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Rename run_cred -> cur_cred and stash existing creds in set_tmpdir().

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For sudo_edit_open() et al what we need is a copy of the current
cred to restore after dir_is_writable() changes to the user cred.
This commit is contained in:
Todd C. Miller
2021-01-06 13:01:09 -07:00
parent ece5adc662
commit 7788581473
4 changed files with 57 additions and 25 deletions
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28
src/edit_open.c
View File

@@ -74,7 +74,7 @@ switch_user(uid_t euid, gid_t egid, int ngroups, GETGROUPS_T *groups)
* Returns true if the open directory fd is owned or writable by the user. * Returns true if the open directory fd is owned or writable by the user.
*/ */
int int
dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *run_cred) dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *cur_cred)
{ {
struct stat sb; struct stat sb;
int rc; int rc;
@@ -92,7 +92,7 @@ dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *run_cred
} }
/* Change uid/gid/groups to invoking user, usually needs root perms. */ /* Change uid/gid/groups to invoking user, usually needs root perms. */
if (run_cred->euid != ROOT_UID) { if (cur_cred->euid != ROOT_UID) {
if (seteuid(ROOT_UID) != 0) if (seteuid(ROOT_UID) != 0)
sudo_fatal("seteuid(ROOT_UID)"); sudo_fatal("seteuid(ROOT_UID)");
} }
@@ -102,13 +102,13 @@ dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *run_cred
/* Access checks are done using the euid/egid and group vector. */ /* Access checks are done using the euid/egid and group vector. */
rc = faccessat(dfd, ".", W_OK, AT_EACCESS); rc = faccessat(dfd, ".", W_OK, AT_EACCESS);
/* Change uid/gid/groups back to target user, may need root perms. */ /* Restore uid/gid/groups, may need root perms. */
if (user_cred->uid != ROOT_UID) { if (user_cred->uid != ROOT_UID) {
if (seteuid(ROOT_UID) != 0) if (seteuid(ROOT_UID) != 0)
sudo_fatal("seteuid(ROOT_UID)"); sudo_fatal("seteuid(ROOT_UID)");
} }
switch_user(run_cred->euid, run_cred->egid, run_cred->ngroups, switch_user(cur_cred->euid, cur_cred->egid, cur_cred->ngroups,
run_cred->groups); cur_cred->groups);
if (rc == 0) if (rc == 0)
debug_return_int(true); debug_return_int(true);
@@ -144,7 +144,7 @@ group_matches(gid_t target, struct sudo_cred *cred)
* Returns true if the open directory fd is owned or writable by the user. * Returns true if the open directory fd is owned or writable by the user.
*/ */
int int
dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *run_cred) dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *cur_cred)
{ {
struct stat sb; struct stat sb;
debug_decl(dir_is_writable, SUDO_DEBUG_EDIT); debug_decl(dir_is_writable, SUDO_DEBUG_EDIT);
@@ -272,7 +272,7 @@ done:
static int static int
sudo_edit_open_nonwritable(char *path, int oflags, mode_t mode, sudo_edit_open_nonwritable(char *path, int oflags, mode_t mode,
struct sudo_cred *user_cred, struct sudo_cred *run_cred) struct sudo_cred *user_cred, struct sudo_cred *cur_cred)
{ {
const int dflags = DIR_OPEN_FLAGS; const int dflags = DIR_OPEN_FLAGS;
int dfd, fd, is_writable; int dfd, fd, is_writable;
@@ -297,7 +297,7 @@ sudo_edit_open_nonwritable(char *path, int oflags, mode_t mode,
* Look up one component at a time, avoiding symbolic links in * Look up one component at a time, avoiding symbolic links in
* writable directories. * writable directories.
*/ */
is_writable = dir_is_writable(dfd, user_cred, run_cred); is_writable = dir_is_writable(dfd, user_cred, cur_cred);
if (is_writable == -1) { if (is_writable == -1) {
close(dfd); close(dfd);
debug_return_int(-1); debug_return_int(-1);
@@ -339,7 +339,7 @@ sudo_edit_open_nonwritable(char *path, int oflags, mode_t mode,
#ifdef O_NOFOLLOW #ifdef O_NOFOLLOW
int int
sudo_edit_open(char *path, int oflags, mode_t mode, int sflags, sudo_edit_open(char *path, int oflags, mode_t mode, int sflags,
struct sudo_cred *user_cred, struct sudo_cred *run_cred) struct sudo_cred *user_cred, struct sudo_cred *cur_cred)
{ {
int fd; int fd;
debug_decl(sudo_edit_open, SUDO_DEBUG_EDIT); debug_decl(sudo_edit_open, SUDO_DEBUG_EDIT);
@@ -348,7 +348,7 @@ sudo_edit_open(char *path, int oflags, mode_t mode, int sflags,
oflags |= O_NOFOLLOW; oflags |= O_NOFOLLOW;
if (ISSET(sflags, CD_SUDOEDIT_CHECKDIR) && user_cred->uid != ROOT_UID) { if (ISSET(sflags, CD_SUDOEDIT_CHECKDIR) && user_cred->uid != ROOT_UID) {
fd = sudo_edit_open_nonwritable(path, oflags|O_NONBLOCK, mode, fd = sudo_edit_open_nonwritable(path, oflags|O_NONBLOCK, mode,
user_cred, run_cred); user_cred, cur_cred);
} else { } else {
fd = open(path, oflags|O_NONBLOCK, mode); fd = open(path, oflags|O_NONBLOCK, mode);
} }
@@ -359,7 +359,7 @@ sudo_edit_open(char *path, int oflags, mode_t mode, int sflags,
#else #else
int int
sudo_edit_open(char *path, int oflags, mode_t mode, int sflags, sudo_edit_open(char *path, int oflags, mode_t mode, int sflags,
struct sudo_cred *user_cred, struct sudo_cred *run_cred) struct sudo_cred *user_cred, struct sudo_cred *cur_cred)
{ {
struct stat sb; struct stat sb;
int fd; int fd;
@@ -380,7 +380,7 @@ sudo_edit_open(char *path, int oflags, mode_t mode, int sflags,
if (ISSET(sflags, CD_SUDOEDIT_CHECKDIR) && user_cred->uid != ROOT_UID) { if (ISSET(sflags, CD_SUDOEDIT_CHECKDIR) && user_cred->uid != ROOT_UID) {
fd = sudo_edit_open_nonwritable(path, oflags|O_NONBLOCK, mode, fd = sudo_edit_open_nonwritable(path, oflags|O_NONBLOCK, mode,
user_cred, run_cred); user_cred, cur_cred);
} else { } else {
fd = open(path, oflags|O_NONBLOCK, mode); fd = open(path, oflags|O_NONBLOCK, mode);
} }
@@ -412,7 +412,7 @@ sudo_edit_open(char *path, int oflags, mode_t mode, int sflags,
*/ */
bool bool
sudo_edit_parent_valid(char *path, int sflags, struct sudo_cred *user_cred, sudo_edit_parent_valid(char *path, int sflags, struct sudo_cred *user_cred,
struct sudo_cred *run_cred) struct sudo_cred *cur_cred)
{ {
const int serrno = errno; const int serrno = errno;
struct stat sb; struct stat sb;
@@ -438,7 +438,7 @@ sudo_edit_parent_valid(char *path, int sflags, struct sudo_cred *user_cred,
* *its* parent is writable and CD_SUDOEDIT_CHECK is set. * *its* parent is writable and CD_SUDOEDIT_CHECK is set.
*/ */
dfd = sudo_edit_open(path, DIR_OPEN_FLAGS, S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH, dfd = sudo_edit_open(path, DIR_OPEN_FLAGS, S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH,
sflags|CD_SUDOEDIT_FOLLOW, user_cred, run_cred); sflags|CD_SUDOEDIT_FOLLOW, user_cred, cur_cred);
if (dfd != -1) { if (dfd != -1) {
if (fstat(dfd, &sb) == 0 && S_ISDIR(sb.st_mode)) if (fstat(dfd, &sb) == 0 && S_ISDIR(sb.st_mode))
ret = true; ret = true;

3
src/sesh.c
View File

@@ -251,6 +251,9 @@ sesh_sudoedit(int argc, char *argv[])
sudo_warn("%s", U_("unable to get group list")); sudo_warn("%s", U_("unable to get group list"));
debug_return_int(SESH_ERR_FAILURE); debug_return_int(SESH_ERR_FAILURE);
} }
} else {
run_cred.ngroups = 0;
run_cred.groups = NULL;
} }
for (i = 0; i < argc - 1; i += 2) { for (i = 0; i < argc - 1; i += 2) {

45
src/sudo_edit.c
View File

@@ -60,7 +60,7 @@ static char edit_tmpdir[MAX(sizeof(_PATH_VARTMP), sizeof(_PATH_TMP))];
* Returns true on success, else false; * Returns true on success, else false;
*/ */
static bool static bool
set_tmpdir(struct command_details *command_details) set_tmpdir(struct sudo_cred *user_cred)
{ {
const char *tdir = NULL; const char *tdir = NULL;
const char *tmpdirs[] = { const char *tmpdirs[] = {
@@ -70,21 +70,49 @@ set_tmpdir(struct command_details *command_details)
#endif #endif
_PATH_TMP _PATH_TMP
}; };
struct sudo_cred saved_cred;
unsigned int i; unsigned int i;
size_t len; size_t len;
int dfd; int dfd;
debug_decl(set_tmpdir, SUDO_DEBUG_EDIT); debug_decl(set_tmpdir, SUDO_DEBUG_EDIT);
/* Stash old credentials. */
saved_cred.uid = getuid();
saved_cred.euid = geteuid();
saved_cred.gid = getgid();
saved_cred.egid = getegid();
saved_cred.ngroups = getgroups(0, NULL);
if (saved_cred.ngroups > 0) {
saved_cred.groups =
reallocarray(NULL, saved_cred.ngroups, sizeof(GETGROUPS_T));
if (saved_cred.groups == NULL) {
sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
debug_return_bool(false);
}
if (getgroups(saved_cred.ngroups, saved_cred.groups) < 0) {
sudo_warn("%s", U_("unable to get group list"));
free(saved_cred.groups);
debug_return_bool(false);
}
} else {
saved_cred.ngroups = 0;
saved_cred.groups = NULL;
}
for (i = 0; tdir == NULL && i < nitems(tmpdirs); i++) { for (i = 0; tdir == NULL && i < nitems(tmpdirs); i++) {
if ((dfd = open(tmpdirs[i], O_RDONLY)) != -1) { if ((dfd = open(tmpdirs[i], O_RDONLY)) != -1) {
if (dir_is_writable(dfd, &user_details.cred, &command_details->cred) == true) if (dir_is_writable(dfd, user_cred, &saved_cred) == true)
tdir = tmpdirs[i]; tdir = tmpdirs[i];
close(dfd); close(dfd);
} }
} }
if (tdir == NULL) free(saved_cred.groups);
sudo_fatalx("%s", U_("no writable temporary directory found"));
if (tdir == NULL) {
sudo_warnx("%s", U_("no writable temporary directory found"));
debug_return_bool(false);
}
len = strlcpy(edit_tmpdir, tdir, sizeof(edit_tmpdir)); len = strlcpy(edit_tmpdir, tdir, sizeof(edit_tmpdir));
if (len >= sizeof(edit_tmpdir)) { if (len >= sizeof(edit_tmpdir)) {
errno = ENAMETOOLONG; errno = ENAMETOOLONG;
@@ -609,9 +637,6 @@ sudo_edit(struct command_details *command_details)
struct tempfile *tf = NULL; struct tempfile *tf = NULL;
debug_decl(sudo_edit, SUDO_DEBUG_EDIT); debug_decl(sudo_edit, SUDO_DEBUG_EDIT);
if (!set_tmpdir(command_details))
goto cleanup;
/* /*
* Set real, effective and saved uids to root. * Set real, effective and saved uids to root.
* We will change the euid as needed below. * We will change the euid as needed below.
@@ -623,6 +648,10 @@ sudo_edit(struct command_details *command_details)
goto cleanup; goto cleanup;
} }
/* Find a temporary directory writable by the user. */
if (!set_tmpdir(&user_details.cred))
goto cleanup;
/* /*
* The user's editor must be separated from the files to be * The user's editor must be separated from the files to be
* edited by a "--" option. * edited by a "--" option.

6
src/sudo_edit.h
View File

@@ -48,8 +48,8 @@ bool sudo_check_temp_file(int tfd, const char *tname, uid_t uid, struct stat *sb
/* edit_open.c */ /* edit_open.c */
struct sudo_cred; struct sudo_cred;
void switch_user(uid_t euid, gid_t egid, int ngroups, GETGROUPS_T *groups); void switch_user(uid_t euid, gid_t egid, int ngroups, GETGROUPS_T *groups);
int sudo_edit_open(char *path, int oflags, mode_t mode, int sflags, struct sudo_cred *user_cred, struct sudo_cred *run_cred); int sudo_edit_open(char *path, int oflags, mode_t mode, int sflags, struct sudo_cred *user_cred, struct sudo_cred *cur_cred);
int dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *run_cred); int dir_is_writable(int dfd, struct sudo_cred *user_cred, struct sudo_cred *cur_cred);
bool sudo_edit_parent_valid(char *path, int sflags, struct sudo_cred *user_cred, struct sudo_cred *run_cred); bool sudo_edit_parent_valid(char *path, int sflags, struct sudo_cred *user_cred, struct sudo_cred *cur_cred);
#endif /* SUDO_EDIT_H */ #endif /* SUDO_EDIT_H */