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57caafa433
gnupg/g10/armor.c
Werner Koch 57caafa433 Rewritten
1998-01-27 12:32:28 +00:00

800 lines
19 KiB
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/* armor.c - Armor filter
* Copyright (c) 1997 by Werner Koch (dd9jn)
*
* This file is part of G10.
*
* G10 is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* G10 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include "errors.h"
#include "iobuf.h"
#include "memory.h"
#include "util.h"
#include "filter.h"
#include "packet.h"
#include "options.h"
#define CRCINIT 0xB704CE
#define CRCPOLY 0X864CFB
#define CRCUPDATE(a,c) do { \
a = ((a) << 8) ^ crc_table[((a)&0xff >> 16) ^ (c)]; \
a &= 0x00ffffff; \
} while(0)
static u32 crc_table[256];
static byte bintoasc[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";
static byte asctobin[256]; /* runtime initialized */
static int is_initialized;
typedef enum {
fhdrHASArmor,
fhdrNOArmor,
fhdrINIT,
fhdrINITCont,
fhdrINITSkip,
fhdrCHECKBegin,
fhdrWAITHeader,
fhdrWAITClearsig,
fhdrSKIPHeader,
fhdrCLEARSIG,
fhdrREADClearsig,
fhdrEMPTYClearsig,
fhdrCHECKClearsig,
fhdrCHECKClearsig2,
fhdrREADClearsigNext,
fhdrENDClearsig,
fhdrTEXT,
fhdrERROR,
fhdrERRORShow,
fhdrEOF
} fhdr_state_t;
/* if we encounter this armor string with this index, go
* into a mode, which fakes packets and wait for the next armor */
#define BEGIN_SIGNED_MSG_IDX 3
static char *head_strings[] = {
"BEGIN PGP MESSAGE",
"BEGIN PGP PUBLIC KEY BLOCK",
"BEGIN PGP SIGNATURE",
"BEGIN PGP SIGNED MESSAGE",
NULL
};
static char *tail_strings[] = {
"END PGP MESSAGE",
"END PGP PUBLIC KEY BLOCK",
"END PGP SIGNATURE",
NULL
};
static fhdr_state_t find_header( fhdr_state_t state,
byte *buf, size_t *r_buflen, IOBUF a, size_t n);
static void
initialize(void)
{
int i, j;
u32 t;
byte *s;
/* init the crc lookup table */
crc_table[0] = 0;
for(i=j=0; j < 128; j++ ) {
t = crc_table[j];
if( t & 0x00800000 ) {
t <<= 1;
crc_table[i++] = t ^ CRCPOLY;
crc_table[i++] = t;
}
else {
t <<= 1;
crc_table[i++] = t;
crc_table[i++] = t ^ CRCPOLY;
}
}
/* build the helptable for radix64 to bin conversion */
for(i=0; i < 256; i++ )
asctobin[i] = 255; /* used to detect invalid characters */
for(s=bintoasc,i=0; *s; s++,i++ )
asctobin[*s] = i;
is_initialized=1;
}
/****************
* Check wether this is a armored file or not
* See also parse-packet.c for details on this code
* Returns: True if it seems to be armored
*/
static int
is_armored( byte *buf )
{
int ctb, pkttype;
ctb = *buf;
if( !(ctb & 0x80) )
return 1; /* invalid packet: assume it is armored */
pkttype = ctb & 0x40 ? (ctb & 0x3f) : ((ctb>>2)&0xf);
switch( pkttype ) {
case PKT_PUBLIC_CERT:
case PKT_SECRET_CERT:
case PKT_PUBKEY_ENC:
case PKT_SIGNATURE:
case PKT_COMMENT:
case PKT_PLAINTEXT:
case PKT_COMPRESSED:
case PKT_ENCRYPTED:
return 0; /* seems to be a regular packet: not armored */
}
return 1;
}
/****************
* parse an ascii armor.
* Returns: the state,
* the remaining bytes in BUF are returned in RBUFLEN.
*/
static fhdr_state_t
find_header( fhdr_state_t state, byte *buf, size_t *r_buflen, IOBUF a, size_t n)
{
int c, i;
const char *s;
char *p;
size_t buflen;
int cont;
int clearsig=0;
int hdr_line=0;
buflen = *r_buflen;
assert(buflen >= 100 );
buflen--;
do {
switch( state ) {
case fhdrHASArmor:
/* read 28 bytes, which is the bare minimum for a BEGIN...
* and check wether this has a Armor. */
c = 0;
for(n=0; n < 28 && (c=iobuf_get(a)) != -1 && c != '\n'; )
buf[n++] = c;
if( n < 28 || c == -1 )
state = fhdrNOArmor; /* too short */
else if( !is_armored( buf ) )
state = fhdrNOArmor;
else
state = fhdrINITCont;
break;
case fhdrINIT: /* read some stuff into buffer */
n = 0;
case fhdrINITCont: /* read more stuff into buffer */
c = 0;
for(; n < buflen && (c=iobuf_get(a)) != -1 && c != '\n'; )
buf[n++] = c;
state = c == '\n' ? fhdrCHECKBegin :
c == -1 ? fhdrEOF : fhdrINITSkip;
break;
case fhdrINITSkip:
while( (c=iobuf_get(a)) != -1 && c != '\n' )
;
state = c == -1? fhdrEOF : fhdrINIT;
break;
case fhdrSKIPHeader:
while( (c=iobuf_get(a)) != -1 && c != '\n' )
;
state = c == -1? fhdrEOF : fhdrWAITHeader;
break;
case fhdrWAITHeader: /* wait for Header lines */
c = 0;
for(n=0; n < buflen && (c=iobuf_get(a)) != -1 && c != '\n'; )
buf[n++] = c;
buf[n] = 0;
if( n < buflen || c == '\n' ) {
if( n && buf[0] != '\r') { /* maybe a header */
if( strchr( buf, ':') ) { /* yes */
log_debug("armor header: ");
print_string( stderr, buf, n );
putc('\n', stderr);
state = fhdrWAITHeader;
}
else
state = fhdrTEXT;
}
else if( !n || (buf[0] == '\r' && !buf[1]) ) { /* empty line */
if( clearsig )
state = fhdrWAITClearsig;
else {
/* this is not really correct: if we do not have
* a clearsig and not armor lines we are not allowed
* to have an empty line */
n = 0;
state = fhdrTEXT;
}
}
else {
log_debug("invalid armor header: ");
print_string( stderr, buf, n );
putc('\n', stderr);
state = fhdrERROR;
}
}
else if( c != -1 ) {
if( strchr( buf, ':') ) { /* buffer to short, but this is okay*/
log_debug("armor header: ");
print_string( stderr, buf, n );
fputs("[...]\n", stderr); /* indicate it is truncated */
state = fhdrSKIPHeader; /* skip rest of line */
}
else /* line too long */
state = fhdrERROR;
}
else
state = fhdrEOF;
break;
case fhdrWAITClearsig: /* skip all empty lines (for clearsig) */
c = 0;
for(n=0; n < buflen && (c=iobuf_get(a)) != -1 && c != '\n'; )
buf[n++] = c;
if( n < buflen || c == '\n' ) {
buf[n] = 0;
if( !n || (buf[0]=='\r' && !buf[1]) ) /* empty line */
;
else
state = fhdrTEXT;
}
else
state = fhdrEOF;
break;
case fhdrENDClearsig:
case fhdrCHECKBegin:
state = state == fhdrCHECKBegin ? fhdrINITSkip : fhdrERRORShow;
if( n < 15 )
break; /* too short */
if( memcmp( buf, "-----", 5 ) )
break;
buf[n] = 0;
p = strstr(buf+5, "-----");
if( !p )
break;
*p = 0;
p += 5;
if( *p == '\r' )
p++;
if( *p )
break; /* garbage after dashes */
p = buf+5;
for(i=0; (s=head_strings[i]); i++ )
if( !strcmp(s, p) )
break;
if( !s )
break; /* unknown begin line */
/* found the begin line */
hdr_line = i;
state = fhdrWAITHeader;
if( hdr_line == BEGIN_SIGNED_MSG_IDX )
clearsig = 1;
log_debug("armor: %s\n", head_strings[hdr_line]);
break;
case fhdrCLEARSIG:
case fhdrEMPTYClearsig:
case fhdrREADClearsig:
/* we are at the start of a line: read a clearsig into the buffer
* we have to look for a the header line or dashd escaped text*/
n = 0;
c = 0;
for(; n < buflen && (c=iobuf_get(a)) != -1 && c != '\n'; )
buf[n++] = c;
buf[n] = 0;
if( c == -1 )
state = fhdrEOF;
else if( !n || ( buf[0]=='\r' && !buf[1] ) ) {
state = fhdrEMPTYClearsig;
/* FIXME: handle it */
}
else if( c == '\n' )
state = fhdrCHECKClearsig2;
else
state = fhdrCHECKClearsig;
break;
case fhdrCHECKClearsig:
case fhdrCHECKClearsig2:
/* check the clearsig line */
if( n > 15 && !memcmp(buf, "-----", 5 ) )
state = fhdrENDClearsig;
else if( buf[0] == '-' && buf[1] == ' ' ) {
/* dash escaped line */
if( buf[2] == '-' || ( n > 6 && !memcmp(buf+2, "From ", 5))) {
for(i=2; i < n; i++ )
buf[i-2] = buf[i];
n -= 2;
buf[n] = 0; /* not really needed */
state = state == fhdrCHECKClearsig2 ?
fhdrREADClearsig : fhdrREADClearsigNext;
/* FIXME: add the lf to the buffer */
}
else {
log_debug("invalid dash escaped line: ");
print_string( stderr, buf, n );
putc('\n', stderr);
state = fhdrERROR;
}
}
else {
state = state == fhdrCHECKClearsig2 ?
fhdrREADClearsig : fhdrREADClearsigNext;
/* FIXME: add the lf to the buffer */
}
break;
case fhdrREADClearsigNext:
/* Read to the end of the line, do not care about checking
* for dashed escaped text of headers */
break;
case fhdrERRORShow:
log_debug("invalid clear text header: ");
print_string( stderr, buf, n );
putc('\n', stderr);
state = fhdrERROR;
break;
default: BUG();
}
switch( state ) {
case fhdrINIT:
case fhdrINITCont:
case fhdrINITSkip:
case fhdrCHECKBegin:
case fhdrWAITHeader:
case fhdrWAITClearsig:
case fhdrSKIPHeader:
case fhdrEMPTYClearsig:
case fhdrCHECKClearsig:
case fhdrCHECKClearsig2:
case fhdrERRORShow:
cont = 1;
break;
default: cont = 0;
}
} while( cont );
if( clearsig && state == fhdrTEXT )
state = fhdrCLEARSIG;
*r_buflen = n;
return state;
}
/* figure out wether the data is armored or not */
static int
check_input( armor_filter_context_t *afx, IOBUF a )
{
int rc = 0;
size_t n;
fhdr_state_t state = afx->parse_state;
if( state != fhdrENDClearsig )
state = fhdrHASArmor;
n = DIM(afx->helpbuf);
state = find_header( state, afx->helpbuf, &n, a, afx->helplen );
switch( state ) {
case fhdrNOArmor:
afx->inp_checked = 1;
afx->inp_bypass = 1;
afx->helplen = n;
break;
case fhdrERROR:
case fhdrEOF:
rc = -1;
break;
case fhdrCLEARSIG: /* start fake package mode (for clear signatures) */
afx->helplen = n;
afx->helpidx = 0;
afx->faked = 1;
break;
case fhdrTEXT:
afx->helplen = n;
afx->helpidx = 0;
afx->inp_checked = 1;
afx->crc = CRCINIT;
afx->idx = 0;
afx->radbuf[0] = 0;
break;
default: BUG();
}
afx->parse_state = state;
return rc;
}
/* fake a literal data packet and wait for an armor line */
static int
fake_packet( armor_filter_context_t *afx, IOBUF a,
size_t *retn, byte *buf, size_t size )
{
int rc = 0;
size_t len = 0;
size_t n, nn;
fhdr_state_t state = afx->parse_state;
size = 100; /* FIXME: only used for testing (remove it) */
len = 2; /* reserve 2 bytes for the length header */
size -= 2; /* and 2 for the term header */
while( !rc && len < size ) {
if( afx->helpidx < afx->helplen ) { /* flush the last buffer */
n = afx->helplen;
for(nn=afx->helpidx; len < size && nn < n ; nn++ )
buf[len++] = afx->helpbuf[nn];
afx->helpidx = nn;
continue;
}
if( state == fhdrEOF ) {
rc = -1;
continue;
}
/* read a new one */
n = DIM(afx->helpbuf);
afx->helpidx = 0;
state = find_header( state, afx->helpbuf, &n, a, 0 );
switch( state) {
case fhdrERROR:
case fhdrEOF:
rc = -1;
break;
case fhdrCLEARSIG:
case fhdrREADClearsig:
case fhdrREADClearsigNext:
afx->helplen = n;
break;
case fhdrENDClearsig:
afx->helplen = n;
afx->faked = 0;
rc = -1;
break;
default: BUG();
}
}
buf[0] = (len-2) >> 8;
buf[1] = (len-2);
if( state == fhdrENDClearsig ) { /* write last (ending) length header */
buf[len++] = 0;
buf[len++] = 0;
rc = 0;
}
afx->parse_state = state;
*retn = len;
return rc;
}
static int
radix64_read( armor_filter_context_t *afx, IOBUF a, size_t *retn,
byte *buf, size_t size )
{
byte val;
int c, c2;
int checkcrc=0;
int rc = 0;
size_t n = 0;
int idx, i;
u32 crc;
crc = afx->crc;
idx = afx->idx;
val = afx->radbuf[0];
for( n=0; n < size; ) {
if( afx->helpidx < afx->helplen )
c = afx->helpbuf[afx->helpidx++];
else if( (c=iobuf_get(a)) == -1 )
break;
if( c == '\n' || c == ' ' || c == '\r' || c == '\t' )
continue;
else if( c == '=' ) { /* pad character: stop */
if( idx == 1 )
buf[n++] = val;
checkcrc++;
break;
}
else if( (c = asctobin[(c2=c)]) == 255 ) {
log_error("invalid radix64 character %02x skipped\n", c2);
continue;
}
switch(idx) {
case 0: val = c << 2; break;
case 1: val |= (c>>4)&3; buf[n++]=val;val=(c<<4)&0xf0;break;
case 2: val |= (c>>2)&15; buf[n++]=val;val=(c<<6)&0xc0;break;
case 3: val |= c&0x3f; buf[n++] = val; break;
}
idx = (idx+1) % 4;
}
for(i=0; i < n; i++ )
crc = (crc << 8) ^ crc_table[((crc >> 16)&0xff) ^ buf[i]];
crc &= 0x00ffffff;
afx->crc = crc;
afx->idx = idx;
afx->radbuf[0] = val;
if( checkcrc ) {
afx->inp_eof = 1; /*assume eof */
for(;;) { /* skip lf and pad characters */
if( afx->helpidx < afx->helplen )
c = afx->helpbuf[afx->helpidx++];
else if( (c=iobuf_get(a)) == -1 )
break;
if( c == '\n' || c == ' ' || c == '\r'
|| c == '\t' || c == '=' )
continue;
break;
}
if( c == -1 )
log_error("premature eof (no CRC)\n");
else {
u32 mycrc = 0;
idx = 0;
do {
if( (c = asctobin[c]) == 255 )
break;
switch(idx) {
case 0: val = c << 2; break;
case 1: val |= (c>>4)&3; mycrc |= val << 16;val=(c<<4)&0xf0;break;
case 2: val |= (c>>2)&15; mycrc |= val << 8;val=(c<<6)&0xc0;break;
case 3: val |= c&0x3f; mycrc |= val; break;
}
if( afx->helpidx < afx->helplen )
c = afx->helpbuf[afx->helpidx++];
else if( (c=iobuf_get(a)) == -1 )
break;
} while( ++idx < 4 );
if( c == -1 )
log_error("premature eof (in CRC)\n");
else if( idx != 4 )
log_error("malformed CRC\n");
else if( mycrc != afx->crc )
log_error("CRC error; %06lx - %06lx\n",
(ulong)afx->crc, (ulong)mycrc);
else {
for(rc=0;!rc;) {
rc = 0 /*check_trailer( &fhdr, c )*/;
if( !rc ) {
if( afx->helpidx < afx->helplen )
c = afx->helpbuf[afx->helpidx++];
else if( (c=iobuf_get(a)) == -1 )
rc = 2;
}
}
if( rc == -1 )
rc = 0;
else if( rc == 2 )
log_error("premature eof (in Trailer)\n");
else
log_error("error in trailer line\n");
}
}
}
if( !n )
rc = -1;
*retn = n;
return rc;
}
/****************
* The filter is used to handle the armor stuff
*/
int
armor_filter( void *opaque, int control,
IOBUF a, byte *buf, size_t *ret_len)
{
size_t size = *ret_len;
armor_filter_context_t *afx = opaque;
int rc=0, i, c;
byte radbuf[3];
int idx, idx2;
size_t n=0;
u32 crc;
if( DBG_FILTER )
log_debug("armor-filter: control: %d\n", control );
if( control == IOBUFCTRL_UNDERFLOW && afx->inp_bypass ) {
for( n=0; n < size; n++ ) {
if( (c=iobuf_get(a)) == -1 )
break;
buf[n] = c & 0xff;
}
if( !n )
rc = -1;
*ret_len = n;
}
else if( control == IOBUFCTRL_UNDERFLOW ) {
if( size < 20 )
BUG(); /* supplied buffer maybe too short */
if( afx->inp_eof ) {
*ret_len = 0;
if( DBG_FILTER )
log_debug("armor-filter: eof due to inp_eof flag\n" );
return -1;
}
if( afx->faked )
rc = fake_packet( afx, a, &n, buf, size );
else if( !afx->inp_checked ) {
rc = check_input( afx, a );
if( afx->inp_bypass )
;
else if( afx->faked ) {
/* the buffer is at least 20 bytes long, so it
* is easy to construct a packet */
buf[0] = 0xaf; /* old packet format, type 11, var length */
buf[1] = 0; /* set the length header */
buf[2] = 6;
buf[3] = 't'; /* canonical text */
buf[4] = 0; /* namelength */
buf[5] = buf[6] = buf[7] = buf[8] = 0; /* timestamp */
n = 9;
}
else if( !rc )
rc = radix64_read( afx, a, &n, buf, size );
}
else
rc = radix64_read( afx, a, &n, buf, size );
*ret_len = n;
}
else if( control == IOBUFCTRL_FLUSH ) {
if( !afx->status ) { /* write the header line */
if( afx->what >= DIM(head_strings) )
log_bug("afx->what=%d", afx->what);
iobuf_writestr(a, "-----");
iobuf_writestr(a, head_strings[afx->what] );
iobuf_writestr(a, "-----\n");
iobuf_writestr(a, "Version: G10 pre-release " VERSION "\n");
iobuf_writestr(a, "Comment: This is a alpha test version!\n\n");
afx->status++;
afx->idx = 0;
afx->idx2 = 0;
afx->crc = CRCINIT;
}
crc = afx->crc;
idx = afx->idx;
idx2 = afx->idx2;
for(i=0; i < idx; i++ )
radbuf[i] = afx->radbuf[i];
for(i=0; i < size; i++ )
crc = (crc << 8) ^ crc_table[((crc >> 16)&0xff) ^ buf[i]];
crc &= 0x00ffffff;
for( ; size; buf++, size-- ) {
radbuf[idx++] = *buf;
if( idx > 2 ) {
idx = 0;
c = bintoasc[(*radbuf >> 2) & 077];
iobuf_put(a, c);
c = bintoasc[(((*radbuf<<4)&060)|((radbuf[1] >> 4)&017))&077];
iobuf_put(a, c);
c = bintoasc[(((radbuf[1]<<2)&074)|((radbuf[2]>>6)&03))&077];
iobuf_put(a, c);
c = bintoasc[radbuf[2]&077];
iobuf_put(a, c);
if( ++idx2 > (72/4) ) {
iobuf_put(a, '\n');
idx2=0;
}
}
}
for(i=0; i < idx; i++ )
afx->radbuf[i] = radbuf[i];
afx->idx = idx;
afx->idx2 = idx2;
afx->crc = crc;
}
else if( control == IOBUFCTRL_INIT ) {
if( !is_initialized )
initialize();
}
else if( control == IOBUFCTRL_FREE ) {
if( afx->status ) { /* pad, write cecksum, and bottom line */
crc = afx->crc;
idx = afx->idx;
idx2 = afx->idx2;
for(i=0; i < idx; i++ )
radbuf[i] = afx->radbuf[i];
if( idx ) {
c = bintoasc[(*radbuf>>2)&077];
iobuf_put(a, c);
if( idx == 1 ) {
c = bintoasc[((*radbuf << 4) & 060) & 077];
iobuf_put(a, c);
iobuf_put(a, '=');
iobuf_put(a, '=');
}
else { /* 2 */
c = bintoasc[(((*radbuf<<4)&060)|((radbuf[1]>>4)&017))&077];
iobuf_put(a, c);
c = bintoasc[((radbuf[1] << 2) & 074) & 077];
iobuf_put(a, c);
iobuf_put(a, '=');
}
++idx2;
}
/* may need a linefeed */
if( idx2 < (72/4) )
iobuf_put(a, '\n');
/* write the CRC */
iobuf_put(a, '=');
radbuf[0] = crc >>16;
radbuf[1] = crc >> 8;
radbuf[2] = crc;
c = bintoasc[(*radbuf >> 2) & 077];
iobuf_put(a, c);
c = bintoasc[(((*radbuf<<4)&060)|((radbuf[1] >> 4)&017))&077];
iobuf_put(a, c);
c = bintoasc[(((radbuf[1]<<2)&074)|((radbuf[2]>>6)&03))&077];
iobuf_put(a, c);
c = bintoasc[radbuf[2]&077];
iobuf_put(a, c);
iobuf_put(a, '\n');
/* and the the trailer */
if( afx->what >= DIM(tail_strings) )
log_bug("afx->what=%d", afx->what);
iobuf_writestr(a, "-----");
iobuf_writestr(a, tail_strings[afx->what] );
iobuf_writestr(a, "-----\n");
}
}
else if( control == IOBUFCTRL_DESC )
*(char**)buf = "armor_filter";
return rc;
}
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