/*
 * Copyright (c) 2005-2008 Nominet UK (www.nic.uk)
 * All rights reserved.
 * Contributors: Ben Laurie, Rachel Willmer. The Contributors have asserted
 * their moral rights under the UK Copyright Design and Patents Act 1988 to
 * be recorded as the authors of this copyright work.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. 
 * 
 * You may obtain a copy of the License at 
 *     http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
 * 
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/** \file
 * \brief Code for dealing with ASCII-armoured packets
 */

#include <openpgpsdk/errors.h>
#include <openpgpsdk/callback.h>
#include <openpgpsdk/configure.h>
#include <openpgpsdk/armour.h>
#include <openpgpsdk/util.h>
#include <openpgpsdk/crypto.h>
#include <openpgpsdk/create.h>
#include <openpgpsdk/readerwriter.h>
#include <openpgpsdk/signature.h>
#include <openpgpsdk/version.h>
#include <openpgpsdk/hash.h>
#include <openpgpsdk/packet-parse.h>
#include "parse_local.h"

#include <string.h>

#include <openpgpsdk/final.h>

static int debug=0;

#define CRC24_POLY 0x1864cfbL

/**
 * \struct dearmour_arg_t
 */
typedef struct
    {
    enum
	{
	OUTSIDE_BLOCK=0,
	BASE64,
	AT_TRAILER_NAME,
	} state;

    enum
        {
        NONE=0,
        BEGIN_PGP_MESSAGE,
        BEGIN_PGP_PUBLIC_KEY_BLOCK,
        BEGIN_PGP_PRIVATE_KEY_BLOCK,
        BEGIN_PGP_MULTI,
        BEGIN_PGP_SIGNATURE,

        END_PGP_MESSAGE,
        END_PGP_PUBLIC_KEY_BLOCK,
        END_PGP_PRIVATE_KEY_BLOCK,
        END_PGP_MULTI,
        END_PGP_SIGNATURE,

        BEGIN_PGP_SIGNED_MESSAGE
        } lastseen;

    ops_parse_info_t *parse_info;
    ops_boolean_t seen_nl:1;
    ops_boolean_t prev_nl:1;
    ops_boolean_t allow_headers_without_gap:1; /*!< allow headers in
						  armoured data that
						  are not separated
						  from the data by a
						  blank line */
    ops_boolean_t allow_no_gap:1; /*!< allow no blank line at the
				       start of armoured data */
    ops_boolean_t allow_trailing_whitespace:1; /*!< allow armoured
						 stuff to have
						 trailing whitespace
						 where we wouldn't
						 strictly expect it */

    // it is an error to get a cleartext message without a sig
    ops_boolean_t expect_sig:1;
    ops_boolean_t got_sig:1;

    // base64 stuff
    unsigned buffered;
    unsigned char buffer[3];
    ops_boolean_t eof64;
    unsigned long checksum;
    unsigned long read_checksum;
    // unarmoured text blocks
    unsigned char unarmoured[8192];
    size_t num_unarmoured;
    // pushed back data (stored backwards)
    unsigned char *pushed_back;
    unsigned npushed_back;
    // armoured block headers
    ops_headers_t headers;
    } dearmour_arg_t;

static void push_back(dearmour_arg_t *arg,const unsigned char *buf, unsigned length)
{
	unsigned n;

	//ASSERT(!arg->pushed_back); // in the least, there will be a memory leak. Not a big issue.
	arg->pushed_back=malloc(length);
	for(n=0 ; n < length ; ++n)
		arg->pushed_back[n]=buf[length-n-1];
	arg->npushed_back=length;
}
    
static int set_lastseen_headerline(dearmour_arg_t* arg, char* buf, ops_error_t **errors)
    {
    char* begin_msg="BEGIN PGP MESSAGE";
    char* begin_public="BEGIN PGP PUBLIC KEY BLOCK";
    char* begin_private="BEGIN PGP PRIVATE KEY BLOCK";
    char* begin_multi="BEGIN PGP MESSAGE, PART ";
    char* begin_sig="BEGIN PGP SIGNATURE";

    char* end_msg="END PGP MESSAGE";
    char* end_public="END PGP PUBLIC KEY BLOCK";
    char* end_private="END PGP PRIVATE KEY BLOCK";
    char* end_multi="END PGP MESSAGE, PART ";
    char* end_sig="END PGP SIGNATURE";

    char* begin_signed_msg="BEGIN PGP SIGNED MESSAGE";

    int prev=arg->lastseen;

    if (!strncmp(buf,begin_msg,strlen(begin_msg)))
        arg->lastseen=BEGIN_PGP_MESSAGE;
    else if (!strncmp(buf,begin_public,strlen(begin_public)))
        arg->lastseen=BEGIN_PGP_PUBLIC_KEY_BLOCK;
    else if (!strncmp(buf,begin_private,strlen(begin_private)))
        arg->lastseen=BEGIN_PGP_PRIVATE_KEY_BLOCK;
    else if (!strncmp(buf,begin_multi,strlen(begin_multi)))
        arg->lastseen=BEGIN_PGP_MULTI;
    else if (!strncmp(buf,begin_sig,strlen(begin_sig)))
        arg->lastseen=BEGIN_PGP_SIGNATURE;

    else if (!strncmp(buf,end_msg,strlen(end_msg)))
        arg->lastseen=END_PGP_MESSAGE;
    else if (!strncmp(buf,end_public,strlen(end_public)))
        arg->lastseen=END_PGP_PUBLIC_KEY_BLOCK;
    else if (!strncmp(buf,end_private,strlen(end_private)))
        arg->lastseen=END_PGP_PRIVATE_KEY_BLOCK;
    else if (!strncmp(buf,end_multi,strlen(end_multi)))
        arg->lastseen=END_PGP_MULTI;
    else if (!strncmp(buf,end_sig,strlen(end_sig)))
        arg->lastseen=END_PGP_SIGNATURE;

    else if (!strncmp(buf,begin_signed_msg,strlen(begin_signed_msg)))
        arg->lastseen=BEGIN_PGP_SIGNED_MESSAGE;

    else
        {
        OPS_ERROR_1(errors,OPS_E_R_BAD_FORMAT,"Unrecognised Header Line %s", buf);
        return 0;
        }

    if (debug)
        printf("set header: buf=%s, arg->lastseen=%d, prev=%d\n", buf, arg->lastseen, prev);

    switch (arg->lastseen) 
        {
    case NONE:
        OPS_ERROR_1(errors,OPS_E_R_BAD_FORMAT,"Unrecognised last seen Header Line %s", buf);
        break;

    case END_PGP_MESSAGE:
        if (prev!=BEGIN_PGP_MESSAGE)
            OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Got END PGP MESSAGE, but not after BEGIN");
        break;

    case END_PGP_PUBLIC_KEY_BLOCK:
        if (prev!=BEGIN_PGP_PUBLIC_KEY_BLOCK)
            OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Got END PGP PUBLIC KEY BLOCK, but not after BEGIN");
        break;

    case END_PGP_PRIVATE_KEY_BLOCK:
        if (prev!=BEGIN_PGP_PRIVATE_KEY_BLOCK)
            OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Got END PGP PRIVATE KEY BLOCK, but not after BEGIN");
        break;

    case BEGIN_PGP_MULTI:
    case END_PGP_MULTI:
            OPS_ERROR(errors,OPS_E_R_UNSUPPORTED,"Multi-part messages are not yet supported");
        break;

    case END_PGP_SIGNATURE:
        if (prev!=BEGIN_PGP_SIGNATURE)
            OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Got END PGP SIGNATURE, but not after BEGIN");
        break;

    case BEGIN_PGP_MESSAGE:
    case BEGIN_PGP_PUBLIC_KEY_BLOCK:
    case BEGIN_PGP_PRIVATE_KEY_BLOCK:
    case BEGIN_PGP_SIGNATURE:
    case BEGIN_PGP_SIGNED_MESSAGE:
        break;
        }

    return 1;
    }

static int read_char(dearmour_arg_t *arg,ops_error_t **errors,
		     ops_reader_info_t *rinfo,
		     ops_parse_cb_info_t *cbinfo,
		     ops_boolean_t skip)
    {
    unsigned char c[1];

    do
	{
	if(arg->npushed_back)
	    {
	    c[0]=arg->pushed_back[--arg->npushed_back];
	    if(!arg->npushed_back)
		{
		free(arg->pushed_back);
		arg->pushed_back=NULL;
		}
	    }
	/* XXX: should ops_stacked_read exist? Shouldn't this be a limited_read? */
	else if(ops_stacked_read(c,1,errors,rinfo,cbinfo) != 1)
	    return -1;
	}
    while(skip && c[0] == '\r');

    arg->prev_nl=arg->seen_nl;
    arg->seen_nl=c[0] == '\n';

    return c[0];
    }

static int eat_whitespace(int first,
			  dearmour_arg_t *arg,ops_error_t **errors,
			  ops_reader_info_t *rinfo,
			  ops_parse_cb_info_t *cbinfo,
			  ops_boolean_t skip)
    {
    int c=first;

    while(c == ' ' || c == '\t')
	c=read_char(arg,errors,rinfo,cbinfo,skip);

    return c;
    }

static int read_and_eat_whitespace(dearmour_arg_t *arg,
				   ops_error_t **errors,
				   ops_reader_info_t *rinfo,
				   ops_parse_cb_info_t *cbinfo,
				   ops_boolean_t skip)
    {
    int c;

    do
	c=read_char(arg,errors,rinfo,cbinfo,skip);
    while(c == ' ' || c == '\t');

    return c;
    }

static void flush(dearmour_arg_t *arg,ops_parse_cb_info_t *cbinfo)
    {
    ops_parser_content_t content;

    if(arg->num_unarmoured == 0)
	return;

    content.content.unarmoured_text.data=arg->unarmoured;
    content.content.unarmoured_text.length=arg->num_unarmoured;
    CB(cbinfo,OPS_PTAG_CT_UNARMOURED_TEXT,&content);
    arg->num_unarmoured=0;
    }

static int unarmoured_read_char(dearmour_arg_t *arg,ops_error_t **errors,
				ops_reader_info_t *rinfo,
				ops_parse_cb_info_t *cbinfo,
				ops_boolean_t skip)
    {
    int c;

    do
	{
	c=read_char(arg,errors,rinfo,cbinfo,ops_false);
	if(c < 0)
	    return c;
	arg->unarmoured[arg->num_unarmoured++]=c;
	if(arg->num_unarmoured == sizeof arg->unarmoured)
	    flush(arg,cbinfo);
	}
    while(skip && c == '\r');

    return c;
    }

/**
 * \param headers
 * \param key
 *
 * \return header value if found, otherwise NULL
 */
const char *ops_find_header(ops_headers_t *headers,const char *key)
    {
    unsigned n;

    for(n=0 ; n < headers->nheaders ; ++n)
	if(!strcmp(headers->headers[n].key,key))
	    return headers->headers[n].value;
    return NULL;
    }

/**
 * \param dest
 * \param src
 */
void ops_dup_headers(ops_headers_t *dest,const ops_headers_t *src)
    {
    unsigned n;

    dest->headers=malloc(src->nheaders*sizeof *dest->headers);
    dest->nheaders=src->nheaders;

    for(n=0 ; n < src->nheaders ; ++n)
	{
	dest->headers[n].key=strdup(src->headers[n].key);
	dest->headers[n].value=strdup(src->headers[n].value);
	}
    }

/* Note that this skips CRs so implementations always see just
   straight LFs as line terminators */
static int process_dash_escaped(dearmour_arg_t *arg,ops_error_t **errors,
				ops_reader_info_t *rinfo,
				ops_parse_cb_info_t *cbinfo)
{
	ops_parser_content_t content;
	ops_parser_content_t content2;
	ops_signed_cleartext_body_t	*body=&content.content.signed_cleartext_body;
	ops_signed_cleartext_trailer_t *trailer
		=&content2.content.signed_cleartext_trailer;
	const char *hashstr;
	ops_hash_t *hash;
	int total;

	hash=malloc(sizeof *hash);
	hashstr=ops_find_header(&arg->headers,"Hash");
	if(hashstr)
	{
		ops_hash_algorithm_t alg;

		alg=ops_hash_algorithm_from_text(hashstr);

		if(!ops_is_hash_alg_supported(&alg))
		{
			free(hash);
			OPS_ERROR_1(errors,OPS_E_R_BAD_FORMAT,"Unsupported hash algorithm '%s'",hashstr);
			return -1;
		}
		if(alg == OPS_HASH_UNKNOWN)
		{
			free(hash);
			OPS_ERROR_1(errors,OPS_E_R_BAD_FORMAT,"Unknown hash algorithm '%s'",hashstr);
			return -1;
		}
		ops_hash_any(hash,alg);
	}
	else
		ops_hash_md5(hash);

	hash->init(hash);

	body->length=0;
	total=0;
	for( ; ; )
	{
		int c;
		unsigned count;

		if((c=read_char(arg,errors,rinfo,cbinfo,ops_true)) < 0)
			return -1;
		if(arg->prev_nl && c == '-')
		{
			if((c=read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
				return -1;
			if(c != ' ')
			{
				/* then this had better be a trailer! */
				if(c != '-')
					OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Bad dash-escaping");
				for(count=2 ; count < 5 ; ++count)
				{
					if((c=read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
						return -1;
					if(c != '-')
						OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Bad dash-escaping (2)");
				}
				arg->state=AT_TRAILER_NAME;
				break;
			}
			/* otherwise we read the next character */
			if((c=read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
				return -1;
		}
		if(c == '\n' && body->length)
		{
			if(!(memchr(body->data+1,'\n',body->length-1) == NULL)) // ASSERT(memchr(body->data+1,'\n',body->length-1) == NULL);
			{
				fprintf(stderr,"no \\n in armoured file.") ;
				return -1 ;
			}
			if(body->data[0] == '\n')
				hash->add(hash,(unsigned char *)"\r",1);
			hash->add(hash,body->data,body->length);
			if (debug)
			{ fprintf(stderr,"Got body:\n%s\n",body->data); }
			CB(cbinfo,OPS_PTAG_CT_SIGNED_CLEARTEXT_BODY,&content);
			body->length=0;
		}

		body->data[body->length++]=c;
		++total;
		if(body->length == sizeof body->data)
		{
			if (debug)
			{ fprintf(stderr,"Got body (2):\n%s\n",body->data); }
			CB(cbinfo,OPS_PTAG_CT_SIGNED_CLEARTEXT_BODY,&content);
			body->length=0;
		}
	}

	if(!(body->data[0] == '\n'))	// ASSERT(body->data[0] == '\n');
	{
		fprintf(stderr,"Body should end with \\n\n"); 
		return -1 ;
	}
	if(!(body->length == 1))	// ASSERT(body->length == 1);
	{
		fprintf(stderr,"Body length error\n"); 
		return -1 ;
	}
	/* don't send that one character, because its part of the trailer. */

	trailer->hash=hash;
	CB(cbinfo,OPS_PTAG_CT_SIGNED_CLEARTEXT_TRAILER,&content2);

	return total;
}

static int add_header(dearmour_arg_t *arg,const char *key,const char
		       *value)
    {
    /*
     * Check that the header is valid
     */
    if ( !strcmp(key,"Version") || !strcmp(key,"Comment") 
         || !strcmp(key,"MessageID") || !strcmp(key,"Hash")
         || !strcmp(key,"Charset"))
        {
        arg->headers.headers=realloc(arg->headers.headers,
                                     (arg->headers.nheaders+1)
                                     *sizeof *arg->headers.headers);
        arg->headers.headers[arg->headers.nheaders].key=strdup(key);
        arg->headers.headers[arg->headers.nheaders].value=strdup(value);
        ++arg->headers.nheaders;
        return 1;
        }
    else
        {
        return 0;
        }
    }

/* \todo what does a return value of 0 indicate? 1 is good, -1 is bad */
static int parse_headers(dearmour_arg_t *arg,ops_error_t **errors,
			 ops_reader_info_t *rinfo,ops_parse_cb_info_t *cbinfo)
{
	int rtn=1;
	char *buf;
	unsigned nbuf;
	unsigned size;
	ops_boolean_t first=ops_true;
	//ops_parser_content_t content;

	buf=NULL;
	nbuf=size=0;

	for( ;  ; )
	{
		int c;

		if((c=read_char(arg,errors,rinfo,cbinfo,ops_true)) < 0)
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Unexpected EOF");
			rtn=-1;
			break;
		}

		if(c == '\n')
		{
			char *s;

			if(nbuf == 0)
				break;

			if(!(nbuf < size)) // ASSERT(nbuf < size);
			{
				OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Size error in armour header");
				return -1 ;
			}
			buf[nbuf]='\0';

			s=strchr(buf,':');
			if(!s)
				if(!first && !arg->allow_headers_without_gap)
				{
					// then we have seriously malformed armour
					OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"No colon in armour header");
					rtn=-1;
					break;
				}
				else
				{
					if(first &&
							!(arg->allow_headers_without_gap || arg->allow_no_gap))
					{
						OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"No colon in armour header (2)");
						// then we have a nasty armoured block with no
						// headers, not even a blank line.
						buf[nbuf]='\n';
						push_back(arg,(unsigned char *)buf,nbuf+1);
						rtn=-1;
						break;
					}
				}
			else
			{
				*s='\0';
				if(s[1] != ' ')
				{
					OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"No space in armour header");
					rtn=-1;
					goto end;
				}
				if (!add_header(arg,buf,s+2))
				{
					OPS_ERROR_1(errors,OPS_E_R_BAD_FORMAT,"Invalid header %s", buf);
					rtn=-1;
					goto end;
				}
				nbuf=0;
			}
			first=ops_false;
		}
		else
		{
			if(size <= nbuf+1)
			{
				size+=size+80;
				buf=realloc(buf,size);
			}
			buf[nbuf++]=c;
		}
	}

end:
	free(buf);

	return rtn;
}

static int read4(dearmour_arg_t *arg,ops_error_t **errors,
		 ops_reader_info_t *rinfo,ops_parse_cb_info_t *cbinfo,
		 int *pc,unsigned *pn,unsigned long *pl)
    {
    int n,c;
    unsigned long l=0;

    for(n=0 ; n < 4 ; ++n)
	{
	c=read_char(arg,errors,rinfo,cbinfo,ops_true);
	if(c < 0)
	    {
	    arg->eof64=ops_true;
	    return -1;
	    }
	if(c == '-')
	    break;
	if(c == '=')
	    break;
	l <<= 6;
	if(c >= 'A' && c <= 'Z')
	    l+=c-'A';
	else if(c >= 'a' && c <= 'z')
	    l+=c-'a'+26;
	else if(c >= '0' && c <= '9')
	    l+=c-'0'+52;
	else if(c == '+')
	    l+=62;
	else if(c == '/')
	    l+=63;
	else
	    {
	    --n;
	    l >>= 6;
	    }
	}

    *pc=c;
    *pn=n;
    *pl=l;

    return 4;
    }

unsigned ops_crc24(unsigned checksum,unsigned char c)
    {
    unsigned i;

    checksum ^= c << 16;
    for(i=0 ; i < 8 ; i++)
	{
	checksum <<= 1;
	if(checksum & 0x1000000)
	    checksum ^= CRC24_POLY;
	}
    return checksum&0xffffffL;
    }

static int decode64(dearmour_arg_t *arg,ops_error_t **errors,
		    ops_reader_info_t *rinfo,ops_parse_cb_info_t *cbinfo)
{
	unsigned n;
	int n2;
	unsigned long l;
	int c;
	int ret;

	if(!(arg->buffered == 0))		// ASSERT(arg->buffered == 0);
	{
		OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly formed base64");
		return 0;
	}

	ret=read4(arg,errors,rinfo,cbinfo,&c,&n,&l);
	if(ret < 0)
	{
		OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly formed base64");
		return 0;
	}

	if(n == 3)
	{
		if(c != '=')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly terminated base64 (2)");
			return 0;
		}
		arg->buffered=2;
		arg->eof64=ops_true;
		l >>= 2;
	}
	else if(n == 2)
	{
		if(c != '=')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly terminated base64 (3)");
			return 0;
		}
		arg->buffered=1;
		arg->eof64=ops_true;
		l >>= 4;
		c=read_char(arg,errors,rinfo,cbinfo,ops_false);
		if(c != '=')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly terminated base64");
			return 0;
		}
	}
	else if(n == 0)
	{
		if(!arg->prev_nl || c != '=')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly terminated base64 (4)");
			return 0;
		}
		arg->buffered=0;
	}
	else
	{
		if(n != 4) // ASSERT(n == 4);
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"n should be  4");
			return 0;
		}
		arg->buffered=3;

		if(!(c != '-' && c != '=')) // ASSERT(c != '-' && c != '=');
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly terminated Base64 chunk");
			return 0;
		}
	}

	if(arg->buffered < 3 && arg->buffered > 0)
	{
		// then we saw padding
		if(!(c == '='))	// ASSERT(c == '=');
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly terminated Base64 chunk");
			return 0;
		}
		c=read_and_eat_whitespace(arg,errors,rinfo,cbinfo,ops_true);
		if(c != '\n')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"No newline at base64 end");
			return 0;
		}
		c=read_char(arg,errors,rinfo,cbinfo,ops_false);
		if(c != '=')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"No checksum at base64 end");
			return 0;
		}
	}

	if(c == '=')
	{
		// now we are at the checksum
		ret=read4(arg,errors,rinfo,cbinfo,&c,&n,&arg->read_checksum);
		if(ret < 0 || n != 4)
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Error in checksum");
			return 0;
		}
		c=read_char(arg,errors,rinfo,cbinfo,ops_true);
		if(arg->allow_trailing_whitespace)
			c=eat_whitespace(c,arg,errors,rinfo,cbinfo,ops_true);
		if(c != '\n')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Badly terminated checksum");
			return 0;
		}
		c=read_char(arg,errors,rinfo,cbinfo,ops_false);
		if(c != '-')
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Bad base64 trailer (2)");
			return 0;
		}
	}

	if(c == '-')
	{
		for(n=0 ; n < 4 ; ++n)
			if(read_char(arg,errors,rinfo,cbinfo,ops_false) != '-')
			{
				OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Bad base64 trailer");
				return 0;
			}
		arg->eof64=ops_true;
	}
	else if(!(arg->buffered))	// ASSERT(arg->buffered);
	{
		OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Buffer error");
		return 0;
	}

	for(n=0 ; n < arg->buffered ; ++n)
	{
		arg->buffer[n]=l;
		l >>= 8;
	}

	for(n2=arg->buffered-1 ; n2 >= 0 ; --n2)
		arg->checksum=ops_crc24(arg->checksum,arg->buffer[n2]);

	if(arg->eof64 && arg->read_checksum != arg->checksum)
	{
		OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Checksum mismatch");
		return 0;
	}

	return 1;
}

static void base64(dearmour_arg_t *arg)
    {
    arg->state=BASE64;
    arg->checksum=CRC24_INIT;
    arg->eof64=ops_false;
    arg->buffered=0;
    }

// This reader is rather strange in that it can generate callbacks for
// content - this is because plaintext is not encapsulated in PGP
// packets... it also calls back for the text between the blocks.

static int armoured_data_reader(void *dest_,size_t length,ops_error_t **errors,
				ops_reader_info_t *rinfo,
				ops_parse_cb_info_t *cbinfo)
{
	dearmour_arg_t *arg=ops_reader_get_arg(rinfo);
	ops_parser_content_t content;
	int ret;
	ops_boolean_t first;
	unsigned char *dest=dest_;
	int saved=length;

	if(arg->eof64 && !arg->buffered)
		if(!(arg->state == OUTSIDE_BLOCK || arg->state == AT_TRAILER_NAME))	//  ASSERT(arg->state == OUTSIDE_BLOCK || arg->state == AT_TRAILER_NAME);
		{
			OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Outside block or trailer name expected");
			return -1 ;
		}

	while(length > 0)
	{
		unsigned count;
		unsigned n;
		char buf[1024];
		int c;

		flush(arg,cbinfo);
		switch(arg->state)
		{
			case OUTSIDE_BLOCK:
				/* This code returns EOF rather than EARLY_EOF because if
					we don't see a header line at all, then it is just an
					EOF (and not a BLOCK_END) */
				while(!arg->seen_nl)
					if((c=unarmoured_read_char(arg,errors,rinfo,cbinfo,ops_true)) < 0)
						return 0;

				/* flush at this point so we definitely have room for the
					header, and so we can easily erase it from the buffer */
				flush(arg,cbinfo);
				/* Find and consume the 5 leading '-' */
				for(count=0 ; count < 5 ; ++count)
				{
					if((c=unarmoured_read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
						return 0;
					if(c != '-')
						goto reloop;
				}

				/* Now find the block type */
				for(n=0 ; n < sizeof buf-1 ; )
				{
					if((c=unarmoured_read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
						return 0;
					if(c == '-')
						goto got_minus;
					buf[n++]=c;
				}
				/* then I guess this wasn't a proper header */
				break;

got_minus:
				buf[n]='\0';

				/* Consume trailing '-' */
				for(count=1 ; count < 5 ; ++count)
				{
					if((c=unarmoured_read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
						return 0;
					if(c != '-')
						/* wasn't a header after all */
						goto reloop;
				}

				/* Consume final NL */
				if((c=unarmoured_read_char(arg,errors,rinfo,cbinfo,ops_true)) < 0)
					return 0;
				if(arg->allow_trailing_whitespace)
					if((c=eat_whitespace(c,arg,errors,rinfo,cbinfo,
									ops_true)) < 0)
						return 0;
				if(c != '\n')
					/* wasn't a header line after all */
					break;

				/* Now we've seen the header, scrub it from the buffer */
				arg->num_unarmoured=0;

				/* But now we've seen a header line, then errors are
					EARLY_EOF */
				if((ret=parse_headers(arg,errors,rinfo,cbinfo)) <= 0)
					return -1;

				if (!set_lastseen_headerline(arg,buf,errors))
					return -1;

				if(!strcmp(buf,"BEGIN PGP SIGNED MESSAGE"))
				{
					ops_dup_headers(&content.content.signed_cleartext_header.headers,&arg->headers);
					CB(cbinfo,OPS_PTAG_CT_SIGNED_CLEARTEXT_HEADER,&content);
					ret=process_dash_escaped(arg,errors,rinfo,cbinfo);
					if(ret <= 0)
						return ret;
				}
				else
				{
					content.content.armour_header.type=buf;
					content.content.armour_header.headers=arg->headers;
					memset(&arg->headers,'\0',sizeof arg->headers);
					CB(cbinfo,OPS_PTAG_CT_ARMOUR_HEADER,&content);
					base64(arg);
				}
				break;

			case BASE64:
				first=ops_true;
				while(length > 0)
				{
					if(!arg->buffered)
					{
						if(!arg->eof64)
						{
							ret=decode64(arg,errors,rinfo,cbinfo);
							if(ret <= 0)
								return ret;
						}
						if(!arg->buffered)
						{
							if(!(arg->eof64))	// ASSERT(arg->eof64);
							{
								OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Format error");
								return -1 ;
							}
							if(first)
							{
								arg->state=AT_TRAILER_NAME;
								goto reloop;
							}
							return -1;
						}
					}

					if(!(arg->buffered))		// ASSERT(arg->buffered);
					{
						OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Format error");
						return -1 ;
					}
					*dest=arg->buffer[--arg->buffered];
					++dest;
					--length;
					first=ops_false;
				}
				if(arg->eof64 && !arg->buffered)
					arg->state=AT_TRAILER_NAME;
				break;

			case AT_TRAILER_NAME:
				for(n=0 ; n < sizeof buf-1 ; )
				{
					if((c=read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
						return -1;
					if(c == '-')
						goto got_minus2;
					buf[n++]=c;
				}
				/* then I guess this wasn't a proper trailer */
				OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Bad ASCII armour trailer");
				break;

got_minus2:
				buf[n]='\0';

				if (!set_lastseen_headerline(arg,buf,errors))
					return -1;

				/* Consume trailing '-' */
				for(count=1 ; count < 5 ; ++count)
				{
					if((c=read_char(arg,errors,rinfo,cbinfo,ops_false)) < 0)
						return -1;
					if(c != '-')
						/* wasn't a trailer after all */
						OPS_ERROR(errors, OPS_E_R_BAD_FORMAT,"Bad ASCII armour trailer (2)");
				}

				/* Consume final NL */
				if((c=read_char(arg,errors,rinfo,cbinfo,ops_true)) < 0)
					return -1;
				if(arg->allow_trailing_whitespace)
					if((c=eat_whitespace(c,arg,errors,rinfo,cbinfo,
									ops_true)) < 0)
						return 0;
				if(c != '\n')
					/* wasn't a trailer line after all */
					OPS_ERROR(errors,OPS_E_R_BAD_FORMAT,"Bad ASCII armour trailer (3)");

				if(!strncmp(buf,"BEGIN ",6))
				{
					if (!set_lastseen_headerline(arg,buf,errors))
						return -1;
					if((ret=parse_headers(arg,errors,rinfo,cbinfo)) <= 0)
						return ret;
					content.content.armour_header.type=buf;
					content.content.armour_header.headers=arg->headers;
					memset(&arg->headers,'\0',sizeof arg->headers);
					CB(cbinfo,OPS_PTAG_CT_ARMOUR_HEADER,&content);
					base64(arg);
				}
				else
				{
					content.content.armour_trailer.type=buf;
					CB(cbinfo,OPS_PTAG_CT_ARMOUR_TRAILER,&content);
					arg->state=OUTSIDE_BLOCK;
				}
				break;
		}
reloop:
		continue;
	}

	return saved;
}

static void armoured_data_destroyer(ops_reader_info_t *rinfo)
    { free(ops_reader_get_arg(rinfo)); }

/**
 * \ingroup Core_Readers_Armour
 * \brief Pushes dearmouring reader onto stack
 * \param parse_info Usual structure containing information about to how to do the parse
 * \sa ops_reader_pop_dearmour()
 */
void ops_reader_push_dearmour(ops_parse_info_t *parse_info)
    /* 
       This function originally had these parameters to cater for
       packets which didn't strictly match the RFC.
       The initial 0.5 release is only going to support
       strict checking. 
       If it becomes desirable to support loose checking of armoured packets
       and these params are reinstated, parse_headers() must be fixed
       so that these flags work correctly.

       // Allow headers in armoured data that are not separated from the data by a blank line
       ops_boolean_t without_gap, 

       // Allow no blank line at the start of armoured data
       ops_boolean_t no_gap,

       //Allow armoured data to have trailing whitespace where we strictly would not expect it			      
       ops_boolean_t trailing_whitespace 
    */
    {
    dearmour_arg_t *arg;

    arg=ops_mallocz(sizeof *arg);
    arg->seen_nl=ops_true;
/*
    arg->allow_headers_without_gap=without_gap;
    arg->allow_no_gap=no_gap;
    arg->allow_trailing_whitespace=trailing_whitespace;
*/
    arg->expect_sig=ops_false;
    arg->got_sig=ops_false;

    ops_reader_push(parse_info,armoured_data_reader,armoured_data_destroyer,arg);
    }

/**
 * \ingroup Core_Readers_Armour
 * \brief Pops dearmour reader from stock
 * \param pinfo
 * \sa ops_reader_push_dearmour()
 */
void ops_reader_pop_dearmour(ops_parse_info_t *pinfo)
    {
    dearmour_arg_t *arg=ops_reader_get_arg(ops_parse_get_rinfo(pinfo));
    free(arg);
    ops_reader_pop(pinfo);
    }

// EOF
