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Date:      Sat, 4 Mar 2017 20:50:17 +0000 (UTC)
From:      Baptiste Daroussin <bapt@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-user@freebsd.org
Subject:   svn commit: r314678 - user/bapt/diff
Message-ID:  <201703042050.v24KoHDA062712@repo.freebsd.org>
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Author: bapt
Date: Sat Mar  4 20:50:17 2017
New Revision: 314678
URL: https://svnweb.freebsd.org/changeset/base/314678

Log:
  Capsicumize diff on regular files
  
  To allow to work in capsicum mode:
  - early spawn pr(1) if needed (lflag)
  - use pdfork instead of fork
  - use kevent to track the exit of pr(1) as pdwait4 does not exist yet

Modified:
  user/bapt/diff/diffreg.c

Modified: user/bapt/diff/diffreg.c
==============================================================================
--- user/bapt/diff/diffreg.c	Sat Mar  4 20:46:57 2017	(r314677)
+++ user/bapt/diff/diffreg.c	Sat Mar  4 20:50:17 2017	(r314678)
@@ -67,9 +67,14 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <sys/capsicum.h>
+#include <sys/procdesc.h>
 #include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/event.h>
 #include <sys/wait.h>
 
+#include <capsicum_helpers.h>
 #include <ctype.h>
 #include <err.h>
 #include <errno.h>
@@ -307,7 +312,9 @@ diffreg(char *file1, char *file2, int fl
 	FILE *f1, *f2;
 	int i, rval;
 	int	ostdout = -1;
-	pid_t pid = -1;
+	int pr_pd, kq;
+	struct kevent *e;
+	cap_rights_t rights_ro;
 
 	f1 = f2 = NULL;
 	rval = D_SAME;
@@ -366,26 +373,10 @@ diffreg(char *file1, char *file2, int fl
 		goto closem;
 	}
 
-	switch (files_differ(f1, f2, flags)) {
-	case 0:
-		goto closem;
-	case 1:
-		break;
-	default:
-		/* error */
-		status |= 2;
-		goto closem;
-	}
-
-	if ((flags & D_FORCEASCII) == 0 &&
-	    (!asciifile(f1) || !asciifile(f2))) {
-		rval = D_BINARY;
-		status |= 1;
-		goto closem;
-	}
 	if (lflag) {
 		/* redirect stdout to pr */
 		int	 pfd[2];
+		pid_t	pid;
 		char	*header;
 
 		xasprintf(&header, "%s %s %s", diffargs, file1, file2);
@@ -393,7 +384,7 @@ diffreg(char *file1, char *file2, int fl
 		fflush(stdout);
 		rewind(stdout);
 		pipe(pfd);
-		switch ((pid = fork())) {
+		switch ((pid = pdfork(&pr_pd, PD_CLOEXEC))) {
 		case -1:
 			status |= 2;
 			free(header);
@@ -408,6 +399,7 @@ diffreg(char *file1, char *file2, int fl
 			execl(_PATH_PR, _PATH_PR, "-h", header, (char *)0);
 			_exit(127);
 		default:
+
 			/* parent */
 			if (pfd[1] != STDOUT_FILENO) {
 				ostdout = dup(STDOUT_FILENO);
@@ -417,8 +409,46 @@ diffreg(char *file1, char *file2, int fl
 			close(pfd[0]);
 			rewind(stdout);
 			free(header);
+			kq = kqueue();
+			if (kq == -1)
+				err(2, "kqueue");
+			e = xmalloc(sizeof(struct kevent));
+			EV_SET(e, pr_pd, EVFILT_PROCDESC, EV_ADD, NOTE_EXIT, 0,
+			    NULL);
+			if (kevent(kq, e, 1, NULL, 0, NULL) == -1)
+				err(2, "kevent");
 		}
 	}
+
+	cap_rights_init(&rights_ro, CAP_READ, CAP_FSTAT, CAP_SEEK);
+	if (cap_rights_limit(fileno(f1), &rights_ro) < 0)
+		err(2, "unable to limit rights on: %s", file1);
+	if (cap_rights_limit(fileno(f2), &rights_ro) < 0)
+		err(2, "unable to limit rights on: %s", file2);
+	if (caph_limit_stdio() == -1)
+		err(2, "unable to limit stdio");
+
+	caph_cache_catpages();
+	if (cap_enter() < 0 && errno != ENOSYS)
+		err(2, "unable to enter capability mode");
+
+	switch (files_differ(f1, f2, flags)) {
+	case 0:
+		goto closem;
+	case 1:
+		break;
+	default:
+		/* error */
+		status |= 2;
+		goto closem;
+	}
+
+	if ((flags & D_FORCEASCII) == 0 &&
+	    (!asciifile(f1) || !asciifile(f2))) {
+		rval = D_BINARY;
+		status |= 1;
+		goto closem;
+	}
 	prepare(0, f1, stb1.st_size, flags);
 	prepare(1, f2, stb2.st_size, flags);
 
@@ -452,19 +482,25 @@ diffreg(char *file1, char *file2, int fl
 	check(f1, f2, flags);
 	output(file1, f1, file2, f2, flags);
 	if (ostdout != -1) {
+		/* close the pipe to pr and restore stdout */
 		int wstatus;
 
-		/* close the pipe to pr and restore stdout */
 		fflush(stdout);
-		rewind(stdout);
 		if (ostdout != STDOUT_FILENO) {
 			close(STDOUT_FILENO);
 			dup2(ostdout, STDOUT_FILENO);
 			close(ostdout);
 		}
-		waitpid(pid, &wstatus, 0);
+		if (kevent(kq, NULL, 0, e, 1, NULL) == -1)
+			err(2, "kevent");
+		wstatus = e[0].data;
+		if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) != 0)
+			errx(2, "pr exited abnormally");
+		else if (WIFSIGNALED(wstatus))
+			errx(2, "pr killed by signal %d",
+			    WTERMSIG(wstatus));
 	}
-	
+
 closem:
 	if (anychange) {
 		status |= 1;

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