/*      $OpenBSD: socks.c,v 1.34 2025/05/22 06:40:26 djm 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 <readpassphrase.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

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

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;

        memset(&hints, 0, 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");
        }
        memcpy(addr, res->ai_addr, res->ai_addrlen);
        freeaddrinfo(res);
        return (0);
}

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;
                }
                off++;
        }
        return (off);
}

static void
getproxypass(const char *proxyuser, const char *proxyhost,
    char *pw, size_t pwlen)
{
        char prompt[512];

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

/*
 * Error strings adapted from the generally accepted SOCKSv4 spec:
 *
 * http://ftp.icm.edu.pl/packages/socks/socks4/SOCKS4.protocol
 */
static const char *
socks4_strerror(int e)
{
        switch (e) {
        case 90:
                return "Succeeded";
        case 91:
                return "Request rejected or failed";
        case 92:
                return "SOCKS server cannot connect to identd on the client";
        case 93:
                return "Client program and identd report different user-ids";
        default:
                return "Unknown error";
        }
}

/*
 * Error strings taken almost directly from RFC 1928.
 */
static const char *
socks5_strerror(int e)
{
        switch (e) {
        case 0:
                return "Succeeded";
        case 1:
                return "General SOCKS server failure";
        case 2:
                return "Connection not allowed by ruleset";
        case 3:
                return "Network unreachable";
        case 4:
                return "Host unreachable";
        case 5:
                return "Connection refused";
        case 6:
                return "TTL expired";
        case 7:
                return "Command not supported";
        case 8:
                return "Address type not supported";
        default:
                return "Unknown error";
        }
}

int
socks_connect(const char *host, const char *port,
    struct addrinfo hints __attribute__ ((__unused__)),
    const char *proxyhost, const char *proxyport, struct addrinfo proxyhints,
    int socksv, const char *proxyuser)
{
        int proxyfd, r, authretry = 0;
        size_t hlen, wlen;
        unsigned 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;

        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, NULL);

        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/3)", cnt);

                if (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;
                        memcpy(buf + 5, host, hlen);
                        memcpy(buf + 5 + hlen, &serverport, sizeof serverport);
                        wlen = 7 + hlen;
                        break;
                case AF_INET:
                        /* Version 5, connect: IPv4 address */
                        buf[0] = SOCKS_V5;
                        buf[1] = SOCKS_CONNECT;
                        buf[2] = 0;
                        buf[3] = SOCKS_IPV4;
                        memcpy(buf + 4, &in4->sin_addr, sizeof in4->sin_addr);
                        memcpy(buf + 8, &in4->sin_port, sizeof in4->sin_port);
                        wlen = 10;
                        break;
                case AF_INET6:
                        /* Version 5, connect: IPv6 address */
                        buf[0] = SOCKS_V5;
                        buf[1] = SOCKS_CONNECT;
                        buf[2] = 0;
                        buf[3] = SOCKS_IPV6;
                        memcpy(buf + 4, &in6->sin6_addr, sizeof in6->sin6_addr);
                        memcpy(buf + 20, &in6->sin6_port,
                            sizeof in6->sin6_port);
                        wlen = 22;
                        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);

                cnt = atomicio(read, proxyfd, buf, 4);
                if (cnt != 4)
                        err(1, "read failed (%zu/4)", cnt);
                if (buf[1] != 0) {
                        errx(1, "connection failed, SOCKSv5 error: %s",
                            socks5_strerror(buf[1]));
                }
                switch (buf[3]) {
                case SOCKS_IPV4:
                        cnt = atomicio(read, proxyfd, buf + 4, 6);
                        if (cnt != 6)
                                err(1, "read failed (%zu/6)", cnt);
                        break;
                case SOCKS_IPV6:
                        cnt = atomicio(read, proxyfd, buf + 4, 18);
                        if (cnt != 18)
                                err(1, "read failed (%zu/18)", cnt);
                        break;
                default:
                        errx(1, "connection failed, unsupported address type");
                }
        } else if (socksv == 4 || socksv == 44) {
                if (socksv == 4) {
                        /* This will exit on lookup failure */
                        decode_addrport(host, port, (struct sockaddr *)&addr,
                            sizeof(addr), 1, 0);
                }

                /* Version 4 */
                buf[0] = SOCKS_V4;
                buf[1] = SOCKS_CONNECT; /* connect */
                memcpy(buf + 2, &in4->sin_port, sizeof in4->sin_port);
                if (socksv == 4) {
                        memcpy(buf + 4, &in4->sin_addr, sizeof in4->sin_addr);
                } else {
                        /* SOCKS4A uses addr of 0.0.0.x, and hostname later */
                        buf[4] = buf[5] = buf[6] = 0;
                        buf[7] = 1;
                }
                buf[8] = 0;     /* empty username */
                wlen = 9;
                if (socksv == 44) {
                        /* SOCKS4A has nul-terminated hostname after user */
                        if (strlcpy(buf + 9, host,
                            sizeof(buf) - 9) >= sizeof(buf) - 9)
                                errx(1, "hostname too big");
                        wlen = 9 + strlen(host) + 1;
                }
                cnt = atomicio(vwrite, proxyfd, buf, wlen);
                if (cnt != wlen)
                        err(1, "write failed (%zu/%zu)", cnt, wlen);

                cnt = atomicio(read, proxyfd, buf, 8);
                if (cnt != 8)
                        err(1, "read failed (%zu/8)", cnt);
                if (buf[1] != 90) {
                        errx(1, "connection failed, SOCKSv4 error: %s",
                            socks4_strerror(buf[1]));
                }
        } else if (socksv == -1) {
                /* HTTP proxy CONNECT */

                /* 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 < 0 || (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 proxypass[256];
                        char resp[1024];

                        getproxypass(proxyuser, proxyhost,
                            proxypass, sizeof proxypass);
                        r = snprintf(buf, sizeof(buf), "%s:%s",
                            proxyuser, proxypass);
                        explicit_bzero(proxypass, sizeof proxypass);
                        if (r == -1 || (size_t)r >= sizeof(buf) ||
                            b64_ntop(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 < 0 || (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);
                        explicit_bzero(proxypass, sizeof proxypass);
                        explicit_bzero(buf, sizeof buf);
                }

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

                /* Read status reply */
                proxy_read_line(proxyfd, buf, sizeof(buf));
                if (proxyuser != NULL &&
                    (strncmp(buf, "HTTP/1.0 407 ", 13) == 0 ||
                    strncmp(buf, "HTTP/1.1 407 ", 13) == 0)) {
                        if (authretry > 1) {
                                fprintf(stderr, "Proxy authentication "
                                    "failed\n");
                        }
                        close(proxyfd);
                        goto again;
                } else if (strncmp(buf, "HTTP/1.0 200 ", 13) != 0 &&
                    strncmp(buf, "HTTP/1.1 200 ", 13) != 0)
                        errx(1, "Proxy error: \"%s\"", buf);

                /* Headers continue until we hit an empty line */
                for (r = 0; r < HTTP_MAXHDRS; r++) {
                        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);
}