From: Roy Marples <roy@marples.name>
Date: Thu, 20 Aug 2020 15:28:47 +0000 (+0100)
Subject: privsep: Only the master process accepts signals
X-Git-Tag: v9.2.0~25
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2d18b2a25e2e95595ff7b643d2a2754540549e3d;p=thirdparty%2Fdhcpcd.git

privsep: Only the master process accepts signals

The master process dictates when processes should stop, which
allows for a clean shutdown when the admin issues `pkill dhcpcd`.
---

diff --git a/src/eloop.c b/src/eloop.c
index d43dbe83..16bb9b2a 100644
--- a/src/eloop.c
+++ b/src/eloop.c
@@ -703,9 +703,10 @@ eloop_start(struct eloop *eloop, sigset_t *signals)
 		if (eloop->exitnow)
 			break;
 
-		if (_eloop_nsig != 0 && eloop->signal_cb != NULL) {
+		if (_eloop_nsig != 0) {
 			n = _eloop_sig[--_eloop_nsig];
-			eloop->signal_cb(n, eloop->signal_cb_ctx);
+			if (eloop->signal_cb != NULL)
+				eloop->signal_cb(n, eloop->signal_cb_ctx);
 			continue;
 		}
 
diff --git a/src/privsep-bpf.c b/src/privsep-bpf.c
index 6892bf2a..3025fda8 100644
--- a/src/privsep-bpf.c
+++ b/src/privsep-bpf.c
@@ -40,7 +40,6 @@
 #include <assert.h>
 #include <pwd.h>
 #include <errno.h>
-#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -170,17 +169,6 @@ ps_bpf_start_bpf(void *arg)
 	return -1;
 }
 
-static void
-ps_bpf_signal_bpfcb(int sig, void *arg)
-{
-	struct dhcpcd_ctx *ctx = arg;
-
-	if (sig != SIGTERM)
-		return;
-
-	eloop_exit(ctx->eloop, EXIT_SUCCESS);
-}
-
 ssize_t
 ps_bpf_cmd(struct dhcpcd_ctx *ctx, struct ps_msghdr *psm, struct msghdr *msg)
 {
@@ -249,7 +237,7 @@ ps_bpf_cmd(struct dhcpcd_ctx *ctx, struct ps_msghdr *psm, struct msghdr *msg)
 	start = ps_dostart(ctx,
 	    &psp->psp_pid, &psp->psp_fd,
 	    ps_bpf_recvmsg, NULL, psp,
-	    ps_bpf_start_bpf, ps_bpf_signal_bpfcb,
+	    ps_bpf_start_bpf, NULL,
 	    PSF_DROPPRIVS);
 	switch (start) {
 	case -1:
diff --git a/src/privsep-control.c b/src/privsep-control.c
index 306ab58f..e0f9088f 100644
--- a/src/privsep-control.c
+++ b/src/privsep-control.c
@@ -27,7 +27,6 @@
  */
 
 #include <errno.h>
-#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -95,18 +94,6 @@ ps_ctl_recvmsg(void *arg)
 		logerr(__func__);
 }
 
-static void
-ps_ctl_signalcb(int sig, void *arg)
-{
-	struct dhcpcd_ctx *ctx = arg;
-
-	if (sig != SIGTERM)
-		return;
-
-	shutdown(ctx->ps_control_fd, SHUT_RDWR);
-	eloop_exit(ctx->eloop, EXIT_SUCCESS);
-}
-
 ssize_t
 ps_ctl_handleargs(struct fd_list *fd, char *data, size_t len)
 {
@@ -251,7 +238,7 @@ ps_ctl_start(struct dhcpcd_ctx *ctx)
 
 	pid = ps_dostart(ctx, &ctx->ps_control_pid, &ctx->ps_control_fd,
 	    ps_ctl_recvmsg, ps_ctl_dodispatch, ctx,
-	    ps_ctl_startcb, ps_ctl_signalcb,
+	    ps_ctl_startcb, NULL,
 	    PSF_DROPPRIVS);
 
 	if (pid == -1)
diff --git a/src/privsep-inet.c b/src/privsep-inet.c
index 8bc0c2ea..89ba79e0 100644
--- a/src/privsep-inet.c
+++ b/src/privsep-inet.c
@@ -34,7 +34,6 @@
 
 #include <assert.h>
 #include <errno.h>
-#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -291,18 +290,6 @@ ps_inet_recvmsg(void *arg)
 		logerr(__func__);
 }
 
-static void
-ps_inet_signalcb(int sig, void *arg)
-{
-	struct dhcpcd_ctx *ctx = arg;
-
-	if (sig != SIGTERM)
-		return;
-
-	shutdown(ctx->ps_inet_fd, SHUT_RDWR);
-	eloop_exit(ctx->eloop, EXIT_SUCCESS);
-}
-
 ssize_t
 ps_inet_dispatch(void *arg, struct ps_msghdr *psm, struct msghdr *msg)
 {
@@ -347,7 +334,7 @@ ps_inet_start(struct dhcpcd_ctx *ctx)
 
 	pid = ps_dostart(ctx, &ctx->ps_inet_pid, &ctx->ps_inet_fd,
 	    ps_inet_recvmsg, ps_inet_dodispatch, ctx,
-	    ps_inet_startcb, ps_inet_signalcb,
+	    ps_inet_startcb, NULL,
 	    PSF_DROPPRIVS);
 
 #ifdef HAVE_CAPSICUM
@@ -576,7 +563,7 @@ ps_inet_cmd(struct dhcpcd_ctx *ctx, struct ps_msghdr *psm, struct msghdr *msg)
 	start = ps_dostart(ctx,
 	    &psp->psp_pid, &psp->psp_fd,
 	    ps_inet_recvmsgpsp, NULL, psp,
-	    start_func, ps_inet_signalcb,
+	    start_func, NULL,
 	    PSF_DROPPRIVS);
 	switch (start) {
 	case -1:
diff --git a/src/privsep-root.c b/src/privsep-root.c
index 3e2046ad..1a438b67 100644
--- a/src/privsep-root.c
+++ b/src/privsep-root.c
@@ -693,22 +693,14 @@ ps_root_startcb(void *arg)
 }
 
 static void
-ps_root_signalcb(int sig, void *arg)
+ps_root_signalcb(int sig, __unused void *arg)
 {
-	struct dhcpcd_ctx *ctx = arg;
 
 	if (sig == SIGCHLD) {
 		while (waitpid(-1, NULL, WNOHANG) > 0)
 			;
 		return;
 	}
-
-	if (sig != SIGTERM)
-		return;
-
-	shutdown(ctx->ps_root_fd, SHUT_RDWR);
-	shutdown(ctx->ps_data_fd, SHUT_RDWR);
-	eloop_exit(ctx->eloop, EXIT_SUCCESS);
 }
 
 int (*handle_interface)(void *, int, const char *);
diff --git a/src/privsep.c b/src/privsep.c
index c5e89baf..aa5cd9ab 100644
--- a/src/privsep.c
+++ b/src/privsep.c
@@ -34,6 +34,7 @@
  * Spawn an unpriv process to send/receive common network data.
  * Then drop all privs and start running.
  * Every process aside from the privileged actioneer is chrooted.
+ * All privsep processes ignore signals - only the master process accepts them.
  *
  * dhcpcd will maintain the config file in the chroot, no need to handle
  * this in a script or something.