s", format_hex(BPTR(buf), BLEN(buf), 80, &gc));

    gc_free(&gc);
    return;

err:
    crypto_clear_error();
    buf->len = 0;
    gc_free(&gc);
    return;
}

static void
openvpn_encrypt_v1(struct buffer *buf, struct buffer work, struct crypto_options *opt)
{
    struct gc_arena gc;
    gc_init(&gc);

    if (buf->len > 0 && opt)
    {
        const struct key_ctx *ctx = &opt->key_ctx_bi.encrypt;
        uint8_t *mac_out = NULL;
        const uint8_t *hmac_start = NULL;

        /* Do Encrypt from buf -> work */
        if (ctx->cipher)
        {
            uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH] = { 0 };
            const unsigned int iv_size = cipher_ctx_iv_length(ctx->cipher);

            /* Reserve space for HMAC */
            if (ctx->hmac)
            {
                mac_out = buf_write_alloc(&work, hmac_ctx_size(ctx->hmac));
                ASSERT(mac_out);
                hmac_start = BEND(&work);
            }

            if (cipher_ctx_mode_cbc(ctx->cipher))
            {
                /* generate pseudo-random IV */
                prng_bytes(iv_buf, iv_size);

                /* Put packet ID in plaintext buffer */
                if (packet_id_initialized(&opt->packet_id)
                    && !packet_id_write(&opt->packet_id.send, buf,
                                        opt->flags & CO_PACKET_ID_LONG_FORM, true))
                {
                    msg(D_CRYPT_ERRORS, "ENCRYPT ERROR: packet ID roll over");
                    goto err;
                }
            }
            else if (cipher_ctx_mode_ofb_cfb(ctx->cipher))
            {
                struct buffer b;

                /* packet-ID required for this mode. */
                ASSERT(packet_id_initialized(&opt->packet_id));

                buf_set_write(&b, iv_buf, iv_size);
                ASSERT(packet_id_write(&opt->packet_id.send, &b, true, false));
            }
            else /* We only support CBC, CFB, or OFB modes right now */
            {
                ASSERT(0);
            }

            /* write the pseudo-randomly IV (CBC)/packet ID (OFB/CFB) */
            ASSERT(buf_write(&work, iv_buf, iv_size));
            dmsg(D_PACKET_CONTENT, "ENCRYPT IV: %s", format_hex(iv_buf, iv_size, 0, &gc));

            dmsg(D_PACKET_CONTENT, "ENCRYPT FROM: %s", format_hex(BPTR(buf), BLEN(buf), 80, &gc));

            /* cipher_ctx was already initialized with key & keylen */
            ASSERT(cipher_ctx_reset(ctx->cipher, iv_buf));

            /* Buffer overflow check */
            if (!buf_safe(&work, buf->len + cipher_ctx_block_size(ctx->cipher)))
            {
                msg(D_CRYPT_ERRORS,
                    "ENCRYPT: buffer size error, bc=%d bo=%d bl=%d wc=%d wo=%d wl=%d cbs=%d",
                    buf->capacity, buf->offset, buf->len, work.capacity, work.offset, work.len,
                    cipher_ctx_block_size(ctx->cipher));
                goto err;
            }

            /* Encrypt packet ID, payload */
            int outlen;
            ASSERT(cipher_ctx_update(ctx->cipher, BEND(&work), &outlen, BPTR(buf), BLEN(buf)));
            ASSERT(buf_inc_len(&work, outlen));

            /* Flush the encryption buffer */
            ASSERT(cipher_ctx_final(ctx->cipher, BEND(&work), &outlen));
            ASSERT(buf_inc_len(&work, outlen));

            /* For all CBC mode ciphers, check the last block is complete */
            ASSERT(cipher_ctx_mode(ctx->cipher) != OPENVPN_MODE_CBC || outlen == (int)iv_size);
        }
        else /* No Encryption */
        {
            if (packet_id_initialized(&opt->packet_id)
                && !packet_id_write(&opt->packet_id.send, buf, opt->flags & CO_PACKET_ID_LONG_FORM,
                                    true))
            {
                msg(D_CRYPT_ERRORS, "ENCRYPT ERROR: packet ID roll over");
                goto err;
            }
            if (ctx->hmac)
            {
                hmac_start = BPTR(buf);
                ASSERT(mac_out = buf_prepend(buf, hmac_ctx_size(ctx->hmac)));
            }
            if (BLEN(&work))
            {
                buf_write_prepend(buf, BPTR(&work), BLEN(&work));
            }
            work = *buf;
        }

        /* HMAC the ciphertext (or plaintext if !cipher) */
        if (ctx->hmac)
        {
            hmac_ctx_reset(ctx->hmac);
            hmac_ctx_update(ctx->hmac, hmac_start, (int)(BEND(&work) - hmac_start));
            hmac_ctx_final(ctx->hmac, mac_out);
            dmsg(D_PACKET_CONTENT, "ENCRYPT HMAC: %s",
                 format_hex(mac_out, hmac_ctx_size(ctx->hmac), 80, &gc));
        }

        *buf = work;

        dmsg(D_PACKET_CONTENT, "ENCRYPT TO: %s", format_hex(BPTR(&work), BLEN(&work), 80, &gc));
    }

    gc_free(&gc);
    return;

err:
    crypto_clear_error();
    buf->len = 0;
    gc_free(&gc);
    return;
}

void
openvpn_encrypt(struct buffer *buf, struct buffer work, struct crypto_options *opt)
{
    if (buf->len > 0 && opt)
    {
        if (cipher_ctx_mode_aead(opt->key_ctx_bi.encrypt.cipher))
        {
            openvpn_encrypt_aead(buf, work, opt);
        }
        else
        {
            openvpn_encrypt_v1(buf, work, opt);
        }
    }
}

uint64_t
cipher_get_aead_limits(const char *ciphername)
{
    if (!cipher_kt_mode_aead(ciphername))
    {
        return 0;
    }

    if (cipher_kt_name(ciphername) == cipher_kt_name("CHACHA20-POLY1305"))
    {
        return 0;
    }

    /* Assume all other ciphers require the limit */

    /* We focus here on the equation
     *
     *       q + s <= p^(1/2) * 2^(129/2) - 1
     *
     * as is the one that is limiting us.
     *
     *  With p = 2^-57 this becomes
     *
     *      q + s <= (2^36 - 1)
     *
     */
    uint64_t rs = (1ull << 36) - 1;

    return rs;
}

bool
crypto_check_replay(struct crypto_options *opt, const struct packet_id_net *pin, uint16_t epoch,
                    const char *error_prefix, struct gc_arena *gc)
{
    bool ret = false;
    struct packet_id_rec *recv;

    if (epoch == 0 || opt->key_ctx_bi.decrypt.epoch == epoch)
    {
        recv = &opt->packet_id.rec;
    }
    else if (epoch == opt->epoch_retiring_data_receive_key.epoch)
    {
        recv = &opt->epoch_retiring_key_pid_recv;
    }
    else
    {
        /* We have an epoch that is neither current or old recv key but
         * is authenticated, ie we need to move to a new current recv key */
        msg(D_GENKEY,
            "Received data packet with new epoch %d. Updating "
            "receive key",
            epoch);
        epoch_replace_update_recv_key(opt, epoch);
        recv = &opt->packet_id.rec;
    }

    packet_id_reap_test(recv);
    if (packet_id_test(recv, pin))
    {
        packet_id_add(recv, pin);
        if (opt->pid_persist && (opt->flags & CO_PACKET_ID_LONG_FORM))
        {
            packet_id_persist_save_obj(opt->pid_persist, &opt->packet_id);
        }
        ret = true;
    }
    else
    {
        if (!(opt->flags & CO_MUTE_REPLAY_WARNINGS))
        {
            msg(D_REPLAY_ERRORS,
                "%s: bad packet ID (may be a replay): %s -- "
                "see the man page entry for --replay-window for "
                "more info or silence this warning with --mute-replay-warnings",
                error_prefix, packet_id_net_print(pin, true, gc));
        }
    }
    return ret;
}

/**
 * Unwrap (authenticate, decrypt and check replay protection) AEAD-mode data
 * channel packets.
 *
 * Set buf->len to 0 and return false on decrypt error.
 *
 * On success, buf is set to point to plaintext, true is returned.
 */
static bool
openvpn_decrypt_aead(struct buffer *buf, struct buffer work, struct crypto_options *opt,
                     const struct frame *frame, const uint8_t *ad_start)
{
    static const char error_prefix[] = "AEAD Decrypt error";
    struct packet_id_net pin = { 0 };
    struct gc_arena gc;
    gc_init(&gc);

    struct key_ctx *ctx = &opt->key_ctx_bi.decrypt;
    const bool use_epoch_data_format = opt->flags & CO_EPOCH_DATA_KEY_FORMAT;
    if (!use_epoch_data_format && cipher_decrypt_verify_fail_exceeded(ctx))
    {
        CRYPT_DROP("Decryption failed verification limit reached.");
    }

    const int tag_size = OPENVPN_AEAD_TAG_LENGTH;


    ASSERT(opt);
    ASSERT(frame);
    ASSERT(buf->len > 0);
    ASSERT(ctx->cipher);

    dmsg(D_PACKET_CONTENT, "DECRYPT FROM: %s", format_hex(BPTR(buf), BLEN(buf), 80, &gc));

    ASSERT(ad_start >= buf->data && ad_start <= BPTR(buf));

    ASSERT(buf_init(&work, frame->buf.headroom));

    /* IV and Packet ID required for this mode */
    ASSERT(packet_id_initialized(&opt->packet_id));

    /* Ensure that the packet size is long enough */
    int min_packet_len = packet_id_size(false) + tag_size + 1;

    if (use_epoch_data_format)
    {
        min_packet_len += sizeof(uint32_t);
    }

    if (buf->len < min_packet_len)
    {
        CRYPT_ERROR("missing IV info, missing tag or no payload");
    }

    uint16_t epoch = 0;
    /* Combine IV from explicit part from packet and implicit part from context */
    {
        uint8_t iv[OPENVPN_MAX_IV_LENGTH] = { 0 };
        const unsigned int iv_len = cipher_ctx_iv_length(ctx->cipher);

        /* Read packet id. For epoch data format also lookup the epoch key
         * to be able to use the implicit IV of the correct decryption key */
        if (use_epoch_data_format)
        {
            /* packet ID format is 16 bit epoch + 48 per epoch packet-counter */
            const size_t packet_iv_len = sizeof(uint64_t);

            /* copy the epoch-counter part into the IV */
            memcpy(iv, BPTR(buf), packet_iv_len);

            epoch = packet_id_read_epoch(&pin, buf);
            if (epoch == 0)
            {
                CRYPT_ERROR("error reading packet-id");
            }
            ctx = epoch_lookup_decrypt_key(opt, epoch);
            if (!ctx)
            {
                CRYPT_ERROR("data packet with unknown epoch");
            }
            else if (cipher_decrypt_verify_fail_exceeded(ctx))
            {
                CRYPT_DROP("Decryption failed verification limit reached");
            }
        }
        else
        {
            const size_t packet_iv_len = packet_id_size(false);
            /* Packet ID form is a 32 bit packet counter */
            memcpy(iv, BPTR(buf), packet_iv_len);
            if (!packet_id_read(&pin, buf, false))
            {
                CRYPT_ERROR("error reading packet-id");
            }
        }

        /* This generates the IV by XORing the implicit part of the IV
         * with the packet id already written to the iv buffer */
        for (unsigned int i = 0; i < iv_len; i++)
        {
            iv[i] = iv[i] ^ ctx->implicit_iv[i];
        }

        dmsg(D_PACKET_CONTENT, "DECRYPT IV: %s", format_hex(iv, iv_len, 0, &gc));

        /* Load IV, ctx->cipher was already initialized with key & keylen */
        if (!cipher_ctx_reset(ctx->cipher, iv))
        {
            CRYPT_ERROR("cipher init failed");
        }
    }

    const int ad_size = (int)(BPTR(buf) - ad_start);

    uint8_t *tag_ptr = NULL;
    int data_len = 0;

    if (use_epoch_data_format)
    {
        data_len = BLEN(buf) - tag_size;
        tag_ptr = BPTR(buf) + data_len;
    }
    else
    {
        tag_ptr = BPTR(buf);
        ASSERT(buf_advance(buf, tag_size));
        data_len = BLEN(buf);
    }

    dmsg(D_PACKET_CONTENT, "DECRYPT MAC: %s", format_hex(tag_ptr, tag_size, 0, &gc));
    dmsg(D_PACKET_CONTENT, "DECRYPT FROM: %s", format_hex(BPTR(buf), BLEN(buf), 0, &gc));

    /* Buffer overflow check (should never fail) */
    if (!buf_safe(&work, buf->len + cipher_ctx_block_size(ctx->cipher)))
    {
        CRYPT_ERROR("potential buffer overflow");
    }

    /* feed in tag and the authenticated data */
    ASSERT(cipher_ctx_update_ad(ctx->cipher, ad_start, ad_size));
    dmsg(D_PACKET_CONTENT, "DECRYPT AD: %s", format_hex(ad_start, ad_size, 0, &gc));

    /* Decrypt and authenticate packet */
    int outlen;
    if (!cipher_ctx_update(ctx->cipher, BPTR(&work), &outlen, BPTR(buf), data_len))
    {
        CRYPT_ERROR("packet decryption failed");
    }

    ASSERT(buf_inc_len(&work, outlen));
    if (!cipher_ctx_final_check_tag(ctx->cipher, BPTR(&work) + outlen, &outlen, tag_ptr, tag_size))
    {
        ctx->failed_verifications++;
        CRYPT_DROP("packet tag authentication failed");
    }
    ASSERT(buf_inc_len(&work, outlen));

    dmsg(D_PACKET_CONTENT, "DECRYPT TO: %s", format_hex(BPTR(&work), BLEN(&work), 80, &gc));

    if (!crypto_check_replay(opt, &pin, epoch, error_prefix, &gc))
    {
        goto error_exit;
    }

    /* update number of plaintext blocks decrypted. Use the (x + (n-1))/n trick
     * to round up the result to the number of blocks used. */
    const int blocksize = AEAD_LIMIT_BLOCKSIZE;
    opt->key_ctx_bi.decrypt.plaintext_blocks += (BLEN(&work) + (blocksize - 1)) / blocksize;

    *buf = work;

    gc_free(&gc);
    return true;

error_exit:
    crypto_clear_error();
    buf->len = 0;
    gc_free(&gc);
    return false;
}

/*
 * Unwrap (authenticate, decrypt and check replay protection) CBC, OFB or CFB
 * mode data channel packets.
 *
 * Set buf->len to 0 and return false on decrypt error.
 *
 * On success, buf is set to point to plaintext, true is returned.
 */
static bool
openvpn_decrypt_v1(struct buffer *buf, struct buffer work, struct crypto_options *opt,
                   const struct frame *frame)
{
    static const char error_prefix[] = "Authenticate/Decrypt packet error";
    struct gc_arena gc;
    gc_init(&gc);

    if (buf->len > 0 && opt)
    {
        const struct key_ctx *ctx = &opt->key_ctx_bi.decrypt;
        struct packet_id_net pin;
        bool have_pin = false;

        dmsg(D_PACKET_CONTENT, "DECRYPT FROM: %s", format_hex(BPTR(buf), BLEN(buf), 80, &gc));

        /* Verify the HMAC */
        if (ctx->hmac)
        {
            int hmac_len;
            uint8_t local_hmac[MAX_HMAC_KEY_LENGTH]; /* HMAC of ciphertext computed locally */

            hmac_ctx_reset(ctx->hmac);

            /* Assume the length of the input HMAC */
            hmac_len = hmac_ctx_size(ctx->hmac);

            /* Authentication fails if insufficient data in packet for HMAC */
            if (buf->len < hmac_len)
            {
                CRYPT_ERROR("missing authentication info");
            }

            hmac_ctx_update(ctx->hmac, BPTR(buf) + hmac_len, BLEN(buf) - hmac_len);
            hmac_ctx_final(ctx->hmac, local_hmac);

            /* Compare locally computed HMAC with packet HMAC */
            if (memcmp_constant_time(local_hmac, BPTR(buf), hmac_len))
            {
                CRYPT_DROP("packet HMAC authentication failed");
            }

            ASSERT(buf_advance(buf, hmac_len));
        }

        /* Decrypt packet ID + payload */

        if (ctx->cipher)
        {
            const unsigned int iv_size = cipher_ctx_iv_length(ctx->cipher);
            uint8_t iv_buf[OPENVPN_MAX_IV_LENGTH] = { 0 };
            int outlen;

            /* initialize work buffer with buf.headroom bytes of prepend capacity */
            ASSERT(buf_init(&work, frame->buf.headroom));

            /* read the IV from the packet */
            if (buf->len < (int)iv_size)
            {
                CRYPT_ERROR("missing IV info");
            }
            memcpy(iv_buf, BPTR(buf), iv_size);
            ASSERT(buf_advance(buf, iv_size));
            dmsg(D_PACKET_CONTENT, "DECRYPT IV: %s", format_hex(iv_buf, iv_size, 0, &gc));

            if (buf->len < 1)
            {
                CRYPT_ERROR("missing payload");
            }

            /* ctx->cipher was already initialized with key & keylen */
            if (!cipher_ctx_reset(ctx->cipher, iv_buf))
            {
                CRYPT_ERROR("decrypt initialization failed");
            }

            /* Buffer overflow check (should never happen) */
            if (!buf_safe(&work, buf->len + cipher_ctx_block_size(ctx->cipher)))
            {
                CRYPT_ERROR("packet too big to decrypt");
            }

            /* Decrypt packet ID, payload */
            if (!cipher_ctx_update(ctx->cipher, BPTR(&work), &outlen, BPTR(buf), BLEN(buf)))
            {
                CRYPT_ERROR("packet decryption failed");
            }
            ASSERT(buf_inc_len(&work, outlen));

            /* Flush the decryption buffer */
            if (!cipher_ctx_final(ctx->cipher, BPTR(&work) + outlen, &outlen))
            {
                CRYPT_DROP("packet authentication failed, dropping.");
            }
            ASSERT(buf_inc_len(&work, outlen));

            dmsg(D_PACKET_CONTENT, "DECRYPT TO: %s", format_hex(BPTR(&work), BLEN(&work), 80, &gc));

            /* Get packet ID from plaintext buffer or IV, depending on cipher mode */
            {
                if (cipher_ctx_mode_cbc(ctx->cipher))
                {
                    if (packet_id_initialized(&opt->packet_id))
                    {
                        if (!packet_id_read(&pin, &work,
                                            BOOL_CAST(opt->flags & CO_PACKET_ID_LONG_FORM)))
                        {
                            CRYPT_ERROR("error reading CBC packet-id");
                        }
                        have_pin = true;
                    }
                }
                else if (cipher_ctx_mode_ofb_cfb(ctx->cipher))
                {
                    struct buffer b;

                    /* packet-ID required for this mode. */
                    ASSERT(packet_id_initialized(&opt->packet_id));

                    buf_set_read(&b, iv_buf, iv_size);
                    if (!packet_id_read(&pin, &b, true))
                    {
                        CRYPT_ERROR("error reading CFB/OFB packet-id");
                    }
                    have_pin = true;
                }
                else /* We only support CBC, CFB, or OFB modes right now */
                {
                    ASSERT(0);
                }
            }
        }
        else
        {
            work = *buf;
            if (packet_id_initialized(&opt->packet_id))
            {
                if (!packet_id_read(&pin, &work, BOOL_CAST(opt->flags & CO_PACKET_ID_LONG_FORM)))
                {
                    CRYPT_ERROR("error reading packet-id");
                }
                have_pin = !BOOL_CAST(opt->flags & CO_IGNORE_PACKET_ID);
            }
        }

        if (have_pin && !crypto_check_replay(opt, &pin, 0, error_prefix, &gc))
        {
            goto error_exit;
        }
        *buf = work;
    }

    gc_free(&gc);
    return true;

error_exit:
    crypto_clear_error();
    buf->len = 0;
    gc_free(&gc);
    return false;
}


bool
openvpn_decrypt(struct buffer *buf, struct buffer work, struct crypto_options *opt,
                const struct frame *frame, const uint8_t *ad_start)
{
    bool ret = false;

    if (buf->len > 0 && opt)
    {
        if (cipher_ctx_mode_aead(opt->key_ctx_bi.decrypt.cipher))
        {
            ret = openvpn_decrypt_aead(buf, work, opt, frame, ad_start);
        }
        else
        {
            ret = openvpn_decrypt_v1(buf, work, opt, frame);
        }
    }
    else
    {
        ret = true;
    }
    return ret;
}

size_t
calculate_crypto_overhead(const struct key_type *kt, unsigned int pkt_id_size, bool occ)
{
    size_t crypto_overhead = 0;

    if (!cipher_kt_mode_cbc(kt->cipher))
    {
        /* In CBC mode, the packet id is part of the payload size/overhead */
        crypto_overhead += pkt_id_size;
    }

    if (cipher_kt_mode_aead(kt->cipher))
    {
        /* For AEAD ciphers, we basically use a stream cipher/CTR for
         * the encryption, so no overhead apart from the extra bytes
         * we add */
        crypto_overhead += cipher_kt_tag_size(kt->cipher);

        if (occ)
        {
            /* the frame calculation of old clients adds these to the link-mtu
             * even though they are not part of the actual packet */
            crypto_overhead += cipher_kt_iv_size(kt->cipher);
            crypto_overhead += cipher_kt_block_size(kt->cipher);
        }
    }
    else
    {
        if (cipher_defined(kt->cipher))
        {
            /* CBC, OFB or CFB mode */
            if (occ)
            {
                crypto_overhead += cipher_kt_block_size(kt->cipher);
            }
            /* IV is always added (no-iv has been removed a while ago) */
            crypto_overhead += cipher_kt_iv_size(kt->cipher);
        }
        if (md_defined(kt->digest))
        {
            crypto_overhead += md_kt_size(kt->digest);
        }
    }

    return crypto_overhead;
}

unsigned int
crypto_max_overhead(void)
{
    return packet_id_size(true) + OPENVPN_MAX_IV_LENGTH + OPENVPN_MAX_CIPHER_BLOCK_SIZE
           + max_int(OPENVPN_MAX_HMAC_SIZE, OPENVPN_AEAD_TAG_LENGTH);
}

static void
warn_insecure_key_type(const char *ciphername)
{
    if (cipher_kt_insecure(ciphername))
    {
        msg(M_WARN,
            "WARNING: INSECURE cipher (%s) with block size less than 128"
            " bit (%u bit).  This allows attacks like SWEET32.  Mitigate by "
            "using a --cipher with a larger block size (e.g. AES-256-CBC). "
            "Support for these insecure ciphers will be removed in "
            "OpenVPN 2.8.",
            ciphername, cipher_kt_block_size(ciphername) * 8);
    }
}

/*
 * Build a struct key_type.
 */
void
init_key_type(struct key_type *kt, const char *ciphername, const char *authname, bool tls_mode,
              bool warn)
{
    bool aead_cipher = false;

    ASSERT(ciphername);
    ASSERT(authname);

    CLEAR(*kt);
    kt->cipher = ciphername;
    if (strcmp(ciphername, "none") != 0)
    {
        if (!cipher_valid(ciphername))
        {
            msg(M_FATAL, "Cipher %s not supported", ciphername);
        }

        /* check legal cipher mode */
        aead_cipher = cipher_kt_mode_aead(kt->cipher);
        if (!(cipher_kt_mode_cbc(kt->cipher) || (tls_mode && aead_cipher)
#ifdef ENABLE_OFB_CFB_MODE
              || (tls_mode && cipher_kt_mode_ofb_cfb(kt->cipher))
#endif
                  ))
        {
            msg(M_FATAL, "Cipher '%s' mode not supported", ciphername);
        }

        if (OPENVPN_MAX_CIPHER_BLOCK_SIZE < cipher_kt_block_size(kt->cipher))
        {
            msg(M_FATAL, "Cipher '%s' not allowed: block size too big.", ciphername);
        }
        if (warn)
        {
            warn_insecure_key_type(ciphername);
        }
    }
    else
    {
        if (warn)
        {
            msg(M_WARN, "******* WARNING *******: '--cipher none' was specified. "
                        "This means NO encryption will be performed and tunnelled "
                        "data WILL be transmitted in clear text over the network! "
                        "PLEASE DO RECONSIDER THIS SETTING!");
        }
    }
    kt->digest = authname;
    if (strcmp(authname, "none") != 0)
    {
        if (aead_cipher) /* Ignore auth for AEAD ciphers */
        {
            kt->digest = "none";
        }
        else
        {
            int hmac_length = md_kt_size(kt->digest);

            if (OPENVPN_MAX_HMAC_SIZE < hmac_length)
            {
                msg(M_FATAL, "HMAC '%s' not allowed: digest size too big.", authname);
            }
        }
    }
    else if (!aead_cipher)
    {
        if (warn)
        {
            msg(M_WARN, "******* WARNING *******: '--auth none' was specified. "
                        "This means no authentication will be performed on received "
                        "packets, meaning you CANNOT trust that the data received by "
                        "the remote side have NOT been manipulated. "
                        "PLEASE DO RECONSIDER THIS SETTING!");
        }
    }
}

/**
 * Update the implicit IV for a key_ctx based on TLS session ids and cipher
 * used.
 *
 * Note that the implicit IV is based on the HMAC key of the \c key parameter,
 * but only in AEAD modes where the HMAC key is not used for an actual HMAC.
 *
 * @param ctx                   Encrypt/decrypt key context
 * @param key                   key parameters holding the key and hmac/
 *                              implicit iv used to calculate implicit IV
 */
static void
key_ctx_update_implicit_iv(struct key_ctx *ctx, const struct key_parameters *key)
{
    /* Only use implicit IV in AEAD cipher mode, where HMAC key is not used */
    if (cipher_ctx_mode_aead(ctx->cipher))
    {
        size_t impl_iv_len = 0;
        size_t impl_iv_offset = 0;
        ASSERT(cipher_ctx_iv_length(ctx->cipher) >= OPENVPN_AEAD_MIN_IV_LEN);

        /* Epoch keys use XOR of full IV length with the packet id to generate
         * IVs. Old data format uses concatenation instead (XOR with 0 for the
         * first 4 bytes (sizeof(packet_id_type) */
        if (key->epoch)
        {
            impl_iv_len = cipher_ctx_iv_length(ctx->cipher);
            impl_iv_offset = 0;
        }
        else
        {
            impl_iv_len = cipher_ctx_iv_length(ctx->cipher) - sizeof(packet_id_type);
            impl_iv_offset = sizeof(packet_id_type);
        }
        ASSERT(impl_iv_offset + impl_iv_len <= OPENVPN_MAX_IV_LENGTH);
        ASSERT(impl_iv_len <= MAX_HMAC_KEY_LENGTH);
        ASSERT(impl_iv_len <= key->hmac_size);
        CLEAR(ctx->implicit_iv);
        memcpy(ctx->implicit_iv + impl_iv_offset, key->hmac, impl_iv_len);
    }
}

/* given a key and key_type, build a key_ctx */
void
init_key_ctx(struct key_ctx *ctx, const struct key_parameters *key, const struct key_type *kt,
             int enc, const char *prefix)
{
    struct gc_arena gc = gc_new();
    CLEAR(*ctx);
    if (cipher_defined(kt->cipher))
    {
        ASSERT(key->cipher_size >= cipher_kt_key_size(kt->cipher));
        ctx->cipher = cipher_ctx_new();
        cipher_ctx_init(ctx->cipher, key->cipher, kt->cipher, enc);

        const char *ciphername = cipher_kt_name(kt->cipher);
        msg(D_CIPHER_INIT, "%s: Cipher '%s' initialized with %u bit key", prefix, ciphername,
            cipher_kt_key_size(kt->cipher) * 8);

        dmsg(D_SHOW_KEYS, "%s: CIPHER KEY: %s", prefix,
             format_hex(key->cipher, cipher_kt_key_size(kt->cipher), 0, &gc));
        dmsg(D_CRYPTO_DEBUG, "%s: CIPHER block_size=%u iv_size=%u", prefix,
             cipher_kt_block_size(kt->cipher), cipher_kt_iv_size(kt->cipher));
        warn_insecure_key_type(ciphername);
    }

    if (md_defined(kt->digest))
    {
        ASSERT(key->hmac_size >= md_kt_size(kt->digest));
        ctx->hmac = hmac_ctx_new();
        hmac_ctx_init(ctx->hmac, key->hmac, kt->digest);

        msg(D_CIPHER_INIT, "%s: Using %d bit message hash '%s' for HMAC authentication", prefix,
            md_kt_size(kt->digest) * 8, md_kt_name(kt->digest));

        dmsg(D_SHOW_KEYS, "%s: HMAC KEY: %s", prefix,
             format_hex(key->hmac, md_kt_size(kt->digest), 0, &gc));

        dmsg(D_CRYPTO_DEBUG, "%s: HMAC size=%d block_size=%d", prefix, md_kt_size(kt->digest),
             hmac_ctx_size(ctx->hmac));
    }
    ctx->epoch = key->epoch;
    gc_free(&gc);
}

void
init_key_bi_ctx_send(struct key_ctx *ctx, const struct key_parameters *key_params,
                     const struct key_type *kt, const char *name)
{
    char log_prefix[128] = { 0 };

    snprintf(log_prefix, sizeof(log_prefix), "Outgoing %s", name);
    init_key_ctx(ctx, key_params, kt, OPENVPN_OP_ENCRYPT, log_prefix);
    key_ctx_update_implicit_iv(ctx, key_params);
    ctx->epoch = key_params->epoch;
}

void
init_key_bi_ctx_recv(struct key_ctx *ctx, const struct key_parameters *key_params,
                     const struct key_type *kt, const char *name)
{
    char log_prefix[128] = { 0 };

    snprintf(log_prefix, sizeof(log_prefix), "Incoming %s", name);
    init_key_ctx(ctx, key_params, kt, OPENVPN_OP_DECRYPT, log_prefix);
    key_ctx_update_implicit_iv(ctx, key_params);
    ctx->epoch = key_params->epoch;
}

void
init_key_ctx_bi(struct key_ctx_bi *ctx, const struct key2 *key2, int key_direction,
                const struct key_type *kt, const char *name)
{
    struct key_direction_state kds;

    key_direction_state_init(&kds, key_direction);

    struct key_parameters send_key;
    struct key_parameters recv_key;

    key_parameters_from_key(&send_key, &key2->keys[kds.out_key]);
    key_parameters_from_key(&recv_key, &key2->keys[kds.in_key]);

    init_key_bi_ctx_send(&ctx->encrypt, &send_key, kt, name);
    init_key_bi_ctx_recv(&ctx->decrypt, &recv_key, kt, name);
    ctx->initialized = true;
}

void
free_key_ctx(struct key_ctx *ctx)
{
    if (ctx->cipher)
    {
        cipher_ctx_free(ctx->cipher);
        ctx->cipher = NULL;
    }
    if (ctx->hmac)
    {
        hmac_ctx_cleanup(ctx->hmac);
        hmac_ctx_free(ctx->hmac);
        ctx->hmac = NULL;
    }
    CLEAR(ctx->implicit_iv);
    ctx->plaintext_blocks = 0;
    ctx->epoch = 0;
}

void
free_key_ctx_bi(struct key_ctx_bi *ctx)
{
    free_key_ctx(&ctx->encrypt);
    free_key_ctx(&ctx->decrypt);
    ctx->initialized = false;
}

static bool
key_is_zero(struct key *key, const struct key_type *kt)
{
    size_t cipher_length = cipher_kt_key_size(kt->cipher);
    for (size_t i = 0; i < cipher_length; ++i)
    {
        if (key->cipher[i])
        {
            return false;
        }
    }
    msg(D_CRYPT_ERRORS, "CRYPTO INFO: WARNING: zero key detected");
    return true;
}

/*
 * Make sure that cipher key is a valid key for current key_type.
 */
bool
check_key(struct key *key, const struct key_type *kt)
{
    if (cipher_defined(kt->cipher))
    {
        /*
         * Check for zero key
         */
        if (key_is_zero(key, kt))
        {
            return false;
        }
    }
    return true;
}

/*
 * Generate a random key.
 */
static void
generate_key_random(struct key *key)
{
    int cipher_len = MAX_CIPHER_KEY_LENGTH;
    int hmac_len = MAX_HMAC_KEY_LENGTH;

    struct gc_arena gc = gc_new();

    CLEAR(*key);
    if (!rand_bytes(key->cipher, cipher_len) || !rand_bytes(key->hmac, hmac_len))
    {
        msg(M_FATAL, "ERROR: Random number generator cannot obtain entropy for key generation");
    }

    dmsg(D_SHOW_KEY_SOURCE, "Cipher source entropy: %s",
         format_hex(key->cipher, cipher_len, 0, &gc));
    dmsg(D_SHOW_KEY_SOURCE, "HMAC source entropy: %s", format_hex(key->hmac, hmac_len, 0, &gc));

    gc_free(&gc);
}

static void
key_print(const struct key *key, const struct key_type *kt, const char *prefix)
{
    struct gc_arena gc = gc_new();
    dmsg(D_SHOW_KEY_SOURCE, "%s (cipher, %s, %u bits): %s", prefix, cipher_kt_name(kt->cipher),
         cipher_kt_key_size(kt->cipher) * 8,
         format_hex(key->cipher, cipher_kt_key_size(kt->cipher), 0, &gc));
    dmsg(D_SHOW_KEY_SOURCE, "%s (hmac, %s, %d bits): %s", prefix, md_kt_name(kt->digest),
         md_kt_size(kt->digest) * 8, format_hex(key->hmac, md_kt_size(kt->digest), 0, &gc));
    gc_free(&gc);
}
/**
 * Prints the keys in a key2 structure.
 */
void
key2_print(const struct key2 *k, const struct key_type *kt, const char *prefix0,
           const char *prefix1)
{
    ASSERT(k->n == 2);
    key_print(&k->keys[0], kt, prefix0);
    key_print(&k->keys[1], kt, prefix1);
}

void
key_parameters_from_key(struct key_parameters *key_params, const struct key *key)
{
    CLEAR(*key_params);
    memcpy(key_params->cipher, key->cipher, MAX_CIPHER_KEY_LENGTH);
    key_params->cipher_size = MAX_CIPHER_KEY_LENGTH;
    memcpy(key_params->hmac, key->hmac, MAX_HMAC_KEY_LENGTH);
    key_params->hmac_size = MAX_HMAC_KEY_LENGTH;
}

void
test_crypto(struct crypto_options *co, struct frame *frame)
{
    int i, j;
    struct gc_arena gc = gc_new();
    struct buffer src = alloc_buf_gc(frame->buf.payload_size, &gc);
    struct buffer work = alloc_buf_gc(BUF_SIZE(frame), &gc);
    struct buffer encrypt_workspace = alloc_buf_gc(BUF_SIZE(frame), &gc);
    struct buffer decrypt_workspace = alloc_buf_gc(BUF_SIZE(frame), &gc);
    struct buffer buf = clear_buf();
    void *buf_p;

    /* init work */
    ASSERT(buf_init(&work, frame->buf.headroom));

    /* init implicit IV */
    {
        cipher_ctx_t *cipher = co->key_ctx_bi.encrypt.cipher;
        if (cipher_ctx_mode_aead(cipher))
        {
            ASSERT(cipher_ctx_iv_length(cipher) <= OPENVPN_MAX_IV_LENGTH);
            ASSERT(cipher_ctx_iv_length(cipher) >= OPENVPN_AEAD_MIN_IV_LEN);

            /* Generate dummy implicit IV */
            ASSERT(rand_bytes(co->key_ctx_bi.encrypt.implicit_iv, OPENVPN_MAX_IV_LENGTH));

            memcpy(co->key_ctx_bi.decrypt.implicit_iv, co->key_ctx_bi.encrypt.implicit_iv,
                   OPENVPN_MAX_IV_LENGTH);
        }
    }

    msg(M_INFO, "Entering " PACKAGE_NAME " crypto self-test mode.");
    for (i = 1; i <= frame->buf.payload_size; ++i)
    {
        update_time();

        msg(M_INFO, "TESTING ENCRYPT/DECRYPT of packet length=%d", i);

        /*
         * Load src with random data.
         */
        ASSERT(buf_init(&src, 0));
        ASSERT(i <= src.capacity);
        src.len = i;
        ASSERT(rand_bytes(BPTR(&src), BLEN(&src)));

        /* copy source to input buf */
        buf = work;
        buf_p = buf_write_alloc(&buf, BLENZ(&src));
        ASSERT(buf_p);
        memcpy(buf_p, BPTR(&src), BLENZ(&src));

        /* initialize work buffer with buf.headroom bytes of prepend capacity */
        ASSERT(buf_init(&encrypt_workspace, frame->buf.headroom));

        /* encrypt */
        openvpn_encrypt(&buf, encrypt_workspace, co);

        /* decrypt */
        openvpn_decrypt(&buf, decrypt_workspace, co, frame, BPTR(&buf));

        /* compare */
        if (buf.len != src.len)
        {
            msg(M_FATAL, "SELF TEST FAILED, src.len=%d buf.len=%d", src.len, buf.len);
        }
        for (j = 0; j < i; ++j)
        {
            const uint8_t in = *(BPTR(&src) + j);
            const uint8_t out = *(BPTR(&buf) + j);
            if (in != out)
            {
                msg(M_FATAL, "SELF TEST FAILED, pos=%d in=%d out=%d", j, in, out);
            }
        }
    }
    msg(M_INFO, PACKAGE_NAME " crypto self-test mode SUCCEEDED.");
    gc_free(&gc);
}

const char *
print_key_filename(const char *str, bool is_inline)
{
    if (is_inline)
    {
        return "[[INLINE]]";
    }

    return np(str);
}

void
crypto_read_openvpn_key(const struct key_type *key_type, struct key_ctx_bi *ctx,
                        const char *key_file, bool key_inline, const int key_direction,
                        const char *key_name, const char *opt_name, struct key2 *keydata)
{
    struct key2 key2;
    struct key_direction_state kds;
    unsigned int flags = RKF_MUST_SUCCEED;

    if (key_inline)
    {
        flags |= RKF_INLINE;
    }
    read_key_file(&key2, key_file, flags);

    if (key2.n != 2)
    {
        msg(M_ERR,
            "File '%s' does not have OpenVPN Static Key format.  Using "
            "free-form passphrase file is not supported anymore.",
            print_key_filename(key_file, key_inline));
    }

    /* check for and fix highly unlikely key problems */
    verify_fix_key2(&key2, key_type, key_file);

    /* handle key direction */
    key_direction_state_init(&kds, key_direction);
    must_have_n_keys(key_file, opt_name, &key2, kds.need_keys);

    /* initialize key in both directions */
    init_key_ctx_bi(ctx, &key2, key_direction, key_type, key_name);
    if (keydata)
    {
        *keydata = key2;
    }
    secure_memzero(&key2, sizeof(key2));
}

void
generate_test_crypto_random_key(const struct key_type *key_type, struct key_ctx_bi *ctx,
                                const char *key_name)
{
    struct key2 key2;
    key2.n = 2;
    generate_key_random(&key2.keys[0]);
    generate_key_random(&key2.keys[1]);
    init_key_ctx_bi(ctx, &key2, KEY_DIRECTION_BIDIRECTIONAL, key_type, key_name);
}


/* header and footer for static key file */
static const char static_key_head[] = "-----BEGIN OpenVPN Static key V1-----";
static const char static_key_foot[] = "-----END OpenVPN Static key V1-----";

static const char printable_char_fmt[] =
    "Non-Hex character ('%c') found at line %d in key file '%s' (%d/%d/%d bytes found/min/max)";

static const char unprintable_char_fmt[] =
    "Non-Hex, unprintable character (0x%02x) found at line %d in key file '%s' (%d/%d/%d bytes found/min/max)";

/* read key from file */

void
read_key_file(struct key2 *key2, const char *file, const unsigned int flags)
{
    struct gc_arena gc = gc_new();
    struct buffer in;
    int size;
    uint8_t hex_byte[3] = { 0, 0, 0 };

    /* parse info */
    const unsigned char *cp;
    int hb_index = 0;
    int line_num = 1;
    int line_index = 0;
    int match = 0;

    /* output */
    uint8_t *out = (uint8_t *)&key2->keys;
    const int keylen = sizeof(key2->keys);
    int count = 0;

    /* parse states */
#define PARSE_INITIAL       0
#define PARSE_HEAD          1
#define PARSE_DATA          2
#define PARSE_DATA_COMPLETE 3
#define PARSE_FOOT          4
#define PARSE_FINISHED      5
    int state = PARSE_INITIAL;

    /* constants */
    const int hlen = (int)strlen(static_key_head);
    const int flen = (int)strlen(static_key_foot);
    const int onekeylen = sizeof(key2->keys[0]);

    CLEAR(*key2);

    /*
     * Key can be provided as a filename in 'file' or if RKF_INLINE
     * is set, the actual key data itself in ascii form.
     */
    if (flags & RKF_INLINE) /* 'file' is a string containing ascii representation of key */
    {
        size_t buf_size = strlen(file) + 1;
        ASSERT(buf_size <= INT_MAX);
        size = (int)buf_size;
        buf_set_read(&in, (const uint8_t *)file, size);
    }
    else /* 'file' is a filename which refers to a file containing the ascii key */
    {
        in = buffer_read_from_file(file, &gc);
        if (!buf_valid(&in))
        {
            msg(M_FATAL, "Read error on key file ('%s')", file);
        }

        size = in.len;
    }

    cp = (unsigned char *)in.data;
    while (size > 0)
    {
        const unsigned char c = *cp;

#if 0
        msg(M_INFO, "char='%c'[%d] s=%d ln=%d li=%d m=%d c=%d",
            c, (int)c, state, line_num, line_index, match, count);
#endif

        if (c == '\n')
        {
            line_index = match = 0;
            ++line_num;
        }
        else
        {
            /* first char of new line */
            if (!line_index)
            {
                /* first char of line after header line? */
                if (state == PARSE_HEAD)
                {
                    state = PARSE_DATA;
                }

                /* first char of footer */
                if ((state == PARSE_DATA || state == PARSE_DATA_COMPLETE) && c == '-')
                {
                    state = PARSE_FOOT;
                }
            }

            /* compare read chars with header line */
            if (state == PARSE_INITIAL)
            {
                if (line_index < hlen && c == static_key_head[line_index])
                {
                    if (++match == hlen)
                    {
                        state = PARSE_HEAD;
                    }
                }
            }

            /* compare read chars with footer line */
            if (state == PARSE_FOOT)
            {
                if (line_index < flen && c == static_key_foot[line_index])
                {
                    if (++match == flen)
                    {
                        state = PARSE_FINISHED;
                    }
                }
            }

            /* reading key */
            if (state == PARSE_DATA)
            {
                if (isxdigit(c))
                {
                    ASSERT(hb_index >= 0 && hb_index < 2);
                    hex_byte[hb_index++] = c;
                    if (hb_index == 2)
                    {
                        uint8_t u;
                        ASSERT(sscanf((const char *)hex_byte, "%" SCNx8, &u) == 1);
                        *out++ = u;
                        hb_index = 0;
                        if (++count == keylen)
                        {
                            state = PARSE_DATA_COMPLETE;
                        }
                    }
                }
                else if (isspace(c))
                {
                    /* ignore white space characters */
                }
                else
                {
                    msg(M_FATAL, (isprint(c) ? printable_char_fmt : unprintable_char_fmt), c,
                        line_num, print_key_filename(file, flags & RKF_INLINE), count, onekeylen,
                        keylen);
                }
            }
            ++line_index;
        }
        ++cp;
        --size;
    }

    /*
     * Normally we will read either 1 or 2 keys from file.
     */
    key2->n = count / onekeylen;

    ASSERT(key2->n >= 0 && key2->n <= (int)SIZE(key2->keys));

    if (flags & RKF_MUST_SUCCEED)
    {
        if (!key2->n)
        {
            msg(M_FATAL,
                "Insufficient key material or header text not found in file '%s' (%d/%d/%d bytes found/min/max)",
                print_key_filename(file, flags & RKF_INLINE), count, onekeylen, keylen);
        }

        if (state != PARSE_FINISHED)
        {
            msg(M_FATAL, "Footer text not found in file '%s' (%d/%d/%d bytes found/min/max)",
                print_key_filename(file, flags & RKF_INLINE), count, onekeylen, keylen);
        }
    }

    /* zero file read buffer if not an inline file */
    if (!(flags & RKF_INLINE))
    {
        buf_clear(&in);
    }

#if 0
    /* DEBUGGING */
    {
        int i;
        printf("KEY READ, n=%d\n", key2->n);
        for (i = 0; i < (int) SIZE(key2->keys); ++i)
        {
            /* format key as ascii */
            const char *fmt = format_hex_ex((const uint8_t *)&key2->keys[i],
                                            sizeof(key2->keys[i]),
                                            0,
                                            16,
                                            "\n",
                                            &gc);
            printf("[%d]\n%s\n\n", i, fmt);
        }
    }
#endif

    /* pop our garbage collection level */
    gc_free(&gc);
}

int
write_key_file(const int nkeys, const char *filename)
{
    struct gc_arena gc = gc_new();

    int nbits = nkeys * sizeof(struct key) * 8;

    /* must be large enough to hold full key file */
    struct buffer out = alloc_buf_gc(2048, &gc);

    /* how to format the ascii file representation of key */
    const int bytes_per_line = 16;

    /* write header */
    buf_printf(&out, "#\n# %d bit OpenVPN static key\n#\n", nbits);
    buf_printf(&out, "%s\n", static_key_head);

    for (int i = 0; i < nkeys; ++i)
    {
        struct key key;
        char *fmt;

        /* generate random bits */
        generate_key_random(&key);

        /* format key as ascii */
        fmt = format_hex_ex((const uint8_t *)&key, sizeof(key), 0, bytes_per_line, "\n", &gc);

        /* write to holding buffer */
        buf_printf(&out, "%s\n", fmt);

        /* zero memory which held key component (will be freed by GC) */
        secure_memzero(fmt, strlen(fmt));
        secure_memzero(&key, sizeof(key));
    }

    buf_printf(&out, "%s\n", static_key_foot);

    /* write key file to stdout if no filename given */
    if (!filename || strcmp(filename, "") == 0)
    {
        printf("%.*s\n", BLEN(&out), BPTR(&out));
    }
    /* write key file, now formatted in out, to file */
    else if (!buffer_write_file(filename, &out))
    {
        nbits = -1;
    }

    /* zero memory which held file content (memory will be freed by GC) */
    buf_clear(&out);

    /* pop our garbage collection level */
    gc_free(&gc);

    return nbits;
}

void
must_have_n_keys(const char *filename, const char *option, const struct key2 *key2, int n)
{
    if (key2->n < n)
    {
#ifdef ENABLE_SMALL
        msg(M_FATAL,
            "Key file '%s' used in --%s contains insufficient key material [keys found=%d required=%d]",
            filename, option, key2->n, n);
#else
        msg(M_FATAL,
            "Key file '%s' used in --%s contains insufficient key material [keys found=%d required=%d] -- try generating a new key file with '" PACKAGE
            " --genkey secret [file]', or use the existing key file in bidirectional mode by specifying --%s without a key direction parameter",
            filename, option, key2->n, n, option);
#endif
    }
}

int
ascii2keydirection(msglvl_t msglevel, const char *str)
{
    if (!str)
    {
        return KEY_DIRECTION_BIDIRECTIONAL;
    }
    else if (!strcmp(str, "0"))
    {
        return KEY_DIRECTION_NORMAL;
    }
    else if (!strcmp(str, "1"))
    {
        return KEY_DIRECTION_INVERSE;
    }
    else
    {
        msg(msglevel, "Unknown key direction '%s' -- must be '0' or '1'", str);
        return -1;
    }
    return KEY_DIRECTION_BIDIRECTIONAL; /* NOTREACHED */
}

const char *
keydirection2ascii(int kd, bool remote, bool humanreadable)
{
    if (kd == KEY_DIRECTION_BIDIRECTIONAL)
    {
        if (humanreadable)
        {
            return "not set";
        }
        else
        {
            return NULL;
        }
    }
    else if (kd == KEY_DIRECTION_NORMAL)
    {
        return remote ? "1" : "0";
    }
    else if (kd == KEY_DIRECTION_INVERSE)
    {
        return remote ? "0" : "1";
    }
    else
    {
        ASSERT(0);
    }
    return NULL; /* NOTREACHED */
}

void
key_direction_state_init(struct key_direction_state *kds, int key_direction)
{
    CLEAR(*kds);
    switch (key_direction)
    {
        case KEY_DIRECTION_NORMAL:
            kds->out_key = 0;
            kds->in_key = 1;
            kds->need_keys = 2;
            break;

        case KEY_DIRECTION_INVERSE:
            kds->out_key = 1;
            kds->in_key = 0;
            kds->need_keys = 2;
            break;

        case KEY_DIRECTION_BIDIRECTIONAL:
            kds->out_key = 0;
            kds->in_key = 0;
            kds->need_keys = 1;
            break;

        default:
            ASSERT(0);
    }
}

void
verify_fix_key2(struct key2 *key2, const struct key_type *kt, const char *shared_secret_file)
{
    int i;

    for (i = 0; i < key2->n; ++i)
    {
        /* This should be a very improbable failure */
        if (!check_key(&key2->keys[i], kt))
        {
            msg(M_FATAL, "Key #%d in '%s' is bad.  Try making a new key with --genkey.", i + 1,
                shared_secret_file);
        }
    }
}

void
prng_bytes(uint8_t *output, int len)
{
    ASSERT(rand_bytes(output, len));
}

/* an analogue to the random() function, but use prng_bytes */
long int
get_random(void)
{
    long int l;
    prng_bytes((unsigned char *)&l, sizeof(l));
    if (l < 0)
    {
        l = -l;
    }
    return l;
}

void
print_cipher(const char *ciphername)
{
    printf("%s  (%u bit key, ", cipher_kt_name(ciphername), cipher_kt_key_size(ciphername) * 8);

    if (cipher_kt_block_size(ciphername) == 1)
    {
        printf("stream cipher");
    }
    else
    {
        printf("%u bit block", cipher_kt_block_size(ciphername) * 8);
    }

    if (!cipher_kt_mode_cbc(ciphername))
    {
        printf(", TLS client/server mode only");
    }

    const char *reason;
    if (!cipher_valid_reason(ciphername, &reason))
    {
        printf(", %s", reason);
    }

    printf(")\n");
}

static const cipher_name_pair *
get_cipher_name_pair(const char *cipher_name)
{
    const cipher_name_pair *pair;
    size_t i = 0;

    /* Search for a cipher name translation */
    for (; i < cipher_name_translation_table_count; i++)
    {
        pair = &cipher_name_translation_table[i];
        if (0 == strcmp(cipher_name, pair->openvpn_name)
            || 0 == strcmp(cipher_name, pair->lib_name))
        {
            return pair;
        }
    }

    /* Nothing found, return null */
    return NULL;
}

const char *
translate_cipher_name_from_openvpn(const char *cipher_name)
{
    const cipher_name_pair *pair = get_cipher_name_pair(cipher_name);

    if (NULL == pair)
    {
        return cipher_name;
    }

    return pair->lib_name;
}

const char *
translate_cipher_name_to_openvpn(const char *cipher_name)
{
    const cipher_name_pair *pair = get_cipher_name_pair(cipher_name);

    if (NULL == pair)
    {
        return cipher_name;
    }

    return pair->openvpn_name;
}

void
write_pem_key_file(const char *filename, const char *pem_name)
{
    struct gc_arena gc = gc_new();
    struct key server_key = { 0 };
    struct buffer server_key_buf = clear_buf();
    struct buffer server_key_pem = clear_buf();

    if (!rand_bytes((void *)&server_key, sizeof(server_key)))
    {
        msg(M_NONFATAL, "ERROR: could not generate random key");
        goto cleanup;
    }
    buf_set_read(&server_key_buf, (void *)&server_key, sizeof(server_key));
    if (!crypto_pem_encode(pem_name, &server_key_pem, &server_key_buf, &gc))
    {
        msg(M_WARN, "ERROR: could not PEM-encode key");
        goto cleanup;
    }

    if (!filename || strcmp(filename, "") == 0)
    {
        printf("%.*s", BLEN(&server_key_pem), BPTR(&server_key_pem));
    }
    else if (!buffer_write_file(filename, &server_key_pem))
    {
        msg(M_ERR, "ERROR: could not write key file");
        goto cleanup;
    }

cleanup:
    secure_memzero(&server_key, sizeof(server_key));
    buf_clear(&server_key_pem);
    gc_free(&gc);
    return;
}

bool
generate_ephemeral_key(struct buffer *key, const char *key_name)
{
    const int len = BCAP(key);

    msg(M_INFO, "Using random %s.", key_name);

    if (!rand_bytes(BEND(key), len))
    {
        msg(M_WARN, "ERROR: could not generate random key");
        return false;
    }

    buf_inc_len(key, len);

    return true;
}

bool
read_pem_key_file(struct buffer *key, const char *pem_name, const char *key_file, bool key_inline)
{
    bool ret = false;
    struct buffer key_pem = { 0 };
    struct gc_arena gc = gc_new();

    if (!key_inline)
    {
        key_pem = buffer_read_from_file(key_file, &gc);
        if (!buf_valid(&key_pem))
        {
            msg(M_WARN, "ERROR: failed to read %s file (%s)", pem_name, key_file);
            goto cleanup;
        }
    }
    else
    {
        buf_set_read(&key_pem, (const void *)key_file, strlen(key_file) + 1);
    }

    if (!crypto_pem_decode(pem_name, key, &key_pem))
    {
        msg(M_WARN, "ERROR: %s pem decode failed", pem_name);
        goto cleanup;
    }

    ret = true;
cleanup:
    if (!key_inline)
    {
        buf_clear(&key_pem);
    }
    gc_free(&gc);
    return ret;
}

bool
check_tls_prf_working(void)
{
    /* Modern TLS libraries might no longer support the TLS 1.0 PRF with
     * MD5+SHA1. This allows us to establish connections only
     * with other 2.6.0+ OpenVPN peers.
     * Do a simple dummy test here to see if it works. */
    const char *seed = "tls1-prf-test";
    const char *secret = "tls1-prf-test-secret";
    uint8_t out[8];
    uint8_t expected_out[] = { 'q', 'D', 0xfe, '%', '@', 's', 'u', 0x95 };

    int ret = ssl_tls1_PRF((uint8_t *)seed, strlen(seed), (uint8_t *)secret,
                           strlen(secret), out, sizeof(out));

    return (ret && memcmp(out, expected_out, sizeof(out)) == 0);
}
