diff options
| -rw-r--r-- | qga/commands-posix.c | 123 | ||||
| -rw-r--r-- | qga/main.c | 2 |
2 files changed, 120 insertions, 5 deletions
diff --git a/qga/commands-posix.c b/qga/commands-posix.c index 3b5c536e41..04c69515e7 100644 --- a/qga/commands-posix.c +++ b/qga/commands-posix.c @@ -18,6 +18,9 @@ #include <unistd.h> #include <errno.h> #include <fcntl.h> +#include <stdio.h> +#include <string.h> +#include <sys/stat.h> #include <inttypes.h> #include "qga/guest-agent-core.h" #include "qga-qmp-commands.h" @@ -237,9 +240,122 @@ static GuestFileHandle *guest_file_handle_find(int64_t id, Error **err) return NULL; } +typedef const char * const ccpc; + +/* http://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html */ +static const struct { + ccpc *forms; + int oflag_base; +} guest_file_open_modes[] = { + { (ccpc[]){ "r", "rb", NULL }, O_RDONLY }, + { (ccpc[]){ "w", "wb", NULL }, O_WRONLY | O_CREAT | O_TRUNC }, + { (ccpc[]){ "a", "ab", NULL }, O_WRONLY | O_CREAT | O_APPEND }, + { (ccpc[]){ "r+", "rb+", "r+b", NULL }, O_RDWR }, + { (ccpc[]){ "w+", "wb+", "w+b", NULL }, O_RDWR | O_CREAT | O_TRUNC }, + { (ccpc[]){ "a+", "ab+", "a+b", NULL }, O_RDWR | O_CREAT | O_APPEND } +}; + +static int +find_open_flag(const char *mode_str, Error **err) +{ + unsigned mode; + + for (mode = 0; mode < ARRAY_SIZE(guest_file_open_modes); ++mode) { + ccpc *form; + + form = guest_file_open_modes[mode].forms; + while (*form != NULL && strcmp(*form, mode_str) != 0) { + ++form; + } + if (*form != NULL) { + break; + } + } + + if (mode == ARRAY_SIZE(guest_file_open_modes)) { + error_setg(err, "invalid file open mode '%s'", mode_str); + return -1; + } + return guest_file_open_modes[mode].oflag_base | O_NOCTTY | O_NONBLOCK; +} + +#define DEFAULT_NEW_FILE_MODE (S_IRUSR | S_IWUSR | \ + S_IRGRP | S_IWGRP | \ + S_IROTH | S_IWOTH) + +static FILE * +safe_open_or_create(const char *path, const char *mode, Error **err) +{ + Error *local_err = NULL; + int oflag; + + oflag = find_open_flag(mode, &local_err); + if (local_err == NULL) { + int fd; + + /* If the caller wants / allows creation of a new file, we implement it + * with a two step process: open() + (open() / fchmod()). + * + * First we insist on creating the file exclusively as a new file. If + * that succeeds, we're free to set any file-mode bits on it. (The + * motivation is that we want to set those file-mode bits independently + * of the current umask.) + * + * If the exclusive creation fails because the file already exists + * (EEXIST is not possible for any other reason), we just attempt to + * open the file, but in this case we won't be allowed to change the + * file-mode bits on the preexistent file. + * + * The pathname should never disappear between the two open()s in + * practice. If it happens, then someone very likely tried to race us. + * In this case just go ahead and report the ENOENT from the second + * open() to the caller. + * + * If the caller wants to open a preexistent file, then the first + * open() is decisive and its third argument is ignored, and the second + * open() and the fchmod() are never called. + */ + fd = open(path, oflag | ((oflag & O_CREAT) ? O_EXCL : 0), 0); + if (fd == -1 && errno == EEXIST) { + oflag &= ~(unsigned)O_CREAT; + fd = open(path, oflag); + } + + if (fd == -1) { + error_setg_errno(&local_err, errno, "failed to open file '%s' " + "(mode: '%s')", path, mode); + } else { + qemu_set_cloexec(fd); + + if ((oflag & O_CREAT) && fchmod(fd, DEFAULT_NEW_FILE_MODE) == -1) { + error_setg_errno(&local_err, errno, "failed to set permission " + "0%03o on new file '%s' (mode: '%s')", + (unsigned)DEFAULT_NEW_FILE_MODE, path, mode); + } else { + FILE *f; + + f = fdopen(fd, mode); + if (f == NULL) { + error_setg_errno(&local_err, errno, "failed to associate " + "stdio stream with file descriptor %d, " + "file '%s' (mode: '%s')", fd, path, mode); + } else { + return f; + } + } + + close(fd); + } + } + + error_propagate(err, local_err); + return NULL; +} + int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode, Error **err) { FILE *fh; + Error *local_err = NULL; int fd; int64_t ret = -1, handle; @@ -247,10 +363,9 @@ int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode, E mode = "r"; } slog("guest-file-open called, filepath: %s, mode: %s", path, mode); - fh = fopen(path, mode); - if (!fh) { - error_setg_errno(err, errno, "failed to open file '%s' (mode: '%s')", - path, mode); + fh = safe_open_or_create(path, mode, &local_err); + if (local_err != NULL) { + error_propagate(err, local_err); return -1; } diff --git a/qga/main.c b/qga/main.c index 1841759db2..44a283686b 100644 --- a/qga/main.c +++ b/qga/main.c @@ -478,7 +478,7 @@ static void become_daemon(const char *pidfile) } } - umask(0); + umask(S_IRWXG | S_IRWXO); sid = setsid(); if (sid < 0) { goto fail; |