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socket-util: introduce type-safe, dereferencing wrapper CMSG_FIND_DATA around cmsg_find() 

let's take this once step further, and add type-safety to cmsg_find(),
and imply the CMSG_DATA() macro for finding the cmsg payload.
This commit is contained in:
Lennart Poettering 2020-04-17 11:52:48 +02:00
parent dac556fa7b
commit 371d72e05b
6 changed files with 23 additions and 51 deletions
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8
src/basic/socket-util.h
View File

@ -158,6 +158,14 @@ int flush_accept(int fd);
struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length);
/* Type-safe, dereferencing version of cmsg_find() */
#define CMSG_FIND_DATA(mh, level, type, ctype) \
({ \
struct cmsghdr *_found; \
_found = cmsg_find(mh, level, type, CMSG_LEN(sizeof(ctype))); \
(ctype*) (_found ? CMSG_DATA(_found) : NULL); \
})
/*
* Certain hardware address types (e.g Infiniband) do not fit into sll_addr
* (8 bytes) and run over the structure. This macro returns the correct size that

10
src/import/importd.c
View File

@ -557,9 +557,8 @@ static int manager_on_notify(sd_event_source *s, int fd, uint32_t revents, void
.msg_control = &control,
.msg_controllen = sizeof(control),
};
struct ucred *ucred = NULL;
struct ucred *ucred;
Manager *m = userdata;
struct cmsghdr *cmsg;
char *p, *e;
Transfer *t;
Iterator i;
@ -574,17 +573,12 @@ static int manager_on_notify(sd_event_source *s, int fd, uint32_t revents, void
cmsg_close_all(&msghdr);
CMSG_FOREACH(cmsg, &msghdr)
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_CREDENTIALS &&
cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred)))
ucred = (struct ucred*) CMSG_DATA(cmsg);
if (msghdr.msg_flags & MSG_TRUNC) {
log_warning("Got overly long notification datagram, ignoring.");
return 0;
}
ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
if (!ucred || ucred->pid <= 0) {
log_warning("Got notification datagram lacking credential information, ignoring.");
return 0;

26
src/journal/journald-stream.c
View File

@ -491,8 +491,7 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
StdoutStream *s = userdata;
struct ucred *ucred = NULL;
struct cmsghdr *cmsg;
struct ucred *ucred;
struct iovec iovec;
size_t limit;
ssize_t l;
@ -541,25 +540,14 @@ static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents,
goto terminate;
}
CMSG_FOREACH(cmsg, &msghdr)
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_CREDENTIALS &&
cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred))) {
assert(!ucred);
ucred = (struct ucred *)CMSG_DATA(cmsg);
break;
}
/* Invalidate the context if the pid of the sender changed.
* This happens when a forked process inherits stdout / stderr
* from a parent. In this case getpeercred returns the ucred
* of the parent, which can be invalid if the parent has exited
* in the meantime.
/* Invalidate the context if the pid of the sender changed. This happens when a forked process
* inherits stdout / stderr from a parent. In this case getpeercred returns the ucred of the parent,
* which can be invalid if the parent has exited in the meantime.
*/
ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
if (ucred && ucred->pid != s->ucred.pid) {
/* force out any previously half-written lines from a
* different process, before we switch to the new ucred
* structure for everything we just added */
/* force out any previously half-written lines from a different process, before we switch to
* the new ucred structure for everything we just added */
r = stdout_stream_scan(s, true);
if (r < 0)
goto terminate;

13
src/nspawn/nspawn.c
View File

@ -3698,8 +3698,7 @@ static int nspawn_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t r
.msg_control = &control,
.msg_controllen = sizeof(control),
};
struct cmsghdr *cmsg;
struct ucred *ucred = NULL;
struct ucred *ucred;
ssize_t n;
pid_t inner_child_pid;
_cleanup_strv_free_ char **tags = NULL;
@ -3721,15 +3720,7 @@ static int nspawn_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t r
cmsg_close_all(&msghdr);
CMSG_FOREACH(cmsg, &msghdr) {
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_CREDENTIALS &&
cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred))) {
ucred = (struct ucred*) CMSG_DATA(cmsg);
}
}
ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
if (!ucred || ucred->pid != inner_child_pid) {
log_debug("Received notify message without valid credentials. Ignoring.");
return 0;

7
src/shared/ask-password-api.c
View File

@ -940,15 +940,12 @@ int ask_password_agent(
continue;
}
if (msghdr.msg_controllen < CMSG_LEN(sizeof(struct ucred)) ||
control.cmsghdr.cmsg_level != SOL_SOCKET ||
control.cmsghdr.cmsg_type != SCM_CREDENTIALS ||
control.cmsghdr.cmsg_len != CMSG_LEN(sizeof(struct ucred))) {
ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
if (!ucred) {
log_debug("Received message without credentials. Ignoring.");
continue;
}
ucred = (struct ucred*) CMSG_DATA(&control.cmsghdr);
if (ucred->uid != 0) {
log_debug("Got request from unprivileged user. Ignoring.");
continue;

10
src/udev/udevd.c
View File

@ -916,9 +916,8 @@ static int on_worker(sd_event_source *s, int fd, uint32_t revents, void *userdat
.msg_control = &control,
.msg_controllen = sizeof(control),
};
struct cmsghdr *cmsg;
ssize_t size;
struct ucred *ucred = NULL;
struct ucred *ucred;
struct worker *worker;
size = recvmsg_safe(fd, &msghdr, MSG_DONTWAIT);
@ -937,12 +936,7 @@ static int on_worker(sd_event_source *s, int fd, uint32_t revents, void *userdat
continue;
}
CMSG_FOREACH(cmsg, &msghdr)
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_CREDENTIALS &&
cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred)))
ucred = (struct ucred*) CMSG_DATA(cmsg);
ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
if (!ucred || ucred->pid <= 0) {
log_warning("Ignoring worker message without valid PID");
continue;