Add emulation of pread(3) and pwrite(3) for systems without them.

This makes it possible to remove some ugly #ifdefs and only affects
very old systems.

MANIFEST

@@ -182,8 +182,10 @@ lib/util/nanosleep.c
 lib/util/openat.c
 lib/util/parseln.c
 lib/util/pipe2.c
+lib/util/pread.c
 lib/util/progname.c
 lib/util/pw_dup.c
+lib/util/pwrite.c
 lib/util/reallocarray.c
 lib/util/regress/fnmatch/fnm_test.c
 lib/util/regress/fnmatch/fnm_test.in

configure

@@ -2928,8 +2928,6 @@ as_fn_append ac_header_list " sys/statvfs.h"
 as_fn_append ac_func_list " fexecve"
 as_fn_append ac_func_list " killpg"
 as_fn_append ac_func_list " nl_langinfo"
-as_fn_append ac_func_list " pread"
-as_fn_append ac_func_list " pwrite"
 as_fn_append ac_func_list " faccessat"
 as_fn_append ac_func_list " wordexp"
 as_fn_append ac_func_list " getauxval"
@@ -19437,10 +19435,6 @@ done
 
 
 
-
-
-
-
 case "$host_os" in
     hpux*)
 	if test X"$ac_cv_func_pread" = X"yes"; then
@@ -19466,6 +19460,58 @@ done
 	fi
 	;;
 esac
+for ac_func in pread
+do :
+  ac_fn_c_check_func "$LINENO" "pread" "ac_cv_func_pread"
+if test "x$ac_cv_func_pread" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PREAD 1
+_ACEOF
+
+else
+
+    case " $LIBOBJS " in
+  *" pread.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS pread.$ac_objext"
+ ;;
+esac
+
+
+    for _sym in sudo_pread; do
+	COMPAT_EXP="${COMPAT_EXP}${_sym}
+"
+    done
+
+
+fi
+done
+
+for ac_func in pwrite
+do :
+  ac_fn_c_check_func "$LINENO" "pwrite" "ac_cv_func_pwrite"
+if test "x$ac_cv_func_pwrite" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PWRITE 1
+_ACEOF
+
+else
+
+    case " $LIBOBJS " in
+  *" pwrite.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS pwrite.$ac_objext"
+ ;;
+esac
+
+
+    for _sym in sudo_pwrite; do
+	COMPAT_EXP="${COMPAT_EXP}${_sym}
+"
+    done
+
+
+fi
+done
+
 for ac_func in cfmakeraw
 do :
   ac_fn_c_check_func "$LINENO" "cfmakeraw" "ac_cv_func_cfmakeraw"

configure.ac

@@ -2641,7 +2641,7 @@ dnl
 dnl Function checks
 dnl
 AC_FUNC_GETGROUPS
-AC_CHECK_FUNCS_ONCE([fexecve killpg nl_langinfo pread pwrite faccessat wordexp getauxval fseeko])
+AC_CHECK_FUNCS_ONCE([fexecve killpg nl_langinfo faccessat wordexp getauxval fseeko])
 case "$host_os" in
     hpux*)
 	if test X"$ac_cv_func_pread" = X"yes"; then
@@ -2654,6 +2654,14 @@ case "$host_os" in
 	fi
 	;;
 esac
+AC_CHECK_FUNCS([pread], [], [
+    AC_LIBOBJ(pread)
+    SUDO_APPEND_COMPAT_EXP(sudo_pread)
+])
+AC_CHECK_FUNCS([pwrite], [], [
+    AC_LIBOBJ(pwrite)
+    SUDO_APPEND_COMPAT_EXP(sudo_pwrite)
+])
 AC_CHECK_FUNCS([cfmakeraw], [], [
     AC_LIBOBJ(cfmakeraw)
     SUDO_APPEND_COMPAT_EXP(sudo_cfmakeraw)

include/sudo_compat.h

@@ -595,6 +595,16 @@ sudo_dso_public int sudo_pipe2(int fildes[2], int flags);
 # undef pipe2
 # define pipe2(_a, _b) sudo_pipe2((_a), (_b))
 #endif /* HAVE_PIPE2 */
+#ifndef HAVE_PREAD
+sudo_dso_public int sudo_pread(int fd, void *buf, size_t nbytes, off_t offset);
+# undef pread
+# define pread(_a, _b, _c, _d) sudo_pread((_a), (_b), (_c), (_d))
+#endif /* HAVE_PREAD */
+#ifndef HAVE_PWRITE
+sudo_dso_public int sudo_pwrite(int fd, const void *buf, size_t nbytes, off_t offset);
+# undef pwrite
+# define pwrite(_a, _b, _c, _d) sudo_pwrite((_a), (_b), (_c), (_d))
+#endif /* HAVE_PWRITE */
 #ifndef HAVE_UNLINKAT
 sudo_dso_public int sudo_unlinkat(int dfd, const char *path, int flag);
 # undef unlinkat

lib/util/Makefile.in

@@ -985,6 +985,12 @@ pipe2.i: $(srcdir)/pipe2.c $(incdir)/sudo_compat.h $(top_builddir)/config.h
 	$(CC) -E -o $@ $(CPPFLAGS) $<
 pipe2.plog: pipe2.i
 	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/pipe2.c --i-file $< --output-file $@
+pread.lo: $(srcdir)/pread.c $(incdir)/sudo_compat.h $(top_builddir)/config.h
+	$(LIBTOOL) $(LTFLAGS) --mode=compile $(CC) -c -o $@ $(CPPFLAGS) $(CFLAGS) $(ASAN_CFLAGS) $(PIE_CFLAGS) $(SSP_CFLAGS) $(srcdir)/pread.c
+pread.i: $(srcdir)/pread.c $(incdir)/sudo_compat.h $(top_builddir)/config.h
+	$(CC) -E -o $@ $(CPPFLAGS) $<
+pread.plog: pread.i
+	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/pread.c --i-file $< --output-file $@
 progname.lo: $(srcdir)/progname.c $(incdir)/compat/stdbool.h \
              $(incdir)/sudo_compat.h $(incdir)/sudo_util.h \
              $(top_builddir)/config.h
@@ -1011,6 +1017,12 @@ pw_dup.i: $(srcdir)/pw_dup.c $(incdir)/sudo_compat.h $(top_builddir)/config.h
 	$(CC) -E -o $@ $(CPPFLAGS) $<
 pw_dup.plog: pw_dup.i
 	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/pw_dup.c --i-file $< --output-file $@
+pwrite.lo: $(srcdir)/pwrite.c $(incdir)/sudo_compat.h $(top_builddir)/config.h
+	$(LIBTOOL) $(LTFLAGS) --mode=compile $(CC) -c -o $@ $(CPPFLAGS) $(CFLAGS) $(ASAN_CFLAGS) $(PIE_CFLAGS) $(SSP_CFLAGS) $(srcdir)/pwrite.c
+pwrite.i: $(srcdir)/pwrite.c $(incdir)/sudo_compat.h $(top_builddir)/config.h
+	$(CC) -E -o $@ $(CPPFLAGS) $<
+pwrite.plog: pwrite.i
+	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/pwrite.c --i-file $< --output-file $@
 reallocarray.lo: $(srcdir)/reallocarray.c $(incdir)/sudo_compat.h \
                  $(top_builddir)/config.h
 	$(LIBTOOL) $(LTFLAGS) --mode=compile $(CC) -c -o $@ $(CPPFLAGS) $(CFLAGS) $(ASAN_CFLAGS) $(PIE_CFLAGS) $(SSP_CFLAGS) $(srcdir)/reallocarray.c

lib/util/pread.c

@@ -0,0 +1,48 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <errno.h>
+#include <unistd.h>
+
+#include "sudo_compat.h"
+
+#if !defined(HAVE_PREAD) && !defined(HAVE_PREAD64)
+ssize_t
+sudo_pread(int fd, void *buf, size_t nbytes, off_t offset)
+{
+    ssize_t nread;
+    off_t old_offset;
+
+    old_offset = lseek(fd, (off_t)0, SEEK_CUR);
+    if (old_offset == -1 || lseek(fd, offset, SEEK_SET) == -1)
+	return -1;
+
+    nread = read(fd, buf, nbytes);
+    if (lseek(fd, old_offset, SEEK_SET) == -1)
+	return -1;
+
+    return nread;
+}
+#endif /* !HAVE_PREAD && !HAVE_PREAD64 */

lib/util/pwrite.c

@@ -0,0 +1,48 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <errno.h>
+#include <unistd.h>
+
+#include "sudo_compat.h"
+
+#if !defined(HAVE_PWRITE) && !defined(HAVE_PWRITE64)
+ssize_t
+sudo_pwrite(int fd, const void *buf, size_t nbytes, off_t offset)
+{
+    ssize_t nwritten;
+    off_t old_offset;
+
+    old_offset = lseek(fd, (off_t)0, SEEK_CUR);
+    if (old_offset == -1 || lseek(fd, offset, SEEK_SET) == -1)
+	return -1;
+
+    nwritten = write(fd, buf, nbytes);
+    if (lseek(fd, old_offset, SEEK_SET) == -1)
+	return -1;
+
+    return nwritten;
+}
+#endif /* HAVE_PWRITE && !HAVE_PWRITE64 */

scripts/mkdep.pl

@@ -116,7 +116,7 @@ sub mkdep {
     # XXX - fill in AUTH_OBJS from contents of the auth dir instead
     $makefile =~ s:\@AUTH_OBJS\@:afs.lo aix_auth.lo bsdauth.lo dce.lo fwtk.lo getspwuid.lo kerb5.lo pam.lo passwd.lo rfc1938.lo secureware.lo securid5.lo sia.lo:;
     $makefile =~ s:\@DIGEST\@:digest.lo digest_openssl.lo digest_gcrypt.lo:;
-    $makefile =~ s:\@LTLIBOBJS\@:arc4random.lo arc4random_uniform.lo cfmakeraw.lo closefrom.lo dup3.lo explicit_bzero.lo fchmodat.lo freezero.lo fstatat.lo fnmatch.lo getaddrinfo.lo getcwd.lo getentropy.lo getgrouplist.lo getdelim.lo getopt_long.lo getusershell.lo glob.lo inet_ntop_lo inet_pton.lo isblank.lo memrchr.lo mksiglist.lo mksigname.lo mktemp.lo nanosleep.lo openat.lo pipe2.lo pw_dup.lo reallocarray.lo sha2.lo sig2str.lo siglist.lo signame.lo snprintf.lo str2sig.lo strlcat.lo strlcpy.lo strndup.lo strnlen.lo strsignal.lo unlinkat.lo utimens.lo vsyslog.lo:;
+    $makefile =~ s:\@LTLIBOBJS\@:arc4random.lo arc4random_uniform.lo cfmakeraw.lo closefrom.lo dup3.lo explicit_bzero.lo fchmodat.lo freezero.lo fstatat.lo fnmatch.lo getaddrinfo.lo getcwd.lo getentropy.lo getgrouplist.lo getdelim.lo getopt_long.lo getusershell.lo glob.lo inet_ntop_lo inet_pton.lo isblank.lo memrchr.lo mksiglist.lo mksigname.lo mktemp.lo nanosleep.lo openat.lo pipe2.lo pread.lo pwrite.lo pw_dup.lo reallocarray.lo sha2.lo sig2str.lo siglist.lo signame.lo snprintf.lo str2sig.lo strlcat.lo strlcpy.lo strndup.lo strnlen.lo strsignal.lo unlinkat.lo utimens.lo vsyslog.lo:;
 
     # Parse OBJS lines
     my %objs;