1 files changed, 1153 insertions, 0 deletions

diff --git a/session.c b/session.c
new file mode 100644
index 000000000..2128fe394
--- /dev/null
+++ b/session.c
@@ -0,0 +1,1153 @@
+/*
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ *                    All rights reserved
+ */
+
+#include "includes.h"
+RCSID("$OpenBSD: session.c,v 1.1 2000/03/28 21:15:45 markus Exp $");
+
+#include "xmalloc.h"
+#include "ssh.h"
+#include "pty.h"
+#include "packet.h"
+#include "buffer.h"
+#include "cipher.h"
+#include "mpaux.h"
+#include "servconf.h"
+#include "uidswap.h"
+#include "compat.h"
+#include "channels.h"
+#include "nchan.h"
+
+/* types */
+
+#define TTYSZ 64
+typedef struct Session Session;
+struct Session {
+        int     used;
+        int     self;
+        struct  passwd *pw;
+        pid_t   pid;
+        /* tty */
+        char    *term;
+        int     ptyfd, ttyfd, ptymaster;
+        int     row, col, xpixel, ypixel;
+        char    tty[TTYSZ];
+        /* X11 */
+        char    *display;
+        int     screen;
+        char    *auth_proto;
+        char    *auth_data;
+        /* proto 2 */
+        int     chanid;
+};
+
+/* func */
+
+Session *session_new(void);
+void    session_set_fds(Session *s, int fdin, int fdout, int fderr);
+void    session_pty_cleanup(Session *s);
+void    do_exec_pty(Session *s, const char *command, struct passwd * pw);
+void    do_exec_no_pty(Session *s, const char *command, struct passwd * pw);
+
+void
+do_child(const char *command, struct passwd * pw, const char *term,
+    const char *display, const char *auth_proto,
+    const char *auth_data, const char *ttyname);
+
+/* import */
+extern ServerOptions options;
+extern char *__progname;
+extern int log_stderr;
+extern int debug_flag;
+
+/* Local Xauthority file. */
+static char *xauthfile;
+
+/* data */
+#define MAX_SESSIONS 10
+Session sessions[MAX_SESSIONS];
+
+/* Flags set in auth-rsa from authorized_keys flags.  These are set in auth-rsa.c. */
+int no_port_forwarding_flag = 0;
+int no_agent_forwarding_flag = 0;
+int no_x11_forwarding_flag = 0;
+int no_pty_flag = 0;
+
+/* RSA authentication "command=" option. */
+char *forced_command = NULL;
+
+/* RSA authentication "environment=" options. */
+struct envstring *custom_environment = NULL;
+
+/*
+ * Remove local Xauthority file.
+ */
+void
+xauthfile_cleanup_proc(void *ignore)
+{
+        debug("xauthfile_cleanup_proc called");
+
+        if (xauthfile != NULL) {
+                char *p;
+                unlink(xauthfile);
+                p = strrchr(xauthfile, '/');
+                if (p != NULL) {
+                        *p = '\0';
+                        rmdir(xauthfile);
+                }
+                xfree(xauthfile);
+                xauthfile = NULL;
+        }
+}
+
+/*
+ * Function to perform cleanup if we get aborted abnormally (e.g., due to a
+ * dropped connection).
+ */
+void 
+pty_cleanup_proc(void *session)
+{
+        Session *s=session;
+        if (s == NULL)
+                fatal("pty_cleanup_proc: no session");
+        debug("pty_cleanup_proc: %s", s->tty);
+
+        if (s->pid != 0) {
+                /* Record that the user has logged out. */
+                record_logout(s->pid, s->tty);
+        }
+
+        /* Release the pseudo-tty. */
+        pty_release(s->tty);
+}
+
+/*
+ * Prepares for an interactive session.  This is called after the user has
+ * been successfully authenticated.  During this message exchange, pseudo
+ * terminals are allocated, X11, TCP/IP, and authentication agent forwardings
+ * are requested, etc.
+ */
+void 
+do_authenticated(struct passwd * pw)
+{
+        Session *s;
+        int type;
+        int compression_level = 0, enable_compression_after_reply = 0;
+        int have_pty = 0;
+        char *command;
+        int n_bytes;
+        int plen;
+        unsigned int proto_len, data_len, dlen;
+
+        /*
+         * Cancel the alarm we set to limit the time taken for
+         * authentication.
+         */
+        alarm(0);
+
+        /*
+         * Inform the channel mechanism that we are the server side and that
+         * the client may request to connect to any port at all. (The user
+         * could do it anyway, and we wouldn\'t know what is permitted except
+         * by the client telling us, so we can equally well trust the client
+         * not to request anything bogus.)
+         */
+        if (!no_port_forwarding_flag)
+                channel_permit_all_opens();
+
+        s = session_new();
+
+        /*
+         * We stay in this loop until the client requests to execute a shell
+         * or a command.
+         */
+        for (;;) {
+                int success = 0;
+
+                /* Get a packet from the client. */
+                type = packet_read(&plen);
+
+                /* Process the packet. */
+                switch (type) {
+                case SSH_CMSG_REQUEST_COMPRESSION:
+                        packet_integrity_check(plen, 4, type);
+                        compression_level = packet_get_int();
+                        if (compression_level < 1 || compression_level > 9) {
+                                packet_send_debug("Received illegal compression level %d.",
+                                     compression_level);
+                                break;
+                        }
+                        /* Enable compression after we have responded with SUCCESS. */
+                        enable_compression_after_reply = 1;
+                        success = 1;
+                        break;
+
+                case SSH_CMSG_REQUEST_PTY:
+                        if (no_pty_flag) {
+                                debug("Allocating a pty not permitted for this authentication.");
+                                break;
+                        }
+                        if (have_pty)
+                                packet_disconnect("Protocol error: you already have a pty.");
+
+                        debug("Allocating pty.");
+
+                        /* Allocate a pty and open it. */
+                        if (!pty_allocate(&s->ptyfd, &s->ttyfd, s->tty,
+                            sizeof(s->tty))) {
+                                error("Failed to allocate pty.");
+                                break;
+                        }
+                        fatal_add_cleanup(pty_cleanup_proc, (void *)s);
+                        pty_setowner(pw, s->tty);
+
+                        /* Get TERM from the packet.  Note that the value may be of arbitrary length. */
+                        s->term = packet_get_string(&dlen);
+                        packet_integrity_check(dlen, strlen(s->term), type);
+                        /* packet_integrity_check(plen, 4 + dlen + 4*4 + n_bytes, type); */
+                        /* Remaining bytes */
+                        n_bytes = plen - (4 + dlen + 4 * 4);
+
+                        if (strcmp(s->term, "") == 0) {
+                                xfree(s->term);
+                                s->term = NULL;
+                        }
+                        /* Get window size from the packet. */
+                        s->row = packet_get_int();
+                        s->col = packet_get_int();
+                        s->xpixel = packet_get_int();
+                        s->ypixel = packet_get_int();
+                        pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel);
+
+                        /* Get tty modes from the packet. */
+                        tty_parse_modes(s->ttyfd, &n_bytes);
+                        packet_integrity_check(plen, 4 + dlen + 4 * 4 + n_bytes, type);
+
+                        /* Indicate that we now have a pty. */
+                        success = 1;
+                        have_pty = 1;
+                        break;
+
+                case SSH_CMSG_X11_REQUEST_FORWARDING:
+                        if (!options.x11_forwarding) {
+                                packet_send_debug("X11 forwarding disabled in server configuration file.");
+                                break;
+                        }
+#ifdef XAUTH_PATH
+                        if (no_x11_forwarding_flag) {
+                                packet_send_debug("X11 forwarding not permitted for this authentication.");
+                                break;
+                        }
+                        debug("Received request for X11 forwarding with auth spoofing.");
+                        if (s->display != NULL)
+                                packet_disconnect("Protocol error: X11 display already set.");
+
+                        s->auth_proto = packet_get_string(&proto_len);
+                        s->auth_data = packet_get_string(&data_len);
+                        packet_integrity_check(plen, 4 + proto_len + 4 + data_len + 4, type);
+
+                        if (packet_get_protocol_flags() & SSH_PROTOFLAG_SCREEN_NUMBER)
+                                s->screen = packet_get_int();
+                        else
+                                s->screen = 0;
+                        s->display = x11_create_display_inet(s->screen, options.x11_display_offset);
+
+                        if (s->display == NULL)
+                                break;
+
+                        /* Setup to always have a local .Xauthority. */
+                        xauthfile = xmalloc(MAXPATHLEN);
+                        strlcpy(xauthfile, "/tmp/ssh-XXXXXXXX", MAXPATHLEN);
+                        temporarily_use_uid(pw->pw_uid);
+                        if (mkdtemp(xauthfile) == NULL) {
+                                restore_uid();
+                                error("private X11 dir: mkdtemp %s failed: %s",
+                                    xauthfile, strerror(errno));
+                                xfree(xauthfile);
+                                xauthfile = NULL;
+                                break;
+                        }
+                        strlcat(xauthfile, "/cookies", MAXPATHLEN);
+                        open(xauthfile, O_RDWR|O_CREAT|O_EXCL, 0600);
+                        restore_uid();
+                        fatal_add_cleanup(xauthfile_cleanup_proc, NULL);
+                        success = 1;
+                        break;
+#else /* XAUTH_PATH */
+                        packet_send_debug("No xauth program; cannot forward with spoofing.");
+                        break;
+#endif /* XAUTH_PATH */
+
+                case SSH_CMSG_AGENT_REQUEST_FORWARDING:
+                        if (no_agent_forwarding_flag || compat13) {
+                                debug("Authentication agent forwarding not permitted for this authentication.");
+                                break;
+                        }
+                        debug("Received authentication agent forwarding request.");
+                        auth_input_request_forwarding(pw);
+                        success = 1;
+                        break;
+
+                case SSH_CMSG_PORT_FORWARD_REQUEST:
+                        if (no_port_forwarding_flag) {
+                                debug("Port forwarding not permitted for this authentication.");
+                                break;
+                        }
+                        debug("Received TCP/IP port forwarding request.");
+                        channel_input_port_forward_request(pw->pw_uid == 0);
+                        success = 1;
+                        break;
+
+                case SSH_CMSG_MAX_PACKET_SIZE:
+                        if (packet_set_maxsize(packet_get_int()) > 0)
+                                success = 1;
+                        break;
+
+                case SSH_CMSG_EXEC_SHELL:
+                case SSH_CMSG_EXEC_CMD:
+                        /* Set interactive/non-interactive mode. */
+                        packet_set_interactive(have_pty || s->display != NULL,
+                            options.keepalives);
+
+                        if (type == SSH_CMSG_EXEC_CMD) {
+                                command = packet_get_string(&dlen);
+                                debug("Exec command '%.500s'", command);
+                                packet_integrity_check(plen, 4 + dlen, type);
+                        } else {
+                                command = NULL;
+                                packet_integrity_check(plen, 0, type);
+                        }
+                        if (forced_command != NULL) {
+                                command = forced_command;
+                                debug("Forced command '%.500s'", forced_command);
+                        }
+                        if (have_pty)
+                                do_exec_pty(s, command, pw);
+                        else
+                                do_exec_no_pty(s, command, pw);
+
+                        if (command != NULL)
+                                xfree(command);
+                        /* Cleanup user's local Xauthority file. */
+                        if (xauthfile)
+                                xauthfile_cleanup_proc(NULL);
+                        return;
+
+                default:
+                        /*
+                         * Any unknown messages in this phase are ignored,
+                         * and a failure message is returned.
+                         */
+                        log("Unknown packet type received after authentication: %d", type);
+                }
+                packet_start(success ? SSH_SMSG_SUCCESS : SSH_SMSG_FAILURE);
+                packet_send();
+                packet_write_wait();
+
+                /* Enable compression now that we have replied if appropriate. */
+                if (enable_compression_after_reply) {
+                        enable_compression_after_reply = 0;
+                        packet_start_compression(compression_level);
+                }
+        }
+}
+
+/*
+ * This is called to fork and execute a command when we have no tty.  This
+ * will call do_child from the child, and server_loop from the parent after
+ * setting up file descriptors and such.
+ */
+void 
+do_exec_no_pty(Session *s, const char *command, struct passwd * pw)
+{
+        int pid;
+
+#ifdef USE_PIPES
+        int pin[2], pout[2], perr[2];
+        /* Allocate pipes for communicating with the program. */
+        if (pipe(pin) < 0 || pipe(pout) < 0 || pipe(perr) < 0)
+                packet_disconnect("Could not create pipes: %.100s",
+                                  strerror(errno));
+#else /* USE_PIPES */
+        int inout[2], err[2];
+        /* Uses socket pairs to communicate with the program. */
+        if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0 ||
+            socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0)
+                packet_disconnect("Could not create socket pairs: %.100s",
+                                  strerror(errno));
+#endif /* USE_PIPES */
+        if (s == NULL)
+                fatal("do_exec_no_pty: no session");
+
+        setproctitle("%s@notty", pw->pw_name);
+
+#ifdef USE_PAM
+                        do_pam_setcred();
+#endif /* USE_PAM */
+
+        /* Fork the child. */
+        if ((pid = fork()) == 0) {
+                /* Child.  Reinitialize the log since the pid has changed. */
+                log_init(__progname, options.log_level, options.log_facility, log_stderr);
+
+                /*
+                 * Create a new session and process group since the 4.4BSD
+                 * setlogin() affects the entire process group.
+                 */
+                if (setsid() < 0)
+                        error("setsid failed: %.100s", strerror(errno));
+
+#ifdef USE_PIPES
+                /*
+                 * Redirect stdin.  We close the parent side of the socket
+                 * pair, and make the child side the standard input.
+                 */
+                close(pin[1]);
+                if (dup2(pin[0], 0) < 0)
+                        perror("dup2 stdin");
+                close(pin[0]);
+
+                /* Redirect stdout. */
+                close(pout[0]);
+                if (dup2(pout[1], 1) < 0)
+                        perror("dup2 stdout");
+                close(pout[1]);
+
+                /* Redirect stderr. */
+                close(perr[0]);
+                if (dup2(perr[1], 2) < 0)
+                        perror("dup2 stderr");
+                close(perr[1]);
+#else /* USE_PIPES */
+                /*
+                 * Redirect stdin, stdout, and stderr.  Stdin and stdout will
+                 * use the same socket, as some programs (particularly rdist)
+                 * seem to depend on it.
+                 */
+                close(inout[1]);
+                close(err[1]);
+                if (dup2(inout[0], 0) < 0)      /* stdin */
+                        perror("dup2 stdin");
+                if (dup2(inout[0], 1) < 0)      /* stdout.  Note: same socket as stdin. */
+                        perror("dup2 stdout");
+                if (dup2(err[0], 2) < 0)        /* stderr */
+                        perror("dup2 stderr");
+#endif /* USE_PIPES */
+
+                /* Do processing for the child (exec command etc). */
+                do_child(command, pw, NULL, s->display, s->auth_proto, s->auth_data, NULL);
+                /* NOTREACHED */
+        }
+        if (pid < 0)
+                packet_disconnect("fork failed: %.100s", strerror(errno));
+        s->pid = pid;
+#ifdef USE_PIPES
+        /* We are the parent.  Close the child sides of the pipes. */
+        close(pin[0]);
+        close(pout[1]);
+        close(perr[1]);
+
+        /* Enter the interactive session. */
+        server_loop(pid, pin[1], pout[0], perr[0]);
+        /* server_loop has closed pin[1], pout[1], and perr[1]. */
+#else /* USE_PIPES */
+        /* We are the parent.  Close the child sides of the socket pairs. */
+        close(inout[0]);
+        close(err[0]);
+
+        /*
+         * Enter the interactive session.  Note: server_loop must be able to
+         * handle the case that fdin and fdout are the same.
+         */
+        server_loop(pid, inout[1], inout[1], err[1]);
+        /* server_loop has closed inout[1] and err[1]. */
+#endif /* USE_PIPES */
+}
+
+/*
+ * This is called to fork and execute a command when we have a tty.  This
+ * will call do_child from the child, and server_loop from the parent after
+ * setting up file descriptors, controlling tty, updating wtmp, utmp,
+ * lastlog, and other such operations.
+ */
+void 
+do_exec_pty(Session *s, const char *command, struct passwd * pw)
+{
+        FILE *f;
+        char buf[100], *time_string;
+        char line[256];
+        const char *hostname;
+        int fdout, ptyfd, ttyfd, ptymaster;
+        int quiet_login;
+        pid_t pid;
+        socklen_t fromlen;
+        struct sockaddr_storage from;
+        struct stat st;
+        time_t last_login_time;
+
+        if (s == NULL)
+                fatal("do_exec_pty: no session");
+        ptyfd = s->ptyfd;
+        ttyfd = s->ttyfd;
+
+        /* Get remote host name. */
+        hostname = get_canonical_hostname();
+
+        /*
+         * Get the time when the user last logged in.  Buf will be set to
+         * contain the hostname the last login was from.
+         */
+        if (!options.use_login) {
+                last_login_time = get_last_login_time(pw->pw_uid, pw->pw_name,
+                                                      buf, sizeof(buf));
+        }
+        setproctitle("%s@%s", pw->pw_name, strrchr(s->tty, '/') + 1);
+
+#ifdef USE_PAM
+                        do_pam_session(pw->pw_name, s->tty);
+                        do_pam_setcred();
+#endif /* USE_PAM */
+
+        /* Fork the child. */
+        if ((pid = fork()) == 0) {
+                pid = getpid();
+
+                /* Child.  Reinitialize the log because the pid has
+                   changed. */
+                log_init(__progname, options.log_level, options.log_facility, log_stderr);
+
+                /* Close the master side of the pseudo tty. */
+                close(ptyfd);
+
+                /* Make the pseudo tty our controlling tty. */
+                pty_make_controlling_tty(&ttyfd, s->tty);
+
+                /* Redirect stdin from the pseudo tty. */
+                if (dup2(ttyfd, fileno(stdin)) < 0)
+                        error("dup2 stdin failed: %.100s", strerror(errno));
+
+                /* Redirect stdout to the pseudo tty. */
+                if (dup2(ttyfd, fileno(stdout)) < 0)
+                        error("dup2 stdin failed: %.100s", strerror(errno));
+
+                /* Redirect stderr to the pseudo tty. */
+                if (dup2(ttyfd, fileno(stderr)) < 0)
+                        error("dup2 stdin failed: %.100s", strerror(errno));
+
+                /* Close the extra descriptor for the pseudo tty. */
+                close(ttyfd);
+
+///XXXX ? move to do_child() ??
+                /*
+                 * Get IP address of client.  This is needed because we want
+                 * to record where the user logged in from.  If the
+                 * connection is not a socket, let the ip address be 0.0.0.0.
+                 */
+                memset(&from, 0, sizeof(from));
+                if (packet_connection_is_on_socket()) {
+                        fromlen = sizeof(from);
+                        if (getpeername(packet_get_connection_in(),
+                             (struct sockaddr *) & from, &fromlen) < 0) {
+                                debug("getpeername: %.100s", strerror(errno));
+                                fatal_cleanup();
+                        }
+                }
+                /* Record that there was a login on that terminal. */
+                record_login(pid, s->tty, pw->pw_name, pw->pw_uid, hostname,
+                             (struct sockaddr *)&from);
+
+                /* Check if .hushlogin exists. */
+                snprintf(line, sizeof line, "%.200s/.hushlogin", pw->pw_dir);
+                quiet_login = stat(line, &st) >= 0;
+
+#ifdef USE_PAM
+                if (!quiet_login)
+                        print_pam_messages();
+#endif /* USE_PAM */
+
+                /*
+                 * If the user has logged in before, display the time of last
+                 * login. However, don't display anything extra if a command
+                 * has been specified (so that ssh can be used to execute
+                 * commands on a remote machine without users knowing they
+                 * are going to another machine). Login(1) will do this for
+                 * us as well, so check if login(1) is used
+                 */
+                if (command == NULL && last_login_time != 0 && !quiet_login &&
+                    !options.use_login) {
+                        /* Convert the date to a string. */
+                        time_string = ctime(&last_login_time);
+                        /* Remove the trailing newline. */
+                        if (strchr(time_string, '\n'))
+                                *strchr(time_string, '\n') = 0;
+                        /* Display the last login time.  Host if displayed
+                           if known. */
+                        if (strcmp(buf, "") == 0)
+                                printf("Last login: %s\r\n", time_string);
+                        else
+                                printf("Last login: %s from %s\r\n", time_string, buf);
+                }
+                /*
+                 * Print /etc/motd unless a command was specified or printing
+                 * it was disabled in server options or login(1) will be
+                 * used.  Note that some machines appear to print it in
+                 * /etc/profile or similar.
+                 */
+                if (command == NULL && options.print_motd && !quiet_login &&
+                    !options.use_login) {
+                        /* Print /etc/motd if it exists. */
+                        f = fopen("/etc/motd", "r");
+                        if (f) {
+                                while (fgets(line, sizeof(line), f))
+                                        fputs(line, stdout);
+                                fclose(f);
+                        }
+                }
+                /* Do common processing for the child, such as execing the command. */
+                do_child(command, pw, s->term, s->display, s->auth_proto, s->auth_data, s->tty);
+                /* NOTREACHED */
+        }
+        if (pid < 0)
+                packet_disconnect("fork failed: %.100s", strerror(errno));
+        s->pid = pid;
+
+        /* Parent.  Close the slave side of the pseudo tty. */
+        close(ttyfd);
+
+        /*
+         * Create another descriptor of the pty master side for use as the
+         * standard input.  We could use the original descriptor, but this
+         * simplifies code in server_loop.  The descriptor is bidirectional.
+         */
+        fdout = dup(ptyfd);
+        if (fdout < 0)
+                packet_disconnect("dup #1 failed: %.100s", strerror(errno));
+
+        /* we keep a reference to the pty master */
+        ptymaster = dup(ptyfd);
+        if (ptymaster < 0)
+                packet_disconnect("dup #2 failed: %.100s", strerror(errno));
+        s->ptymaster = ptymaster;
+
+        /* Enter interactive session. */
+        server_loop(pid, ptyfd, fdout, -1);
+        /* server_loop _has_ closed ptyfd and fdout. */
+        session_pty_cleanup(s);
+}
+
+/*
+ * Sets the value of the given variable in the environment.  If the variable
+ * already exists, its value is overriden.
+ */
+void 
+child_set_env(char ***envp, unsigned int *envsizep, const char *name,
+              const char *value)
+{
+        unsigned int i, namelen;
+        char **env;
+
+        /*
+         * Find the slot where the value should be stored.  If the variable
+         * already exists, we reuse the slot; otherwise we append a new slot
+         * at the end of the array, expanding if necessary.
+         */
+        env = *envp;
+        namelen = strlen(name);
+        for (i = 0; env[i]; i++)
+                if (strncmp(env[i], name, namelen) == 0 && env[i][namelen] == '=')
+                        break;
+        if (env[i]) {
+                /* Reuse the slot. */
+                xfree(env[i]);
+        } else {
+                /* New variable.  Expand if necessary. */
+                if (i >= (*envsizep) - 1) {
+                        (*envsizep) += 50;
+                        env = (*envp) = xrealloc(env, (*envsizep) * sizeof(char *));
+                }
+                /* Need to set the NULL pointer at end of array beyond the new slot. */
+                env[i + 1] = NULL;
+        }
+
+        /* Allocate space and format the variable in the appropriate slot. */
+        env[i] = xmalloc(strlen(name) + 1 + strlen(value) + 1);
+        snprintf(env[i], strlen(name) + 1 + strlen(value) + 1, "%s=%s", name, value);
+}
+
+/*
+ * Reads environment variables from the given file and adds/overrides them
+ * into the environment.  If the file does not exist, this does nothing.
+ * Otherwise, it must consist of empty lines, comments (line starts with '#')
+ * and assignments of the form name=value.  No other forms are allowed.
+ */
+void 
+read_environment_file(char ***env, unsigned int *envsize,
+                      const char *filename)
+{
+        FILE *f;
+        char buf[4096];
+        char *cp, *value;
+
+        f = fopen(filename, "r");
+        if (!f)
+                return;
+
+        while (fgets(buf, sizeof(buf), f)) {
+                for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
+                        ;
+                if (!*cp || *cp == '#' || *cp == '\n')
+                        continue;
+                if (strchr(cp, '\n'))
+                        *strchr(cp, '\n') = '\0';
+                value = strchr(cp, '=');
+                if (value == NULL) {
+                        fprintf(stderr, "Bad line in %.100s: %.200s\n", filename, buf);
+                        continue;
+                }
+                /* Replace the equals sign by nul, and advance value to the value string. */
+                *value = '\0';
+                value++;
+                child_set_env(env, envsize, cp, value);
+        }
+        fclose(f);
+}
+
+#ifdef USE_PAM
+/*
+ * Sets any environment variables which have been specified by PAM
+ */
+void do_pam_environment(char ***env, int *envsize)
+{
+        char *equals, var_name[512], var_val[512];
+        char **pam_env;
+        int i;
+
+        if ((pam_env = fetch_pam_environment()) == NULL)
+                return;
+        
+        for(i = 0; pam_env[i] != NULL; i++) {
+                if ((equals = strstr(pam_env[i], "=")) == NULL)
+                        continue;
+                        
+                if (strlen(pam_env[i]) < (sizeof(var_name) - 1)) {
+                        memset(var_name, '\0', sizeof(var_name));
+                        memset(var_val, '\0', sizeof(var_val));
+
+                        strncpy(var_name, pam_env[i], equals - pam_env[i]);
+                        strcpy(var_val, equals + 1);
+
+                        debug("PAM environment: %s=%s", var_name, var_val);
+
+                        child_set_env(env, envsize, var_name, var_val);
+                }
+        }
+}
+#endif /* USE_PAM */
+
+/*
+ * Performs common processing for the child, such as setting up the
+ * environment, closing extra file descriptors, setting the user and group
+ * ids, and executing the command or shell.
+ */
+void 
+do_child(const char *command, struct passwd * pw, const char *term,
+         const char *display, const char *auth_proto,
+         const char *auth_data, const char *ttyname)
+{
+        const char *shell, *cp = NULL;
+        char buf[256];
+        FILE *f;
+        unsigned int envsize, i;
+        char **env;
+        extern char **environ;
+        struct stat st;
+        char *argv[10];
+
+#ifndef USE_PAM /* pam_nologin handles this */
+        f = fopen("/etc/nologin", "r");
+        if (f) {
+                /* /etc/nologin exists.  Print its contents and exit. */
+                while (fgets(buf, sizeof(buf), f))
+                        fputs(buf, stderr);
+                fclose(f);
+                if (pw->pw_uid != 0)
+                        exit(254);
+        }
+#endif /* USE_PAM */
+
+        /* Set login name in the kernel. */
+        if (setlogin(pw->pw_name) < 0)
+                error("setlogin failed: %s", strerror(errno));
+
+        /* Set uid, gid, and groups. */
+        /* Login(1) does this as well, and it needs uid 0 for the "-h"
+           switch, so we let login(1) to this for us. */
+        if (!options.use_login) {
+                if (getuid() == 0 || geteuid() == 0) {
+                        if (setgid(pw->pw_gid) < 0) {
+                                perror("setgid");
+                                exit(1);
+                        }
+                        /* Initialize the group list. */
+                        if (initgroups(pw->pw_name, pw->pw_gid) < 0) {
+                                perror("initgroups");
+                                exit(1);
+                        }
+                        endgrent();
+
+                        /* Permanently switch to the desired uid. */
+                        permanently_set_uid(pw->pw_uid);
+                }
+                if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid)
+                        fatal("Failed to set uids to %d.", (int) pw->pw_uid);
+        }
+        /*
+         * Get the shell from the password data.  An empty shell field is
+         * legal, and means /bin/sh.
+         */
+        shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
+
+#ifdef AFS
+        /* Try to get AFS tokens for the local cell. */
+        if (k_hasafs()) {
+                char cell[64];
+
+                if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0)
+                        krb_afslog(cell, 0);
+
+                krb_afslog(0, 0);
+        }
+#endif /* AFS */
+
+        /* Initialize the environment. */
+        envsize = 100;
+        env = xmalloc(envsize * sizeof(char *));
+        env[0] = NULL;
+
+        if (!options.use_login) {
+                /* Set basic environment. */
+                child_set_env(&env, &envsize, "USER", pw->pw_name);
+                child_set_env(&env, &envsize, "LOGNAME", pw->pw_name);
+                child_set_env(&env, &envsize, "HOME", pw->pw_dir);
+                child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
+
+                snprintf(buf, sizeof buf, "%.200s/%.50s",
+                         _PATH_MAILDIR, pw->pw_name);
+                child_set_env(&env, &envsize, "MAIL", buf);
+
+                /* Normal systems set SHELL by default. */
+                child_set_env(&env, &envsize, "SHELL", shell);
+        }
+        if (getenv("TZ"))
+                child_set_env(&env, &envsize, "TZ", getenv("TZ"));
+
+        /* Set custom environment options from RSA authentication. */
+        while (custom_environment) {
+                struct envstring *ce = custom_environment;
+                char *s = ce->s;
+                int i;
+                for (i = 0; s[i] != '=' && s[i]; i++);
+                if (s[i] == '=') {
+                        s[i] = 0;
+                        child_set_env(&env, &envsize, s, s + i + 1);
+                }
+                custom_environment = ce->next;
+                xfree(ce->s);
+                xfree(ce);
+        }
+
+        snprintf(buf, sizeof buf, "%.50s %d %d",
+                 get_remote_ipaddr(), get_remote_port(), get_local_port());
+        child_set_env(&env, &envsize, "SSH_CLIENT", buf);
+
+        if (ttyname)
+                child_set_env(&env, &envsize, "SSH_TTY", ttyname);
+        if (term)
+                child_set_env(&env, &envsize, "TERM", term);
+        if (display)
+                child_set_env(&env, &envsize, "DISPLAY", display);
+
+#ifdef _AIX
+        {
+           char *authstate,*krb5cc;
+
+           if ((authstate = getenv("AUTHSTATE")) != NULL)
+                 child_set_env(&env,&envsize,"AUTHSTATE",authstate);
+
+           if ((krb5cc = getenv("KRB5CCNAME")) != NULL)
+                 child_set_env(&env,&envsize,"KRB5CCNAME",krb5cc);
+        }
+#endif
+
+#ifdef KRB4
+        {
+                extern char *ticket;
+
+                if (ticket)
+                        child_set_env(&env, &envsize, "KRBTKFILE", ticket);
+        }
+#endif /* KRB4 */
+
+#ifdef USE_PAM
+        /* Pull in any environment variables that may have been set by PAM. */
+        do_pam_environment(&env, &envsize);
+#endif /* USE_PAM */
+
+        read_environment_file(&env,&envsize,"/etc/environment");
+
+        if (xauthfile)
+                child_set_env(&env, &envsize, "XAUTHORITY", xauthfile);
+        if (auth_get_socket_name() != NULL)
+                child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,
+                              auth_get_socket_name());
+
+        /* read $HOME/.ssh/environment. */
+        if (!options.use_login) {
+                snprintf(buf, sizeof buf, "%.200s/.ssh/environment", pw->pw_dir);
+                read_environment_file(&env, &envsize, buf);
+        }
+        if (debug_flag) {
+                /* dump the environment */
+                fprintf(stderr, "Environment:\n");
+                for (i = 0; env[i]; i++)
+                        fprintf(stderr, "  %.200s\n", env[i]);
+        }
+        /*
+         * Close the connection descriptors; note that this is the child, and
+         * the server will still have the socket open, and it is important
+         * that we do not shutdown it.  Note that the descriptors cannot be
+         * closed before building the environment, as we call
+         * get_remote_ipaddr there.
+         */
+        if (packet_get_connection_in() == packet_get_connection_out())
+                close(packet_get_connection_in());
+        else {
+                close(packet_get_connection_in());
+                close(packet_get_connection_out());
+        }
+        /*
+         * Close all descriptors related to channels.  They will still remain
+         * open in the parent.
+         */
+        /* XXX better use close-on-exec? -markus */
+        channel_close_all();
+
+        /*
+         * Close any extra file descriptors.  Note that there may still be
+         * descriptors left by system functions.  They will be closed later.
+         */
+        endpwent();
+
+        /*
+         * Close any extra open file descriptors so that we don\'t have them
+         * hanging around in clients.  Note that we want to do this after
+         * initgroups, because at least on Solaris 2.3 it leaves file
+         * descriptors open.
+         */
+        for (i = 3; i < 64; i++)
+                close(i);
+
+        /* Change current directory to the user\'s home directory. */
+        if (chdir(pw->pw_dir) < 0)
+                fprintf(stderr, "Could not chdir to home directory %s: %s\n",
+                        pw->pw_dir, strerror(errno));
+
+        /*
+         * Must take new environment into use so that .ssh/rc, /etc/sshrc and
+         * xauth are run in the proper environment.
+         */
+        environ = env;
+
+        /*
+         * Run $HOME/.ssh/rc, /etc/sshrc, or xauth (whichever is found first
+         * in this order).
+         */
+        if (!options.use_login) {
+                if (stat(SSH_USER_RC, &st) >= 0) {
+                        if (debug_flag)
+                                fprintf(stderr, "Running /bin/sh %s\n", SSH_USER_RC);
+
+                        f = popen("/bin/sh " SSH_USER_RC, "w");
+                        if (f) {
+                                if (auth_proto != NULL && auth_data != NULL)
+                                        fprintf(f, "%s %s\n", auth_proto, auth_data);
+                                pclose(f);
+                        } else
+                                fprintf(stderr, "Could not run %s\n", SSH_USER_RC);
+                } else if (stat(SSH_SYSTEM_RC, &st) >= 0) {
+                        if (debug_flag)
+                                fprintf(stderr, "Running /bin/sh %s\n", SSH_SYSTEM_RC);
+
+                        f = popen("/bin/sh " SSH_SYSTEM_RC, "w");
+                        if (f) {
+                                if (auth_proto != NULL && auth_data != NULL)
+                                        fprintf(f, "%s %s\n", auth_proto, auth_data);
+                                pclose(f);
+                        } else
+                                fprintf(stderr, "Could not run %s\n", SSH_SYSTEM_RC);
+                }
+#ifdef XAUTH_PATH
+                else {
+                        /* Add authority data to .Xauthority if appropriate. */
+                        if (auth_proto != NULL && auth_data != NULL) {
+                                if (debug_flag)
+                                        fprintf(stderr, "Running %.100s add %.100s %.100s %.100s\n",
+                                                XAUTH_PATH, display, auth_proto, auth_data);
+
+                                f = popen(XAUTH_PATH " -q -", "w");
+                                if (f) {
+                                        fprintf(f, "add %s %s %s\n", display, auth_proto, auth_data);
+                                        pclose(f);
+                                } else
+                                        fprintf(stderr, "Could not run %s -q -\n", XAUTH_PATH);
+                        }
+                }
+#endif /* XAUTH_PATH */
+
+                /* Get the last component of the shell name. */
+                cp = strrchr(shell, '/');
+                if (cp)
+                        cp++;
+                else
+                        cp = shell;
+        }
+        /*
+         * If we have no command, execute the shell.  In this case, the shell
+         * name to be passed in argv[0] is preceded by '-' to indicate that
+         * this is a login shell.
+         */
+        if (!command) {
+                if (!options.use_login) {
+                        char buf[256];
+
+                        /*
+                         * Check for mail if we have a tty and it was enabled
+                         * in server options.
+                         */
+                        if (ttyname && options.check_mail) {
+                                char *mailbox;
+                                struct stat mailstat;
+                                mailbox = getenv("MAIL");
+                                if (mailbox != NULL) {
+                                        if (stat(mailbox, &mailstat) != 0 || mailstat.st_size == 0)
+                                                printf("No mail.\n");
+                                        else if (mailstat.st_mtime < mailstat.st_atime)
+                                                printf("You have mail.\n");
+                                        else
+                                                printf("You have new mail.\n");
+                                }
+                        }
+                        /* Start the shell.  Set initial character to '-'. */
+                        buf[0] = '-';
+                        strncpy(buf + 1, cp, sizeof(buf) - 1);
+                        buf[sizeof(buf) - 1] = 0;
+
+                        /* Execute the shell. */
+                        argv[0] = buf;
+                        argv[1] = NULL;
+                        execve(shell, argv, env);
+
+                        /* Executing the shell failed. */
+                        perror(shell);
+                        exit(1);
+
+                } else {
+                        /* Launch login(1). */
+
+                        execl("/usr/bin/login", "login", "-h", get_remote_ipaddr(),
+                              "-p", "-f", "--", pw->pw_name, NULL);
+
+                        /* Login couldn't be executed, die. */
+
+                        perror("login");
+                        exit(1);
+                }
+        }
+        /*
+         * Execute the command using the user's shell.  This uses the -c
+         * option to execute the command.
+         */
+        argv[0] = (char *) cp;
+        argv[1] = "-c";
+        argv[2] = (char *) command;
+        argv[3] = NULL;
+        execve(shell, argv, env);
+        perror(shell);
+        exit(1);
+}
+
+Session *
+session_new(void)
+{
+        int i;
+        static int did_init = 0;
+        if (!did_init) {
+                debug("session_new: init");
+                for(i = 0; i < MAX_SESSIONS; i++) {
+                        sessions[i].used = 0;
+                        sessions[i].self = i;
+                }
+                did_init = 1;
+        }
+        for(i = 0; i < MAX_SESSIONS; i++) {
+                Session *s = &sessions[i];
+                if (! s->used) {
+                        s->pid = 0;
+                        s->chanid = -1;
+                        s->ptyfd = -1;
+                        s->ttyfd = -1;
+                        s->term = NULL;
+                        s->pw = NULL;
+                        s->display = NULL;
+                        s->screen = 0;
+                        s->auth_data = NULL;
+                        s->auth_proto = NULL;
+                        s->used = 1;
+                        debug("session_new: session %d", i);
+                        return s;
+                }
+        }
+        return NULL;
+}
+
+void
+session_dump(void)
+{
+        int i;
+        for(i = 0; i < MAX_SESSIONS; i++) {
+                Session *s = &sessions[i];
+                debug("dump: used %d session %d %p channel %d pid %d",
+                    s->used,
+                    s->self,
+                    s,
+                    s->chanid,
+                    s->pid);
+        }
+}
+
+void
+session_pty_cleanup(Session *s)
+{
+        if (s == NULL || s->ttyfd == -1)
+                return;
+
+        debug("session_pty_cleanup: session %i release %s", s->self, s->tty);
+
+        /* Cancel the cleanup function. */
+        fatal_remove_cleanup(pty_cleanup_proc, (void *)s);
+
+        /* Record that the user has logged out. */
+        record_logout(s->pid, s->tty);
+
+        /* Release the pseudo-tty. */
+        pty_release(s->tty);
+
+        /*
+         * Close the server side of the socket pairs.  We must do this after
+         * the pty cleanup, so that another process doesn't get this pty
+         * while we're still cleaning up.
+         */
+        if (close(s->ptymaster) < 0)
+                error("close(s->ptymaster): %s", strerror(errno));
+}