dexstrings - see older revisions for what it used to output before I made it less verbose

dexstrings.c

/*
 * gcc -Os -odexstrings dexstrings.c
 * ./dexstrings /path/to/dex.dex
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <ctype.h>

typedef uint8_t u8;
typedef uint32_t u32;

typedef struct dex_header {
    u8 magic[8];
    u32 checksum;
    u8 signature[20];
    u32 file_size;
    u32 header_size;
    u32 endian_tag;
    u32 link_size;
    u32 link_off;
    u32 map_off;
    u32 string_ids_size;
    u32 string_ids_off;
    u32 type_ids_size;
    u32 type_ids_off;
    u32 proto_ids_size;
    u32 proto_ids_off;
    u32 field_ids_size;
    u32 field_ids_off;
    u32 method_ids_size;
    u32 method_ids_off;
    u32 class_defs_size;
    u32 class_defs_off;
    u32 data_size;
    u32 data_off;
} __attribute__ ((packed)) dex_header_t;

u32 dex_unleb128(FILE *f) {
    u32 ret = 0;
    u8 byte;
    for (int i = 0; i < 5; i++) {
        fread(&byte, 1, 1, f);
        ret |= (byte & 0x7f) << (7 * i);
        if ((byte & 0x80) == 0) {
            break;
        }
    }
    return ret;
}

u32 dex_print_string(FILE *f, u32 *string_ids, u32 id) {
    u32 length;
    fseek(f, string_ids[id], SEEK_SET);
    length = dex_unleb128(f);
    for (u32 j = 0; j < length; j++) {
        u8 byte;
        fread(&byte, 1, sizeof(u8), f);
        if (isprint(byte)) {
            printf("%c", byte);
        } else {
            printf("[%02x]", byte);
        }
    }
    printf("\n");
    return length;
}

int main(int argc, char **argv) {
    dex_header_t header;
    u32 *string_ids;
    u32 string_ids_size;

    FILE *f = fopen(argv[argc - 1], "r");
    if (f == NULL) {
        fprintf(stderr, "error opening %s\n", argv[argc - 1]);
        return 1;
    }

    // read the header
    fread(&header, sizeof(header), 1, f);

    // create a string table
    string_ids_size = header.string_ids_size;
    string_ids = malloc(sizeof(u32) * string_ids_size);

    // seek to the string id offset
    fseek(f, header.string_ids_off, SEEK_SET);

    // read the string table
    fread(string_ids, sizeof(u32), string_ids_size, f);

    // print strings
    for (u32 i = 0; i < string_ids_size; i++) {
        dex_print_string(f, string_ids, i);
    }

    free(string_ids);
    return 0;
}