pgp-pubkey.c

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/*
 * pgp-pubkey.c
 *    Read public or secret key.
 *
 * Copyright (c) 2005 Marko Kreen
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * contrib/pgcrypto/pgp-pubkey.c
 */
#include "postgres.h"

#include "mbuf.h"
#include "pgp.h"
#include "px.h"

int
pgp_key_alloc(PGP_PubKey **pk_p)
{
    PGP_PubKey *pk;

    pk = palloc0(sizeof(*pk));
    *pk_p = pk;
    return 0;
}

void
pgp_key_free(PGP_PubKey *pk)
{
    if (pk == NULL)
        return;

    switch (pk->algo)
    {
        case PGP_PUB_ELG_ENCRYPT:
            pgp_mpi_free(pk->pub.elg.p);
            pgp_mpi_free(pk->pub.elg.g);
            pgp_mpi_free(pk->pub.elg.y);
            pgp_mpi_free(pk->sec.elg.x);
            break;
        case PGP_PUB_RSA_SIGN:
        case PGP_PUB_RSA_ENCRYPT:
        case PGP_PUB_RSA_ENCRYPT_SIGN:
            pgp_mpi_free(pk->pub.rsa.n);
            pgp_mpi_free(pk->pub.rsa.e);
            pgp_mpi_free(pk->sec.rsa.d);
            pgp_mpi_free(pk->sec.rsa.p);
            pgp_mpi_free(pk->sec.rsa.q);
            pgp_mpi_free(pk->sec.rsa.u);
            break;
        case PGP_PUB_DSA_SIGN:
            pgp_mpi_free(pk->pub.dsa.p);
            pgp_mpi_free(pk->pub.dsa.q);
            pgp_mpi_free(pk->pub.dsa.g);
            pgp_mpi_free(pk->pub.dsa.y);
            pgp_mpi_free(pk->sec.dsa.x);
            break;
    }
    px_memset(pk, 0, sizeof(*pk));
    pfree(pk);
}

static int
calc_key_id(PGP_PubKey *pk)
{
    int         res;
    PX_MD      *md;
    int         len;
    uint8       hdr[3];
    uint8       hash[20];

    res = pgp_load_digest(PGP_DIGEST_SHA1, &md);
    if (res < 0)
        return res;

    len = 1 + 4 + 1;
    switch (pk->algo)
    {
        case PGP_PUB_ELG_ENCRYPT:
            len += 2 + pk->pub.elg.p->bytes;
            len += 2 + pk->pub.elg.g->bytes;
            len += 2 + pk->pub.elg.y->bytes;
            break;
        case PGP_PUB_RSA_SIGN:
        case PGP_PUB_RSA_ENCRYPT:
        case PGP_PUB_RSA_ENCRYPT_SIGN:
            len += 2 + pk->pub.rsa.n->bytes;
            len += 2 + pk->pub.rsa.e->bytes;
            break;
        case PGP_PUB_DSA_SIGN:
            len += 2 + pk->pub.dsa.p->bytes;
            len += 2 + pk->pub.dsa.q->bytes;
            len += 2 + pk->pub.dsa.g->bytes;
            len += 2 + pk->pub.dsa.y->bytes;
            break;
    }

    hdr[0] = 0x99;
    hdr[1] = len >> 8;
    hdr[2] = len & 0xFF;
    px_md_update(md, hdr, 3);

    px_md_update(md, &pk->ver, 1);
    px_md_update(md, pk->time, 4);
    px_md_update(md, &pk->algo, 1);

    switch (pk->algo)
    {
        case PGP_PUB_ELG_ENCRYPT:
            pgp_mpi_hash(md, pk->pub.elg.p);
            pgp_mpi_hash(md, pk->pub.elg.g);
            pgp_mpi_hash(md, pk->pub.elg.y);
            break;
        case PGP_PUB_RSA_SIGN:
        case PGP_PUB_RSA_ENCRYPT:
        case PGP_PUB_RSA_ENCRYPT_SIGN:
            pgp_mpi_hash(md, pk->pub.rsa.n);
            pgp_mpi_hash(md, pk->pub.rsa.e);
            break;
        case PGP_PUB_DSA_SIGN:
            pgp_mpi_hash(md, pk->pub.dsa.p);
            pgp_mpi_hash(md, pk->pub.dsa.q);
            pgp_mpi_hash(md, pk->pub.dsa.g);
            pgp_mpi_hash(md, pk->pub.dsa.y);
            break;
    }

    px_md_finish(md, hash);
    px_md_free(md);

    memcpy(pk->key_id, hash + 12, 8);
    px_memset(hash, 0, 20);

    return 0;
}

int
_pgp_read_public_key(PullFilter *pkt, PGP_PubKey **pk_p)
{
    int         res;
    PGP_PubKey *pk;

    res = pgp_key_alloc(&pk);
    if (res < 0)
        return res;

    /* get version */
    GETBYTE(pkt, pk->ver);
    if (pk->ver != 4)
    {
        res = PXE_PGP_NOT_V4_KEYPKT;
        goto out;
    }

    /* read time */
    res = pullf_read_fixed(pkt, 4, pk->time);
    if (res < 0)
        goto out;

    /* pubkey algorithm */
    GETBYTE(pkt, pk->algo);

    switch (pk->algo)
    {
        case PGP_PUB_DSA_SIGN:
            res = pgp_mpi_read(pkt, &pk->pub.dsa.p);
            if (res < 0)
                break;
            res = pgp_mpi_read(pkt, &pk->pub.dsa.q);
            if (res < 0)
                break;
            res = pgp_mpi_read(pkt, &pk->pub.dsa.g);
            if (res < 0)
                break;
            res = pgp_mpi_read(pkt, &pk->pub.dsa.y);
            if (res < 0)
                break;

            res = calc_key_id(pk);
            break;

        case PGP_PUB_RSA_SIGN:
        case PGP_PUB_RSA_ENCRYPT:
        case PGP_PUB_RSA_ENCRYPT_SIGN:
            res = pgp_mpi_read(pkt, &pk->pub.rsa.n);
            if (res < 0)
                break;
            res = pgp_mpi_read(pkt, &pk->pub.rsa.e);
            if (res < 0)
                break;

            res = calc_key_id(pk);

            if (pk->algo != PGP_PUB_RSA_SIGN)
                pk->can_encrypt = 1;
            break;

        case PGP_PUB_ELG_ENCRYPT:
            res = pgp_mpi_read(pkt, &pk->pub.elg.p);
            if (res < 0)
                break;
            res = pgp_mpi_read(pkt, &pk->pub.elg.g);
            if (res < 0)
                break;
            res = pgp_mpi_read(pkt, &pk->pub.elg.y);
            if (res < 0)
                break;

            res = calc_key_id(pk);

            pk->can_encrypt = 1;
            break;

        default:
            px_debug("unknown public algo: %d", pk->algo);
            res = PXE_PGP_UNKNOWN_PUBALGO;
    }

out:
    if (res < 0)
        pgp_key_free(pk);
    else
        *pk_p = pk;

    return res;
}

#define HIDE_CLEAR 0
#define HIDE_CKSUM 255
#define HIDE_SHA1 254

static int
check_key_sha1(PullFilter *src, PGP_PubKey *pk)
{
    int         res;
    uint8       got_sha1[20];
    uint8       my_sha1[20];
    PX_MD      *md;

    res = pullf_read_fixed(src, 20, got_sha1);
    if (res < 0)
        return res;

    res = pgp_load_digest(PGP_DIGEST_SHA1, &md);
    if (res < 0)
        goto err;
    switch (pk->algo)
    {
        case PGP_PUB_ELG_ENCRYPT:
            pgp_mpi_hash(md, pk->sec.elg.x);
            break;
        case PGP_PUB_RSA_SIGN:
        case PGP_PUB_RSA_ENCRYPT:
        case PGP_PUB_RSA_ENCRYPT_SIGN:
            pgp_mpi_hash(md, pk->sec.rsa.d);
            pgp_mpi_hash(md, pk->sec.rsa.p);
            pgp_mpi_hash(md, pk->sec.rsa.q);
            pgp_mpi_hash(md, pk->sec.rsa.u);
            break;
        case PGP_PUB_DSA_SIGN:
            pgp_mpi_hash(md, pk->sec.dsa.x);
            break;
    }
    px_md_finish(md, my_sha1);
    px_md_free(md);

    if (memcmp(my_sha1, got_sha1, 20) != 0)
    {
        px_debug("key sha1 check failed");
        res = PXE_PGP_KEYPKT_CORRUPT;
    }
err:
    px_memset(got_sha1, 0, 20);
    px_memset(my_sha1, 0, 20);
    return res;
}

static int
check_key_cksum(PullFilter *src, PGP_PubKey *pk)
{
    int         res;
    unsigned    got_cksum,
                my_cksum = 0;
    uint8       buf[2];

    res = pullf_read_fixed(src, 2, buf);
    if (res < 0)
        return res;

    got_cksum = ((unsigned) buf[0] << 8) + buf[1];
    switch (pk->algo)
    {
        case PGP_PUB_ELG_ENCRYPT:
            my_cksum = pgp_mpi_cksum(0, pk->sec.elg.x);
            break;
        case PGP_PUB_RSA_SIGN:
        case PGP_PUB_RSA_ENCRYPT:
        case PGP_PUB_RSA_ENCRYPT_SIGN:
            my_cksum = pgp_mpi_cksum(0, pk->sec.rsa.d);
            my_cksum = pgp_mpi_cksum(my_cksum, pk->sec.rsa.p);
            my_cksum = pgp_mpi_cksum(my_cksum, pk->sec.rsa.q);
            my_cksum = pgp_mpi_cksum(my_cksum, pk->sec.rsa.u);
            break;
        case PGP_PUB_DSA_SIGN:
            my_cksum = pgp_mpi_cksum(0, pk->sec.dsa.x);
            break;
    }
    if (my_cksum != got_cksum)
    {
        px_debug("key cksum check failed");
        return PXE_PGP_KEYPKT_CORRUPT;
    }
    return 0;
}

static int
process_secret_key(PullFilter *pkt, PGP_PubKey **pk_p,
                   const uint8 *key, int key_len)
{
    int         res;
    int         hide_type;
    int         cipher_algo;
    int         bs;
    uint8       iv[512];
    PullFilter *pf_decrypt = NULL,
               *pf_key;
    PGP_CFB    *cfb = NULL;
    PGP_S2K     s2k;
    PGP_PubKey *pk;

    /* first read public key part */
    res = _pgp_read_public_key(pkt, &pk);
    if (res < 0)
        return res;

    /*
     * is secret key encrypted?
     */
    GETBYTE(pkt, hide_type);
    if (hide_type == HIDE_SHA1 || hide_type == HIDE_CKSUM)
    {
        if (key == NULL)
            return PXE_PGP_NEED_SECRET_PSW;
        GETBYTE(pkt, cipher_algo);
        res = pgp_s2k_read(pkt, &s2k);
        if (res < 0)
            return res;

        res = pgp_s2k_process(&s2k, cipher_algo, key, key_len);
        if (res < 0)
            return res;

        bs = pgp_get_cipher_block_size(cipher_algo);
        if (bs == 0)
        {
            px_debug("unknown cipher algo=%d", cipher_algo);
            return PXE_PGP_UNSUPPORTED_CIPHER;
        }
        res = pullf_read_fixed(pkt, bs, iv);
        if (res < 0)
            return res;

        /*
         * create decrypt filter
         */
        res = pgp_cfb_create(&cfb, cipher_algo, s2k.key, s2k.key_len, 0, iv);
        if (res < 0)
            return res;
        res = pullf_create(&pf_decrypt, &pgp_decrypt_filter, cfb, pkt);
        if (res < 0)
            return res;
        pf_key = pf_decrypt;
    }
    else if (hide_type == HIDE_CLEAR)
    {
        pf_key = pkt;
    }
    else
    {
        px_debug("unknown hide type");
        return PXE_PGP_KEYPKT_CORRUPT;
    }

    /* read secret key */
    switch (pk->algo)
    {
        case PGP_PUB_RSA_SIGN:
        case PGP_PUB_RSA_ENCRYPT:
        case PGP_PUB_RSA_ENCRYPT_SIGN:
            res = pgp_mpi_read(pf_key, &pk->sec.rsa.d);
            if (res < 0)
                break;
            res = pgp_mpi_read(pf_key, &pk->sec.rsa.p);
            if (res < 0)
                break;
            res = pgp_mpi_read(pf_key, &pk->sec.rsa.q);
            if (res < 0)
                break;
            res = pgp_mpi_read(pf_key, &pk->sec.rsa.u);
            if (res < 0)
                break;
            break;
        case PGP_PUB_ELG_ENCRYPT:
            res = pgp_mpi_read(pf_key, &pk->sec.elg.x);
            break;
        case PGP_PUB_DSA_SIGN:
            res = pgp_mpi_read(pf_key, &pk->sec.dsa.x);
            break;
        default:
            px_debug("unknown public algo: %d", pk->algo);
            res = PXE_PGP_KEYPKT_CORRUPT;
    }
    /* read checksum / sha1 */
    if (res >= 0)
    {
        if (hide_type == HIDE_SHA1)
            res = check_key_sha1(pf_key, pk);
        else
            res = check_key_cksum(pf_key, pk);
    }
    if (res >= 0)
        res = pgp_expect_packet_end(pf_key);

    if (pf_decrypt)
        pullf_free(pf_decrypt);
    if (cfb)
        pgp_cfb_free(cfb);

    if (res < 0)
        pgp_key_free(pk);
    else
        *pk_p = pk;

    return res;
}

static int
internal_read_key(PullFilter *src, PGP_PubKey **pk_p,
                  const uint8 *psw, int psw_len, int pubtype)
{
    PullFilter *pkt = NULL;
    int         res;
    uint8       tag;
    int         len;
    PGP_PubKey *enc_key = NULL;
    PGP_PubKey *pk = NULL;
    int         got_main_key = 0;

    /*
     * Search for encryption key.
     *
     * Error out on anything fancy.
     */
    while (1)
    {
        res = pgp_parse_pkt_hdr(src, &tag, &len, 0);
        if (res <= 0)
            break;
        res = pgp_create_pkt_reader(&pkt, src, len, res, NULL);
        if (res < 0)
            break;

        switch (tag)
        {
            case PGP_PKT_PUBLIC_KEY:
            case PGP_PKT_SECRET_KEY:
                if (got_main_key)
                {
                    res = PXE_PGP_MULTIPLE_KEYS;
                    break;
                }
                got_main_key = 1;
                res = pgp_skip_packet(pkt);
                break;

            case PGP_PKT_PUBLIC_SUBKEY:
                if (pubtype != 0)
                    res = PXE_PGP_EXPECT_SECRET_KEY;
                else
                    res = _pgp_read_public_key(pkt, &pk);
                break;

            case PGP_PKT_SECRET_SUBKEY:
                if (pubtype != 1)
                    res = PXE_PGP_EXPECT_PUBLIC_KEY;
                else
                    res = process_secret_key(pkt, &pk, psw, psw_len);
                break;

            case PGP_PKT_SIGNATURE:
            case PGP_PKT_MARKER:
            case PGP_PKT_TRUST:
            case PGP_PKT_USER_ID:
            case PGP_PKT_USER_ATTR:
            case PGP_PKT_PRIV_61:
                res = pgp_skip_packet(pkt);
                break;
            default:
                px_debug("unknown/unexpected packet: %d", tag);
                res = PXE_PGP_UNEXPECTED_PKT;
        }
        pullf_free(pkt);
        pkt = NULL;

        if (pk != NULL)
        {
            if (res >= 0 && pk->can_encrypt)
            {
                if (enc_key == NULL)
                {
                    enc_key = pk;
                    pk = NULL;
                }
                else
                    res = PXE_PGP_MULTIPLE_SUBKEYS;
            }

            if (pk)
                pgp_key_free(pk);
            pk = NULL;
        }

        if (res < 0)
            break;
    }

    if (pkt)
        pullf_free(pkt);

    if (res < 0)
    {
        if (enc_key)
            pgp_key_free(enc_key);
        return res;
    }

    if (!enc_key)
        res = PXE_PGP_NO_USABLE_KEY;
    else
        *pk_p = enc_key;
    return res;
}

int
pgp_set_pubkey(PGP_Context *ctx, MBuf *keypkt,
               const uint8 *key, int key_len, int pubtype)
{
    int         res;
    PullFilter *src;
    PGP_PubKey *pk = NULL;

    res = pullf_create_mbuf_reader(&src, keypkt);
    if (res < 0)
        return res;

    res = internal_read_key(src, &pk, key, key_len, pubtype);
    pullf_free(src);

    if (res >= 0)
        ctx->pub_key = pk;

    return res < 0 ? res : 0;
}