greenplumn pgp-decrypt 源码
greenplumn pgp-decrypt 代码
文件路径：/contrib/pgcrypto/pgp-decrypt.c
/*
* pgp-decrypt.c
* OpenPGP decrypt.
*
* 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-decrypt.c
*/
#include "postgres.h"
#include "px.h"
#include "mbuf.h"
#include "pgp.h"
#define NO_CTX_SIZE 0
#define ALLOW_CTX_SIZE 1
#define NO_COMPR 0
#define ALLOW_COMPR 1
#define NO_MDC 0
#define NEED_MDC 1
#define PKT_NORMAL 1
#define PKT_STREAM 2
#define PKT_CONTEXT 3
#define MAX_CHUNK (16*1024*1024)
static int
parse_new_len(PullFilter *src, int *len_p)
{
uint8 b;
int len;
int pkttype = PKT_NORMAL;
GETBYTE(src, b);
if (b <= 191)
len = b;
else if (b >= 192 && b <= 223)
{
len = ((unsigned) (b) - 192) << 8;
GETBYTE(src, b);
len += 192 + b;
}
else if (b == 255)
{
GETBYTE(src, b);
len = b;
GETBYTE(src, b);
len = (len << 8) | b;
GETBYTE(src, b);
len = (len << 8) | b;
GETBYTE(src, b);
len = (len << 8) | b;
}
else
{
len = 1 << (b & 0x1F);
pkttype = PKT_STREAM;
}
if (len < 0 || len > MAX_CHUNK)
{
px_debug("parse_new_len: weird length");
return PXE_PGP_CORRUPT_DATA;
}
*len_p = len;
return pkttype;
}
static int
parse_old_len(PullFilter *src, int *len_p, int lentype)
{
uint8 b;
int len;
GETBYTE(src, b);
len = b;
if (lentype == 1)
{
GETBYTE(src, b);
len = (len << 8) | b;
}
else if (lentype == 2)
{
GETBYTE(src, b);
len = (len << 8) | b;
GETBYTE(src, b);
len = (len << 8) | b;
GETBYTE(src, b);
len = (len << 8) | b;
}
if (len < 0 || len > MAX_CHUNK)
{
px_debug("parse_old_len: weird length");
return PXE_PGP_CORRUPT_DATA;
}
*len_p = len;
return PKT_NORMAL;
}
/* returns pkttype or 0 on eof */
int
pgp_parse_pkt_hdr(PullFilter *src, uint8 *tag, int *len_p, int allow_ctx)
{
int lentype;
int res;
uint8 *p;
/* EOF is normal here, thus we don't use GETBYTE */
res = pullf_read(src, 1, &p);
if (res < 0)
return res;
if (res == 0)
return 0;
if ((*p & 0x80) == 0)
{
px_debug("pgp_parse_pkt_hdr: not pkt hdr");
return PXE_PGP_CORRUPT_DATA;
}
if (*p & 0x40)
{
*tag = *p & 0x3f;
res = parse_new_len(src, len_p);
}
else
{
lentype = *p & 3;
*tag = (*p >> 2) & 0x0F;
if (lentype == 3)
res = allow_ctx ? PKT_CONTEXT : PXE_PGP_CORRUPT_DATA;
else
res = parse_old_len(src, len_p, lentype);
}
return res;
}
/*
* Packet reader
*/
struct PktData
{
int type;
int len;
};
static int
pktreader_pull(void *priv, PullFilter *src, int len,
uint8 **data_p, uint8 *buf, int buflen)
{
int res;
struct PktData *pkt = priv;
/* PKT_CONTEXT means: whatever there is */
if (pkt->type == PKT_CONTEXT)
return pullf_read(src, len, data_p);
while (pkt->len == 0)
{
/* this was last chunk in stream */
if (pkt->type == PKT_NORMAL)
return 0;
/* next chunk in stream */
res = parse_new_len(src, &pkt->len);
if (res < 0)
return res;
pkt->type = res;
}
if (len > pkt->len)
len = pkt->len;
res = pullf_read(src, len, data_p);
if (res > 0)
pkt->len -= res;
return res;
}
static void
pktreader_free(void *priv)
{
struct PktData *pkt = priv;
px_memset(pkt, 0, sizeof(*pkt));
px_free(pkt);
}
static struct PullFilterOps pktreader_filter = {
NULL, pktreader_pull, pktreader_free
};
/* needs helper function to pass several parameters */
int
pgp_create_pkt_reader(PullFilter **pf_p, PullFilter *src, int len,
int pkttype, PGP_Context *ctx)
{
int res;
struct PktData *pkt = px_alloc(sizeof(*pkt));
pkt->type = pkttype;
pkt->len = len;
res = pullf_create(pf_p, &pktreader_filter, pkt, src);
if (res < 0)
px_free(pkt);
return res;
}
/*
* Prefix check filter
* https://tools.ietf.org/html/rfc4880#section-5.7
* https://tools.ietf.org/html/rfc4880#section-5.13
*/
static int
prefix_init(void **priv_p, void *arg, PullFilter *src)
{
PGP_Context *ctx = arg;
int len;
int res;
uint8 *buf;
uint8 tmpbuf[PGP_MAX_BLOCK + 2];
len = pgp_get_cipher_block_size(ctx->cipher_algo);
if (len > sizeof(tmpbuf))
return PXE_BUG;
res = pullf_read_max(src, len + 2, &buf, tmpbuf);
if (res < 0)
return res;
if (res != len + 2)
{
px_debug("prefix_init: short read");
px_memset(tmpbuf, 0, sizeof(tmpbuf));
return PXE_PGP_CORRUPT_DATA;
}
if (buf[len - 2] != buf[len] || buf[len - 1] != buf[len + 1])
{
px_debug("prefix_init: corrupt prefix");
/* report error in pgp_decrypt() */
ctx->corrupt_prefix = 1;
}
px_memset(tmpbuf, 0, sizeof(tmpbuf));
return 0;
}
static struct PullFilterOps prefix_filter = {
prefix_init, NULL, NULL
};
/*
* Decrypt filter
*/
static int
decrypt_init(void **priv_p, void *arg, PullFilter *src)
{
PGP_CFB *cfb = arg;
*priv_p = cfb;
/* we need to write somewhere, so ask for a buffer */
return 4096;
}
static int
decrypt_read(void *priv, PullFilter *src, int len,
uint8 **data_p, uint8 *buf, int buflen)
{
PGP_CFB *cfb = priv;
uint8 *tmp;
int res;
res = pullf_read(src, len, &tmp);
if (res > 0)
{
pgp_cfb_decrypt(cfb, tmp, res, buf);
*data_p = buf;
}
return res;
}
struct PullFilterOps pgp_decrypt_filter = {
decrypt_init, decrypt_read, NULL
};
/*
* MDC hasher filter
*/
static int
mdc_init(void **priv_p, void *arg, PullFilter *src)
{
PGP_Context *ctx = arg;
*priv_p = ctx;
return pgp_load_digest(PGP_DIGEST_SHA1, &ctx->mdc_ctx);
}
static void
mdc_free(void *priv)
{
PGP_Context *ctx = priv;
if (ctx->use_mdcbuf_filter)
return;
px_md_free(ctx->mdc_ctx);
ctx->mdc_ctx = NULL;
}
static int
mdc_finish(PGP_Context *ctx, PullFilter *src, int len)
{
int res;
uint8 hash[20];
uint8 tmpbuf[20];
uint8 *data;
/* should not happen */
if (ctx->use_mdcbuf_filter)
return PXE_BUG;
/* It's SHA1 */
if (len != 20)
return PXE_PGP_CORRUPT_DATA;
/* mdc_read should not call md_update */
ctx->in_mdc_pkt = 1;
/* read data */
res = pullf_read_max(src, len, &data, tmpbuf);
if (res < 0)
return res;
if (res == 0)
{
px_debug("no mdc");
return PXE_PGP_CORRUPT_DATA;
}
/* is the packet sane? */
if (res != 20)
{
px_debug("mdc_finish: read failed, res=%d", res);
return PXE_PGP_CORRUPT_DATA;
}
/*
* ok, we got the hash, now check
*/
px_md_finish(ctx->mdc_ctx, hash);
res = memcmp(hash, data, 20);
px_memset(hash, 0, 20);
px_memset(tmpbuf, 0, sizeof(tmpbuf));
if (res != 0)
{
px_debug("mdc_finish: mdc failed");
return PXE_PGP_CORRUPT_DATA;
}
ctx->mdc_checked = 1;
return 0;
}
static int
mdc_read(void *priv, PullFilter *src, int len,
uint8 **data_p, uint8 *buf, int buflen)
{
int res;
PGP_Context *ctx = priv;
/* skip this filter? */
if (ctx->use_mdcbuf_filter || ctx->in_mdc_pkt)
return pullf_read(src, len, data_p);
res = pullf_read(src, len, data_p);
if (res < 0)
return res;
if (res == 0)
{
px_debug("mdc_read: unexpected eof");
return PXE_PGP_CORRUPT_DATA;
}
px_md_update(ctx->mdc_ctx, *data_p, res);
return res;
}
static struct PullFilterOps mdc_filter = {
mdc_init, mdc_read, mdc_free
};
/*
* Combined Pkt reader and MDC hasher.
*
* For the case of SYMENCRYPTED_MDC packet, where
* the data part has 'context length', which means
* that data packet ends 22 bytes before end of parent
* packet, which is silly.
*/
#define MDCBUF_LEN 8192
struct MDCBufData
{
PGP_Context *ctx;
int eof;
int buflen;
int avail;
uint8 *pos;
int mdc_avail;
uint8 mdc_buf[22];
uint8 buf[MDCBUF_LEN];
};
static int
mdcbuf_init(void **priv_p, void *arg, PullFilter *src)
{
PGP_Context *ctx = arg;
struct MDCBufData *st;
st = px_alloc(sizeof(*st));
memset(st, 0, sizeof(*st));
st->buflen = sizeof(st->buf);
st->ctx = ctx;
*priv_p = st;
/* take over the work of mdc_filter */
ctx->use_mdcbuf_filter = 1;
return 0;
}
static int
mdcbuf_finish(struct MDCBufData *st)
{
uint8 hash[20];
int res;
st->eof = 1;
if (st->mdc_buf[0] != 0xD3 || st->mdc_buf[1] != 0x14)
{
px_debug("mdcbuf_finish: bad MDC pkt hdr");
return PXE_PGP_CORRUPT_DATA;
}
px_md_update(st->ctx->mdc_ctx, st->mdc_buf, 2);
px_md_finish(st->ctx->mdc_ctx, hash);
res = memcmp(hash, st->mdc_buf + 2, 20);
px_memset(hash, 0, 20);
if (res)
{
px_debug("mdcbuf_finish: MDC does not match");
res = PXE_PGP_CORRUPT_DATA;
}
return res;
}
static void
mdcbuf_load_data(struct MDCBufData *st, uint8 *src, int len)
{
uint8 *dst = st->pos + st->avail;
memcpy(dst, src, len);
px_md_update(st->ctx->mdc_ctx, src, len);
st->avail += len;
}
static void
mdcbuf_load_mdc(struct MDCBufData *st, uint8 *src, int len)
{
memmove(st->mdc_buf + st->mdc_avail, src, len);
st->mdc_avail += len;
}
static int
mdcbuf_refill(struct MDCBufData *st, PullFilter *src)
{
uint8 *data;
int res;
int need;
/* put avail data in start */
if (st->avail > 0 && st->pos != st->buf)
memmove(st->buf, st->pos, st->avail);
st->pos = st->buf;
/* read new data */
need = st->buflen + 22 - st->avail - st->mdc_avail;
res = pullf_read(src, need, &data);
if (res < 0)
return res;
if (res == 0)
return mdcbuf_finish(st);
/* add to buffer */
if (res >= 22)
{
mdcbuf_load_data(st, st->mdc_buf, st->mdc_avail);
st->mdc_avail = 0;
mdcbuf_load_data(st, data, res - 22);
mdcbuf_load_mdc(st, data + res - 22, 22);
}
else
{
int canmove = st->mdc_avail + res - 22;
if (canmove > 0)
{
mdcbuf_load_data(st, st->mdc_buf, canmove);
st->mdc_avail -= canmove;
memmove(st->mdc_buf, st->mdc_buf + canmove, st->mdc_avail);
}
mdcbuf_load_mdc(st, data, res);
}
return 0;
}
static int
mdcbuf_read(void *priv, PullFilter *src, int len,
uint8 **data_p, uint8 *buf, int buflen)
{
struct MDCBufData *st = priv;
int res;
if (!st->eof && len > st->avail)
{
res = mdcbuf_refill(st, src);
if (res < 0)
return res;
}
if (len > st->avail)
len = st->avail;
*data_p = st->pos;
st->pos += len;
st->avail -= len;
return len;
}
static void
mdcbuf_free(void *priv)
{
struct MDCBufData *st = priv;
px_md_free(st->ctx->mdc_ctx);
st->ctx->mdc_ctx = NULL;
px_memset(st, 0, sizeof(*st));
px_free(st);
}
static struct PullFilterOps mdcbuf_filter = {
mdcbuf_init, mdcbuf_read, mdcbuf_free
};
/*
* Decrypt separate session key
*/
static int
decrypt_key(PGP_Context *ctx, const uint8 *src, int len)
{
int res;
uint8 algo;
PGP_CFB *cfb;
res = pgp_cfb_create(&cfb, ctx->s2k_cipher_algo,
ctx->s2k.key, ctx->s2k.key_len, 0, NULL);
if (res < 0)
return res;
pgp_cfb_decrypt(cfb, src, 1, &algo);
src++;
len--;
pgp_cfb_decrypt(cfb, src, len, ctx->sess_key);
pgp_cfb_free(cfb);
ctx->sess_key_len = len;
ctx->cipher_algo = algo;
if (pgp_get_cipher_key_size(algo) != len)
{
px_debug("sesskey bad len: algo=%d, expected=%d, got=%d",
algo, pgp_get_cipher_key_size(algo), len);
return PXE_PGP_CORRUPT_DATA;
}
return 0;
}
/*
* Handle key packet
*/
static int
parse_symenc_sesskey(PGP_Context *ctx, PullFilter *src)
{
uint8 *p;
int res;
uint8 tmpbuf[PGP_MAX_KEY + 2];
uint8 ver;
GETBYTE(src, ver);
GETBYTE(src, ctx->s2k_cipher_algo);
if (ver != 4)
{
px_debug("bad key pkt ver");
return PXE_PGP_CORRUPT_DATA;
}
/*
* read S2K info
*/
res = pgp_s2k_read(src, &ctx->s2k);
if (res < 0)
return res;
ctx->s2k_mode = ctx->s2k.mode;
ctx->s2k_count = s2k_decode_count(ctx->s2k.iter);
ctx->s2k_digest_algo = ctx->s2k.digest_algo;
/*
* generate key from password
*/
res = pgp_s2k_process(&ctx->s2k, ctx->s2k_cipher_algo,
ctx->sym_key, ctx->sym_key_len);
if (res < 0)
return res;
/*
* do we have separate session key?
*/
res = pullf_read_max(src, PGP_MAX_KEY + 2, &p, tmpbuf);
if (res < 0)
return res;
if (res == 0)
{
/*
* no, s2k key is session key
*/
memcpy(ctx->sess_key, ctx->s2k.key, ctx->s2k.key_len);
ctx->sess_key_len = ctx->s2k.key_len;
ctx->cipher_algo = ctx->s2k_cipher_algo;
res = 0;
ctx->use_sess_key = 0;
}
else
{
/*
* yes, decrypt it
*/
if (res < 17 || res > PGP_MAX_KEY + 1)
{
px_debug("expect key, but bad data");
return PXE_PGP_CORRUPT_DATA;
}
ctx->use_sess_key = 1;
res = decrypt_key(ctx, p, res);
}
px_memset(tmpbuf, 0, sizeof(tmpbuf));
return res;
}
static int
copy_crlf(MBuf *dst, uint8 *data, int len, int *got_cr)
{
uint8 *data_end = data + len;
uint8 tmpbuf[1024];
uint8 *tmp_end = tmpbuf + sizeof(tmpbuf);
uint8 *p;
int res;
p = tmpbuf;
if (*got_cr)
{
if (*data != '\n')
*p++ = '\r';
*got_cr = 0;
}
while (data < data_end)
{
if (*data == '\r')
{
if (data + 1 < data_end)
{
if (*(data + 1) == '\n')
data++;
}
else
{
*got_cr = 1;
break;
}
}
*p++ = *data++;
if (p >= tmp_end)
{
res = mbuf_append(dst, tmpbuf, p - tmpbuf);
if (res < 0)
return res;
p = tmpbuf;
}
}
if (p - tmpbuf > 0)
{
res = mbuf_append(dst, tmpbuf, p - tmpbuf);
if (res < 0)
return res;
}
px_memset(tmpbuf, 0, sizeof(tmpbuf));
return 0;
}
static int
parse_literal_data(PGP_Context *ctx, MBuf *dst, PullFilter *pkt)
{
int type;
int name_len;
int res;
uint8 *buf;
uint8 tmpbuf[4];
int got_cr = 0;
GETBYTE(pkt, type);
GETBYTE(pkt, name_len);
/* skip name */
while (name_len > 0)
{
res = pullf_read(pkt, name_len, &buf);
if (res < 0)
return res;
if (res == 0)
break;
name_len -= res;
}
if (name_len > 0)
{
px_debug("parse_literal_data: unexpected eof");
return PXE_PGP_CORRUPT_DATA;
}
/* skip date */
res = pullf_read_max(pkt, 4, &buf, tmpbuf);
if (res != 4)
{
px_debug("parse_literal_data: unexpected eof");
return PXE_PGP_CORRUPT_DATA;
}
px_memset(tmpbuf, 0, 4);
/*
* If called from an SQL function that returns text, pgp_decrypt() rejects
* inputs not self-identifying as text.
*/
if (ctx->text_mode)
if (type != 't' && type != 'u')
{
px_debug("parse_literal_data: data type=%c", type);
ctx->unexpected_binary = true;
}
ctx->unicode_mode = (type == 'u') ? 1 : 0;
/* read data */
while (1)
{
res = pullf_read(pkt, 32 * 1024, &buf);
if (res <= 0)
break;
if (ctx->text_mode && ctx->convert_crlf)
res = copy_crlf(dst, buf, res, &got_cr);
else
res = mbuf_append(dst, buf, res);
if (res < 0)
break;
}
if (res >= 0 && got_cr)
res = mbuf_append(dst, (const uint8 *) "\r", 1);
return res;
}
/* process_data_packets and parse_compressed_data call each other */
static int process_data_packets(PGP_Context *ctx, MBuf *dst,
PullFilter *src, int allow_compr, int need_mdc);
static int
parse_compressed_data(PGP_Context *ctx, MBuf *dst, PullFilter *pkt)
{
int res;
uint8 type;
PullFilter *pf_decompr;
uint8 *discard_buf;
GETBYTE(pkt, type);
ctx->compress_algo = type;
switch (type)
{
case PGP_COMPR_NONE:
res = process_data_packets(ctx, dst, pkt, NO_COMPR, NO_MDC);
break;
case PGP_COMPR_ZIP:
case PGP_COMPR_ZLIB:
res = pgp_decompress_filter(&pf_decompr, ctx, pkt);
if (res >= 0)
{
res = process_data_packets(ctx, dst, pf_decompr,
NO_COMPR, NO_MDC);
pullf_free(pf_decompr);
}
break;
case PGP_COMPR_BZIP2:
px_debug("parse_compressed_data: bzip2 unsupported");
/* report error in pgp_decrypt() */
ctx->unsupported_compr = 1;
/*
* Discard the compressed data, allowing it to first affect any
* MDC digest computation.
*/
while (1)
{
res = pullf_read(pkt, 32 * 1024, &discard_buf);
if (res <= 0)
break;
}
break;
default:
px_debug("parse_compressed_data: unknown compr type");
res = PXE_PGP_CORRUPT_DATA;
}
return res;
}
static int
process_data_packets(PGP_Context *ctx, MBuf *dst, PullFilter *src,
int allow_compr, int need_mdc)
{
uint8 tag;
int len,
res;
int got_data = 0;
int got_mdc = 0;
PullFilter *pkt = NULL;
while (1)
{
res = pgp_parse_pkt_hdr(src, &tag, &len, ALLOW_CTX_SIZE);
if (res <= 0)
break;
/* mdc packet should be last */
if (got_mdc)
{
px_debug("process_data_packets: data after mdc");
res = PXE_PGP_CORRUPT_DATA;
break;
}
/* context length inside SYMENC_MDC needs special handling */
if (need_mdc && res == PKT_CONTEXT)
res = pullf_create(&pkt, &mdcbuf_filter, ctx, src);
else
res = pgp_create_pkt_reader(&pkt, src, len, res, ctx);
if (res < 0)
break;
switch (tag)
{
case PGP_PKT_LITERAL_DATA:
got_data = 1;
res = parse_literal_data(ctx, dst, pkt);
break;
case PGP_PKT_COMPRESSED_DATA:
if (allow_compr == 0)
{
px_debug("process_data_packets: unexpected compression");
res = PXE_PGP_CORRUPT_DATA;
}
else if (got_data)
{
/*
* compr data must be alone
*/
px_debug("process_data_packets: only one cmpr pkt allowed");
res = PXE_PGP_CORRUPT_DATA;
}
else
{
got_data = 1;
res = parse_compressed_data(ctx, dst, pkt);
}
break;
case PGP_PKT_MDC:
if (need_mdc == NO_MDC)
{
px_debug("process_data_packets: unexpected MDC");
res = PXE_PGP_CORRUPT_DATA;
break;
}
res = mdc_finish(ctx, pkt, len);
if (res >= 0)
got_mdc = 1;
break;
default:
px_debug("process_data_packets: unexpected pkt tag=%d", tag);
res = PXE_PGP_CORRUPT_DATA;
}
pullf_free(pkt);
pkt = NULL;
if (res < 0)
break;
}
if (pkt)
pullf_free(pkt);
if (res < 0)
return res;
if (!got_data)
{
px_debug("process_data_packets: no data");
res = PXE_PGP_CORRUPT_DATA;
}
if (need_mdc && !got_mdc && !ctx->use_mdcbuf_filter)
{
px_debug("process_data_packets: got no mdc");
res = PXE_PGP_CORRUPT_DATA;
}
return res;
}
static int
parse_symenc_data(PGP_Context *ctx, PullFilter *pkt, MBuf *dst)
{
int res;
PGP_CFB *cfb = NULL;
PullFilter *pf_decrypt = NULL;
PullFilter *pf_prefix = NULL;
res = pgp_cfb_create(&cfb, ctx->cipher_algo,
ctx->sess_key, ctx->sess_key_len, 1, NULL);
if (res < 0)
goto out;
res = pullf_create(&pf_decrypt, &pgp_decrypt_filter, cfb, pkt);
if (res < 0)
goto out;
res = pullf_create(&pf_prefix, &prefix_filter, ctx, pf_decrypt);
if (res < 0)
goto out;
res = process_data_packets(ctx, dst, pf_prefix, ALLOW_COMPR, NO_MDC);
out:
if (pf_prefix)
pullf_free(pf_prefix);
if (pf_decrypt)
pullf_free(pf_decrypt);
if (cfb)
pgp_cfb_free(cfb);
return res;
}
static int
parse_symenc_mdc_data(PGP_Context *ctx, PullFilter *pkt, MBuf *dst)
{
int res;
PGP_CFB *cfb = NULL;
PullFilter *pf_decrypt = NULL;
PullFilter *pf_prefix = NULL;
PullFilter *pf_mdc = NULL;
uint8 ver;
GETBYTE(pkt, ver);
if (ver != 1)
{
px_debug("parse_symenc_mdc_data: pkt ver != 1");
return PXE_PGP_CORRUPT_DATA;
}
res = pgp_cfb_create(&cfb, ctx->cipher_algo,
ctx->sess_key, ctx->sess_key_len, 0, NULL);
if (res < 0)
goto out;
res = pullf_create(&pf_decrypt, &pgp_decrypt_filter, cfb, pkt);
if (res < 0)
goto out;
res = pullf_create(&pf_mdc, &mdc_filter, ctx, pf_decrypt);
if (res < 0)
goto out;
res = pullf_create(&pf_prefix, &prefix_filter, ctx, pf_mdc);
if (res < 0)
goto out;
res = process_data_packets(ctx, dst, pf_prefix, ALLOW_COMPR, NEED_MDC);
out:
if (pf_prefix)
pullf_free(pf_prefix);
if (pf_mdc)
pullf_free(pf_mdc);
if (pf_decrypt)
pullf_free(pf_decrypt);
if (cfb)
pgp_cfb_free(cfb);
return res;
}
/*
* skip over packet contents
*/
int
pgp_skip_packet(PullFilter *pkt)
{
int res = 1;
uint8 *tmp;
while (res > 0)
res = pullf_read(pkt, 32 * 1024, &tmp);
return res;
}
/*
* expect to be at packet end, any data is error
*/
int
pgp_expect_packet_end(PullFilter *pkt)
{
int res;
uint8 *tmp;
res = pullf_read(pkt, 32 * 1024, &tmp);
if (res > 0)
{
px_debug("pgp_expect_packet_end: got data");
return PXE_PGP_CORRUPT_DATA;
}
return res;
}
int
pgp_decrypt(PGP_Context *ctx, MBuf *msrc, MBuf *mdst)
{
int res;
PullFilter *src = NULL;
PullFilter *pkt = NULL;
uint8 tag;
int len;
int got_key = 0;
int got_data = 0;
res = pullf_create_mbuf_reader(&src, msrc);
while (res >= 0)
{
res = pgp_parse_pkt_hdr(src, &tag, &len, NO_CTX_SIZE);
if (res <= 0)
break;
res = pgp_create_pkt_reader(&pkt, src, len, res, ctx);
if (res < 0)
break;
res = PXE_PGP_CORRUPT_DATA;
switch (tag)
{
case PGP_PKT_MARKER:
res = pgp_skip_packet(pkt);
break;
case PGP_PKT_PUBENCRYPTED_SESSKEY:
/* fixme: skip those */
res = pgp_parse_pubenc_sesskey(ctx, pkt);
got_key = 1;
break;
case PGP_PKT_SYMENCRYPTED_SESSKEY:
if (got_key)
/*
* Theoretically, there could be several keys, both public
* and symmetric, all of which encrypt same session key.
* Decrypt should try with each one, before failing.
*/
px_debug("pgp_decrypt: using first of several keys");
else
{
got_key = 1;
res = parse_symenc_sesskey(ctx, pkt);
}
break;
case PGP_PKT_SYMENCRYPTED_DATA:
if (!got_key)
px_debug("pgp_decrypt: have data but no key");
else if (got_data)
px_debug("pgp_decrypt: got second data packet");
else
{
got_data = 1;
ctx->disable_mdc = 1;
res = parse_symenc_data(ctx, pkt, mdst);
}
break;
case PGP_PKT_SYMENCRYPTED_DATA_MDC:
if (!got_key)
px_debug("pgp_decrypt: have data but no key");
else if (got_data)
px_debug("pgp_decrypt: several data pkts not supported");
else
{
got_data = 1;
ctx->disable_mdc = 0;
res = parse_symenc_mdc_data(ctx, pkt, mdst);
}
break;
default:
px_debug("pgp_decrypt: unknown tag: 0x%02x", tag);
}
pullf_free(pkt);
pkt = NULL;
}
if (pkt)
pullf_free(pkt);
if (src)
pullf_free(src);
if (res < 0)
return res;
/*
* Report a failure of the prefix_init() "quick check" now, rather than
* upon detection, to hinder timing attacks. pgcrypto is not generally
* secure against timing attacks, but this helps.
*/
if (!got_data || ctx->corrupt_prefix)
return PXE_PGP_CORRUPT_DATA;
/*
* Code interpreting purportedly-decrypted data prior to this stage shall
* report no error other than PXE_PGP_CORRUPT_DATA. (PXE_BUG is okay so
* long as it remains unreachable.) This ensures that an attacker able to
* choose a ciphertext and receive a corresponding decryption error
* message cannot use that oracle to gather clues about the decryption
* key. See "An Attack on CFB Mode Encryption As Used By OpenPGP" by
* Serge Mister and Robert Zuccherato.
*
* A problematic value in the first octet of a Literal Data or Compressed
* Data packet may indicate a simple user error, such as the need to call
* pgp_sym_decrypt_bytea instead of pgp_sym_decrypt. Occasionally,
* though, it is the first symptom of the encryption key not matching the
* decryption key. When this was the only problem encountered, report a
* specific error to guide the user; otherwise, we will have reported
* PXE_PGP_CORRUPT_DATA before now. A key mismatch makes the other errors
* into red herrings, and this avoids leaking clues to attackers.
*/
if (ctx->unsupported_compr)
return PXE_PGP_UNSUPPORTED_COMPR;
if (ctx->unexpected_binary)
return PXE_PGP_NOT_TEXT;
return res;
}
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