diff options
Diffstat (limited to 'fsdev')
| -rw-r--r-- | fsdev/virtfs-proxy-helper.c | 179 |
1 files changed, 176 insertions, 3 deletions
diff --git a/fsdev/virtfs-proxy-helper.c b/fsdev/virtfs-proxy-helper.c index 5fc2fc41ab..e0af257f22 100644 --- a/fsdev/virtfs-proxy-helper.c +++ b/fsdev/virtfs-proxy-helper.c @@ -9,6 +9,7 @@ * the COPYING file in the top-level directory. */ #include <stdio.h> +#include <sys/socket.h> #include <string.h> #include <sys/un.h> #include <limits.h> @@ -27,6 +28,7 @@ #include "qemu-common.h" #include "virtio-9p-marshal.h" #include "hw/9pfs/virtio-9p-proxy.h" +#include "fsdev/virtio-9p-marshal.h" #define PROGNAME "virtfs-proxy-helper" @@ -187,6 +189,140 @@ static int read_request(int sockfd, struct iovec *iovec, ProxyHeader *header) return 0; } +static int send_fd(int sockfd, int fd) +{ + struct msghdr msg; + struct iovec iov; + int retval, data; + struct cmsghdr *cmsg; + union MsgControl msg_control; + + iov.iov_base = &data; + iov.iov_len = sizeof(data); + + memset(&msg, 0, sizeof(msg)); + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + /* No ancillary data on error */ + if (fd < 0) { + /* fd is really negative errno if the request failed */ + data = fd; + } else { + data = V9FS_FD_VALID; + msg.msg_control = &msg_control; + msg.msg_controllen = sizeof(msg_control); + + cmsg = &msg_control.cmsg; + cmsg->cmsg_len = CMSG_LEN(sizeof(fd)); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_RIGHTS; + memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd)); + } + + do { + retval = sendmsg(sockfd, &msg, 0); + } while (retval < 0 && errno == EINTR); + if (fd >= 0) { + close(fd); + } + if (retval < 0) { + return retval; + } + return 0; +} + +/* + * from man 7 capabilities, section + * Effect of User ID Changes on Capabilities: + * 4. If the file system user ID is changed from 0 to nonzero (see setfsuid(2)) + * then the following capabilities are cleared from the effective set: + * CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH, CAP_FOWNER, CAP_FSETID, + * CAP_LINUX_IMMUTABLE (since Linux 2.2.30), CAP_MAC_OVERRIDE, and CAP_MKNOD + * (since Linux 2.2.30). If the file system UID is changed from nonzero to 0, + * then any of these capabilities that are enabled in the permitted set + * are enabled in the effective set. + */ +static int setfsugid(int uid, int gid) +{ + /* + * We still need DAC_OVERRIDE because we don't change + * supplementary group ids, and hence may be subjected DAC rules + */ + cap_value_t cap_list[] = { + CAP_DAC_OVERRIDE, + }; + + setfsgid(gid); + setfsuid(uid); + + if (uid != 0 || gid != 0) { + return do_cap_set(cap_list, ARRAY_SIZE(cap_list), 0); + } + return 0; +} + +/* + * create a file and send fd on success + * return -errno on error + */ +static int do_create(struct iovec *iovec) +{ + int ret; + V9fsString path; + int flags, mode, uid, gid, cur_uid, cur_gid; + + v9fs_string_init(&path); + ret = proxy_unmarshal(iovec, PROXY_HDR_SZ, "sdddd", + &path, &flags, &mode, &uid, &gid); + if (ret < 0) { + goto unmarshal_err_out; + } + cur_uid = geteuid(); + cur_gid = getegid(); + ret = setfsugid(uid, gid); + if (ret < 0) { + /* + * On failure reset back to the + * old uid/gid + */ + ret = -errno; + goto err_out; + } + ret = open(path.data, flags, mode); + if (ret < 0) { + ret = -errno; + } + +err_out: + setfsugid(cur_uid, cur_gid); +unmarshal_err_out: + v9fs_string_free(&path); + return ret; +} + +/* + * open a file and send fd on success + * return -errno on error + */ +static int do_open(struct iovec *iovec) +{ + int flags, ret; + V9fsString path; + + v9fs_string_init(&path); + ret = proxy_unmarshal(iovec, PROXY_HDR_SZ, "sd", &path, &flags); + if (ret < 0) { + goto err_out; + } + ret = open(path.data, flags); + if (ret < 0) { + ret = -errno; + } +err_out: + v9fs_string_free(&path); + return ret; +} + static void usage(char *prog) { fprintf(stderr, "usage: %s\n" @@ -196,22 +332,59 @@ static void usage(char *prog) basename(prog)); } +static int process_reply(int sock, int type, int retval) +{ + switch (type) { + case T_OPEN: + case T_CREATE: + if (send_fd(sock, retval) < 0) { + return -1; + } + break; + default: + return -1; + break; + } + return 0; +} + static int process_requests(int sock) { - int retval; + int retval = 0; ProxyHeader header; struct iovec in_iovec; in_iovec.iov_base = g_malloc(PROXY_MAX_IO_SZ + PROXY_HDR_SZ); in_iovec.iov_len = PROXY_MAX_IO_SZ + PROXY_HDR_SZ; while (1) { + /* + * initialize the header type, so that we send + * response to proper request type. + */ + header.type = 0; retval = read_request(sock, &in_iovec, &header); if (retval < 0) { - goto error; + goto err_out; + } + + switch (header.type) { + case T_OPEN: + retval = do_open(&in_iovec); + break; + case T_CREATE: + retval = do_create(&in_iovec); + break; + default: + goto err_out; + break; + } + + if (process_reply(sock, header.type, retval) < 0) { + goto err_out; } } (void)socket_write; -error: +err_out: g_free(in_iovec.iov_base); return -1; } |