/*
 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining 
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be 
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <errno.h>

#include "brssl.h"

/* see brssl.h */
unsigned char *
read_file(const char *fname, size_t *len)
{
	bvector vbuf = VEC_INIT;
	FILE *f;

	*len = 0;
	f = fopen(fname, "rb");
	if (f == NULL) {
		fprintf(stderr,
			"ERROR: could not open file '%s' for reading\n", fname);
		return NULL;
	}
	for (;;) {
		unsigned char tmp[1024];
		size_t rlen;

		rlen = fread(tmp, 1, sizeof tmp, f);
		if (rlen == 0) {
			unsigned char *buf;

			if (ferror(f)) {
				fprintf(stderr,
					"ERROR: read error on file '%s'\n",
					fname);
				fclose(f);
				return NULL;
			}
			buf = VEC_TOARRAY(vbuf);
			*len = VEC_LEN(vbuf);
			VEC_CLEAR(vbuf);
			fclose(f);
			return buf;
		}
		VEC_ADDMANY(vbuf, tmp, rlen);
	}
}

/* see brssl.h */
int
write_file(const char *fname, const void *data, size_t len)
{
	FILE *f;
	const unsigned char *buf;

	f = fopen(fname, "wb");
	if (f == NULL) {
		fprintf(stderr,
			"ERROR: could not open file '%s' for reading\n", fname);
		return -1;
	}
	buf = data;
	while (len > 0) {
		size_t wlen;

		wlen = fwrite(buf, 1, len, f);
		if (wlen == 0) {
			fprintf(stderr,
				"ERROR: could not write all bytes to '%s'\n",
				fname);
			fclose(f);
			return -1;
		}
		buf += wlen;
		len -= wlen;
	}
	if (ferror(f)) {
		fprintf(stderr, "ERROR: write error on file '%s'\n", fname);
		fclose(f);
		return -1;
	}
	fclose(f);
	return 0;
}

/* see brssl.h */
int
looks_like_DER(const unsigned char *buf, size_t len)
{
	int fb;
	size_t dlen;

	if (len < 2) {
		return 0;
	}
	if (*buf ++ != 0x30) {
		return 0;
	}
	fb = *buf ++;
	len -= 2;
	if (fb < 0x80) {
		return (size_t)fb == len;
	} else if (fb == 0x80) {
		return 0;
	} else {
		fb -= 0x80;
		if (len < (size_t)fb + 2) {
			return 0;
		}
		len -= (size_t)fb;
		dlen = 0;
		while (fb -- > 0) {
			if (dlen > (len >> 8)) {
				return 0;
			}
			dlen = (dlen << 8) + (size_t)*buf ++;
		}
		return dlen == len;
	}
}

static void
vblob_append(void *cc, const void *data, size_t len)
{
	bvector *bv;

	bv = cc;
	VEC_ADDMANY(*bv, data, len);
}

/* see brssl.h */
void
free_pem_object_contents(pem_object *po)
{
	if (po != NULL) {
		xfree(po->name);
		xfree(po->data);
	}
}

/* see brssl.h */
pem_object *
decode_pem(const void *src, size_t len, size_t *num)
{
	VECTOR(pem_object) pem_list = VEC_INIT;
	br_pem_decoder_context pc;
	pem_object po, *pos;
	const unsigned char *buf;
	bvector bv = VEC_INIT;
	int inobj;
	int extra_nl;

	*num = 0;
	br_pem_decoder_init(&pc);
	buf = src;
	inobj = 0;
	po.name = NULL;
	po.data = NULL;
	po.data_len = 0;
	extra_nl = 1;
	while (len > 0) {
		size_t tlen;

		tlen = br_pem_decoder_push(&pc, buf, len);
		buf += tlen;
		len -= tlen;
		switch (br_pem_decoder_event(&pc)) {

		case BR_PEM_BEGIN_OBJ:
			po.name = xstrdup(br_pem_decoder_name(&pc));
			br_pem_decoder_setdest(&pc, vblob_append, &bv);
			inobj = 1;
			break;

		case BR_PEM_END_OBJ:
			if (inobj) {
				po.data = VEC_TOARRAY(bv);
				po.data_len = VEC_LEN(bv);
				VEC_ADD(pem_list, po);
				VEC_CLEAR(bv);
				po.name = NULL;
				po.data = NULL;
				po.data_len = 0;
				inobj = 0;
			}
			break;

		case BR_PEM_ERROR:
			xfree(po.name);
			VEC_CLEAR(bv);
			fprintf(stderr,
				"ERROR: invalid PEM encoding\n");
			VEC_CLEAREXT(pem_list, &free_pem_object_contents);
			return NULL;
		}

		/*
		 * We add an extra newline at the end, in order to
		 * support PEM files that lack the newline on their last
		 * line (this is somwehat invalid, but PEM format is not
		 * standardised and such files do exist in the wild, so
		 * we'd better accept them).
		 */
		if (len == 0 && extra_nl) {
			extra_nl = 0;
			buf = (const unsigned char *)"\n";
			len = 1;
		}
	}
	if (inobj) {
		fprintf(stderr, "ERROR: unfinished PEM object\n");
		xfree(po.name);
		VEC_CLEAR(bv);
		VEC_CLEAREXT(pem_list, &free_pem_object_contents);
		return NULL;
	}

	*num = VEC_LEN(pem_list);
	VEC_ADD(pem_list, po);
	pos = VEC_TOARRAY(pem_list);
	VEC_CLEAR(pem_list);
	return pos;
}

/* see brssl.h */
br_x509_certificate *
read_certificates(const char *fname, size_t *num)
{
	VECTOR(br_x509_certificate) cert_list = VEC_INIT;
	unsigned char *buf;
	size_t len;
	pem_object *pos;
	size_t u, num_pos;
	br_x509_certificate *xcs;
	br_x509_certificate dummy;

	*num = 0;

	/*
	 * TODO: reading the whole file is crude; we could parse them
	 * in a streamed fashion. But it does not matter much in practice.
	 */
	buf = read_file(fname, &len);
	if (buf == NULL) {
		return NULL;
	}

	/*
	 * Check for a DER-encoded certificate.
	 */
	if (looks_like_DER(buf, len)) {
		xcs = xmalloc(2 * sizeof *xcs);
		xcs[0].data = buf;
		xcs[0].data_len = len;
		xcs[1].data = NULL;
		xcs[1].data_len = 0;
		*num = 1;
		return xcs;
	}

	pos = decode_pem(buf, len, &num_pos);
	xfree(buf);
	if (pos == NULL) {
		return NULL;
	}
	for (u = 0; u < num_pos; u ++) {
		if (eqstr(pos[u].name, "CERTIFICATE")
			|| eqstr(pos[u].name, "X509 CERTIFICATE"))
		{
			br_x509_certificate xc;

			xc.data = pos[u].data;
			xc.data_len = pos[u].data_len;
			pos[u].data = NULL;
			VEC_ADD(cert_list, xc);
		}
	}
	for (u = 0; u < num_pos; u ++) {
		free_pem_object_contents(&pos[u]);
	}
	xfree(pos);

	if (VEC_LEN(cert_list) == 0) {
		fprintf(stderr, "ERROR: no certificate in file '%s'\n", fname);
		return NULL;
	}
	*num = VEC_LEN(cert_list);
	dummy.data = NULL;
	dummy.data_len = 0;
	VEC_ADD(cert_list, dummy);
	xcs = VEC_TOARRAY(cert_list);
	VEC_CLEAR(cert_list);
	return xcs;
}

/* see brssl.h */
void
free_certificates(br_x509_certificate *certs, size_t num)
{
	size_t u;

	for (u = 0; u < num; u ++) {
		xfree(certs[u].data);
	}
	xfree(certs);
}