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      1 /* file.c - describe file type
      2  *
      3  * Copyright 2016 The Android Open Source Project
      4  *
      5  * See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/file.html
      6  *
      7  * TODO: ar
      8 
      9 USE_FILE(NEWTOY(file, "<1", TOYFLAG_USR|TOYFLAG_BIN))
     10 
     11 config FILE
     12   bool "file"
     13   default n
     14   help
     15     usage: file [file...]
     16 
     17     Examine the given files and describe their content types.
     18 */
     19 
     20 #define FOR_file
     21 #include "toys.h"
     22 
     23 GLOBALS(
     24   int max_name_len;
     25 )
     26 
     27 // We don't trust elf.h to be there, and two codepaths for 32/64 is awkward
     28 // anyway, so calculate struct offsets manually. (It's a fixed ABI.)
     29 static void do_elf_file(int fd)
     30 {
     31   int endian = toybuf[5], bits = toybuf[4], i, j;
     32   int64_t (*elf_int)(void *ptr, unsigned size) = peek_le;
     33   // Values from include/linux/elf-em.h (plus arch/*/include/asm/elf.h)
     34   // Names are linux/arch/ directory name
     35   struct {int val; char *name;} type[] = {{0x9026, "alpha"},
     36     {40, "arm"}, {183, "arm"}, {0x18ad, "avr32"}, {106, "blackfin"},
     37     {76, "cris"}, {0x5441, "frv"}, {46, "h8300"}, {50, "ia64"},//ia intel ftaghn
     38     {88, "m32r"}, {4, "m68k"}, {0xbaab, "microblaze"}, {8, "mips"},
     39     {10, "mips"}, {89, "mn10300"}, {15, "parisc"}, {22, "s390"},
     40     {135, "score"}, {42, "sh"}, {2, "sparc"}, {18, "sparc"}, {43, "sparc"},
     41     {187, "tile"}, {188, "tile"}, {191, "tile"}, {3, "x86"}, {6, "x86"},
     42     {62, "x86"}, {94, "xtensa"}, {0xabc7, "xtensa"}};
     43 
     44   xprintf("ELF ");
     45 
     46   // "64-bit"
     47   if (bits == 1) xprintf("32-bit ");
     48   else if (bits == 2) xprintf("64-bit ");
     49   else {
     50     xprintf("(bad class %d) ", bits);
     51     bits = 0;
     52   }
     53 
     54   // e_machine, ala "x86", from big table above
     55   j = elf_int(toybuf+18, 2);
     56   for (i = 0; i<ARRAY_LEN(type); i++) if (j==type[i].val) break;
     57   if (i<ARRAY_LEN(type)) xprintf("%s ", type[i].name);
     58   else xprintf("(unknown arch %d) ", j);
     59 
     60   // "LSB"
     61   if (endian == 1) xprintf("LSB ");
     62   else if (endian == 2) {
     63     xprintf("MSB ");
     64     elf_int = peek_be;
     65   } else {
     66     xprintf("(bad endian %d)\n", endian);
     67     endian = 0;
     68   }
     69 
     70   // ", executable"
     71   i = elf_int(toybuf+16, 2);
     72   if (i == 1) xprintf("relocatable");
     73   else if (i == 2) xprintf("executable");
     74   else if (i == 3) xprintf("shared object");
     75   else if (i == 4) xprintf("core dump");
     76   else xprintf("(bad type %d)", i);
     77 
     78   bits--;
     79   // If we know our bits and endianness and phentsize agrees show dynamic linker
     80   if ((bits&1)==bits && endian &&
     81       (i = elf_int(toybuf+42+12*bits, 2)) == 32+24*bits)
     82   {
     83     char *map, *phdr;
     84     int phsize = i, phnum = elf_int(toybuf+44+12*bits, 2),
     85         psz = sysconf(_SC_PAGE_SIZE), lib = 0;
     86     off_t phoff = elf_int(toybuf+28+4*bits, 4+4*bits),
     87           mapoff = phoff^(phoff&(psz-1));
     88 
     89     // map e_phentsize*e_phnum bytes at e_phoff
     90     map = mmap(0, phsize*phnum, PROT_READ, MAP_SHARED, fd, mapoff);
     91     if (map) {
     92       // Find PT_INTERP entry. (Not: fields got reordered for 64 bit)
     93       for (i = 0; i<phnum; i++) {
     94         long long dlpos, dllen;
     95 
     96         // skip non-PT_INTERP entries
     97         j = elf_int(phdr = map+(phoff-mapoff)+i*phsize, 4);
     98         if (j==2) lib++;
     99         if (j!=3) continue;
    100 
    101         // Read p_offset and p_filesz
    102         j = bits+1;
    103         dlpos = elf_int(phdr+4*j, 4*j);
    104         dllen = elf_int(phdr+16*j, 4*j);
    105         if (dllen<0 || dllen>sizeof(toybuf)-128
    106             || dlpos!=lseek(fd, dlpos, SEEK_SET)
    107             || dllen!=readall(fd, toybuf+128, dllen)) break;
    108         printf(", dynamic (%.*s)", (int)dllen, toybuf+128);
    109       }
    110       if (!lib) printf(", static");
    111       else printf(", needs %d lib%s", lib, lib>1 ? "s" : "");
    112       munmap(map, phsize*phnum);
    113     }
    114   }
    115 
    116   // TODO: we'd need to actually parse the ELF file to report the rest...
    117   // ", dynamically linked"
    118   // " (uses shared libs)"
    119   // ", for Linux 2.6.24"
    120   // ", BuildID[sha1]=SHA"
    121   // ", stripped"
    122   xputc('\n');
    123 }
    124 
    125 static void do_regular_file(int fd, char *name)
    126 {
    127   char *s;
    128   int len = read(fd, s = toybuf, sizeof(toybuf)-256);
    129 
    130   if (len<0) perror_msg("%s", name);
    131 
    132   if (len>40 && strstart(&s, "\177ELF")) do_elf_file(fd);
    133   else if (len>28 && strstart(&s, "\x89PNG\x0d\x0a\x1a\x0a")) {
    134     // PNG is big-endian: https://www.w3.org/TR/PNG/#7Integers-and-byte-order
    135     int chunk_length = peek_be(s, 4);
    136 
    137     xprintf("PNG image data");
    138 
    139     // The IHDR chunk comes first: https://www.w3.org/TR/PNG/#11IHDR
    140     s += 4;
    141     if (chunk_length == 13 && strstart(&s, "IHDR")) {
    142       // https://www.w3.org/TR/PNG/#6Colour-values
    143       char *c = 0, *colors[] = {"grayscale", 0, "color RGB", "indexed color",
    144                                 "grayscale with alpha", 0, "color RGBA"};
    145 
    146       if (s[9]<ARRAY_LEN(colors)) c = colors[s[9]];
    147       if (!c) c = "unknown";
    148 
    149       xprintf(", %d x %d, %d-bit/%s, %sinterlaced", (int)peek_be(s, 4),
    150         (int)peek_be(s+4, 4), s[8], c, s[12] ? "" : "non-");
    151     }
    152 
    153     xputc('\n');
    154 
    155   // https://www.w3.org/Graphics/GIF/spec-gif89a.txt
    156   } else if (len>16 && (strstart(&s, "GIF87a") || strstart(&s, "GIF89a")))
    157     xprintf("GIF image data, %d x %d\n",
    158       (int)peek_le(s, 2), (int)peek_le(s+8, 2));
    159 
    160   // TODO: parsing JPEG for width/height is harder than GIF or PNG.
    161   else if (len>32 && memcmp(toybuf, "\xff\xd8", 2) == 0)
    162     xprintf("JPEG image data\n");
    163 
    164   // https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html
    165   else if (len>8 && strstart(&s, "\xca\xfe\xba\xbe"))
    166     xprintf("Java class file, version %d.%d\n",
    167       (int)peek_be(s+6, 2), (int)peek_be(s, 2));
    168 
    169     // TODO: cpio archive.
    170     // TODO: tar archive.
    171     // TODO: zip/jar/apk archive.
    172   else {
    173     char *what = 0;
    174     int i, bytes;
    175 
    176     // If shell script, report which interpreter
    177     if (len>3 && strstart(&s, "#!")) {
    178       for (what = s; (s-toybuf)<len && !isspace(*s); s++);
    179       strcpy(s, " script");
    180 
    181     // Distinguish ASCII text, UTF-8 text, or data
    182     } else for (i = 0; i<len; ++i) {
    183       if (!(isprint(toybuf[i]) || isspace(toybuf[i]))) {
    184         wchar_t wc;
    185         if ((bytes = mbrtowc(&wc, s+i, len-i, 0))>0 && wcwidth(wc)>=0) {
    186           i += bytes-1;
    187           if (!what) what = "UTF-8 text";
    188         } else {
    189           what = "data";
    190           break;
    191         }
    192       }
    193     }
    194     xputs(what ? what : "ASCII text");
    195   }
    196 }
    197 
    198 static void do_file(int fd, char *name)
    199 {
    200   struct stat sb;
    201   char *what = "unknown";
    202 
    203   xprintf("%s: %*s", name, (int)(TT.max_name_len - strlen(name)), "");
    204 
    205   if (!fstat(fd, &sb)) what = "cannot open";
    206   if (S_ISREG(sb.st_mode)) {
    207     if (sb.st_size == 0) what = "empty";
    208     else {
    209       do_regular_file(fd, name);
    210       return;
    211     }
    212   } else if (S_ISBLK(sb.st_mode)) what = "block special";
    213   else if (S_ISCHR(sb.st_mode)) what = "character special";
    214   else if (S_ISDIR(sb.st_mode)) what = "directory";
    215   else if (S_ISFIFO(sb.st_mode)) what = "fifo";
    216   else if (S_ISSOCK(sb.st_mode)) what = "socket";
    217   else if (S_ISLNK(sb.st_mode)) what = "symbolic link";
    218   xputs(what);
    219 }
    220 
    221 void file_main(void)
    222 {
    223   char **name;
    224 
    225   for (name = toys.optargs; *name; ++name) {
    226     int name_len = strlen(*name);
    227 
    228     if (name_len > TT.max_name_len) TT.max_name_len = name_len;
    229   }
    230 
    231   loopfiles(toys.optargs, do_file);
    232 }
    233