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237 lines
4.8 KiB
C
237 lines
4.8 KiB
C
/*
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* pgp-pubdec.c
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* Decrypt public-key encrypted session key.
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*
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* Copyright (c) 2005 Marko Kreen
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* contrib/pgcrypto/pgp-pubdec.c
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*/
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#include "postgres.h"
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#include "px.h"
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#include "mbuf.h"
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#include "pgp.h"
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/*
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* padded msg = 02 || PS || 00 || M
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* PS - pad bytes
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* M - msg
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*/
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static uint8 *
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check_eme_pkcs1_v15(uint8 *data, int len)
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{
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uint8 *data_end = data + len;
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uint8 *p = data;
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int rnd = 0;
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if (len < 1 + 8 + 1)
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return NULL;
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if (*p++ != 2)
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return NULL;
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while (p < data_end && *p)
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{
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p++;
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rnd++;
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}
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if (p == data_end)
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return NULL;
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if (*p != 0)
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return NULL;
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if (rnd < 8)
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return NULL;
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return p + 1;
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}
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/*
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* secret message: 1 byte algo, sesskey, 2 byte cksum
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* ignore algo in cksum
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*/
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static int
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control_cksum(uint8 *msg, int msglen)
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{
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int i;
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unsigned my_cksum,
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got_cksum;
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if (msglen < 3)
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return PXE_PGP_WRONG_KEY;
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my_cksum = 0;
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for (i = 1; i < msglen - 2; i++)
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my_cksum += msg[i];
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my_cksum &= 0xFFFF;
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got_cksum = ((unsigned) (msg[msglen - 2]) << 8) + msg[msglen - 1];
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if (my_cksum != got_cksum)
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{
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px_debug("pubenc cksum failed");
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return PXE_PGP_WRONG_KEY;
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}
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return 0;
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}
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static int
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decrypt_elgamal(PGP_PubKey *pk, PullFilter *pkt, PGP_MPI **m_p)
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{
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int res;
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PGP_MPI *c1 = NULL;
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PGP_MPI *c2 = NULL;
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if (pk->algo != PGP_PUB_ELG_ENCRYPT)
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return PXE_PGP_WRONG_KEY;
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/* read elgamal encrypted data */
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res = pgp_mpi_read(pkt, &c1);
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if (res < 0)
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goto out;
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res = pgp_mpi_read(pkt, &c2);
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if (res < 0)
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goto out;
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/* decrypt */
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res = pgp_elgamal_decrypt(pk, c1, c2, m_p);
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out:
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pgp_mpi_free(c1);
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pgp_mpi_free(c2);
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return res;
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}
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static int
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decrypt_rsa(PGP_PubKey *pk, PullFilter *pkt, PGP_MPI **m_p)
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{
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int res;
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PGP_MPI *c;
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if (pk->algo != PGP_PUB_RSA_ENCRYPT
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&& pk->algo != PGP_PUB_RSA_ENCRYPT_SIGN)
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return PXE_PGP_WRONG_KEY;
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/* read rsa encrypted data */
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res = pgp_mpi_read(pkt, &c);
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if (res < 0)
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return res;
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/* decrypt */
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res = pgp_rsa_decrypt(pk, c, m_p);
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pgp_mpi_free(c);
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return res;
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}
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/* key id is missing - user is expected to try all keys */
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static const uint8
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any_key[] = {0, 0, 0, 0, 0, 0, 0, 0};
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int
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pgp_parse_pubenc_sesskey(PGP_Context *ctx, PullFilter *pkt)
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{
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int ver;
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int algo;
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int res;
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uint8 key_id[8];
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PGP_PubKey *pk;
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uint8 *msg;
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int msglen;
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PGP_MPI *m;
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pk = ctx->pub_key;
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if (pk == NULL)
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{
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px_debug("no pubkey?");
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return PXE_BUG;
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}
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GETBYTE(pkt, ver);
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if (ver != 3)
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{
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px_debug("unknown pubenc_sesskey pkt ver=%d", ver);
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return PXE_PGP_CORRUPT_DATA;
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}
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/*
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* check if keyid's match - user-friendly msg
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*/
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res = pullf_read_fixed(pkt, 8, key_id);
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if (res < 0)
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return res;
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if (memcmp(key_id, any_key, 8) != 0
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&& memcmp(key_id, pk->key_id, 8) != 0)
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{
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px_debug("key_id's does not match");
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return PXE_PGP_WRONG_KEY;
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}
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/*
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* Decrypt
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*/
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GETBYTE(pkt, algo);
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switch (algo)
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{
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case PGP_PUB_ELG_ENCRYPT:
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res = decrypt_elgamal(pk, pkt, &m);
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break;
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case PGP_PUB_RSA_ENCRYPT:
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case PGP_PUB_RSA_ENCRYPT_SIGN:
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res = decrypt_rsa(pk, pkt, &m);
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break;
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default:
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res = PXE_PGP_UNKNOWN_PUBALGO;
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}
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if (res < 0)
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return res;
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/*
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* extract message
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*/
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msg = check_eme_pkcs1_v15(m->data, m->bytes);
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if (msg == NULL)
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{
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px_debug("check_eme_pkcs1_v15 failed");
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res = PXE_PGP_WRONG_KEY;
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goto out;
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}
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msglen = m->bytes - (msg - m->data);
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res = control_cksum(msg, msglen);
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if (res < 0)
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goto out;
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/*
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* got sesskey
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*/
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ctx->cipher_algo = *msg;
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ctx->sess_key_len = msglen - 3;
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memcpy(ctx->sess_key, msg + 1, ctx->sess_key_len);
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out:
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pgp_mpi_free(m);
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if (res < 0)
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return res;
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return pgp_expect_packet_end(pkt);
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}
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