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Fix issues with clear_rpaths; clarify code; remove signatures automat…
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…ically.
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@culler
culler committed Oct 8, 2023
1 parent 3b16e01 commit 30ab97c
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Showing 3 changed files with 123 additions and 86 deletions.
4 changes: 4 additions & 0 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -26,3 +26,7 @@ example: example/hello example/hello.zip example/main.tcl example/tclsh8.7

clean:
rm -f *.o macher example/hello* package/*.pkg

install:
sudo cp macher /usr/local/bin

11 changes: 11 additions & 0 deletions README.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,8 @@ add_rpath
add the load command if there already exists an LC_RPATH load command with
the same path.

This action also removes all LC_CODE_SIGNATURE load commands.

If there is a LC_DYLIB command containing the substring @rpath then the
loader will search for the library in all paths obtained by replacing
@rpath by one of the paths given in LC_RPATH load commands.
Expand All @@ -77,11 +79,15 @@ remove_rpath

Removes all LC_RPATH load commands specifying the given search path.

This action also removes all LC_CODE_SIGNATURE load commands.

clear_rpaths
$ macher [-options] clear_rpaths <Mach-O file path>

Removes all LC_RPATH load commands.

This action also removes all LC_CODE_SIGNATURE load commands.

remove_signature
$ macher [-options] remove_signature <Mach-O file path>

Expand All @@ -101,10 +107,15 @@ edit_libpath
It uses the file name of the old path to decide whether to do the
replacement.

This action also removes all LC_CODE_SIGNATURE load commands.

set_id
$ macher [-options] set_id <dylib id> <Mach-O file path>

Sets the path in the LC_ID_DYLIB load command to the specified path. The
LC_ID_DYLIB load command exists only for dylib files. When another
executable is linked with the dylib, the linker copies the id into an
LC_DYLIB command for the executable.

This action also removes all LC_CODE_SIGNATURE load commands.

194 changes: 108 additions & 86 deletions macher.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@
* See the file License.txt included with the source code distribution.
*
*/
#define MACHER_VERSION "1.5"
#define MACHER_VERSION "1.6"

#include <stdio.h>
#include <stdlib.h>
Expand Down Expand Up @@ -76,16 +76,56 @@ static MachO macho_init(char *mach_o_path, char *mode, bool verbose);
static void macho_destroy(MachO mach_o);
static void show_slice_info(MachO mach_o, int index);

/* actions */
static int print_command(Slice slice, mach_o_command *command, char **args);
static int print_segment(Slice slice, mach_o_command *command, char **args);
static int add_rpath(Slice slice, mach_o_command *command, char **args);
static int remove_rpath(Slice slice, mach_o_command *command, char **args);
static int edit_libpath(Slice slice, mach_o_command *command, char **args);
static int remove_signature(Slice slice, mach_o_command *command, char **args);
/* Actions: */
/*
* If an action has a non-null action_op field then the action_op
* will be called in a loop for each load command. If the unsign
* flag is set then the (now invalid) LC_CODE_SIGNATURE load command
* will be removed after the loop terminates. If an action_op
* returns OP_BREAK then the loop is terminated when the action_op
* returns.
*/

typedef enum {OP_CONTINUE=0, OP_BREAK} op_result;
typedef op_result (*action_op)(Slice slice, mach_o_command *command, char **arg);
typedef enum {HELP=1, VERSION, SEGMENTS, INFO, APPEND, ADD_RPATH, REMOVE_RPATH,
CLEAR_RPATHS, EDIT_LIBPATH, SET_ID, UNSIGN} action_id;

typedef struct {
action_id id;
char *name;
action_op op;
bool unsign;
} mach_o_action;


static op_result print_command(Slice slice, mach_o_command *command, char **args);
static op_result print_segment(Slice slice, mach_o_command *command, char **args);
static op_result set_id(Slice slice, mach_o_command *command, char **args);
static op_result add_rpath(Slice slice, mach_o_command *command, char **args);
static op_result remove_rpath(Slice slice, mach_o_command *command, char **args);
static op_result clear_rpaths(Slice slice, mach_o_command *command, char **args);
static op_result edit_libpath(Slice slice, mach_o_command *command, char **args);
static op_result remove_signature(Slice slice, mach_o_command *command, char **args);

static mach_o_action actions[] = {
{.id = HELP, .name = "help", .op = NULL, .unsign=false},
{.id = VERSION, .name = "version", .op = NULL, .unsign=false},
{.id = INFO, .name = "info", .op = print_command, .unsign=false},
{.id = SEGMENTS, .name = "segments", .op = print_segment, .unsign=false},
{.id = APPEND, .name = "append", .op = NULL, .unsign=false},
{.id = UNSIGN, .name = "remove_signature", .op = remove_signature, .unsign=false},
{.id = ADD_RPATH, .name = "add_rpath", .op = add_rpath, .unsign=true},
{.id = REMOVE_RPATH, .name = "remove_rpath", .op = remove_rpath, .unsign=true},
{.id = CLEAR_RPATHS, .name = "clear_rpaths", .op = clear_rpaths, .unsign=true},
{.id = EDIT_LIBPATH, .name = "edit_libpath", .op = edit_libpath, .unsign=true},
{.id = SET_ID, .name = "set_id", .op = set_id, .unsign=true},
{0}
};

static void usage();
extern void append_data(char *mach_path, char *data_path, char *output_path);
extern void append_data(char *mach_path, char *data_path, char *output_path);
static void unsign(Slice slice);
static void usage();

static Slice slice_init(FILE *mach_o_file, int offset, bool verbose)
{
Expand Down Expand Up @@ -296,8 +336,8 @@ static void remove_command(Slice slice, int index)
{
mach_o_command *command = slice->commands + index;
mach_o_command empty = {0};
int command_size = command->lc.cmdsize;
int tail_size = slice->command_space - command->position - command_size;
unsigned long command_size = command->lc.cmdsize;
int tail_size = slice->offset + slice->command_space - command->position - command_size;
char *tail = malloc(tail_size);
free(command->data);
command->data = NULL;
Expand Down Expand Up @@ -325,16 +365,10 @@ static void compute_command_space(Slice slice)
if (command->lc.cmd == LC_SEGMENT_64) {
struct segment_command_64 *seg = (struct segment_command_64 *)
command->data;
if (!strcmp(seg->segname, "__TEXT")) {
if (strcmp(seg->segname, "__TEXT") == 0) {
struct section_64 *section = (struct section_64 *)
(command->data + sizeof(struct segment_command_64));
command_space = section->offset;
for (int i = 1; i < seg->nsects; i++){
if (section->offset < command_space) {
command_space = section->offset;
}
section++;
}
break;
}
} else if (command->lc.cmd == LC_SEGMENT) {
Expand All @@ -344,12 +378,6 @@ static void compute_command_space(Slice slice)
struct section *section = (struct section *)
((char *)seg + sizeof(struct segment_command));
command_space = section->offset;
for (int i = 1; i < seg->nsects; i++){
if (section->offset < command_space) {
command_space = section->offset;
}
section++;
}
break;
}
}
Expand Down Expand Up @@ -377,9 +405,13 @@ static bool find_rpath(Slice slice, char *rpath)
return false;
}

static int print_command(Slice slice, mach_o_command *command, char **args)
static op_result print_command(Slice slice, mach_o_command *command, char **args)
{
int command_id = command->lc.cmd & ~LC_REQ_DYLD;
if (slice->verbose) {
printf("<%lu-%lu> ", command->position,
command->position + command->lc.cmdsize);
}
switch (command_id) {
case LC_SEGMENT:
{
Expand Down Expand Up @@ -519,18 +551,18 @@ static int print_command(Slice slice, mach_o_command *command, char **args)
}
break;
}
return 0;
return OP_CONTINUE;
}

static int print_segment(Slice slice, mach_o_command *command, char **args)
static op_result print_segment(Slice slice, mach_o_command *command, char **args)
{
if (command->lc.cmd == LC_SEGMENT || command->lc.cmd == LC_SEGMENT_64) {
print_command(slice, command, args);
}
return 0;
return OP_CONTINUE;
}

static int add_rpath(Slice slice, mach_o_command *command, char **args)
static op_result add_rpath(Slice slice, mach_o_command *command, char **args)
{
char *rpath = args[0];
mach_o_command *mc = slice->commands + slice->num_commands;
Expand Down Expand Up @@ -560,26 +592,28 @@ static int add_rpath(Slice slice, mach_o_command *command, char **args)
fseek(slice->mach_o_file, slice->offset + mc->position, SEEK_SET);
int count = fwrite((char *) mc->data, 1, command_size, slice->mach_o_file);
update_header(slice);
return 1;
return OP_BREAK;
}

static int remove_rpath(Slice slice, mach_o_command *command, char **args)
static op_result remove_rpath(Slice slice, mach_o_command *command, char **args)
{
char *rpath = args[0];
if (command->lc.cmd == LC_RPATH) {
struct rpath_command *rp = (struct rpath_command *) command->data;
char *command_path = (char *) rp + rp->path.offset;
if (!strcmp(rpath, command_path)) {
if (slice->verbose) {
printf("Removed RPATH load command for %s\n", rpath);
}
remove_command(slice, command - slice->commands);
}
if (command->lc.cmd != LC_RPATH) {
return OP_CONTINUE;
}
return 0;
struct rpath_command *rp = (struct rpath_command *) command->data;
char *command_path = (char *) rp + rp->path.offset;
if (strcmp(rpath, command_path)) {
return OP_CONTINUE;
}
remove_command(slice, command - slice->commands);
if (slice->verbose) {
printf("Removed RPATH load command for %s\n", rpath);
}
return OP_BREAK;
}

static int clear_rpaths(Slice slice, mach_o_command *command, char **args)
static op_result clear_rpaths(Slice slice, mach_o_command *command, char **args)
{
if (command->lc.cmd == LC_RPATH) {
if (slice->verbose) {
Expand All @@ -589,20 +623,28 @@ static int clear_rpaths(Slice slice, mach_o_command *command, char **args)
}
remove_command(slice, command - slice->commands);
}
return 0;
return OP_CONTINUE;
}

static void unsign(Slice slice) {
for (int i = 1; i < slice->num_commands; i++) {
if (slice->commands[i].lc.cmd == LC_CODE_SIGNATURE) {
remove_signature(slice, slice->commands + i, NULL);
}
}
}

static int remove_signature(Slice slice, mach_o_command *command, char **args)
static op_result remove_signature(Slice slice, mach_o_command *command, char **args)
{
if (command->lc.cmd == LC_CODE_SIGNATURE) {
struct lc_command *cmd = (struct lc_command *) command->data;
remove_command(slice, command - slice->commands);
if (slice->verbose) {
printf("Removed code signature.\n");
}
if (command->lc.cmd != LC_CODE_SIGNATURE) {
return OP_CONTINUE;
}
return 0;
struct lc_command *cmd = (struct lc_command *) command->data;
remove_command(slice, command - slice->commands);
if (slice->verbose) {
printf("Removed code signature.\n");
}
return OP_BREAK;
}

static void change_dylib_path(Slice slice, mach_o_command *command, char *path)
Expand Down Expand Up @@ -645,7 +687,7 @@ static void change_dylib_path(Slice slice, mach_o_command *command, char *path)
command->data = NULL;
}

static int edit_libpath(Slice slice, mach_o_command *command, char **args)
static op_result edit_libpath(Slice slice, mach_o_command *command, char **args)
{
char *newpath = args[0], *oldpath = args[1];
struct dylib_command *dc = (struct dylib_command *) command->data;
Expand All @@ -656,33 +698,33 @@ static int edit_libpath(Slice slice, mach_o_command *command, char **args)
printf("No LC_LOAD_DYLIB or LC_REEXPORT_DYLIB command matches %s.\n",
oldpath == NULL ? basename(newpath) : oldpath);
}
return 0;
return OP_CONTINUE;
}
if (oldpath == NULL) {
char libname[strlen(basename(newpath)) + 1];
char *current_libname = basename(current_libpath);
strcpy(libname, basename(newpath));
if (strcmp(libname, current_libname) == 0) {
change_dylib_path(slice, command, newpath);
return 1;
return OP_BREAK;
}
} else {
if (strcmp(oldpath, current_libpath) == 0) {
change_dylib_path(slice, command, newpath);
return 1;
return OP_BREAK;
}
}
return 0;
return OP_CONTINUE;
}

static int set_id(Slice slice, mach_o_command *command, char **args)
static op_result set_id(Slice slice, mach_o_command *command, char **args)
{
char *idpath = args[0];
if (command->lc.cmd != LC_ID_DYLIB) {
return 0;
return OP_CONTINUE;
}
change_dylib_path(slice, command, idpath);
return 1;
return OP_BREAK;
}

static MachO macho_init(char *mach_o_path, char *mode, bool verbose){
Expand Down Expand Up @@ -795,34 +837,10 @@ static void usage()
printf(" macher [-v|--verbose] edit_libpath <new path> <Mach-O file path>\n");
printf(" macher [-v|--verbose] edit_libpath <old path> <new path> <Mach-O file path>\n");
printf(" macher [-v|--verbose] set_id <library path> <Mach-O file path>\n");
printf(" macher [-v|--verbose] remove_signature <Mach-O file path>\n");
exit(1);
}

typedef int (*action_op)(Slice slice, mach_o_command *command, char **arg);

typedef enum {HELP=1, VERSION, SEGMENTS, INFO, APPEND, ADD_RPATH, REMOVE_RPATH,
CLEAR_RPATHS, EDIT_LIBPATH, SET_ID, UNSIGN} action_id;

typedef struct {
action_id id;
char *name;
action_op op;
} mach_o_action;

static mach_o_action actions[] = {
{.id = HELP, .name = "help", .op = NULL},
{.id = VERSION, .name = "version", .op = NULL},
{.id = INFO, .name = "info", .op = print_command},
{.id = SEGMENTS, .name = "segments", .op = print_segment},
{.id = APPEND, .name = "append", .op = NULL},
{.id = ADD_RPATH, .name = "add_rpath", .op = add_rpath},
{.id = REMOVE_RPATH, .name = "remove_rpath", .op = remove_rpath},
{.id = CLEAR_RPATHS, .name = "clear_rpaths", .op = clear_rpaths},
{.id = EDIT_LIBPATH, .name = "edit_libpath", .op = edit_libpath},
{.id = SET_ID, .name = "set_id", .op = set_id},
{.id = UNSIGN, .name = "remove_signature", .op = remove_signature},
};

int main(int argc, char **argv)
{
FILE *mach_file;
Expand Down Expand Up @@ -946,14 +964,18 @@ int main(int argc, char **argv)
if (action.op) {
for (int i = 0; i < slice->num_commands; i++) {
int count = slice->num_commands;
if (action.op(slice, slice->commands + i, action_args)) {
if (action.op(slice, slice->commands + i, action_args) == OP_BREAK) {
break;
}
/* If commands were removed, back up. */
while (count-- > slice->num_commands) {
i--;
}
}
}
if (action.unsign) {
unsign(slice);
}
}
macho_destroy(mach_o);
return 0;
Expand Down

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