add extract_syms; rename decrypt_kern to unpack and improve it

Makefile

@@ -2,7 +2,7 @@ DATA = $(word 1,$(wildcard ./data ../data))
 override CFLAGS += -I$(DATA)
 include $(DATA)/Makefile.common
 
-BINS := $(OUTDIR)/check_sanity $(OUTDIR)/make_kernel_patchfile $(OUTDIR)/apply_patchfile $(OUTDIR)/dump $(OUTDIR)/nm $(OUTDIR)/decrypt_kern sandboxc-armv6.c sandboxc-armv7.c
+BINS := $(OUTDIR)/check_sanity $(OUTDIR)/make_kernel_patchfile $(OUTDIR)/apply_patchfile $(OUTDIR)/dump $(OUTDIR)/nm $(OUTDIR)/extract_syms $(OUTDIR)/unpack sandboxc-armv6.c sandboxc-armv7.c
 ifneq "$(GXX)" ""
 BINS += $(OUTDIR)/grapher
 endif
@@ -29,9 +29,11 @@ $(OUTDIR)/dump: $(OUTDIR)/dump.o $(DATA)/$(OUTDIR)/libdata.a
 	$(GCC) -o $@ $^
 $(OUTDIR)/nm: $(OUTDIR)/nm.o $(DATA)/$(OUTDIR)/libdata.a
 	$(GCC) -o $@ $^
+$(OUTDIR)/extract_syms: $(OUTDIR)/extract_syms.o $(DATA)/$(OUTDIR)/libdata.a
+	$(GCC) -o $@ $^
 $(OUTDIR)/grapher: $(OUTDIR)/grapher.o $(DATA)/$(OUTDIR)/libdata.a
 	$(GXX) -o $@ $^ -O3
-$(OUTDIR)/decrypt_kern: $(OUTDIR)/decrypt_kern.o $(DATA)/$(OUTDIR)/libdata.a
+$(OUTDIR)/unpack: $(OUTDIR)/unpack.o $(DATA)/$(OUTDIR)/libdata.a
 	$(GCC) -o $@ $^ -O3
 $(OUTDIR)/codesign_allocate: $(OUTDIR)/codesign_allocate.o
 	$(GCC) -o $@ $^ -O3

decrypt_kern.c

@@ -1,15 +0,0 @@
-#include <data/cc.h>
-int main(int argc, char **argv) {
-    if(argc != 5) {
-        fprintf(stderr, "Usage: decrypt_kern <img3> <key> <iv> <outfile>\n");
-        return 1;
-    }
-    uint32_t key_bits;
-    char *kern_fn;
-    prange_t data = parse_img3(load_file(kern_fn = argv[1], false, NULL), &key_bits);
-    prange_t key = parse_hex_string(argv[2]);
-    prange_t iv = parse_hex_string(argv[3]);
-    prange_t decompressed = decrypt_and_decompress(key_bits, key, iv, data);
-    store_file(decompressed, argv[4], 0644);
-    return 0;
-}

extract_syms.c

@@ -0,0 +1,70 @@
+/* how trivial...
+extract the symbols into a new mach-o
+that contains just the symbols */
+
+#include <data/mach-o/binary.h>
+#include <mach-o/loader.h>
+#include <mach-o/nlist.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <assert.h>
+
+struct header {
+    struct mach_header mh;
+    struct segment_command segment;
+    struct symtab_command symtab;
+    struct nlist nl[0];
+} __attribute__((packed));
+
+int main(int argc, char **argv) {
+    assert(argc == 3);
+
+    struct binary binary;
+    b_init(&binary);
+    b_load_macho(&binary, argv[1]);
+
+    int out = open(argv[2], O_WRONLY | O_TRUNC | O_CREAT, 0755);
+    assert(out != -1);
+
+    int size = sizeof(struct header) + binary.mach->ext_nsyms * sizeof(struct nlist);
+    struct header *hdr = calloc(1, size);
+    lseek(out, size + 1, SEEK_SET);
+
+    int off = 1;
+
+    for(uint32_t i = 0; i < binary.mach->ext_nsyms; i++) {
+        hdr->nl[i] = binary.mach->ext_symtab[i];
+        const char *name = binary.mach->strtab + hdr->nl[i].n_un.n_strx;
+        int diff = strlen(name) + 1;
+        hdr->nl[i].n_un.n_strx = off;
+        assert(write(out, name, diff) == diff);
+        off += diff;
+         
+    }
+    size_t end = lseek(out, 0, SEEK_CUR);
+
+    memcpy(&hdr->mh, binary.mach->hdr, sizeof(hdr->mh));
+    hdr->mh.ncmds = 2;
+    hdr->mh.sizeofcmds = sizeof(*hdr) - sizeof(hdr->mh);
+
+    hdr->segment.cmd = LC_SEGMENT;
+    hdr->segment.cmdsize = sizeof(hdr->segment);
+    strcpy(hdr->segment.segname, "__LINKEDIT");
+    hdr->segment.vmaddr = 0;
+    hdr->segment.vmsize = (end + 0xfff) & ~0xfff;
+    hdr->segment.fileoff = 0;
+    hdr->segment.filesize = end;
+    hdr->segment.maxprot = PROT_READ | PROT_EXEC;
+    hdr->segment.initprot = PROT_READ | PROT_EXEC;
+    hdr->segment.nsects = 0;
+    hdr->segment.flags = 0;
+
+    hdr->symtab.cmd = LC_SYMTAB;
+    hdr->symtab.cmdsize = sizeof(hdr->symtab);
+    hdr->symtab.symoff = sizeof(*hdr);
+    hdr->symtab.nsyms = binary.mach->ext_nsyms;
+    hdr->symtab.stroff = size;
+    hdr->symtab.strsize = end - size;
+
+    assert(pwrite(out, hdr, size, 0) == size);
+}

unpack.c

@@ -0,0 +1,12 @@
+#include <data/cc.h>
+int main(int argc, char **argv) {
+    if(argc < 3 || argc > 5) goto usage;
+
+    prange_t data = unpack(load_file(argv[1], false, NULL), argv[3], argv[4]);
+    store_file(data, argv[2], 0644);
+    return 0;
+
+    usage:
+    fprintf(stderr, "Usage: unpack <infile> <outfile> [<key> <iv> | <arch>]\n");
+    return 1;
+}