netrc: Implement .netrc parsing

This implementation parses the $HOME/.netrc (or a file specified by the
user) through the `--netrc[=file]` or `-R[file]` options.

It uses a simple FSM in order to parse the file and find the credentials
corresponding to the FTP host, or uses the "default" entry otherwise,
if any, according to the specification found on [1]. Tokens not
applicable to axel usage were not considered.

[1] https://docs.oracle.com/cd/E19455-01/806-0633/6j9vn6q5f/index.html

Closes: axel-download-accelerator#116

Signed-off-by: David Polverari <[email protected]>

src/Makefile.am

@@ -12,6 +12,8 @@ axel_SOURCES = \
 	src/ftp.h \
 	src/http.c \
 	src/http.h \
+	src/netrc.c \
+	src/netrc.h \
 	src/search.c \
 	src/search.h \
 	src/ssl.c \

src/conf.h

@@ -43,6 +43,7 @@
 #define AXEL_CONF_H
 
 typedef struct {
+	char netrc_filename[MAX_STRING];
 	char default_filename[MAX_STRING];
 	char http_proxy[MAX_STRING];
 	char no_proxy[MAX_STRING];
@@ -67,6 +68,7 @@ typedef struct {
 	int search_threads;
 	int search_amount;
 	int search_top;
+	int use_netrc;
 
 	unsigned io_timeout;
 

src/conn.c

@@ -43,6 +43,7 @@
 /* Connection stuff */
 
 #include "axel.h"
+#include "netrc.h"
 
 /**
  * Convert an URL to a conn_t structure.
@@ -253,6 +254,8 @@ conn_init(conn_t *conn)
 		conn->ftp->local_if = conn->local_if;
 		conn->ftp->ftp_mode = FTP_PASSIVE;
 		conn->ftp->tcp.ai_family = conn->conf->ai_family;
+		if (conn->conf->use_netrc)
+			netrc_parse(conn);
 		if (!ftp_connect(conn->ftp, conn->proto, conn->host, conn->port,
 				 conn->user, conn->pass,
 				 conn->conf->io_timeout)) {

src/netrc.c

@@ -0,0 +1,114 @@
+/*
+  Axel -- A lighter download accelerator for Linux and other Unices
+
+  Copyright 2019      David da Silva Polverari
+
+  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.
+
+  In addition, as a special exception, the copyright holders give
+  permission to link the code of portions of this program with the
+  OpenSSL library under certain conditions as described in each
+  individual source file, and distribute linked combinations including
+  the two.
+
+  You must obey the GNU General Public License in all respects for all
+  of the code used other than OpenSSL. If you modify file(s) with this
+  exception, you may extend this exception to your version of the
+  file(s), but you are not obligated to do so. If you do not wish to do
+  so, delete this exception statement from your version. If you delete
+  this exception statement from all source files in the program, then
+  also delete it here.
+
+  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, write to the Free Software
+  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+*/
+
+/* .netrc parsing implementation */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include "axel.h"
+#include "netrc.h"
+
+enum lookup_state {
+	NOTHING,
+	DEFAULT,
+	MACHINE,
+	HOST_ENTRY,
+	LOGIN,
+	PASSWORD
+};
+
+void
+netrc_parse(conn_t *conn)
+{
+	FILE *fp;
+	bool found = false;
+	char *home;
+	char *tok, *ntok;
+	char line[MAX_STRING];
+	char const *delims = " \t\n";
+	enum lookup_state state = NOTHING;
+
+	if (conn->conf->netrc_filename[0] == '\0') {
+		home = getenv("HOME");
+		snprintf(conn->conf->netrc_filename, MAX_STRING, "%s/.netrc", home);
+	}
+	if ((fp = fopen(conn->conf->netrc_filename, "r")) == NULL)
+		return;
+	while (!found && fgets(line, MAX_STRING, fp)) {
+		tok = strtok_r(line, delims, &ntok);
+		if (tok && *tok == '#')
+			continue;
+		while (tok != NULL) {
+			switch (state) {
+			case NOTHING:
+				if (!strcmp("machine", tok)) {
+					state = MACHINE;
+				} else if (!strcmp("default", tok)) {
+					state = DEFAULT;
+				}
+				break;
+			case MACHINE:
+				if (!strcmp(conn->host, tok)) {
+					state = HOST_ENTRY;
+				} else {
+					state = NOTHING;
+				}
+				break;
+			case DEFAULT:
+				state = HOST_ENTRY;
+				// fall through
+			case HOST_ENTRY:
+				if (!strcmp("login", tok)) {
+					state = LOGIN;
+				} else if (!strcmp("password", tok)) {
+					state = PASSWORD;
+				}
+				break;
+			case LOGIN:
+				strcpy(conn->user, tok);
+				state = HOST_ENTRY;
+				break;
+			case PASSWORD:
+				strcpy(conn->pass, tok);
+				found = true;
+				break;
+			default:
+				break;
+			}
+			tok = strtok_r(NULL, delims, &ntok);
+		}
+	}
+}

src/netrc.h

@@ -0,0 +1,42 @@
+/*
+  Axel -- A lighter download accelerator for Linux and other Unices
+
+  Copyright 2019      David da Silva Polverari
+
+  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.
+
+  In addition, as a special exception, the copyright holders give
+  permission to link the code of portions of this program with the
+  OpenSSL library under certain conditions as described in each
+  individual source file, and distribute linked combinations including
+  the two.
+
+  You must obey the GNU General Public License in all respects for all
+  of the code used other than OpenSSL. If you modify file(s) with this
+  exception, you may extend this exception to your version of the
+  file(s), but you are not obligated to do so. If you do not wish to do
+  so, delete this exception statement from your version. If you delete
+  this exception statement from all source files in the program, then
+  also delete it here.
+
+  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, write to the Free Software
+  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+*/
+
+/* .netrc parsing include file */
+
+#ifndef AXEL_NETRC_H
+#define AXEL_NETRC_H
+
+void netrc_parse(conn_t *conn);
+
+#endif				/* AXEL_NETRC_H */

src/text.c

@@ -71,6 +71,7 @@ static struct option axel_options[] = {
 	{"max-redirect",    1,      NULL, MAX_REDIR_OPT},
 	{"output",          1,      NULL, 'o'},
 	{"search",          2,      NULL, 'S'},
+	{"netrc",           2,      NULL, 'R'},
 	{"ipv4",            0,      NULL, '4'},
 	{"ipv6",            0,      NULL, '6'},
 	{"no-proxy",        0,      NULL, 'N'},
@@ -117,7 +118,7 @@ main(int argc, char *argv[])
 	j = -1;
 	while (1) {
 		int option = getopt_long(argc, argv,
-					 "s:n:o:S::46NqvhVakcH:U:T:",
+					 "s:n:o:S::R::46NqvhVakcH:U:T:",
 					 axel_options, NULL);
 		if (option == -1)
 			break;
@@ -161,6 +162,15 @@ main(int argc, char *argv[])
 				}
 			}
 			break;
+		case 'R':
+			conf->use_netrc = 1;
+			if (optarg) {
+				if (!sscanf(optarg, "%s", conf->netrc_filename)) {
+					print_help();
+					goto free_conf;
+				}
+			}
+			break;
 		case '6':
 			conf->ai_family = AF_INET6;
 			break;
@@ -659,6 +669,7 @@ print_help(void)
 		 "-n x\tSpecify maximum number of connections\n"
 		 "-o f\tSpecify local output file\n"
 		 "-S[n]\tSearch for mirrors and download from n servers\n"
+		 "-R[file]\tRetrieve credentials from $HOME/.netrc file or filename\n"
 		 "-4\tUse the IPv4 protocol\n"
 		 "-6\tUse the IPv6 protocol\n"
 		 "-H x\tAdd HTTP header string\n"
@@ -682,6 +693,7 @@ print_help(void)
 		 "--max-redirect=x\t\tSpecify maximum number of redirections\n"
 		 "--output=f\t\t-o f\tSpecify local output file\n"
 		 "--search[=n]\t\t-S[n]\tSearch for mirrors and download from n servers\n"
+		 "--netrc[=file]\t\t-R[file]\tRetrieve credentials from $HOME/.netrc file or filename\n"
 		 "--ipv4\t\t\t-4\tUse the IPv4 protocol\n"
 		 "--ipv6\t\t\t-6\tUse the IPv6 protocol\n"
 		 "--header=x\t\t-H x\tAdd HTTP header string\n"