snmplib/transports/snmpUnixDomain.c

#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-features.h>

#include <sys/types.h>
#include <net-snmp/library/snmpUnixDomain.h>

#include <stddef.h>
#include <stdio.h>
#include <ctype.h>
#include <errno.h>

#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif

#include <net-snmp/types.h>
#include <net-snmp/output_api.h>
#include <net-snmp/config_api.h>

#include <net-snmp/library/snmp_transport.h>
#include <net-snmp/library/snmpSocketBaseDomain.h>
#include <net-snmp/library/system.h> /* mkdirhier */
#include <net-snmp/library/tools.h>

#ifndef NETSNMP_NO_SYSTEMD
#include <net-snmp/library/sd-daemon.h>
#endif

netsnmp_feature_child_of(transport_unix_socket_all, transport_all);
netsnmp_feature_child_of(unix_socket_paths, transport_unix_socket_all);

#ifndef NETSNMP_STREAM_QUEUE_LEN
#define NETSNMP_STREAM_QUEUE_LEN  5
#endif

#ifndef SUN_LEN
/*
 * Evaluate to actual length of the `sockaddr_un' structure.
 */
#define SUN_LEN(ptr) ((size_t) (((struct sockaddr_un *) 0)->sun_path)         \
                      + strlen ((ptr)->sun_path))
#endif

oid netsnmp_UnixDomain[] = { TRANSPORT_DOMAIN_LOCAL };
static netsnmp_tdomain unixDomain;


/*
 * This is the structure we use to hold transport-specific data.
 */

typedef struct _sockaddr_un_pair {
    int             local;
    struct sockaddr_un server;
    struct sockaddr_un client;
} sockaddr_un_pair;


/*
 * Return a string representing the address in data, or else the "far end"
 * address if data is NULL.
 */

static char *
netsnmp_unix_fmtaddr(netsnmp_transport *t, const void *data, int len)
{
    const struct sockaddr_un *to = NULL;

    if (data != NULL)
        to = (const struct sockaddr_un *) data;
    else if (t != NULL && t->data != NULL)
        to = &(((const sockaddr_un_pair *) t->data)->server);
    if (to == NULL) {
        /*
         * "Local IPC" is the Posix.1g term for Unix domain protocols,
         * according to W. R. Stevens, ``Unix Network Programming Volume I
         * Second Edition'', p. 374.
         */
        return strdup("Local IPC: unknown");
    } else if (to->sun_path[0] == 0) {
        /*
         * This is an abstract name.  We could render it as hex or something
         * but let's not worry about that for now.
         */
        return strdup("Local IPC: abstract");
    } else {
        char *tmp;

        if (asprintf(&tmp, "Local IPC: %s", to->sun_path) < 0)
            tmp = NULL;
        return tmp;
    }
}

static void
netsnmp_unix_get_taddr(netsnmp_transport *t, void **addr, size_t *addr_len)
{
    *addr_len = t->remote_length;
    *addr = netsnmp_memdup(t->remote, *addr_len);
}

/*
 * You can write something into opaque that will subsequently get passed back
 * to your send function if you like.  For instance, you might want to
 * remember where a PDU came from, so that you can send a reply there...
 */

static int
netsnmp_unix_recv(netsnmp_transport *t, void *buf, int size,
                  void **opaque, int *olength)
{
    int rc = -1;
    socklen_t       tolen = sizeof(struct sockaddr_un);
    struct sockaddr *to;


    if (t != NULL && t->sock >= 0) {
        to = (struct sockaddr *) malloc(sizeof(struct sockaddr_un));
        if (to == NULL) {
            *opaque = NULL;
            *olength = 0;
            return -1;
        } else {
            memset(to, 0, tolen);
        }
        if(getsockname(t->sock, to, &tolen) != 0){
            free(to);
            *opaque = NULL;
            *olength = 0;
            return -1;
        };
        while (rc < 0) {
#ifdef MSG_DONTWAIT
            rc = recvfrom(t->sock, buf, size, MSG_DONTWAIT, NULL, NULL);
#else
            rc = recvfrom(t->sock, buf, size, 0, NULL, NULL);
#endif
            if (rc < 0 && errno != EINTR) {
                DEBUGMSGTL(("netsnmp_unix", "recv fd %d err %d (\"%s\")\n",
                            t->sock, errno, strerror(errno)));
                return rc;
            }
            *opaque = (void*)to;
            *olength = sizeof(struct sockaddr_un);
        }
        DEBUGMSGTL(("netsnmp_unix", "recv fd %d got %d bytes\n", t->sock, rc));
    }
    return rc;
}


static int
netsnmp_unix_send(netsnmp_transport *t, const void *buf, int size,
                  void **opaque, int *olength)
{
    int rc = -1;

    if (t != NULL && t->sock >= 0) {
        DEBUGMSGTL(("netsnmp_unix", "send %d bytes to %p on fd %d\n",
                    size, buf, t->sock));
        while (rc < 0) {
            rc = sendto(t->sock, buf, size, 0, NULL, 0);
            if (rc < 0 && errno != EINTR) {
                break;
            }
        }
    }
    return rc;
}


static int
netsnmp_unix_close(netsnmp_transport *t)
{
    int rc = 0;
    sockaddr_un_pair *sup = (sockaddr_un_pair *) t->data;

    if (t->sock >= 0) {
#ifndef HAVE_CLOSESOCKET
        rc = close(t->sock);
#else
        rc = closesocket(t->sock);
#endif
        t->sock = -1;
        if (sup != NULL) {
            if (sup->local) {
                if (sup->server.sun_path[0] != 0) {
                  DEBUGMSGTL(("netsnmp_unix", "close: server unlink(\"%s\")\n",
                              sup->server.sun_path));
                  unlink(sup->server.sun_path);
                }
            } else {
                if (sup->client.sun_path[0] != 0) {
                  DEBUGMSGTL(("netsnmp_unix", "close: client unlink(\"%s\")\n",
                              sup->client.sun_path));
                  unlink(sup->client.sun_path);
                }
            }
        }
        return rc;
    } else {
        return -1;
    }
}


static int
netsnmp_unix_accept(netsnmp_transport *t)
{
    struct sockaddr *farend = NULL;
    int             newsock = -1;
    socklen_t       farendlen = sizeof(struct sockaddr_un);

    farend = (struct sockaddr *) malloc(farendlen);

    if (farend == NULL) {
        /*
         * Indicate that the acceptance of this socket failed.
         */
        DEBUGMSGTL(("netsnmp_unix", "accept: malloc failed\n"));
        return -1;
    }
    memset(farend, 0, farendlen);

    if (t != NULL && t->sock >= 0) {
        newsock = accept(t->sock, farend, &farendlen);

        if (newsock < 0) {
            DEBUGMSGTL(("netsnmp_unix","accept failed rc %d errno %d \"%s\"\n",
                        newsock, errno, strerror(errno)));
            free(farend);
            return newsock;
        }

        if (t->data != NULL) {
            free(t->data);
        }

        DEBUGMSGTL(("netsnmp_unix", "accept succeeded (farend %p len %d)\n",
                    farend, (int) farendlen));
        t->data = farend;
        t->data_length = sizeof(struct sockaddr_un);
       netsnmp_sock_buffer_set(newsock, SO_SNDBUF, 1, 0);
       netsnmp_sock_buffer_set(newsock, SO_RCVBUF, 1, 0);
        return newsock;
    } else {
        free(farend);
        return -1;
    }
}

static int create_path = 0;
static mode_t create_mode;

#ifndef NETSNMP_FEATURE_REMOVE_UNIX_SOCKET_PATHS
/** If trying to create unix sockets in nonexisting directories then
 *  try to create the directory with mask mode.
 */
void netsnmp_unix_create_path_with_mode(int mode)
{
    create_path = 1;
    create_mode = mode;
}

/** If trying to create unix sockets in nonexisting directories then
 *  fail.
 */
void netsnmp_unix_dont_create_path(void)
{
    create_path = 0;
}
#endif /* NETSNMP_FEATURE_REMOVE_UNIX_SOCKET_PATHS */

/*
 * Open a Unix-domain transport for SNMP.  Local is TRUE if addr is the local
 * address to bind to (i.e. this is a server-type session); otherwise addr is
 * the remote address to send things to (and we make up a temporary name for
 * the local end of the connection).
 */

netsnmp_transport *
netsnmp_unix_transport(const struct sockaddr_un *addr, int local)
{
    netsnmp_transport *t = NULL;
    sockaddr_un_pair *sup = NULL;
    int             rc = 0;
    int             socket_initialized = 0;

#ifdef NETSNMP_NO_LISTEN_SUPPORT
    /* SPECIAL CIRCUMSTANCE: We still want AgentX to be able to operate,
       so we allow for unix domain socktes to still listen when everything
       else isn't allowed to.  Thus, we ignore this define in this file.
    */
#endif /* NETSNMP_NO_LISTEN_SUPPORT */

    if (addr == NULL || addr->sun_family != AF_UNIX) {
        return NULL;
    }

    t = SNMP_MALLOC_TYPEDEF(netsnmp_transport);
    if (t == NULL) {
        return NULL;
    }

    DEBUGIF("netsnmp_unix") {
        char *str = netsnmp_unix_fmtaddr(NULL, addr,
                                         sizeof(struct sockaddr_un));
        DEBUGMSGTL(("netsnmp_unix", "open %s %s\n", local ? "local" : "remote",
                    str));
        free(str);
    }

    t->domain = netsnmp_UnixDomain;
    t->domain_length =
        sizeof(netsnmp_UnixDomain) / sizeof(netsnmp_UnixDomain[0]);

    t->data = malloc(sizeof(sockaddr_un_pair));
    if (t->data == NULL) {
        netsnmp_transport_free(t);
        return NULL;
    }
    memset(t->data, 0, sizeof(sockaddr_un_pair));
    t->data_length = sizeof(sockaddr_un_pair);
    sup = (sockaddr_un_pair *) t->data;

#ifndef NETSNMP_NO_SYSTEMD
    /*
     * Maybe the socket was already provided by systemd...
     */
    if (local) {
        t->sock = netsnmp_sd_find_unix_socket(SOCK_STREAM, 1, addr->sun_path);
        if (t->sock >= 0)
            socket_initialized = 1;
    }
#endif
    if (!socket_initialized)
        t->sock = socket(PF_UNIX, SOCK_STREAM, 0);
    if (t->sock < 0) {
        netsnmp_transport_free(t);
        return NULL;
    }

    t->flags = NETSNMP_TRANSPORT_FLAG_STREAM;

    if (local) {
        t->local_length = strlen(addr->sun_path);
        t->local = strdup(addr->sun_path);
        if (t->local == NULL) {
            netsnmp_transport_free(t);
            return NULL;
        }

        /*
         * This session is inteneded as a server, so we must bind to the given
         * path (unlinking it first, to avoid errors).
         */

        t->flags |= NETSNMP_TRANSPORT_FLAG_LISTEN;

        if (!socket_initialized) {
            unlink(addr->sun_path);
            rc = bind(t->sock, (const struct sockaddr *)addr, SUN_LEN(addr));
            if (rc != 0 && errno == ENOENT && create_path) {
                rc = mkdirhier(addr->sun_path, create_mode, 1);
                if (rc != 0) {
                    netsnmp_unix_close(t);
                    netsnmp_transport_free(t);
                    return NULL;
                }
                rc = bind(t->sock, (const struct sockaddr *)addr,
			  SUN_LEN(addr));
            }
            if (rc != 0) {
                DEBUGMSGTL(("netsnmp_unix_transport",
                        "couldn't bind \"%s\", errno %d (%s)\n",
                        addr->sun_path, errno, strerror(errno)));
                netsnmp_unix_close(t);
                netsnmp_transport_free(t);
                return NULL;
            }
        }

        /*
         * Save the address in the transport-specific data pointer for later
         * use by netsnmp_unix_close.
         */

        sup->server.sun_family = AF_UNIX;
        strcpy(sup->server.sun_path, addr->sun_path);
        sup->local = 1;

        /*
         * Now sit here and listen for connections to arrive.
         */

        if (!socket_initialized) {
            rc = listen(t->sock, NETSNMP_STREAM_QUEUE_LEN);
            if (rc != 0) {
                DEBUGMSGTL(("netsnmp_unix_transport",
                            "couldn't listen to \"%s\", errno %d (%s)\n",
                            addr->sun_path, errno, strerror(errno)));
                netsnmp_unix_close(t);
                netsnmp_transport_free(t);
                return NULL;
            }
        }
    } else {
        t->remote_length = strlen(addr->sun_path);
        t->remote = strdup(addr->sun_path);
        if (t->remote == NULL) {
            netsnmp_transport_free(t);
            return NULL;
        }

        rc = connect(t->sock, (const struct sockaddr *)addr,
		     sizeof(struct sockaddr_un));
        if (rc != 0) {
            DEBUGMSGTL(("netsnmp_unix_transport",
                        "couldn't connect to \"%s\", errno %d (%s)\n",
                        addr->sun_path, errno, strerror(errno)));
            netsnmp_unix_close(t);
            netsnmp_transport_free(t);
            return NULL;
        }

        /*
         * Save the remote address in the transport-specific data pointer for
         * later use by netsnmp_unix_send.
         */

        sup->server.sun_family = AF_UNIX;
        strcpy(sup->server.sun_path, addr->sun_path);
        sup->local = 0;
        netsnmp_sock_buffer_set(t->sock, SO_SNDBUF, local, 0);
        netsnmp_sock_buffer_set(t->sock, SO_RCVBUF, local, 0);
    }

    /*
     * Message size is not limited by this transport (hence msgMaxSize
     * is equal to the maximum legal size of an SNMP message).
     */

    t->msgMaxSize = SNMP_MAX_PACKET_LEN;
    t->f_recv     = netsnmp_unix_recv;
    t->f_send     = netsnmp_unix_send;
    t->f_close    = netsnmp_unix_close;
    t->f_accept   = netsnmp_unix_accept;
    t->f_fmtaddr  = netsnmp_unix_fmtaddr;
    t->f_get_taddr = netsnmp_unix_get_taddr;

    return t;
}

netsnmp_transport *
netsnmp_unix_create_tstring(const char *string, int local,
			    const char *default_target)
{
    struct sockaddr_un addr;

    if (string && *string != '\0') {
    } else if (default_target && *default_target != '\0') {
      string = default_target;
    }

    if ((string != NULL && *string != '\0') &&
	(strlen(string) < sizeof(addr.sun_path))) {
        addr.sun_family = AF_UNIX;
        memset(addr.sun_path, 0, sizeof(addr.sun_path));
        strlcpy(addr.sun_path, string, sizeof(addr.sun_path));
        return netsnmp_unix_transport(&addr, local);
    } else {
        if (string != NULL && *string != '\0') {
            snmp_log(LOG_ERR, "Path too long for Unix domain transport\n");
        }
        return NULL;
    }
}


netsnmp_transport *
netsnmp_unix_create_ostring(const void *ostring, size_t o_len, int local)
{
    struct sockaddr_un addr;

    if (o_len > 0 && o_len < (sizeof(addr.sun_path) - 1)) {
        addr.sun_family = AF_UNIX;
        memset(addr.sun_path, 0, sizeof(addr.sun_path));
        strlcpy(addr.sun_path, ostring, sizeof(addr.sun_path));
        return netsnmp_unix_transport(&addr, local);
    } else {
        if (o_len > 0) {
            snmp_log(LOG_ERR, "Path too long for Unix domain transport\n");
        }
    }
    return NULL;
}


void
netsnmp_unix_ctor(void)
{
    unixDomain.name = netsnmp_UnixDomain;
    unixDomain.name_length = sizeof(netsnmp_UnixDomain) / sizeof(oid);
    unixDomain.prefix = (const char**)calloc(2, sizeof(char *));
    unixDomain.prefix[0] = "unix";

    unixDomain.f_create_from_tstring_new = netsnmp_unix_create_tstring;
    unixDomain.f_create_from_ostring     = netsnmp_unix_create_ostring;

    netsnmp_tdomain_register(&unixDomain);
}

#if !defined(NETSNMP_DISABLE_SNMPV1) || !defined(NETSNMP_DISABLE_SNMPV2C)
/* support for SNMPv1 and SNMPv2c on unix domain*/

#define EXAMPLE_COMMUNITY "COMMUNITY"
typedef struct com2SecUnixEntry_s {
    const char*     sockpath;
    const char*     secName;
    const char*     contextName;
    struct com2SecUnixEntry_s *next;
    unsigned short  pathlen;
    const char      community[1];
} com2SecUnixEntry;

static com2SecUnixEntry   *com2SecUnixList = NULL, *com2SecUnixListLast = NULL;


int
netsnmp_unix_getSecName(void *opaque, int olength,
                        const char *community,
                        size_t community_len,
                        const char **secName, const char **contextName)
{
    const com2SecUnixEntry   *c;
    struct sockaddr_un *to = (struct sockaddr_un *) opaque;
    char           *ztcommunity = NULL;

    if (secName != NULL) {
        *secName = NULL;  /* Haven't found anything yet */
    }

    /*
     * Special case if there are NO entries (as opposed to no MATCHING
     * entries).
     */

    if (com2SecUnixList == NULL) {
        DEBUGMSGTL(("netsnmp_unix_getSecName", "no com2sec entries\n"));
        return 0;
    }

    /*
     * If there is no unix socket path, then there can be no valid security
     * name.
     */

    if (opaque == NULL || olength != sizeof(struct sockaddr_un) ||
        to->sun_family != AF_UNIX) {
        DEBUGMSGTL(("netsnmp_unix_getSecName",
                    "no unix destine address in PDU?\n"));
        return 1;
    }

    DEBUGIF("netsnmp_unix_getSecName") {
        ztcommunity = (char *)malloc(community_len + 1);
        if (ztcommunity != NULL) {
            memcpy(ztcommunity, community, community_len);
            ztcommunity[community_len] = '\0';
        }

        DEBUGMSGTL(("netsnmp_unix_getSecName", "resolve <\"%s\">\n",
                    ztcommunity ? ztcommunity : "<malloc error>"));
    }

    for (c = com2SecUnixList; c != NULL; c = c->next) {
        DEBUGMSGTL(("netsnmp_unix_getSecName","compare <\"%s\",to socket %s>",
                    c->community, c->sockpath ));
        if ((community_len == strlen(c->community)) &&
            (memcmp(community, c->community, community_len) == 0) &&
            /* compare sockpath, if pathlen == 0, always match */
            (strlen(to->sun_path) == c->pathlen || c->pathlen == 0) &&
            (memcmp(to->sun_path, c->sockpath, c->pathlen) == 0)
            ) {
            DEBUGMSG(("netsnmp_unix_getSecName", "... SUCCESS\n"));
            if (secName != NULL) {
                *secName = c->secName;
                *contextName = c->contextName;
            }
            break;
        }
        DEBUGMSG(("netsnmp_unix_getSecName", "... nope\n"));
    }
    if (ztcommunity != NULL) {
        free(ztcommunity);
    }
    return 1;
}

void
netsnmp_unix_parse_security(const char *token, char *param)
{
    char   secName[VACMSTRINGLEN + 1];
    size_t secNameLen;
    char   contextName[VACMSTRINGLEN + 1];
    size_t contextNameLen;
    char   community[COMMUNITY_MAX_LEN + 1];
    size_t communityLen;
    char   sockpath[sizeof(((struct sockaddr_un*)0)->sun_path) + 1];
    size_t sockpathLen;

    param = copy_nword( param, secName, sizeof(secName));
    if (strcmp(secName, "-Cn") == 0) {
        if (!param) {
            config_perror("missing CONTEXT_NAME parameter");
            return;
        }
        param = copy_nword( param, contextName, sizeof(contextName));
        contextNameLen = strlen(contextName) + 1;
        if (contextNameLen > VACMSTRINGLEN) {
            config_perror("context name too long");
            return;
        }
        if (!param) {
            config_perror("missing NAME parameter");
            return;
        }
        param = copy_nword( param, secName, sizeof(secName));
    } else {
        contextNameLen = 0;
    }

    secNameLen = strlen(secName) + 1;
    if (secNameLen == 1) {
        config_perror("empty NAME parameter");
        return;
    } else if (secNameLen > VACMSTRINGLEN) {
        config_perror("security name too long");
        return;
    }

    if (!param) {
        config_perror("missing SOCKPATH parameter");
        return;
    }
    param = copy_nword( param, sockpath, sizeof(sockpath));
    if (sockpath[0] == '\0') {
        config_perror("empty SOCKPATH parameter");
        return;
    }
    sockpathLen = strlen(sockpath) + 1;
    if (sockpathLen > sizeof(((struct sockaddr_un*)0)->sun_path)) {
        config_perror("sockpath too long");
        return;
    }

    if (!param) {
        config_perror("missing COMMUNITY parameter");
        return;
    }
    param = copy_nword( param, community, sizeof(community));
    if (community[0] == '\0') {
        config_perror("empty COMMUNITY parameter");
        return;
    }
    communityLen = strlen(community) + 1;
    if (communityLen >= COMMUNITY_MAX_LEN) {
        config_perror("community name too long");
        return;
    }
    if (communityLen == sizeof(EXAMPLE_COMMUNITY) &&
        memcmp(community, EXAMPLE_COMMUNITY, sizeof(EXAMPLE_COMMUNITY)) == 0) {
        config_perror("example config COMMUNITY not properly configured");
        return;
    }

    /* Deal with the "default" case */
    if(strcmp(sockpath, "default") == 0) {
        sockpathLen = 0;
    }

    {
        void* v = malloc(offsetof(com2SecUnixEntry, community) + communityLen +
                         sockpathLen + secNameLen + contextNameLen);
        com2SecUnixEntry* e = (com2SecUnixEntry*)v;
        char* last = ((char*)v) + offsetof(com2SecUnixEntry, community);
        if (e == NULL) {
            config_perror("memory error");
            return;
        }

        DEBUGMSGTL(("netsnmp_unix_parse_security",
                    "<\"%s\", \"%.*s\"> => \"%s\"\n",
                    community, (int)sockpathLen, sockpath, secName));

        memcpy(last, community, communityLen);
        last += communityLen;

        if (sockpathLen) {
            e->sockpath = last;
            memcpy(last, sockpath, sockpathLen);
            last += sockpathLen;
            e->pathlen = sockpathLen - 1;
        } else {
            e->sockpath = last - 1;
            e->pathlen = 0;
        }

        e->secName = last;
        memcpy(last, secName, secNameLen);
        last += secNameLen;

        if (contextNameLen) {
            e->contextName = last;
            memcpy(last, contextName, contextNameLen);
            last += contextNameLen;
        } else
            e->contextName = last - 1;

        e->next = NULL;

        if (com2SecUnixListLast != NULL) {
            com2SecUnixListLast->next = e;
            com2SecUnixListLast = e;
        } else {
            com2SecUnixListLast = com2SecUnixList = e;
        }
    }
}

void
netsnmp_unix_com2SecList_free(void)
{
    com2SecUnixEntry   *e = com2SecUnixList;
    while (e != NULL) {
        com2SecUnixEntry   *tmp = e;
        e = e->next;
        free(tmp);
    }
    com2SecUnixList = com2SecUnixListLast = NULL;
}
#endif /* support for community based SNMP */

void
netsnmp_unix_agent_config_tokens_register(void)
{
#if !defined(NETSNMP_DISABLE_SNMPV1) || !defined(NETSNMP_DISABLE_SNMPV2C)
    register_app_config_handler("com2secunix", netsnmp_unix_parse_security,
                                netsnmp_unix_com2SecList_free,
                                "[-Cn CONTEXT] secName sockpath community");
#endif /* support for community based SNMP */
}