/*      $OpenBSD: socks.c,v 1.17 2006/09/25 04:51:20 ray Exp $  */

/*
 * Copyright (c) 1999 Niklas Hallqvist.  All rights reserved.
 * Copyright (c) 2004, 2005 Damien Miller.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <err.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <resolv.h>
#include <strings.h>
#include "atomicio.h"

#define SOCKS_PORT      "1080"
#define HTTP_PROXY_PORT "3128"
#define HTTP_MAXHDRS    64
#define SOCKS_V5        5
#define SOCKS_V4        4
#define SOCKS_NOAUTH    0
#define SOCKS_NOMETHOD  0xff
#define SOCKS_CONNECT   1
#define SOCKS_IPV4      1
#define SOCKS_DOMAIN    3
#define SOCKS_IPV6      4

#define HTTP_10_407     "HTTP/1.0 407 "
#define HTTP_10_200     "HTTP/1.0 200 "
#define HTTP_11_200     "HTTP/1.1 200 "

int remote_connect(const char *, const char *, struct addrinfo);
int socks_connect(const char *, const char *,
            const char *, const char *, struct addrinfo, int,
            const char *);

/*
 * Convert string representation of host (h) and service/port (p) into
 * sockaddr structure and return 0 on success, -1 on failure.
 * Indicate whether the host address is IPv4 (v4only) and numeric.
 */
static int
decode_addrport(const char *h, const char *p, struct sockaddr *addr,
    socklen_t addrlen, int v4only, int numeric)
{
        int r;
        struct addrinfo hints, *res;

        bzero(&hints, sizeof (hints));
        hints.ai_family = v4only ? PF_INET : PF_UNSPEC;
        hints.ai_flags = numeric ? AI_NUMERICHOST : 0;
        hints.ai_socktype = SOCK_STREAM;
        r = getaddrinfo(h, p, &hints, &res);
        /* Don't fatal when attempting to convert a numeric address */
        if (r != 0) {
                if (!numeric) {
                        errx(1, "getaddrinfo(\"%.64s\", \"%.64s\"): %s", h, p,
                            gai_strerror(r));
                }
                return (-1);
        }
        if (addrlen < res->ai_addrlen) {
                freeaddrinfo(res);
                errx(1, "internal error: addrlen < res->ai_addrlen");
        }
        (void) memcpy(addr, res->ai_addr, res->ai_addrlen);
        freeaddrinfo(res);
        return (0);
}

/*
 * Read single line from a descriptor into buffer up to bufsz bytes,
 * byte by byte. Returns length of the line (including ending NULL),
 * exits upon failure.
 */
static int
proxy_read_line(int fd, char *buf, size_t bufsz)
{
        size_t off;

        for (off = 0; ; ) {
                if (off >= bufsz)
                        errx(1, "proxy read too long");
                if (atomicio(read, fd, buf + off, 1) != 1)
                        err(1, "proxy read");
                /* Skip CR */
                if (buf[off] == '\r')
                        continue;
                if (buf[off] == '\n') {
                        buf[off] = '\0';
                        break;
                }
                /*
                 * we rewite \r\n to NULL since socks_connect() relies
                 * on *buf being zero in that case.
                 */
                off++;
        }
        return (off);
}

/*
 * Read proxy password from user and return it. The arguments are used
 * only for prompt construction.
 */
static const char *
getproxypass(const char *proxyuser, const char *proxyhost)
{
        char prompt[512];
        const char *pw;

        (void) snprintf(prompt, sizeof (prompt), "Proxy password for %s@%s: ",
            proxyuser, proxyhost);
        if ((pw = getpassphrase(prompt)) == NULL)
                errx(1, "Unable to read proxy passphrase");
        return (pw);
}

/* perform connection via proxy using SOCKSv[45] or HTTP proxy CONNECT */
int
socks_connect(const char *host, const char *port, const char *proxyhost,
    const char *proxyport, struct addrinfo proxyhints, int socksv,
    const char *proxyuser)
{
        int proxyfd, r, authretry = 0;
        size_t hlen, wlen;
        char buf[1024];
        size_t cnt;
        struct sockaddr_storage addr;
        struct sockaddr_in *in4 = (struct sockaddr_in *)&addr;
        struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)&addr;
        in_port_t serverport;
        const char *proxypass = NULL;

        if (proxyport == NULL)
                proxyport = (socksv == -1) ? HTTP_PROXY_PORT : SOCKS_PORT;

        /* Abuse API to lookup port */
        if (decode_addrport("0.0.0.0", port, (struct sockaddr *)&addr,
            sizeof (addr), 1, 1) == -1)
                errx(1, "unknown port \"%.64s\"", port);
        serverport = in4->sin_port;

again:
        if (authretry++ > 3)
                errx(1, "Too many authentication failures");

        proxyfd = remote_connect(proxyhost, proxyport, proxyhints);

        if (proxyfd < 0)
                return (-1);

        if (socksv == 5) {
                if (decode_addrport(host, port, (struct sockaddr *)&addr,
                    sizeof (addr), 0, 1) == -1)
                        addr.ss_family = 0; /* used in switch below */

                /* Version 5, one method: no authentication */
                buf[0] = SOCKS_V5;
                buf[1] = 1;
                buf[2] = SOCKS_NOAUTH;
                cnt = atomicio(vwrite, proxyfd, buf, 3);
                if (cnt != 3)
                        err(1, "write failed (%zu/3)", cnt);

                cnt = atomicio(read, proxyfd, buf, 2);
                if (cnt != 2)
                        err(1, "read failed (%zu/2)", cnt);

                if ((unsigned char)buf[1] == SOCKS_NOMETHOD)
                        errx(1, "authentication method negotiation failed");

                switch (addr.ss_family) {
                case 0:
                        /* Version 5, connect: domain name */

                        /* Max domain name length is 255 bytes */
                        hlen = strlen(host);
                        if (hlen > 255)
                                errx(1, "host name too long for SOCKS5");
                        buf[0] = SOCKS_V5;
                        buf[1] = SOCKS_CONNECT;
                        buf[2] = 0;
                        buf[3] = SOCKS_DOMAIN;
                        buf[4] = hlen;
                        (void) memcpy(buf + 5, host, hlen);
                        (void) memcpy(buf + 5 + hlen, &serverport,
                            sizeof (serverport));
                        wlen = 5 + hlen + sizeof (serverport);
                        break;
                case AF_INET:
                        /* Version 5, connect: IPv4 address */
                        buf[0] = SOCKS_V5;
                        buf[1] = SOCKS_CONNECT;
                        buf[2] = 0;
                        buf[3] = SOCKS_IPV4;
                        (void) memcpy(buf + 4, &in4->sin_addr,
                            sizeof (in4->sin_addr));
                        (void) memcpy(buf + 8, &in4->sin_port,
                            sizeof (in4->sin_port));
                        wlen = 4 + sizeof (in4->sin_addr) +
                            sizeof (in4->sin_port);
                        break;
                case AF_INET6:
                        /* Version 5, connect: IPv6 address */
                        buf[0] = SOCKS_V5;
                        buf[1] = SOCKS_CONNECT;
                        buf[2] = 0;
                        buf[3] = SOCKS_IPV6;
                        (void) memcpy(buf + 4, &in6->sin6_addr,
                            sizeof (in6->sin6_addr));
                        (void) memcpy(buf + 20, &in6->sin6_port,
                            sizeof (in6->sin6_port));
                        wlen = 4 + sizeof (in6->sin6_addr) +
                            sizeof (in6->sin6_port);
                        break;
                default:
                        errx(1, "internal error: silly AF");
                }

                cnt = atomicio(vwrite, proxyfd, buf, wlen);
                if (cnt != wlen)
                        err(1, "write failed (%zu/%zu)", cnt, wlen);

                /*
                 * read proxy reply which is 4 byte "header", BND.ADDR
                 * and BND.PORT according to RFC 1928, section 6. BND.ADDR
                 * is 4 bytes in case of IPv4 which gives us 10 bytes in sum.
                 */
                cnt = atomicio(read, proxyfd, buf, 10);
                if (cnt != 10)
                        err(1, "read failed (%zu/10)", cnt);
                if (buf[1] != 0)
                        errx(1, "connection failed, SOCKS error %d", buf[1]);
        } else if (socksv == 4) {
                /* This will exit on lookup failure */
                (void) decode_addrport(host, port, (struct sockaddr *)&addr,
                    sizeof (addr), 1, 0);

                /* Version 4 */
                buf[0] = SOCKS_V4;
                buf[1] = SOCKS_CONNECT; /* connect */
                (void) memcpy(buf + 2, &in4->sin_port, sizeof (in4->sin_port));
                (void) memcpy(buf + 4, &in4->sin_addr, sizeof (in4->sin_addr));
                buf[8] = 0;     /* empty username */
                wlen = 9;

                cnt = atomicio(vwrite, proxyfd, buf, wlen);
                if (cnt != wlen)
                        err(1, "write failed (%zu/%zu)", cnt, wlen);

                /*
                 * SOCKSv4 proxy replies consists of 2 byte "header",
                 * port number and numeric IPv4 address which gives 8 bytes.
                 */
                cnt = atomicio(read, proxyfd, buf, 8);
                if (cnt != 8)
                        err(1, "read failed (%zu/8)", cnt);
                if (buf[1] != 90)
                        errx(1, "connection failed, SOCKS error %d", buf[1]);
        } else if (socksv == -1) {
                /* HTTP proxy CONNECT according to RFC 2817, section 5 */

                /* Disallow bad chars in hostname */
                if (strcspn(host, "\r\n\t []:") != strlen(host))
                        errx(1, "Invalid hostname");

                /* Try to be sane about numeric IPv6 addresses */
                if (strchr(host, ':') != NULL) {
                        r = snprintf(buf, sizeof (buf),
                            "CONNECT [%s]:%d HTTP/1.0\r\n",
                            host, ntohs(serverport));
                } else {
                        r = snprintf(buf, sizeof (buf),
                            "CONNECT %s:%d HTTP/1.0\r\n",
                            host, ntohs(serverport));
                }
                if (r == -1 || (size_t)r >= sizeof (buf))
                        errx(1, "hostname too long");
                r = strlen(buf);

                cnt = atomicio(vwrite, proxyfd, buf, r);
                if (cnt != r)
                        err(1, "write failed (%zu/%d)", cnt, r);

                if (authretry > 1) {
                        char resp[1024];

                        proxypass = getproxypass(proxyuser, proxyhost);
                        r = snprintf(buf, sizeof (buf), "%s:%s",
                            proxyuser, proxypass);
                        free((void *)proxypass);
                        if (r == -1 || (size_t)r >= sizeof (buf) ||
                            b64_ntop((unsigned char *)buf, strlen(buf), resp,
                            sizeof (resp)) == -1)
                                errx(1, "Proxy username/password too long");
                        r = snprintf(buf, sizeof (buf), "Proxy-Authorization: "
                            "Basic %s\r\n", resp);
                        if (r == -1 || (size_t)r >= sizeof (buf))
                                errx(1, "Proxy auth response too long");
                        r = strlen(buf);
                        if ((cnt = atomicio(vwrite, proxyfd, buf, r)) != r)
                                err(1, "write failed (%zu/%d)", cnt, r);
                }

                /* Terminate headers */
                if ((r = atomicio(vwrite, proxyfd, "\r\n", 2)) != 2)
                        err(1, "write failed (2/%d)", r);

                /* Read status reply */
                (void) proxy_read_line(proxyfd, buf, sizeof (buf));
                if (proxyuser != NULL &&
                    strncmp(buf, HTTP_10_407, strlen(HTTP_10_407)) == 0) {
                        if (authretry > 1) {
                                (void) fprintf(stderr, "Proxy authentication "
                                    "failed\n");
                        }
                        (void) close(proxyfd);
                        goto again;
                } else if (strncmp(buf, HTTP_10_200,
                    strlen(HTTP_10_200)) != 0 && strncmp(buf, HTTP_11_200,
                    strlen(HTTP_11_200)) != 0)
                        errx(1, "Proxy error: \"%s\"", buf);

                /* Headers continue until we hit an empty line */
                for (r = 0; r < HTTP_MAXHDRS; r++) {
                        (void) proxy_read_line(proxyfd, buf, sizeof (buf));
                        if (*buf == '\0')
                                break;
                }
                if (*buf != '\0')
                        errx(1, "Too many proxy headers received");
        } else
                errx(1, "Unknown proxy protocol %d", socksv);

        return (proxyfd);
}