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-rw-r--r--qga/commands-posix.c123
-rw-r--r--qga/main.c2
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;