1 files changed, 412 insertions, 0 deletions
diff --git a/src/libr-elf.c b/src/libr-elf.c
new file mode 100644
index 0000000..be2daae
--- /dev/null
+++ b/src/libr-elf.c
@@ -0,0 +1,412 @@
+/*
+ *
+ *  Copyright (c) 2008 Erich Hoover
+ *
+ *  libr libelf Backend - Add resources into ELF binaries using libelf
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * To provide feedback, report bugs, or otherwise contact me:
+ * ehoover at mines dot edu
+ *
+ */
+
+/* Include compile-time parameters */
+#include "config.h"
+
+#include "libr.h"
+
+#include <sys/stat.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <fcntl.h>
+
+//#define MANUAL_LAYOUT            true
+
+extern void libr_set_error(libr_intstatus error);
+
+/*
+ * Write the output file using libelf
+ */
+void write_output(libr_file *file_handle)
+{
+	/* Update the ELF file on the disk */
+	if(elf_update(file_handle->elf_handle, ELF_C_NULL) < 0)
+	{
+		printf("elf_update() failed: %s.", elf_errmsg(-1));
+		return;
+	}
+	if(elf_update(file_handle->elf_handle, ELF_C_WRITE) < 0)
+	{
+		printf("elf_update() failed: %s.", elf_errmsg(-1));
+		return;
+	}
+	/* Close the handles */
+	elf_end(file_handle->elf_handle);
+	close(file_handle->fd_handle);
+}
+
+/*
+ * Return the size of the file represented by the file descriptor
+ */
+off_t file_size(int fd)
+{
+	struct stat file_stat;
+	
+	if(fstat(fd, &file_stat) == ERROR)
+		return ERROR;
+	return file_stat.st_size;
+}
+
+/*
+ * Open the handles for working with the file using libelf
+ */
+libr_intstatus open_handles(libr_file *file_handle, char *filename, libr_access_t access)
+{
+	const int elf_access[2] = {ELF_C_READ, ELF_C_RDWR};
+	const int fd_access[2] = {O_RDONLY, O_RDWR};
+	Elf *e = NULL;
+	int fd = 0;
+	
+	if((fd = open(filename, fd_access[access], 0)) < 0)
+		RETURN(LIBR_ERROR_OPENFAILED, "Failed to open input file");
+	if((e = elf_begin(fd, elf_access[access], NULL)) == NULL)
+		RETURN(LIBR_ERROR_BEGINFAILED, "Failed to open ELF file: %s.", elf_errmsg(-1));
+	if(elf_kind(e) != ELF_K_ELF)
+		RETURN(LIBR_ERROR_WRONGFORMAT, "Invalid input file format");
+	
+	file_handle->access = access;
+	file_handle->fd_handle = fd;
+	file_handle->elf_handle = e;
+	file_handle->file_size = file_size(fd);
+	file_handle->version = EV_CURRENT; /* This should probably match the rest of the file */
+	RETURN_OK;
+}
+
+/*
+ * Expand a section
+ * (Only used when manually controlling ELF layout)
+ */
+#ifdef MANUAL_LAYOUT
+libr_intstatus expand_section(Elf *e, Elf_Scn *scn, size_t size, int reset)
+{
+	size_t offset = 0, delta = 0;
+	Elf_Scn *tmpscn = NULL;
+	GElf_Shdr shdr;
+	
+	if(gelf_getshdr(scn, &shdr) != &shdr)
+		RETURN(LIBR_INTERROR_GETSHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
+	if(reset)
+	{
+		delta = (size-shdr.sh_size); 
+		shdr.sh_size = size;
+	}
+	else
+	{
+		delta = size;
+		shdr.sh_size += size;
+	}
+	offset = shdr.sh_offset;
+	if(gelf_update_shdr(scn, &shdr) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+	if(elf_update(e, ELF_C_NULL) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+	/* Update any section that follows this one data-wise */
+/*
+****** This does not work yet
+	while((tmpscn = elf_nextscn(e, tmpscn)) != NULL)
+	{
+		if(tmpscn == scn)
+			continue;
+		if(gelf_getshdr(tmpscn, &shdr) != &shdr)
+			return LIBR_INTERROR_GETSHDR;
+		if(offset < shdr.sh_offset)
+		{
+			if((name = elf_strptr(e, ehdr.e_shstrndx, shdr.sh_name)) == NULL)
+				RETURN(LIBR_ERROR_STRPTR, "Failed to obtain section string pointer: %s.", elf_errmsg(-1));
+			shdr.sh_offset += delta;
+			if(gelf_update_shdr(tmpscn, &shdr) < 0)
+				RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+			if(elf_update(e, ELF_C_NULL) < 0)
+				RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+		}
+	}
+*/
+	return LIBR_OK;
+}
+#endif /* MANUAL_LAYOUT */
+
+/*
+ * Obtain the data from a section using libelf
+ */
+libr_data *get_data(libr_file *file_handle, libr_section *scn)
+{
+	return elf_getdata(scn, NULL);
+}
+
+/*
+ * Create new data for a section using libelf
+ */
+libr_data *new_data(libr_file *file_handle, libr_section *scn)
+{
+	return elf_newdata(scn);
+}
+
+/*
+ * Set data for a section using libelf (not written yet)
+ */
+libr_intstatus set_data(libr_file *file_handle, libr_section *scn, libr_data *data, off_t offset, char *buffer, size_t size)
+{
+	data->d_align = 1;
+	data->d_off = offset;
+	data->d_buf = buffer;
+	data->d_type = ELF_T_BYTE;
+	data->d_size = size;
+	data->d_version = file_handle->version;
+#ifdef MANUAL_LAYOUT
+	if(expand_section(file_handle->elf_handle, scn, data->d_size, true) != LIBR_OK)
+		RETURN(LIBR_ERROR_EXPANDSECTION, "Failed to expand section");
+#else
+	if(elf_update(file_handle->elf_handle, ELF_C_NULL) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+	if(elf_update(file_handle->elf_handle, ELF_C_WRITE) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+#endif /* MANUAL_LAYOUT */
+	RETURN_OK;
+}
+
+/*
+ * Find a named section from the ELF file using libelf
+ */
+libr_intstatus find_section(libr_file *file_handle, char *section, libr_section **retscn)
+{
+	Elf *e = file_handle->elf_handle;
+	Elf_Scn *scn = NULL;
+	char *name = NULL;
+	GElf_Ehdr ehdr;
+	GElf_Shdr shdr;
+	uintmax_t si;
+	
+	if(gelf_getehdr(e, &ehdr) == NULL)
+		RETURN(LIBR_ERROR_GETEHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
+	while((scn = elf_nextscn(e, scn)) != NULL)
+	{
+		if(gelf_getshdr(scn, &shdr) != &shdr)
+			RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
+		if((name = elf_strptr(e, ehdr.e_shstrndx, shdr.sh_name)) == NULL)
+			RETURN(LIBR_ERROR_STRPTR, "Failed to obtain section string pointer: %s.", elf_errmsg(-1));
+		
+		si = (uintmax_t) elf_ndxscn(scn);
+/*
+printf("%d: %s (%d %d)\n", (long) si, name, (long) shdr.sh_offset, (long) shdr.sh_size);
+*/
+		if(strcmp(name, section) == 0)
+		{
+			*retscn = scn;
+			RETURN_OK;
+		}
+	}
+	RETURN(LIBR_ERROR_NOSECTION, "ELF resource section not found");
+}
+
+/*
+ * Add a new section and create a name for it in the ELF string table using libelf
+ */
+libr_intstatus add_section(libr_file *file_handle, char *section, Elf_Scn **retscn)
+{
+	Elf_Scn *scn = NULL, *strscn = NULL;
+	Elf *e = file_handle->elf_handle;
+#ifdef MANUAL_LAYOUT
+	size_t tblsize = 0;
+#endif /* MANUAL_LAYOUT */
+	Elf_Data *data;
+	GElf_Ehdr ehdr;
+	GElf_Shdr shdr;
+	
+	if(gelf_getehdr(e, &ehdr) == NULL)
+		RETURN(LIBR_ERROR_GETEHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
+	/* TODO: Support creating a string table for objects that don't have one */
+	if(!ehdr.e_shstrndx)
+		RETURN(LIBR_ERROR_NOTABLE, "No ELF string table");
+	strscn = elf_getscn(e, ehdr.e_shstrndx);
+	if(strscn == NULL) 
+		RETURN(LIBR_ERROR_TABLE, "Failed to open string table: %s.", elf_errmsg(-1));
+	data = elf_newdata(strscn);
+	if(data == NULL)
+		RETURN(LIBR_ERROR_NEWDATA, "Failed to create data for section");
+	data->d_align = 1;
+
+#ifdef MANUAL_LAYOUT
+{
+	GElf_Shdr strshdr;
+	
+	if(gelf_getshdr(strscn, &strshdr) != &strshdr)
+		RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
+	data->d_off = strshdr.sh_size;
+#endif /* MANUAL_LAYOUT */
+
+	data->d_size = (size_t) strlen(section)+1;
+	data->d_type = ELF_T_BYTE;
+	data->d_buf = section;
+	data->d_version = file_handle->version;
+
+#ifdef MANUAL_LAYOUT
+	if(expand_section(e, strscn, data->d_size, false) != LIBR_OK)
+		return false;
+}
+#else
+	/* Update the internal offset information */
+	if(elf_update(e, ELF_C_NULL) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+#endif /* MANUAL_LAYOUT */
+
+	/* seek to the end of the section data */
+	if((scn = elf_newscn(e)) == NULL)
+		RETURN(LIBR_ERROR_NEWSECTION, "Failed to create new section");
+	if(gelf_getshdr(scn, &shdr) != &shdr)
+		RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
+	shdr.sh_addralign = 1;
+#ifdef MANUAL_LAYOUT
+	shdr.sh_offset = file_handle->file_size;
+#endif /* MANUAL_LAYOUT */
+	shdr.sh_size = 0;
+	shdr.sh_name = data->d_off;
+	shdr.sh_type = SHT_NOTE; /* TODO: Does "NOTE" type fit best? */
+	shdr.sh_flags = SHF_WRITE;
+	shdr.sh_entsize = 0;
+	if(gelf_update_shdr(scn, &shdr) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+	*retscn = scn;
+	RETURN_OK;
+}
+
+/*
+ * Remove a section and eliminate it from the ELF string table using libelf
+ */
+libr_intstatus remove_section(libr_file *file_handle, libr_section *scn)
+{
+	unsigned int table_size, str_size;
+	char *buffer = NULL, *tmp = NULL;
+	Elf *e = file_handle->elf_handle;
+	int remaining_size;
+	Elf_Scn *strscn;
+	Elf_Data *data;
+	GElf_Ehdr ehdr;
+	GElf_Shdr shdr;
+	
+	if(gelf_getehdr(e, &ehdr) == NULL)
+		RETURN(LIBR_ERROR_GETEHDR, "Failed to obtain ELF header: %s", elf_errmsg(-1));
+	/* Grab the string table */
+	if(!ehdr.e_shstrndx)
+		RETURN(LIBR_ERROR_NOTABLE, "No ELF string table");
+	strscn = elf_getscn(e, ehdr.e_shstrndx);
+	if(strscn == NULL)
+		RETURN(LIBR_ERROR_TABLE, "Failed to open string table: %s.", elf_errmsg(-1));
+	if((data = elf_getdata(strscn, NULL)) == NULL)
+		RETURN(LIBR_ERROR_GETDATA, "Failed to obtain data of section");
+	/* Find where the section name is in the string table */
+	if(gelf_getshdr(scn, &shdr) != &shdr)
+		RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
+	table_size = data->d_size;
+	buffer = (char *) data->d_buf;
+	/* Excise the string from the table */
+	str_size = strlen(&buffer[shdr.sh_name])+1;
+	remaining_size = table_size-(shdr.sh_name+str_size);
+	if(remaining_size < 0)
+		RETURN(LIBR_ERROR_SIZEMISMATCH, "Section's data size does not make sense");
+	if(remaining_size > 0)
+	{
+		/* If there is data after our icon entry in the table then it must be moved before resizing
+		 * NOTE: Using memcpy with overlapping addresses is not allowed, use temporary buffer. 
+		 */
+		tmp = (char *) malloc(remaining_size);
+		memcpy(tmp, &buffer[shdr.sh_name+str_size], remaining_size);
+		memcpy(&buffer[shdr.sh_name], tmp, remaining_size);
+		free(tmp);
+	}
+	data->d_size -= str_size;
+	/* Update the internal offset information */
+	if(elf_update(e, ELF_C_NULL) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+#ifdef MANUAL_LAYOUT
+{
+	GElf_Shdr strshdr;
+	
+	if(gelf_getshdr(strscn, &strshdr) != &strshdr)
+		RETURN(LIBR_ERROR_GETSHDR, "Failed to obtain ELF section header: %s", elf_errmsg(-1));
+	strshdr.sh_size -= str_size;
+	if(gelf_update_shdr(strscn, &strshdr) < 0)
+		RETURN(LIBR_ERROR_UPDATE, "Failed to perform dynamic update: %s.", elf_errmsg(-1));
+}
+#endif /* MANUAL_LAYOUT */
+
+	/* Clear the section itself and update the offsets */
+	if(elfx_remscn(e, scn) == 0)
+		RETURN(LIBR_ERROR_REMOVESECTION, "Failed to remove section: %s.", elf_errmsg(-1));
+	RETURN_OK;
+}
+
+/*
+ * Return the pointer to the actual data in the section
+ */
+void *data_pointer(libr_section *scn, libr_data *data)
+{ 
+	return data->d_buf;
+}
+
+/*
+ * Return the size of the data in the section
+ */
+size_t data_size(libr_section *scn, libr_data *data)
+{
+	return data->d_size;
+}
+
+/*
+ * Return the next section in the ELF file
+ */
+libr_section *next_section(libr_file *file_handle, libr_section *scn)
+{
+	return elf_nextscn(file_handle->elf_handle, scn);
+}
+
+/*
+ * Retrieve the name of a section
+ */
+char *section_name(libr_file *file_handle, libr_section *scn)
+{
+	char *name = NULL;
+	GElf_Shdr shdr;
+	GElf_Ehdr ehdr;
+	
+	if(gelf_getehdr(file_handle->elf_handle, &ehdr) == NULL)
+		return NULL;
+	if(gelf_getshdr(scn, &shdr) != &shdr)
+		return NULL;
+	if((name = elf_strptr(file_handle->elf_handle, ehdr.e_shstrndx, shdr.sh_name)) == NULL)
+		return NULL;
+	return strdup(name);
+}
+
+/*
+ * Initialize the libelf backend
+ */
+void initialize_backend(void)
+{
+	if(elf_version(EV_CURRENT) == EV_NONE)
+		return; //errx(EX_SOFTWARE, "ELF library initialization failed: %s", elf_errmsg(-1));
+}