opendoas

my fork of doas with custom prompt
git clone git://git.kocotian.pl/opendoas.git
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commit fe5ec5717fe414e9f1e12bbdf0794c18af3238fb
parent 8b2a776ddd47b74bb814a00ea7af3cc970063db7
Author: Duncan Overbruck <mail@duncano.de>
Date:   Fri, 26 Jul 2019 16:39:36 +0200

timestamp: error out if fstat and lstat st_ino and st_dev are not the same

Diffstat:
Mtimestamp.c | 44++++++++++++++++++++++++++++++++++----------
1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/timestamp.c b/timestamp.c @@ -198,14 +198,21 @@ timestamp_name() static int opentsdir() { - struct stat st; + struct stat st, stl; int fd; int isnew; - fd = -1; isnew = 0; + reopen: + if (lstat(TIMESTAMP_DIR, &stl) == -1) { + if (!(errno == ENOENT && isnew == 0)) + err(1, "lstat: %s", TIMESTAMP_DIR); + } else if ((stl.st_mode & S_IFMT) != S_IFDIR) { + errx(1, "%s: not a directory", TIMESTAMP_DIR); + } + if ((fd = open(TIMESTAMP_DIR, O_RDONLY | O_DIRECTORY)) == -1) { if (errno == ENOENT && isnew == 0) { if (mkdir(TIMESTAMP_DIR, (S_IRUSR|S_IWUSR|S_IXUSR)) != 0) @@ -221,8 +228,9 @@ recheck: if (fstat(fd, &st) == -1) err(1, "fstatat"); - if ((st.st_mode & S_IFMT) != S_IFDIR) - errx(1, "timestamp directory is not a directory"); + if (stl.st_ino != st.st_ino || stl.st_dev != st.st_dev) + errx(1, "timestamp directory lstat and fstat are different files"); + if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0) errx(1, "timestamp directory has wrong permissions"); @@ -310,7 +318,7 @@ timestamp_set(int fd, int secs) int timestamp_open(int *valid, int secs) { - struct stat st; + struct stat st, stl; int dirfd, fd; gid_t gid; const char *name; @@ -322,20 +330,36 @@ timestamp_open(int *valid, int secs) if ((dirfd = opentsdir()) == -1) errx(1, "opentsdir"); + if (fstatat(dirfd, name, &stl, AT_SYMLINK_NOFOLLOW) == -1) { + if (errno != ENOENT) + err(1, "fstatat"); + } else if ((stl.st_mode & S_IFMT) != S_IFREG) { + errx(1, "timestamp: not a regular file"); + } + if ((fd = openat(dirfd, name, (O_RDWR), (S_IRUSR|S_IWUSR))) == -1) if (errno != ENOENT) err(1, "open timestamp file"); - if (fd == -1) { + /* + * If the file was opened, check if fstat and lstat results are + * the same file. + * If the file doesn't exist and we create it with O_CREAT|O_EXCL, + * it is already known that the file is a regular file. + */ + if (fd != -1) { + if (fstat(fd, &st) == -1) + err(1, "stat"); + if (stl.st_ino != st.st_ino || stl.st_dev != st.st_dev) + errx(1, "timestamp file lstat and fstat are different files"); + } else { 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 (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 file has wrong permissions");