pseudo: Fix openat() with a symlink pointing to a directory

pseudo: Fix openat() with a symlink pointing to a directory

While working with ostree disk generation in conjunction with wic, I
found a problem with pseudo where it tried to resolve a symlink when
it shouldn't, based on openat() flags. A C program has been
constructed to test pseudo to show that it is working properly with
the correct behavior around openat().

 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <dirent.h>
 #include <unistd.h>
 #include <fcntl.h>

int main()
{
    /*
     * Tested with: gcc -Wall -o app app.c ; echo "no pseudo" ;
     * ./app ; echo "pseudo"; pseudo ./app
     */
    system("rm -rf tdir tlink");
    system("mkdir tdir");
    system("ln -s tdir tlink");
    DIR *dir = opendir(".");
    int dfd = dirfd(dir);

    int target_dfd = openat (dfd, "tlink", O_RDONLY | O_NONBLOCK |
                             O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
    if (target_dfd == -1) {
        printf("Test 1 good\n");
    } else {
        printf("Test 1 failed\n");
        close(target_dfd);
    }
    target_dfd = openat (dfd, "tlink", O_RDONLY | O_NONBLOCK |
                         O_DIRECTORY | O_CLOEXEC);
    if (target_dfd == -1) {
        printf("Test 2 failed\n");
    } else {
        printf("Test 2 good\n");
        close(target_dfd);
    }
    /* Test 3 make sure the owner of the link is root  */
    struct stat sbuf;
    if (!lstat("tlink", &sbuf) && sbuf.st_uid == 0) {
        printf("Test 3 good\n");
    } else {
        printf("Test 3 failed\n");
    }
    /* Test 4 tests open with the "rb" flag, owner should not change */
    int ofd = openat(dfd,"./tlink", O_RDONLY|O_CLOEXEC);
    if (ofd >= 0) {
        if (fstat(ofd, &sbuf) != 0)
            printf("ERROR in fstat test 4\n");
        else if (sbuf.st_uid == 0)
            printf("Test 4 good\n");
        close(ofd);
    } else {
        printf("Test 4 failed with openat()\n");
    }
    /* Test pseudo db to see the fstat() above did not delete the DB entry */
    if (!lstat("tlink", &sbuf) && sbuf.st_uid == 0)
        printf("Test 5 good\n");
    else
        printf("Test 5 failed... tlink is owned by %i and not 0\n", sbuf.st_uid);
    return 0;
}

int main()
{
    /* Tested with: gcc -Wall -o app app.c ; echo "no pseudo" ; ./app ; echo "pseudo"; pseudo ./app */
    system("rm -rf tdir tlink");
    system("mkdir tdir");
    system("ln -s tdir tlink");
    DIR *dir = opendir(".");
    int dfd = dirfd(dir);

    int target_dfd = openat (dfd, "tlink", O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
    if (target_dfd == -1) {
        printf("This is right\n");
    } else {
        printf("This is broken\n");
    }
    return 0;
}

Many thanks to Peter Seebach for fixing the problem in the pseudo code
to use the same logic which was already there for the
AT_SYMLINK_NOFOLLOW.

Also updated is the license MD5 checksum since the master branch of
pseudo has had the SPDX data updated.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>