Consolidated {fix,get}-gnustack.c

2 files changed, 124 insertions, 0 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
new file mode 100644
index 0000000..e63a5f2
--- /dev/null
+++ b/src/Makefile.am
@@ -0,0 +1,3 @@
+bin_PROGRAMS = fix-gnustack
+fix_gnustack_SOURCES = fix-gnustack.c
+fix_gnustack_LDADD = -lelf
diff --git a/src/fix-gnustack.c b/src/fix-gnustack.c
new file mode 100644
index 0000000..00a0c02
--- /dev/null
+++ b/src/fix-gnustack.c
@@ -0,0 +1,121 @@
+/*
+	fix-gnustack.c: check and optionally remove exec flag on Elf GNU_STACK
+	Copyright (C) 2011  Anthony G. Basile
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <error.h>
+
+#include <gelf.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+
+
+char *
+parse_cmd_args( int c, char *v[], int *flagv  )
+{
+	int i, oc;
+
+	if((c != 2)&&(c != 3))
+		error(EXIT_FAILURE, 0, "Usage: %s [-f] elffile", v[0]);
+
+	*flagv = 0 ;
+	while((oc = getopt(c, v,":f")) != -1)
+		switch(oc)
+		{
+			case 'f':
+				*flagv = 1 ;
+				break ;
+			case '?':
+			default:
+				error(EXIT_FAILURE, 0, "option -%c is invalid: ignored.", optopt ) ;
+		}
+
+	return v[optind] ;
+}
+
+
+
+int
+main( int argc, char *argv[])
+{
+	int fd, flagv;
+	char *f_name;
+	size_t i, phnum;
+
+	Elf *elf;
+	GElf_Ehdr ehdr;
+	GElf_Phdr phdr;
+
+	f_name = parse_cmd_args( argc, argv, &flagv );
+
+	if(elf_version(EV_CURRENT) == EV_NONE)
+		error(EXIT_FAILURE, 0, "Library out of date.");
+
+	if(flagv)
+	{
+		if((fd = open(f_name, O_RDWR)) < 0)
+			error(EXIT_FAILURE, 0, "open() fail.");
+		if((elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL)) == NULL)
+			error(EXIT_FAILURE, 0, "elf_begin() fail: %s", elf_errmsg(-1));
+	}
+	else
+	{
+		if((fd = open(f_name, O_RDONLY)) < 0)
+			error(EXIT_FAILURE, 0, "open() fail.");
+		if((elf = elf_begin(fd, ELF_C_READ, NULL)) == NULL)
+			error(EXIT_FAILURE, 0, "elf_begin() fail: %s", elf_errmsg(-1));
+	}
+
+	if(elf_kind(elf) != ELF_K_ELF)
+		error(EXIT_FAILURE, 0, "elf_kind() fail: this is not an elf file.");
+
+	if(gelf_getehdr(elf,&ehdr) == NULL)
+		error(EXIT_FAILURE, 0, "gelf_getehdr() fail: %s", elf_errmsg(-1));
+
+	elf_getphdrnum(elf, &phnum);
+	for(i=0; i<phnum; ++i)
+	{
+		if(gelf_getphdr(elf, i, &phdr) != &phdr)
+			error(EXIT_FAILURE, 0, "gelf_getphdr(): %s", elf_errmsg(-1));
+
+		if(phdr.p_type == PT_GNU_STACK)
+		{
+			printf("GNU_STACK: ");
+			if( phdr.p_flags & PF_R ) printf("R");
+			if( phdr.p_flags & PF_W ) printf("W");
+			if( phdr.p_flags & PF_X ) printf("X");
+			printf("\n");
+
+			if(flagv && (phdr.p_flags & PF_W) && (phdr.p_flags & PF_X))
+			{
+				printf("W&X FOUND: flipping X flag ...\n");
+				phdr.p_flags ^= PF_X;
+				if(!gelf_update_phdr(elf, i, &phdr))
+					error(EXIT_FAILURE, 0, "gelf_update_phdr(): %s", elf_errmsg(-1));
+			}
+		}
+	}
+
+	elf_end(elf);
+	close(fd);
+}