+/*
+ * 1) Timestamp files and directories
+ *
+ * Timestamp files MUST NOT be accessible to users other than root,
+ * this includes the name, metadata and the content of timestamp files
+ * and directories.
+ *
+ * Symlinks can be used to create, manipulate or delete wrong files
+ * and directories. The Implementation MUST reject any symlinks for
+ * timestamp files or directories.
+ *
+ * To avoid race conditions the implementation MUST use the same
+ * file descriptor for permission checks and do read or write
+ * write operations after the permission checks.
+ *
+ * The timestamp files MUST be opened with openat(2) using the
+ * timestamp directory file descriptor. Permissions of the directory
+ * MUST be checked before opening the timestamp file descriptor.
+ *
+ * 2) Clock sources for timestamps
+ *
+ * Timestamp files MUST NOT rely on only one clock source, using the
+ * wall clock would allow to reset the clock to an earlier point in
+ * time to reuse a timestamp.
+ *
+ * The timestamp MUST consist of multiple clocks and MUST reject the
+ * timestamp if there is a change to any clock because there is no way
+ * to differentiate between malicious and legitimate clock changes.
+ *
+ * 3) Timestamp lifetime
+ *
+ * The implementation MUST NOT use the user controlled stdin, stdout
+ * and stderr file descriptors to determine the controlling terminal.
+ * On linux the /proc/$pid/stat file MUST be used to get the terminal
+ * number.
+ *
+ * There is no reliable way to determine the lifetime of a tty/pty.
+ * The start time of the session leader MUST be used as part of the
+ * timestamp to determine if the tty is still the same.
+ * If the start time of the session leader changed the timestamp MUST
+ * be rejected.
+ *
+ */
+
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/vfs.h>
+
+#if !defined(timespecisset) || \
+ !defined(timespeccmp) || \
+ !defined(timespecadd)
+# include "sys-time.h"
+#endif
+
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
-#include <libgen.h>
+#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
-#include <limits.h>
-#include <string.h>
-
-#include <sys/stat.h>
-#include <sys/vfs.h>
#include "includes.h"
#ifndef TIMESTAMP_DIR
-# define TIMESTAMP_DIR "/tmp/doas"
+# define TIMESTAMP_DIR "/tmp/doas"
#endif
-#ifndef TMPFS_MAGIC
-# define TMPFS_MAGIC 0x01021994
-#endif
-
-#define timespecisset(tsp) ((tsp)->tv_sec || (tsp)->tv_nsec)
-#define timespeccmp(tsp, usp, cmp) \
- (((tsp)->tv_sec == (usp)->tv_sec) ? \
- ((tsp)->tv_nsec cmp (usp)->tv_nsec) : \
- ((tsp)->tv_sec cmp (usp)->tv_sec))
-#define timespecadd(tsp, usp, vsp) do { \
- (vsp)->tv_sec = (tsp)->tv_sec + (usp)->tv_sec; \
- (vsp)->tv_nsec = (tsp)->tv_nsec + (usp)->tv_nsec; \
- if ((vsp)->tv_nsec >= 1000000000L) { \
- (vsp)->tv_sec++; \
- (vsp)->tv_nsec -= 1000000000L; \
- } \
- } while (0)
+#if defined(TIMESTAMP_TMPFS) && defined(__linux__)
+# ifndef TMPFS_MAGIC
+# define TMPFS_MAGIC 0x01021994
+# endif
+#endif
#ifdef __linux__
/* Use tty_nr from /proc/self/stat instead of using
* See https://www.sudo.ws/alerts/tty_tickets.html
*/
static int
-ttynr()
+proc_info(pid_t pid, int *ttynr, unsigned long long *starttime)
{
+ char path[128];
char buf[1024];
- char *p, *p1, *saveptr;
+ char *p, *saveptr, *ep;
const char *errstr;
int fd, n;
p = buf;
- if ((fd = open("/proc/self/stat", O_RDONLY)) == -1)
+ if (snprintf(path, sizeof path, "/proc/%d/stat", pid) == -1)
+ return -1;
+
+ if ((fd = open(path, O_RDONLY)) == -1)
return -1;
while ((n = read(fd, p, buf + sizeof buf - p)) != 0) {
if (n == -1) {
if (errno == EAGAIN || errno == EINTR)
continue;
- else
- break;
+ break;
}
p += n;
if (p >= buf + sizeof buf)
break;
}
close(fd);
+
/* error if it contains NULL bytes */
if (n != 0 || memchr(buf, '\0', p - buf))
return -1;
/* Get the 7th field, 5 fields after the last ')',
- * because the 5th field 'comm' can include spaces
- * and closing paranthesis too.
+ * (2th field) because the 5th field 'comm' can include
+ * spaces and closing paranthesis too.
* See https://www.sudo.ws/alerts/linux_tty.html
*/
if ((p = strrchr(buf, ')')) == NULL)
return -1;
- for ((p1 = strtok_r(p, " ", &saveptr)), n = 0; p1;
- (p1 = strtok_r(NULL, " ", &saveptr)), n++)
- if (n == 5)
- break;
- if (p1 == NULL || n != 5)
- return -1;
- n = strtonum(p1, INT_MIN, INT_MAX, &errstr);
- if (errstr)
- return -1;
+ n = 2;
+ for ((p = strtok_r(p, " ", &saveptr)); p;
+ (p = strtok_r(NULL, " ", &saveptr))) {
+ switch (n++) {
+ case 7:
+ *ttynr = strtonum(p, INT_MIN, INT_MAX, &errstr);
+ if (errstr)
+ return -1;
+ break;
+ case 22:
+ errno = 0;
+ *starttime = strtoull(p, &ep, 10);
+ if (p == ep ||
+ (errno == ERANGE && *starttime == ULLONG_MAX))
+ return -1;
+ break;
+ }
+ if (n == 23)
+ break;
+ }
- return n;
+ return 0;
}
#else
-#error "ttynr not implemented"
+#error "proc_info not implemented"
#endif
-static char pathbuf[PATH_MAX];
+static const char *
+tsname()
+{
+ static char buf[128];
+ int tty, fd;
+ unsigned long long starttime;
+ pid_t ppid, sid, leader;
+ if ((fd = open("/dev/tty", O_RDONLY)) == -1)
+ err(1, "open: /dev/tty");
+ if (ioctl(fd, TIOCGSID, &leader) == -1)
+ err(1, "ioctl: failed to get session leader");
+ close(fd);
+ if (proc_info(leader, &tty, &starttime) == -1)
+ errx(1, "failed to get tty number");
+ ppid = getppid();
+ if ((sid = getsid(0)) == -1)
+ err(1, "getsid");
+ if (snprintf(buf, sizeof buf, ".%d_%d_%llu_%d_%d",
+ tty, leader, starttime, ppid, sid) == -1)
+ return NULL;
+ return buf;
+}
static int
-tspath(const char **path)
+checktsdir(int fd)
{
- int tty;
- pid_t ppid;
- if (*pathbuf == '\0') {
- if ((tty = ttynr()) == -1)
- errx(1, "failed to get tty number");
- ppid = getppid();
- if (snprintf(pathbuf, sizeof pathbuf, "%s/.%d_%d",
- TIMESTAMP_DIR, tty, ppid) == -1)
- return -1;
- }
- *path = pathbuf;
+ struct stat st;
+
+ if (fstat(fd, &st) == -1)
+ err(1, "fstatat");
+
+ if ((st.st_mode & S_IFMT) != S_IFDIR)
+ errx(0, "timestamp directory is not a directory");
+ if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0)
+ errx(1, "timestamp directory permissions wrong");
+ if (st.st_uid != 0 || st.st_gid != 0)
+ errx(1, "timestamp directory is not owned by root");
+
+#if defined(TIMESTAMP_TMPFS) && defined(__linux__)
+ struct statfs sf;
+ if (fstatfs(fd, &sf) == -1)
+ err(1, "statfs");
+
+ if (sf.f_type != TMPFS_MAGIC)
+ errx(1, "timestamp directory not on tmpfs");
+#endif
+
return 0;
}
static int
-checktsdir(const char *path)
+opentsdir()
{
- char *dir, *buf;
- struct stat st;
- struct statfs sf;
gid_t gid;
+ int fd;
- if (!(buf = strdup(path)))
- err(1, "strdup");
- dir = dirname(buf);
-
-check:
- if (lstat(dir, &st) == -1) {
+reopen:
+ if ((fd = open(TIMESTAMP_DIR, O_RDONLY | O_DIRECTORY)) == -1) {
if (errno == ENOENT) {
gid = getegid();
if (setegid(0) != 0)
err(1, "setegid");
- if (mkdir(dir, (S_IRUSR|S_IWUSR|S_IXUSR)) != 0)
+ if (mkdir(TIMESTAMP_DIR, (S_IRUSR|S_IWUSR|S_IXUSR)) != 0)
err(1, "mkdir");
if (setegid(gid) != 0)
err(1, "setegid");
- goto check;
+ goto reopen;
} else {
- err(1, "stat");
+ err(1, "failed to open timestamp directory: %s", TIMESTAMP_DIR);
}
}
- if ((st.st_mode & S_IFMT) != S_IFDIR)
- errx(1, "timestamp directory is not a directory");
+ if (checktsdir(fd) != 0)
+ return -1;
+
+ return fd;
+}
+
+static int
+checktsfile(int fd, size_t *tssize)
+{
+ struct stat st;
+ gid_t gid;
+
+ if (fstat(fd, &st) == -1)
+ err(1, "stat");
+ if ((st.st_mode & S_IFMT) != S_IFREG)
+ errx(1, "timestamp is not a regular file");
if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0)
- errx(1, "timestamp directory permissions wrong");
- if (st.st_uid != 0 || st.st_gid != 0)
- errx(1, "timestamp directory is not owned by root");
- if (statfs(dir, &sf) == -1)
- err(1, "statfs");
- if (sf.f_type != TMPFS_MAGIC)
- errx(1, "timestamp directory not on tmpfs");
+ errx(1, "timestamp has wrong permissions");
+
+ gid = getegid();
+ if (st.st_uid != 0 || st.st_gid != gid)
+ errx(1, "timestamp has wrong owner");
+
+ *tssize = st.st_size;
- free(buf);
return 0;
}
-int
-persist_check(int fd, int secs)
+static int
+validts(int fd, int secs)
{
struct timespec mono, real, ts_mono, ts_real, timeout;
if (read(fd, &ts_mono, sizeof ts_mono) != sizeof ts_mono ||
- read(fd, &ts_real, sizeof ts_real) != sizeof ts_mono)
+ read(fd, &ts_real, sizeof ts_real) != sizeof ts_real)
err(1, "read");
if (!timespecisset(&ts_mono) || !timespecisset(&ts_real))
errx(1, "timespecisset");
int
persist_open(int *valid, int secs)
{
- struct stat st;
- int fd;
- gid_t gid;
- const char *path;
+ int dirfd, fd;
+ const char *name;
+
+ *valid = 0;
- if (tspath(&path) == -1)
- errx(1, "failed to get timestamp path");
- if (checktsdir(path))
- errx(1, "checktsdir");
+ if ((name = tsname()) == NULL)
+ errx(1, "failed to get timestamp name");
+ if ((dirfd = opentsdir()) == -1)
+ errx(1, "opentsdir");
- if ((fd = open(path, (O_RDWR), (S_IRUSR|S_IWUSR))) == -1)
+ if ((fd = openat(dirfd, name, (O_RDWR), (S_IRUSR|S_IWUSR))) == -1)
if (errno != ENOENT)
- err(1, "open: %s", path);
+ err(1, "open timestamp file");
if (fd == -1) {
- if ((fd = open(path, (O_RDWR|O_CREAT|O_EXCL), (S_IRUSR|S_IWUSR))) == -1)
- err(1, "open: %s", path);
- *valid = 0;
- return fd;
+ if ((fd = openat(dirfd, name, (O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW),
+ (S_IRUSR|S_IWUSR))) == -1)
+ err(1, "open timestamp file");
}
- if (fstat(fd, &st) == -1)
- err(1, "stat");
- if ((st.st_mode & S_IFMT) != S_IFREG)
- errx(1, "timestamp is not a file");
- if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0)
- errx(1, "timestamp permissions wrong");
-
- gid = getegid();
- if (st.st_uid != 0 || st.st_gid != gid)
- errx(1, "timestamp has wrong owner");
-
- if (st.st_size == 0) {
- *valid = 0;
- return fd;
- }
+ size_t tssize;
+ if (checktsfile(fd, &tssize) == -1)
+ err(1, "checktsfile");
- if (st.st_size != sizeof(struct timespec) * 2)
+ /* The timestamp size is 0 if its a new file or a
+ * timestamp that was never set, its not valid but
+ * can be used to write the new timestamp.
+ * If the size does not match the expected size it
+ * is incomplete and should never be used
+ */
+ if (tssize == sizeof(struct timespec) * 2)
+ *valid = validts(fd, secs) == 0;
+ else if (tssize != 0)
errx(1, "corrupt timestamp file");
- *valid = persist_check(fd, secs) == 0;
-
+ close(dirfd);
return fd;
}
int
persist_clear()
{
- const char *path;
- if (tspath(&path) == -1)
- errx(1, "failed to get timestamp path");
- if (unlink(path) == -1 && errno != ENOENT)
+ const char *name;
+ int dirfd;
+ if ((name = tsname()) == NULL)
+ errx(1, "failed to get timestamp name");
+ if ((dirfd = opentsdir()) == -1)
+ errx(1, "opentsdir");
+ if (unlinkat(dirfd, name, 0) == -1 && errno != ENOENT)
return -1;
+ close(dirfd);
return 0;
}
projects / opendoas.git / blobdiff