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/* This file is part of Eclat.
   Copyright (C) 2012, 2013 Sergey Poznyakoff.
 
   Eclat 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 3, or (at your option)
   any later version.
 
   Eclat 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 Eclat.  If not, see <http://www.gnu.org/licenses/>. */

#include <config.h>
#include <string.h>
#include <time.h>
#include "libeclat.h"
#include "sha256.h"
#include "grecs.h"

struct pname {
	size_t i;
	char **a;
};

static int
get_param_name(void *sym, void *data)
{
	struct grecs_syment *se = sym;
	struct pname *pn = data;
	pn->a[pn->i++] = se->name;
	return 0;
}

static int
compnames(const void *a, const void *b)
{
	char * const *ac = a;
	char * const *bc = b;
	return strcmp(*ac, *bc);
}

static void
querysign2(struct ec2_query *req, char *secret)
{
	char **pnames;
	size_t i, n;
	struct grecs_txtacc *acc;
	struct pname pn;
	char *str;
	char digest[SHA256_DIGEST_SIZE];
	size_t siglen;
	const char *verb;
	char tsbuf[22];
	time_t t;
	
	acc = grecs_txtacc_create();

	/* Add default parameters */
	eclat_query_add_param(req, "SignatureMethod", "HmacSHA256");
	eclat_query_add_param(req, "SignatureVersion", "2");

	time(&t);
	strftime(tsbuf, sizeof(tsbuf), "%Y-%m-%dT%H:%M:%SZ", gmtime(&t));
	eclat_query_add_param(req, "Timestamp", tsbuf);

	eclat_query_encode(req);
	
	/* Collect and sort parameter names */
	n = grecs_symtab_count_entries(req->params);
	pnames = grecs_calloc(n, sizeof(pnames[0]));
	pn.i = 0;
	pn.a = pnames;
	grecs_symtab_enumerate(req->params, get_param_name, &pn);
	qsort(pnames, n, sizeof(pnames[0]), compnames);

	verb = (req->flags & EC2_QF_POST) ? "POST" : "GET";
	grecs_txtacc_grow(acc, verb, strlen(verb));
	grecs_txtacc_grow_char(acc, '\n');
	grecs_txtacc_grow(acc, req->endpoint, strlen(req->endpoint));
	grecs_txtacc_grow_char(acc, '\n');
	grecs_txtacc_grow(acc, req->uri, strlen(req->uri));
	grecs_txtacc_grow_char(acc, '\n');

	/* Append a canonicalized query string */
	for (i = 0; i < n; i++) {
		struct ec2_param *p, key;

		key.name = pnames[i];
		p = grecs_symtab_lookup_or_install(req->params, &key, NULL);
		if (!p)
			abort();
		if (i != 0)
			grecs_txtacc_grow_char(acc, '&');
		grecs_txtacc_grow(acc, p->name, strlen(p->name));
		if (p->value) {
			grecs_txtacc_grow_char(acc, '=');
			grecs_txtacc_grow(acc, p->value, strlen(p->value));
		}
	}
	grecs_txtacc_grow_char(acc, 0);
	str = grecs_txtacc_finish(acc, 0);

	hmac_sha256(str, strlen(str), secret, strlen(secret), digest);

	eclat_base64_encode((unsigned char *)digest, sizeof(digest),
			    (unsigned char**) &req->signature, &siglen);

	grecs_txtacc_free(acc);
	free(pnames);

/*FIXME
	t += req->ttl;
	strftime(tsbuf, sizeof(tsbuf), "%Y-%m-%dT%H:%M:%SZ", gmtime(&t));
	eclat_query_add_param(req, "Expires", tsbuf);
*/
}

static void
querysign4(struct ec2_query *req, char *secret)
{
	abort();
}


struct qsimpl {
	char *qs_version;
	void (*qs_fun)(struct ec2_query *, char *);
};

static struct qsimpl qstab[] = {
	{ "2", querysign2 },
	{ "4", querysign4 },
	{ NULL }
};

void
eclat_query_sign(struct ec2_query *req, char *secret, char *version)
{
	struct qsimpl *qs;

	for (qs = qstab; qs->qs_version && strcmp(qs->qs_version, version);
	     qs++)
		;

	if (qs->qs_version)
		qs->qs_fun(req, secret);
	else {
		err("INTERNAL ERROR: unsupported version %s", version);
		abort();
	}
}

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