/*
 * Copyright (C) 2011 John Szakmeister <john@szakmeister.net>
 *               2012 Philipp A. Hartmann <pah@qo.cx>
 *               2016 Mantas Mikulėnas <grawity@gmail.com>
 *
 *  This program 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.
 *
 *  This program 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, see <http://www.gnu.org/licenses/>.
 */

/*
 * Credits:
 * - GNOME Keyring API handling originally written by John Szakmeister
 * - ported to credential helper API by Philipp A. Hartmann
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <glib.h>
#include <libsecret/secret.h>

/*
 * This credential struct and API is simplified from git's credential.{h,c}
 */
struct credential {
	char *protocol;
	char *host;
	unsigned short port;
	char *path;
	char *username;
	char *password;
	char *password_expiry_utc;
	char *oauth_refresh_token;
};

#define CREDENTIAL_INIT { 0 }

typedef int (*credential_op_cb)(struct credential *);

struct credential_operation {
	char *name;
	credential_op_cb op;
};

#define CREDENTIAL_OP_END { NULL, NULL }

static void credential_clear(struct credential *c);

/* ----------------- Secret Service functions ----------------- */

static const SecretSchema schema = {
	"org.git.Password",
	/* Ignore schema name during search for backwards compatibility */
	SECRET_SCHEMA_DONT_MATCH_NAME,
	{
		/*
		 * libsecret assumes attribute values are non-confidential and
		 * unchanging, so we can't include oauth_refresh_token or
		 * password_expiry_utc.
		 */
		{  "user", SECRET_SCHEMA_ATTRIBUTE_STRING },
		{  "object", SECRET_SCHEMA_ATTRIBUTE_STRING },
		{  "protocol", SECRET_SCHEMA_ATTRIBUTE_STRING },
		{  "port", SECRET_SCHEMA_ATTRIBUTE_INTEGER },
		{  "server", SECRET_SCHEMA_ATTRIBUTE_STRING },
		{  NULL, 0 },
	}
};

static char *make_label(struct credential *c)
{
	if (c->port)
		return g_strdup_printf("Git: %s://%s:%hu/%s",
					c->protocol, c->host, c->port, c->path ? c->path : "");
	else
		return g_strdup_printf("Git: %s://%s/%s",
					c->protocol, c->host, c->path ? c->path : "");
}

static GHashTable *make_attr_list(struct credential *c)
{
	GHashTable *al = g_hash_table_new_full(g_str_hash, g_str_equal, NULL, g_free);

	if (c->username)
		g_hash_table_insert(al, "user", g_strdup(c->username));
	if (c->protocol)
		g_hash_table_insert(al, "protocol", g_strdup(c->protocol));
	if (c->host)
		g_hash_table_insert(al, "server", g_strdup(c->host));
	if (c->port)
		g_hash_table_insert(al, "port", g_strdup_printf("%hu", c->port));
	if (c->path)
		g_hash_table_insert(al, "object", g_strdup(c->path));

	return al;
}

static int keyring_get(struct credential *c)
{
	SecretService *service = NULL;
	GHashTable *attributes = NULL;
	GError *error = NULL;
	GList *items = NULL;

	if (!c->protocol || !(c->host || c->path))
		return EXIT_FAILURE;

	service = secret_service_get_sync(0, NULL, &error);
	if (error != NULL) {
		g_critical("could not connect to Secret Service: %s", error->message);
		g_error_free(error);
		return EXIT_FAILURE;
	}

	attributes = make_attr_list(c);
	items = secret_service_search_sync(service,
					   &schema,
					   attributes,
					   SECRET_SEARCH_LOAD_SECRETS | SECRET_SEARCH_UNLOCK,
					   NULL,
					   &error);
	g_hash_table_unref(attributes);
	if (error != NULL) {
		g_critical("lookup failed: %s", error->message);
		g_error_free(error);
		return EXIT_FAILURE;
	}

	if (items != NULL) {
		SecretItem *item;
		SecretValue *secret;
		const char *s;
		gchar **parts;

		item = items->data;
		secret = secret_item_get_secret(item);
		attributes = secret_item_get_attributes(item);

		s = g_hash_table_lookup(attributes, "user");
		if (s) {
			g_free(c->username);
			c->username = g_strdup(s);
		}

		s = secret_value_get_text(secret);
		if (s) {
			/*
			 * Passwords and other attributes encoded in following format:
			 *   hunter2
			 *   password_expiry_utc=1684189401
			 *   oauth_refresh_token=xyzzy
			 */
			parts = g_strsplit(s, "\n", 0);
			if (g_strv_length(parts) >= 1) {
				g_free(c->password);
				c->password = g_strdup(parts[0]);
			}
			for (int i = 1; i < g_strv_length(parts); i++) {
				if (g_str_has_prefix(parts[i], "password_expiry_utc=")) {
					g_free(c->password_expiry_utc);
					c->password_expiry_utc = g_strdup(&parts[i][20]);
				} else if (g_str_has_prefix(parts[i], "oauth_refresh_token=")) {
					g_free(c->oauth_refresh_token);
					c->oauth_refresh_token = g_strdup(&parts[i][20]);
				}
			}
			g_strfreev(parts);
		}

		g_hash_table_unref(attributes);
		secret_value_unref(secret);
		g_list_free_full(items, g_object_unref);
	}

	return EXIT_SUCCESS;
}


static int keyring_store(struct credential *c)
{
	char *label = NULL;
	GHashTable *attributes = NULL;
	GError *error = NULL;
	GString *secret = NULL;

	/*
	 * Sanity check that what we are storing is actually sensible.
	 * In particular, we can't make a URL without a protocol field.
	 * Without either a host or pathname (depending on the scheme),
	 * we have no primary key. And without a username and password,
	 * we are not actually storing a credential.
	 */
	if (!c->protocol || !(c->host || c->path) ||
	    !c->username || !c->password)
		return EXIT_FAILURE;

	label = make_label(c);
	attributes = make_attr_list(c);
	secret = g_string_new(c->password);
	if (c->password_expiry_utc) {
		g_string_append_printf(secret, "\npassword_expiry_utc=%s",
			c->password_expiry_utc);
	}
	if (c->oauth_refresh_token) {
		g_string_append_printf(secret, "\noauth_refresh_token=%s",
			c->oauth_refresh_token);
	}
	secret_password_storev_sync(&schema,
				    attributes,
				    NULL,
				    label,
				    secret->str,
				    NULL,
				    &error);
	g_string_free(secret, TRUE);
	g_free(label);
	g_hash_table_unref(attributes);

	if (error != NULL) {
		g_critical("store failed: %s", error->message);
		g_error_free(error);
		return EXIT_FAILURE;
	}

	return EXIT_SUCCESS;
}

static int keyring_erase(struct credential *c)
{
	GHashTable *attributes = NULL;
	GError *error = NULL;
	struct credential existing = CREDENTIAL_INIT;

	/*
	 * Sanity check that we actually have something to match
	 * against. The input we get is a restrictive pattern,
	 * so technically a blank credential means "erase everything".
	 * But it is too easy to accidentally send this, since it is equivalent
	 * to empty input. So explicitly disallow it, and require that the
	 * pattern have some actual content to match.
	 */
	if (!c->protocol && !c->host && !c->path && !c->username)
		return EXIT_FAILURE;

	if (c->password) {
		existing.host = g_strdup(c->host);
		existing.path = g_strdup(c->path);
		existing.port = c->port;
		existing.protocol = g_strdup(c->protocol);
		existing.username = g_strdup(c->username);
		keyring_get(&existing);
		if (existing.password && strcmp(c->password, existing.password)) {
			credential_clear(&existing);
			return EXIT_SUCCESS;
		}
		credential_clear(&existing);
	}

	attributes = make_attr_list(c);
	secret_password_clearv_sync(&schema,
				    attributes,
				    NULL,
				    &error);
	g_hash_table_unref(attributes);

	if (error != NULL) {
		g_critical("erase failed: %s", error->message);
		g_error_free(error);
		return EXIT_FAILURE;
	}

	return EXIT_SUCCESS;
}

/*
 * Table with helper operation callbacks, used by generic
 * credential helper main function.
 */
static struct credential_operation const credential_helper_ops[] = {
	{ "get",   keyring_get },
	{ "store", keyring_store },
	{ "erase", keyring_erase },
	CREDENTIAL_OP_END
};

/* ------------------ credential functions ------------------ */

static void credential_init(struct credential *c)
{
	memset(c, 0, sizeof(*c));
}

static void credential_clear(struct credential *c)
{
	g_free(c->protocol);
	g_free(c->host);
	g_free(c->path);
	g_free(c->username);
	g_free(c->password);
	g_free(c->password_expiry_utc);
	g_free(c->oauth_refresh_token);

	credential_init(c);
}

static int credential_read(struct credential *c)
{
	char *buf = NULL;
	size_t alloc;
	ssize_t line_len;
	char *key;
	char *value;

	while ((line_len = getline(&buf, &alloc, stdin)) > 0) {
		key = buf;

		if (buf[line_len-1] == '\n')
			buf[--line_len] = '\0';

		if (!line_len)
			break;

		value = strchr(buf, '=');
		if (!value) {
			g_warning("invalid credential line: %s", key);
			g_free(buf);
			return -1;
		}
		*value++ = '\0';

		if (!strcmp(key, "protocol")) {
			g_free(c->protocol);
			c->protocol = g_strdup(value);
		} else if (!strcmp(key, "host")) {
			g_free(c->host);
			c->host = g_strdup(value);
			value = strrchr(c->host, ':');
			if (value) {
				*value++ = '\0';
				c->port = atoi(value);
			}
		} else if (!strcmp(key, "path")) {
			g_free(c->path);
			c->path = g_strdup(value);
		} else if (!strcmp(key, "username")) {
			g_free(c->username);
			c->username = g_strdup(value);
		} else if (!strcmp(key, "password_expiry_utc")) {
			g_free(c->password_expiry_utc);
			c->password_expiry_utc = g_strdup(value);
		} else if (!strcmp(key, "password")) {
			g_free(c->password);
			c->password = g_strdup(value);
			while (*value)
				*value++ = '\0';
		} else if (!strcmp(key, "oauth_refresh_token")) {
			g_free(c->oauth_refresh_token);
			c->oauth_refresh_token = g_strdup(value);
			while (*value)
				*value++ = '\0';
		}
		/*
		 * Ignore other lines; we don't know what they mean, but
		 * this future-proofs us when later versions of git do
		 * learn new lines, and the helpers are updated to match.
		 */
	}

	free(buf);

	return 0;
}

static void credential_write_item(FILE *fp, const char *key, const char *value)
{
	if (!value)
		return;
	fprintf(fp, "%s=%s\n", key, value);
}

static void credential_write(const struct credential *c)
{
	/* only write username/password, if set */
	credential_write_item(stdout, "username", c->username);
	credential_write_item(stdout, "password", c->password);
	credential_write_item(stdout, "password_expiry_utc",
		c->password_expiry_utc);
	credential_write_item(stdout, "oauth_refresh_token",
		c->oauth_refresh_token);
}

static void usage(const char *name)
{
	struct credential_operation const *try_op = credential_helper_ops;
	const char *basename = strrchr(name, '/');

	basename = (basename) ? basename + 1 : name;
	fprintf(stderr, "usage: %s <", basename);
	while (try_op->name) {
		fprintf(stderr, "%s", (try_op++)->name);
		if (try_op->name)
			fprintf(stderr, "%s", "|");
	}
	fprintf(stderr, "%s", ">\n");
}

int main(int argc, char *argv[])
{
	int ret = EXIT_SUCCESS;

	struct credential_operation const *try_op = credential_helper_ops;
	struct credential cred = CREDENTIAL_INIT;

	if (!argv[1]) {
		usage(argv[0]);
		exit(EXIT_FAILURE);
	}

	g_set_application_name("Git Credential Helper");

	/* lookup operation callback */
	while (try_op->name && strcmp(argv[1], try_op->name))
		try_op++;

	/* unsupported operation given -- ignore silently */
	if (!try_op->name || !try_op->op)
		goto out;

	ret = credential_read(&cred);
	if (ret)
		goto out;

	/* perform credential operation */
	ret = (*try_op->op)(&cred);

	credential_write(&cred);

out:
	credential_clear(&cred);
	return ret;
}
