/* * QEMU Bridge Helper * * Copyright IBM, Corp. 2011 * * Authors: * Anthony Liguori <aliguori@us.ibm.com> * Richa Marwaha <rmarwah@linux.vnet.ibm.com> * Corey Bryant <coreyb@linux.vnet.ibm.com> * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. * */ #include "config-host.h" #include <stdio.h> #include <errno.h> #include <fcntl.h> #include <unistd.h> #include <string.h> #include <stdlib.h> #include <stdbool.h> #include <ctype.h> #include <glib.h> #include <sys/types.h> #include <sys/ioctl.h> #include <sys/socket.h> #include <sys/un.h> #include <sys/prctl.h> #include <net/if.h> #include <linux/sockios.h> #include "qemu-queue.h" #include "net/tap-linux.h" #ifdef CONFIG_LIBCAP #include <cap-ng.h> #endif #define DEFAULT_ACL_FILE CONFIG_QEMU_CONFDIR "/bridge.conf" enum { ACL_ALLOW = 0, ACL_ALLOW_ALL, ACL_DENY, ACL_DENY_ALL, }; typedef struct ACLRule { int type; char iface[IFNAMSIZ]; QSIMPLEQ_ENTRY(ACLRule) entry; } ACLRule; typedef QSIMPLEQ_HEAD(ACLList, ACLRule) ACLList; static void usage(void) { fprintf(stderr, "Usage: qemu-bridge-helper [--use-vnet] --br=bridge --fd=unixfd\n"); } static int parse_acl_file(const char *filename, ACLList *acl_list) { FILE *f; char line[4096]; ACLRule *acl_rule; f = fopen(filename, "r"); if (f == NULL) { return -1; } while (fgets(line, sizeof(line), f) != NULL) { char *ptr = line; char *cmd, *arg, *argend; while (isspace(*ptr)) { ptr++; } /* skip comments and empty lines */ if (*ptr == '#' || *ptr == 0) { continue; } cmd = ptr; arg = strchr(cmd, ' '); if (arg == NULL) { arg = strchr(cmd, '\t'); } if (arg == NULL) { fprintf(stderr, "Invalid config line:\n %s\n", line); fclose(f); errno = EINVAL; return -1; } *arg = 0; arg++; while (isspace(*arg)) { arg++; } argend = arg + strlen(arg); while (arg != argend && isspace(*(argend - 1))) { argend--; } *argend = 0; if (strcmp(cmd, "deny") == 0) { acl_rule = g_malloc(sizeof(*acl_rule)); if (strcmp(arg, "all") == 0) { acl_rule->type = ACL_DENY_ALL; } else { acl_rule->type = ACL_DENY; snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg); } QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); } else if (strcmp(cmd, "allow") == 0) { acl_rule = g_malloc(sizeof(*acl_rule)); if (strcmp(arg, "all") == 0) { acl_rule->type = ACL_ALLOW_ALL; } else { acl_rule->type = ACL_ALLOW; snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg); } QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); } else if (strcmp(cmd, "include") == 0) { /* ignore errors */ parse_acl_file(arg, acl_list); } else { fprintf(stderr, "Unknown command `%s'\n", cmd); fclose(f); errno = EINVAL; return -1; } } fclose(f); return 0; } static bool has_vnet_hdr(int fd) { unsigned int features = 0; if (ioctl(fd, TUNGETFEATURES, &features) == -1) { return false; } if (!(features & IFF_VNET_HDR)) { return false; } return true; } static void prep_ifreq(struct ifreq *ifr, const char *ifname) { memset(ifr, 0, sizeof(*ifr)); snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname); } static int send_fd(int c, int fd) { char msgbuf[CMSG_SPACE(sizeof(fd))]; struct msghdr msg = { .msg_control = msgbuf, .msg_controllen = sizeof(msgbuf), }; struct cmsghdr *cmsg; struct iovec iov; char req[1] = { 0x00 }; cmsg = CMSG_FIRSTHDR(&msg); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_RIGHTS; cmsg->cmsg_len = CMSG_LEN(sizeof(fd)); msg.msg_controllen = cmsg->cmsg_len; iov.iov_base = req; iov.iov_len = sizeof(req); msg.msg_iov = &iov; msg.msg_iovlen = 1; memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd)); return sendmsg(c, &msg, 0); } #ifdef CONFIG_LIBCAP static int drop_privileges(void) { /* clear all capabilities */ capng_clear(CAPNG_SELECT_BOTH); if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED, CAP_NET_ADMIN) < 0) { return -1; } /* change to calling user's real uid and gid, retaining supplemental * groups and CAP_NET_ADMIN */ if (capng_change_id(getuid(), getgid(), CAPNG_CLEAR_BOUNDING)) { return -1; } return 0; } #endif int main(int argc, char **argv) { struct ifreq ifr; int fd, ctlfd, unixfd = -1; int use_vnet = 0; int mtu; const char *bridge = NULL; char iface[IFNAMSIZ]; int index; ACLRule *acl_rule; ACLList acl_list; int access_allowed, access_denied; int ret = EXIT_SUCCESS; #ifdef CONFIG_LIBCAP /* if we're run from an suid binary, immediately drop privileges preserving * cap_net_admin */ if (geteuid() == 0 && getuid() != geteuid()) { if (drop_privileges() == -1) { fprintf(stderr, "failed to drop privileges\n"); return 1; } } #endif /* parse arguments */ for (index = 1; index < argc; index++) { if (strcmp(argv[index], "--use-vnet") == 0) { use_vnet = 1; } else if (strncmp(argv[index], "--br=", 5) == 0) { bridge = &argv[index][5]; } else if (strncmp(argv[index], "--fd=", 5) == 0) { unixfd = atoi(&argv[index][5]); } else { usage(); return EXIT_FAILURE; } } if (bridge == NULL || unixfd == -1) { usage(); return EXIT_FAILURE; } /* parse default acl file */ QSIMPLEQ_INIT(&acl_list); if (parse_acl_file(DEFAULT_ACL_FILE, &acl_list) == -1) { fprintf(stderr, "failed to parse default acl file `%s'\n", DEFAULT_ACL_FILE); ret = EXIT_FAILURE; goto cleanup; } /* validate bridge against acl -- default policy is to deny * according acl policy if we have a deny and allow both * then deny should always win over allow */ access_allowed = 0; access_denied = 0; QSIMPLEQ_FOREACH(acl_rule, &acl_list, entry) { switch (acl_rule->type) { case ACL_ALLOW_ALL: access_allowed = 1; break; case ACL_ALLOW: if (strcmp(bridge, acl_rule->iface) == 0) { access_allowed = 1; } break; case ACL_DENY_ALL: access_denied = 1; break; case ACL_DENY: if (strcmp(bridge, acl_rule->iface) == 0) { access_denied = 1; } break; } } if ((access_allowed == 0) || (access_denied == 1)) { fprintf(stderr, "access denied by acl file\n"); ret = EXIT_FAILURE; goto cleanup; } /* open a socket to use to control the network interfaces */ ctlfd = socket(AF_INET, SOCK_STREAM, 0); if (ctlfd == -1) { fprintf(stderr, "failed to open control socket: %s\n", strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* open the tap device */ fd = open("/dev/net/tun", O_RDWR); if (fd == -1) { fprintf(stderr, "failed to open /dev/net/tun: %s\n", strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* request a tap device, disable PI, and add vnet header support if * requested and it's available. */ prep_ifreq(&ifr, "tap%d"); ifr.ifr_flags = IFF_TAP|IFF_NO_PI; if (use_vnet && has_vnet_hdr(fd)) { ifr.ifr_flags |= IFF_VNET_HDR; } if (ioctl(fd, TUNSETIFF, &ifr) == -1) { fprintf(stderr, "failed to create tun device: %s\n", strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* save tap device name */ snprintf(iface, sizeof(iface), "%s", ifr.ifr_name); /* get the mtu of the bridge */ prep_ifreq(&ifr, bridge); if (ioctl(ctlfd, SIOCGIFMTU, &ifr) == -1) { fprintf(stderr, "failed to get mtu of bridge `%s': %s\n", bridge, strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* save mtu */ mtu = ifr.ifr_mtu; /* set the mtu of the interface based on the bridge */ prep_ifreq(&ifr, iface); ifr.ifr_mtu = mtu; if (ioctl(ctlfd, SIOCSIFMTU, &ifr) == -1) { fprintf(stderr, "failed to set mtu of device `%s' to %d: %s\n", iface, mtu, strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* add the interface to the bridge */ prep_ifreq(&ifr, bridge); ifr.ifr_ifindex = if_nametoindex(iface); if (ioctl(ctlfd, SIOCBRADDIF, &ifr) == -1) { fprintf(stderr, "failed to add interface `%s' to bridge `%s': %s\n", iface, bridge, strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* bring the interface up */ prep_ifreq(&ifr, iface); if (ioctl(ctlfd, SIOCGIFFLAGS, &ifr) == -1) { fprintf(stderr, "failed to get interface flags for `%s': %s\n", iface, strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } ifr.ifr_flags |= IFF_UP; if (ioctl(ctlfd, SIOCSIFFLAGS, &ifr) == -1) { fprintf(stderr, "failed to bring up interface `%s': %s\n", iface, strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* write fd to the domain socket */ if (send_fd(unixfd, fd) == -1) { fprintf(stderr, "failed to write fd to unix socket: %s\n", strerror(errno)); ret = EXIT_FAILURE; goto cleanup; } /* ... */ /* profit! */ cleanup: while ((acl_rule = QSIMPLEQ_FIRST(&acl_list)) != NULL) { QSIMPLEQ_REMOVE_HEAD(&acl_list, entry); g_free(acl_rule); } return ret; }