dropbear: update to 2015.67

[tomato.git] / release / src / router / dropbear / dbutil.c

/*
 * Dropbear - a SSH2 server
 * 
 * Copyright (c) 2002,2003 Matt Johnston
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * strlcat() is copyright as follows:
 * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
 * 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.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``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 "config.h"

#ifdef __linux__
#define _GNU_SOURCE
/* To call clock_gettime() directly */
#include <sys/syscall.h>
#endif /* __linux */

#ifdef HAVE_MACH_MACH_TIME_H
#include <mach/mach_time.h>
#include <mach/mach.h>
#endif

#include "includes.h"
#include "dbutil.h"
#include "buffer.h"
#include "session.h"
#include "atomicio.h"

#define MAX_FMT 100

static void generic_dropbear_exit(int exitcode, const char* format, 
                va_list param) ATTRIB_NORETURN;
static void generic_dropbear_log(int priority, const char* format, 
                va_list param);

void (*_dropbear_exit)(int exitcode, const char* format, va_list param) ATTRIB_NORETURN
                                                = generic_dropbear_exit;
void (*_dropbear_log)(int priority, const char* format, va_list param)
                                                = generic_dropbear_log;

#ifdef DEBUG_TRACE
int debug_trace = 0;
#endif

#ifndef DISABLE_SYSLOG
void startsyslog() {

        openlog(PROGNAME, LOG_PID, LOG_AUTHPRIV);

}
#endif /* DISABLE_SYSLOG */

/* the "format" string must be <= 100 characters */
void dropbear_close(const char* format, ...) {

        va_list param;

        va_start(param, format);
        _dropbear_exit(EXIT_SUCCESS, format, param);
        va_end(param);

}

void dropbear_exit(const char* format, ...) {

        va_list param;

        va_start(param, format);
        _dropbear_exit(EXIT_FAILURE, format, param);
        va_end(param);
}

static void generic_dropbear_exit(int exitcode, const char* format, 
                va_list param) {

        char fmtbuf[300];

        snprintf(fmtbuf, sizeof(fmtbuf), "Exited: %s", format);

        _dropbear_log(LOG_INFO, fmtbuf, param);

        exit(exitcode);
}

void fail_assert(const char* expr, const char* file, int line) {
        dropbear_exit("Failed assertion (%s:%d): `%s'", file, line, expr);
}

static void generic_dropbear_log(int UNUSED(priority), const char* format, 
                va_list param) {

        char printbuf[1024];

        vsnprintf(printbuf, sizeof(printbuf), format, param);

        fprintf(stderr, "%s\n", printbuf);

}

/* this is what can be called to write arbitrary log messages */
void dropbear_log(int priority, const char* format, ...) {

        va_list param;

        va_start(param, format);
        _dropbear_log(priority, format, param);
        va_end(param);
}


#ifdef DEBUG_TRACE
void dropbear_trace(const char* format, ...) {
        va_list param;
        struct timeval tv;

        if (!debug_trace) {
                return;
        }

        gettimeofday(&tv, NULL);

        va_start(param, format);
        fprintf(stderr, "TRACE  (%d) %d.%d: ", getpid(), (int)tv.tv_sec, (int)tv.tv_usec);
        vfprintf(stderr, format, param);
        fprintf(stderr, "\n");
        va_end(param);
}

void dropbear_trace2(const char* format, ...) {
        static int trace_env = -1;
        va_list param;
        struct timeval tv;

        if (trace_env == -1) {
                trace_env = getenv("DROPBEAR_TRACE2") ? 1 : 0;
        }

        if (!(debug_trace && trace_env)) {
                return;
        }

        gettimeofday(&tv, NULL);

        va_start(param, format);
        fprintf(stderr, "TRACE2 (%d) %d.%d: ", getpid(), (int)tv.tv_sec, (int)tv.tv_usec);
        vfprintf(stderr, format, param);
        fprintf(stderr, "\n");
        va_end(param);
}
#endif /* DEBUG_TRACE */

void set_sock_nodelay(int sock) {
        int val;

        /* disable nagle */
        val = 1;
        setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (void*)&val, sizeof(val));
}

void set_sock_priority(int sock, enum dropbear_prio prio) {

        int iptos_val = 0, so_prio_val = 0, rc;

        /* Don't log ENOTSOCK errors so that this can harmlessly be called
         * on a client '-J' proxy pipe */

        /* set the TOS bit for either ipv4 or ipv6 */
#ifdef IPTOS_LOWDELAY
        if (prio == DROPBEAR_PRIO_LOWDELAY) {
                iptos_val = IPTOS_LOWDELAY;
        } else if (prio == DROPBEAR_PRIO_BULK) {
                iptos_val = IPTOS_THROUGHPUT;
        }
#if defined(IPPROTO_IPV6) && defined(IPV6_TCLASS)
        rc = setsockopt(sock, IPPROTO_IPV6, IPV6_TCLASS, (void*)&iptos_val, sizeof(iptos_val));
        if (rc < 0 && errno != ENOTSOCK) {
                TRACE(("Couldn't set IPV6_TCLASS (%s)", strerror(errno)));
        }
#endif
        rc = setsockopt(sock, IPPROTO_IP, IP_TOS, (void*)&iptos_val, sizeof(iptos_val));
        if (rc < 0 && errno != ENOTSOCK) {
                TRACE(("Couldn't set IP_TOS (%s)", strerror(errno)));
        }
#endif

#ifdef SO_PRIORITY
        if (prio == DROPBEAR_PRIO_LOWDELAY) {
                so_prio_val = TC_PRIO_INTERACTIVE;
        } else if (prio == DROPBEAR_PRIO_BULK) {
                so_prio_val = TC_PRIO_BULK;
        }
        /* linux specific, sets QoS class. see tc-prio(8) */
        rc = setsockopt(sock, SOL_SOCKET, SO_PRIORITY, (void*) &so_prio_val, sizeof(so_prio_val));
        if (rc < 0 && errno != ENOTSOCK)
                dropbear_log(LOG_WARNING, "Couldn't set SO_PRIORITY (%s)",
                                strerror(errno));
#endif

}

/* Listen on address:port. 
 * Special cases are address of "" listening on everything,
 * and address of NULL listening on localhost only.
 * Returns the number of sockets bound on success, or -1 on failure. On
 * failure, if errstring wasn't NULL, it'll be a newly malloced error
 * string.*/
int dropbear_listen(const char* address, const char* port,
                int *socks, unsigned int sockcount, char **errstring, int *maxfd) {

        struct addrinfo hints, *res = NULL, *res0 = NULL;
        int err;
        unsigned int nsock;
        struct linger linger;
        int val;
        int sock;

        TRACE(("enter dropbear_listen"))
        
        memset(&hints, 0, sizeof(hints));
        hints.ai_family = AF_UNSPEC; /* TODO: let them flag v4 only etc */
        hints.ai_socktype = SOCK_STREAM;

        /* for calling getaddrinfo:
         address == NULL and !AI_PASSIVE: local loopback
         address == NULL and AI_PASSIVE: all interfaces
         address != NULL: whatever the address says */
        if (!address) {
                TRACE(("dropbear_listen: local loopback"))
        } else {
                if (address[0] == '\0') {
                        TRACE(("dropbear_listen: all interfaces"))
                        address = NULL;
                }
                hints.ai_flags = AI_PASSIVE;
        }
        err = getaddrinfo(address, port, &hints, &res0);

        if (err) {
                if (errstring != NULL && *errstring == NULL) {
                        int len;
                        len = 20 + strlen(gai_strerror(err));
                        *errstring = (char*)m_malloc(len);
                        snprintf(*errstring, len, "Error resolving: %s", gai_strerror(err));
                }
                if (res0) {
                        freeaddrinfo(res0);
                        res0 = NULL;
                }
                TRACE(("leave dropbear_listen: failed resolving"))
                return -1;
        }


        nsock = 0;
        for (res = res0; res != NULL && nsock < sockcount;
                        res = res->ai_next) {

                /* Get a socket */
                socks[nsock] = socket(res->ai_family, res->ai_socktype,
                                res->ai_protocol);

                sock = socks[nsock]; /* For clarity */

                if (sock < 0) {
                        err = errno;
                        TRACE(("socket() failed"))
                        continue;
                }

                /* Various useful socket options */
                val = 1;
                /* set to reuse, quick timeout */
                setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void*) &val, sizeof(val));
                linger.l_onoff = 1;
                linger.l_linger = 5;
                setsockopt(sock, SOL_SOCKET, SO_LINGER, (void*)&linger, sizeof(linger));

#if defined(IPPROTO_IPV6) && defined(IPV6_V6ONLY)
                if (res->ai_family == AF_INET6) {
                        int on = 1;
                        if (setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, 
                                                &on, sizeof(on)) == -1) {
                                dropbear_log(LOG_WARNING, "Couldn't set IPV6_V6ONLY");
                        }
                }
#endif

                set_sock_nodelay(sock);

                if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
                        err = errno;
                        close(sock);
                        TRACE(("bind(%s) failed", port))
                        continue;
                }

                if (listen(sock, DROPBEAR_LISTEN_BACKLOG) < 0) {
                        err = errno;
                        close(sock);
                        TRACE(("listen() failed"))
                        continue;
                }

                *maxfd = MAX(*maxfd, sock);

                nsock++;
        }

        if (res0) {
                freeaddrinfo(res0);
                res0 = NULL;
        }

        if (nsock == 0) {
                if (errstring != NULL && *errstring == NULL) {
                        int len;
                        len = 20 + strlen(strerror(err));
                        *errstring = (char*)m_malloc(len);
                        snprintf(*errstring, len, "Error listening: %s", strerror(err));
                }
                TRACE(("leave dropbear_listen: failure, %s", strerror(err)))
                return -1;
        }

        TRACE(("leave dropbear_listen: success, %d socks bound", nsock))
        return nsock;
}

/* Connect to a given unix socket. The socket is blocking */
#ifdef ENABLE_CONNECT_UNIX
int connect_unix(const char* path) {
        struct sockaddr_un addr;
        int fd = -1;

        memset((void*)&addr, 0x0, sizeof(addr));
        addr.sun_family = AF_UNIX;
        strlcpy(addr.sun_path, path, sizeof(addr.sun_path));
        fd = socket(PF_UNIX, SOCK_STREAM, 0);
        if (fd < 0) {
                TRACE(("Failed to open unix socket"))
                return -1;
        }
        if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
                TRACE(("Failed to connect to '%s' socket", path))
                m_close(fd);
                return -1;
        }
        return fd;
}
#endif

/* Connect via TCP to a host. Connection will try ipv4 or ipv6, will
 * return immediately if nonblocking is set. On failure, if errstring
 * wasn't null, it will be a newly malloced error message */

/* TODO: maxfd */
int connect_remote(const char* remotehost, const char* remoteport,
                int nonblocking, char ** errstring) {

        struct addrinfo *res0 = NULL, *res = NULL, hints;
        int sock;
        int err;

        TRACE(("enter connect_remote"))

        if (errstring != NULL) {
                *errstring = NULL;
        }

        memset(&hints, 0, sizeof(hints));
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_family = PF_UNSPEC;

        err = getaddrinfo(remotehost, remoteport, &hints, &res0);
        if (err) {
                if (errstring != NULL && *errstring == NULL) {
                        int len;
                        len = 100 + strlen(gai_strerror(err));
                        *errstring = (char*)m_malloc(len);
                        snprintf(*errstring, len, "Error resolving '%s' port '%s'. %s", 
                                        remotehost, remoteport, gai_strerror(err));
                }
                TRACE(("Error resolving: %s", gai_strerror(err)))
                return -1;
        }

        sock = -1;
        err = EADDRNOTAVAIL;
        for (res = res0; res; res = res->ai_next) {

                sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
                if (sock < 0) {
                        err = errno;
                        continue;
                }

                if (nonblocking) {
                        setnonblocking(sock);
                }

                if (connect(sock, res->ai_addr, res->ai_addrlen) < 0) {
                        if (errno == EINPROGRESS && nonblocking) {
                                TRACE(("Connect in progress"))
                                break;
                        } else {
                                err = errno;
                                close(sock);
                                sock = -1;
                                continue;
                        }
                }

                break; /* Success */
        }

        if (sock < 0 && !(errno == EINPROGRESS && nonblocking)) {
                /* Failed */
                if (errstring != NULL && *errstring == NULL) {
                        int len;
                        len = 20 + strlen(strerror(err));
                        *errstring = (char*)m_malloc(len);
                        snprintf(*errstring, len, "Error connecting: %s", strerror(err));
                }
                TRACE(("Error connecting: %s", strerror(err)))
        } else {
                /* Success */
                set_sock_nodelay(sock);
        }

        freeaddrinfo(res0);
        if (sock > 0 && errstring != NULL && *errstring != NULL) {
                m_free(*errstring);
        }

        TRACE(("leave connect_remote: sock %d\n", sock))
        return sock;
}

/* Sets up a pipe for a, returning three non-blocking file descriptors
 * and the pid. exec_fn is the function that will actually execute the child process,
 * it will be run after the child has fork()ed, and is passed exec_data.
 * If ret_errfd == NULL then stderr will not be captured.
 * ret_pid can be passed as  NULL to discard the pid. */
int spawn_command(void(*exec_fn)(void *user_data), void *exec_data,
                int *ret_writefd, int *ret_readfd, int *ret_errfd, pid_t *ret_pid) {
        int infds[2];
        int outfds[2];
        int errfds[2];
        pid_t pid;

        const int FDIN = 0;
        const int FDOUT = 1;

        /* redirect stdin/stdout/stderr */
        if (pipe(infds) != 0) {
                return DROPBEAR_FAILURE;
        }
        if (pipe(outfds) != 0) {
                return DROPBEAR_FAILURE;
        }
        if (ret_errfd && pipe(errfds) != 0) {
                return DROPBEAR_FAILURE;
        }

#ifdef USE_VFORK
        pid = vfork();
#else
        pid = fork();
#endif

        if (pid < 0) {
                return DROPBEAR_FAILURE;
        }

        if (!pid) {
                /* child */

                TRACE(("back to normal sigchld"))
                /* Revert to normal sigchld handling */
                if (signal(SIGCHLD, SIG_DFL) == SIG_ERR) {
                        dropbear_exit("signal() error");
                }

                /* redirect stdin/stdout */

                if ((dup2(infds[FDIN], STDIN_FILENO) < 0) ||
                        (dup2(outfds[FDOUT], STDOUT_FILENO) < 0) ||
                        (ret_errfd && dup2(errfds[FDOUT], STDERR_FILENO) < 0)) {
                        TRACE(("leave noptycommand: error redirecting FDs"))
                        dropbear_exit("Child dup2() failure");
                }

                close(infds[FDOUT]);
                close(infds[FDIN]);
                close(outfds[FDIN]);
                close(outfds[FDOUT]);
                if (ret_errfd)
                {
                        close(errfds[FDIN]);
                        close(errfds[FDOUT]);
                }

                exec_fn(exec_data);
                /* not reached */
                return DROPBEAR_FAILURE;
        } else {
                /* parent */
                close(infds[FDIN]);
                close(outfds[FDOUT]);

                setnonblocking(outfds[FDIN]);
                setnonblocking(infds[FDOUT]);

                if (ret_errfd) {
                        close(errfds[FDOUT]);
                        setnonblocking(errfds[FDIN]);
                }

                if (ret_pid) {
                        *ret_pid = pid;
                }

                *ret_writefd = infds[FDOUT];
                *ret_readfd = outfds[FDIN];
                if (ret_errfd) {
                        *ret_errfd = errfds[FDIN];
                }
                return DROPBEAR_SUCCESS;
        }
}

/* Runs a command with "sh -c". Will close FDs (except stdin/stdout/stderr) and
 * re-enabled SIGPIPE. If cmd is NULL, will run a login shell.
 */
void run_shell_command(const char* cmd, unsigned int maxfd, char* usershell) {
        char * argv[4];
        char * baseshell = NULL;
        unsigned int i;

        baseshell = basename(usershell);

        if (cmd != NULL) {
                argv[0] = baseshell;
        } else {
                /* a login shell should be "-bash" for "/bin/bash" etc */
                int len = strlen(baseshell) + 2; /* 2 for "-" */
                argv[0] = (char*)m_malloc(len);
                snprintf(argv[0], len, "-%s", baseshell);
        }

        if (cmd != NULL) {
                argv[1] = "-c";
                argv[2] = (char*)cmd;
                argv[3] = NULL;
        } else {
                /* construct a shell of the form "-bash" etc */
                argv[1] = NULL;
        }

        /* Re-enable SIGPIPE for the executed process */
        if (signal(SIGPIPE, SIG_DFL) == SIG_ERR) {
                dropbear_exit("signal() error");
        }

        /* close file descriptors except stdin/stdout/stderr
         * Need to be sure FDs are closed here to avoid reading files as root */
        for (i = 3; i <= maxfd; i++) {
                m_close(i);
        }

        execv(usershell, argv);
}

void get_socket_address(int fd, char **local_host, char **local_port,
                                                char **remote_host, char **remote_port, int host_lookup)
{
        struct sockaddr_storage addr;
        socklen_t addrlen;
        
        if (local_host || local_port) {
                addrlen = sizeof(addr);
                if (getsockname(fd, (struct sockaddr*)&addr, &addrlen) < 0) {
                        dropbear_exit("Failed socket address: %s", strerror(errno));
                }
                getaddrstring(&addr, local_host, local_port, host_lookup);              
        }
        if (remote_host || remote_port) {
                addrlen = sizeof(addr);
                if (getpeername(fd, (struct sockaddr*)&addr, &addrlen) < 0) {
                        dropbear_exit("Failed socket address: %s", strerror(errno));
                }
                getaddrstring(&addr, remote_host, remote_port, host_lookup);            
        }
}

/* Return a string representation of the socket address passed. The return
 * value is allocated with malloc() */
void getaddrstring(struct sockaddr_storage* addr, 
                        char **ret_host, char **ret_port,
                        int host_lookup) {

        char host[NI_MAXHOST+1], serv[NI_MAXSERV+1];
        unsigned int len;
        int ret;
        
        int flags = NI_NUMERICSERV | NI_NUMERICHOST;

#ifndef DO_HOST_LOOKUP
        host_lookup = 0;
#endif
        
        if (host_lookup) {
                flags = NI_NUMERICSERV;
        }

        len = sizeof(struct sockaddr_storage);
        /* Some platforms such as Solaris 8 require that len is the length
         * of the specific structure. Some older linux systems (glibc 2.1.3
         * such as debian potato) have sockaddr_storage.__ss_family instead
         * but we'll ignore them */
#ifdef HAVE_STRUCT_SOCKADDR_STORAGE_SS_FAMILY
        if (addr->ss_family == AF_INET) {
                len = sizeof(struct sockaddr_in);
        }
#ifdef AF_INET6
        if (addr->ss_family == AF_INET6) {
                len = sizeof(struct sockaddr_in6);
        }
#endif
#endif

        ret = getnameinfo((struct sockaddr*)addr, len, host, sizeof(host)-1, 
                        serv, sizeof(serv)-1, flags);

        if (ret != 0) {
                if (host_lookup) {
                        /* On some systems (Darwin does it) we get EINTR from getnameinfo
                         * somehow. Eew. So we'll just return the IP, since that doesn't seem
                         * to exhibit that behaviour. */
                        getaddrstring(addr, ret_host, ret_port, 0);
                        return;
                } else {
                        /* if we can't do a numeric lookup, something's gone terribly wrong */
                        dropbear_exit("Failed lookup: %s", gai_strerror(ret));
                }
        }

        if (ret_host) {
                *ret_host = m_strdup(host);
        }
        if (ret_port) {
                *ret_port = m_strdup(serv);
        }
}

#ifdef DEBUG_TRACE
void printhex(const char * label, const unsigned char * buf, int len) {

        int i;

        fprintf(stderr, "%s\n", label);
        for (i = 0; i < len; i++) {
                fprintf(stderr, "%02x", buf[i]);
                if (i % 16 == 15) {
                        fprintf(stderr, "\n");
                }
                else if (i % 2 == 1) {
                        fprintf(stderr, " ");
                }
        }
        fprintf(stderr, "\n");
}

void printmpint(const char *label, mp_int *mp) {
        buffer *buf = buf_new(1000);
        buf_putmpint(buf, mp);
        printhex(label, buf->data, buf->len);
        buf_free(buf);

}
#endif

/* Strip all control characters from text (a null-terminated string), except
 * for '\n', '\r' and '\t'.
 * The result returned is a newly allocated string, this must be free()d after
 * use */
char * stripcontrol(const char * text) {

        char * ret;
        int len, pos;
        int i;
        
        len = strlen(text);
        ret = m_malloc(len+1);

        pos = 0;
        for (i = 0; i < len; i++) {
                if ((text[i] <= '~' && text[i] >= ' ') /* normal printable range */
                                || text[i] == '\n' || text[i] == '\r' || text[i] == '\t') {
                        ret[pos] = text[i];
                        pos++;
                }
        }
        ret[pos] = 0x0;
        return ret;
}
                        

/* reads the contents of filename into the buffer buf, from the current
 * position, either to the end of the file, or the buffer being full.
 * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
int buf_readfile(buffer* buf, const char* filename) {

        int fd = -1;
        int len;
        int maxlen;
        int ret = DROPBEAR_FAILURE;

        fd = open(filename, O_RDONLY);

        if (fd < 0) {
                goto out;
        }
        
        do {
                maxlen = buf->size - buf->pos;
                len = read(fd, buf_getwriteptr(buf, maxlen), maxlen);
                if (len < 0) {
                        if (errno == EINTR || errno == EAGAIN) {
                                continue;
                        }
                        goto out;
                }
                buf_incrwritepos(buf, len);
        } while (len < maxlen && len > 0);

        ret = DROPBEAR_SUCCESS;

out:
        if (fd >= 0) {
                m_close(fd);
        }
        return ret;
}

/* get a line from the file into buffer in the style expected for an
 * authkeys file.
 * Will return DROPBEAR_SUCCESS if data is read, or DROPBEAR_FAILURE on EOF.*/
/* Only used for ~/.ssh/known_hosts and ~/.ssh/authorized_keys */
#if defined(DROPBEAR_CLIENT) || defined(ENABLE_SVR_PUBKEY_AUTH)
int buf_getline(buffer * line, FILE * authfile) {

        int c = EOF;

        buf_setpos(line, 0);
        buf_setlen(line, 0);

        while (line->pos < line->size) {

                c = fgetc(authfile); /*getc() is weird with some uClibc systems*/
                if (c == EOF || c == '\n' || c == '\r') {
                        goto out;
                }

                buf_putbyte(line, (unsigned char)c);
        }

        TRACE(("leave getauthline: line too long"))
        /* We return success, but the line length will be zeroed - ie we just
         * ignore that line */
        buf_setlen(line, 0);

out:


        /* if we didn't read anything before EOF or error, exit */
        if (c == EOF && line->pos == 0) {
                return DROPBEAR_FAILURE;
        } else {
                buf_setpos(line, 0);
                return DROPBEAR_SUCCESS;
        }

}       
#endif

/* make sure that the socket closes */
void m_close(int fd) {

        if (fd == -1) {
                return;
        }

        int val;
        do {
                val = close(fd);
        } while (val < 0 && errno == EINTR);

        if (val < 0 && errno != EBADF) {
                /* Linux says EIO can happen */
                dropbear_exit("Error closing fd %d, %s", fd, strerror(errno));
        }
}
        
void * m_malloc(size_t size) {

        void* ret;

        if (size == 0) {
                dropbear_exit("m_malloc failed");
        }
        ret = calloc(1, size);
        if (ret == NULL) {
                dropbear_exit("m_malloc failed");
        }
        return ret;

}

void * m_strdup(const char * str) {
        char* ret;

        ret = strdup(str);
        if (ret == NULL) {
                dropbear_exit("m_strdup failed");
        }
        return ret;
}

void * m_realloc(void* ptr, size_t size) {

        void *ret;

        if (size == 0) {
                dropbear_exit("m_realloc failed");
        }
        ret = realloc(ptr, size);
        if (ret == NULL) {
                dropbear_exit("m_realloc failed");
        }
        return ret;
}

/* Clear the data, based on the method in David Wheeler's
 * "Secure Programming for Linux and Unix HOWTO" */
/* Beware of calling this from within dbutil.c - things might get
 * optimised away */
void m_burn(void *data, unsigned int len) {
        volatile char *p = data;

        if (data == NULL)
                return;
        while (len--) {
                *p++ = 0x0;
        }
}


void setnonblocking(int fd) {

        TRACE(("setnonblocking: %d", fd))

        if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) {
                if (errno == ENODEV) {
                        /* Some devices (like /dev/null redirected in)
                         * can't be set to non-blocking */
                        TRACE(("ignoring ENODEV for setnonblocking"))
                } else {
                        dropbear_exit("Couldn't set nonblocking");
                }
        }
        TRACE(("leave setnonblocking"))
}

void disallow_core() {
        struct rlimit lim;
        lim.rlim_cur = lim.rlim_max = 0;
        setrlimit(RLIMIT_CORE, &lim);
}

/* Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE, with the result in *val */
int m_str_to_uint(const char* str, unsigned int *val) {
        unsigned long l;
        errno = 0;
        l = strtoul(str, NULL, 10);
        /* The c99 spec doesn't actually seem to define EINVAL, but most platforms
         * I've looked at mention it in their manpage */
        if ((l == 0 && errno == EINVAL)
                || (l == ULONG_MAX && errno == ERANGE)
                || (l > UINT_MAX)) {
                return DROPBEAR_FAILURE;
        } else {
                *val = l;
                return DROPBEAR_SUCCESS;
        }
}

/* Returns malloced path. Only expands ~ in first character */
char * expand_tilde(const char *inpath) {
        struct passwd *pw = NULL;
        if (inpath[0] == '~') {
                pw = getpwuid(getuid());
                if (pw && pw->pw_dir) {
                        int len = strlen(inpath) + strlen(pw->pw_dir) + 1;
                        char *buf = m_malloc(len);
                        snprintf(buf, len, "%s/%s", pw->pw_dir, &inpath[1]);
                        return buf;
                }
        }

        /* Fallback */
        return m_strdup(inpath);
}

int constant_time_memcmp(const void* a, const void *b, size_t n)
{
        const char *xa = a, *xb = b;
        uint8_t c = 0;
        size_t i;
        for (i = 0; i < n; i++)
        {
                c |= (xa[i] ^ xb[i]);
        }
        return c;
}

#if defined(__linux__) && defined(SYS_clock_gettime)
/* CLOCK_MONOTONIC_COARSE was added in Linux 2.6.32 but took a while to
reach userspace include headers */
#ifndef CLOCK_MONOTONIC_COARSE
#define CLOCK_MONOTONIC_COARSE 6
#endif
static clockid_t get_linux_clock_source() {
        struct timespec ts;
        if (syscall(SYS_clock_gettime, CLOCK_MONOTONIC_COARSE, &ts) == 0) {
                return CLOCK_MONOTONIC_COARSE;
        }

        if (syscall(SYS_clock_gettime, CLOCK_MONOTONIC, &ts) == 0) {
                return CLOCK_MONOTONIC;
        }
        return -1;
}
#endif 

time_t monotonic_now() {
#if defined(__linux__) && defined(SYS_clock_gettime)
        static clockid_t clock_source = -2;

        if (clock_source == -2) {
                /* First run, find out which one works. 
                -1 will fall back to time() */
                clock_source = get_linux_clock_source();
        }

        if (clock_source >= 0) {
                struct timespec ts;
                if (syscall(SYS_clock_gettime, clock_source, &ts) != 0) {
                        /* Intermittent clock failures should not happen */
                        dropbear_exit("Clock broke");
                }
                return ts.tv_sec;
        }
#endif /* linux clock_gettime */

#if defined(HAVE_MACH_ABSOLUTE_TIME)
        /* OS X, see https://developer.apple.com/library/mac/qa/qa1398/_index.html */
        static mach_timebase_info_data_t timebase_info;
        if (timebase_info.denom == 0) {
                mach_timebase_info(&timebase_info);
        }
        return mach_absolute_time() * timebase_info.numer / timebase_info.denom
                / 1e9;
#endif /* osx mach_absolute_time */

        /* Fallback for everything else - this will sometimes go backwards */
        return time(NULL);
}