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authorRob Landley <rob@landley.net>2018-05-27 16:26:28 -0500
committerRob Landley <rob@landley.net>2018-05-27 16:26:28 -0500
commit9448c33944651c1644ffbd0f52cf9d43cae19599 (patch)
treebb249c30cc89f4a4b898756d729ab522750128a4 /toys/posix
parent8a394040539e45934c20d59e118f620df3512d1c (diff)
downloadtoybox-9448c33944651c1644ffbd0f52cf9d43cae19599.tar.gz
Teach "file -" to recognize ELF files, add bounds checking and comments.
Diffstat (limited to 'toys/posix')
-rw-r--r--toys/posix/file.c61
1 files changed, 43 insertions, 18 deletions
diff --git a/toys/posix/file.c b/toys/posix/file.c
index 2eeb058b..49c7b22a 100644
--- a/toys/posix/file.c
+++ b/toys/posix/file.c
@@ -23,13 +23,16 @@ config FILE
GLOBALS(
int max_name_len;
+
+ off_t len;
)
// We don't trust elf.h to be there, and two codepaths for 32/64 is awkward
// anyway, so calculate struct offsets manually. (It's a fixed ABI.)
-static void do_elf_file(int fd, struct stat *sb)
+static void do_elf_file(int fd)
{
- int endian = toybuf[5], bits = toybuf[4], i, j;
+ int endian = toybuf[5], bits = toybuf[4], i, j, dynamic = 0, stripped = 1,
+ phentsize, phnum, shsize, shnum;
int64_t (*elf_int)(void *ptr, unsigned size);
// Values from include/linux/elf-em.h (plus arch/*/include/asm/elf.h)
// Names are linux/arch/ directory (sometimes before 32/64 bit merges)
@@ -46,11 +49,8 @@ static void do_elf_file(int fd, struct stat *sb)
{191, "tilegx"}, {3, "386"}, {6, "486"}, {62, "x86-64"}, {94, "xtensa"},
{0xabc7, "xtensa-old"}
};
- int dynamic = 0;
- int stripped = 1;
- char *map;
+ char *map = 0;
off_t phoff, shoff;
- int phentsize, phnum, shsize, shnum;
printf("ELF ");
elf_int = (endian==2) ? peek_be : peek_le;
@@ -94,6 +94,12 @@ static void do_elf_file(int fd, struct stat *sb)
return;
}
+ // Parsing ELF means following tables that may point to data earlier in
+ // the file, so sequential reading involves buffering unknown amounts of
+ // data. Just skip it if we can't mmap.
+ if (MAP_FAILED == (map = mmap(0, TT.len, PROT_READ, MAP_SHARED, fd, 0)))
+ goto bad;
+
// Stash what we need from the header; it's okay to reuse toybuf after this.
phentsize = elf_int(toybuf+42+12*bits, 2);
phnum = elf_int(toybuf+44+12*bits, 2);
@@ -105,14 +111,19 @@ static void do_elf_file(int fd, struct stat *sb)
// With binutils, phentsize seems to only be non-zero if phnum is non-zero.
// Such ELF files are rare, but do exist. (Android's crtbegin files, say.)
if (phnum && (phentsize != 32+24*bits)) {
- printf(", corrupt phentsize %d?\n", phentsize);
- return;
+ printf(", corrupt phentsize %d?", phentsize);
+ goto bad;
}
- map = xmmap(0, sb->st_size, PROT_READ, MAP_SHARED, fd, 0);
+ // Parsing ELF means following tables that may point to data earlier in
+ // the file, so sequential reading involves buffering unknown amounts of
+ // data. Just skip it if we can't mmap.
+ if (MAP_FAILED == (map = mmap(0, TT.len, PROT_READ, MAP_SHARED, fd, 0)))
+ goto bad;
// We need to read the phdrs for dynamic vs static.
// (Note: fields got reordered for 64 bit)
+ if (phoff+phnum*phentsize>TT.len) goto bad;
for (i = 0; i<phnum; i++) {
char *phdr = map+phoff+i*phentsize;
int p_type = elf_int(phdr, 4);
@@ -125,8 +136,10 @@ static void do_elf_file(int fd, struct stat *sb)
p_offset = elf_int(phdr+4*j, 4*j);
p_filesz = elf_int(phdr+16*j, 4*j);
- if (p_type==3 /*PT_INTERP*/)
+ if (p_type==3 /*PT_INTERP*/) {
+ if (p_offset+p_filesz>TT.len) goto bad;
printf(", dynamic (%.*s)", (int)p_filesz, map+p_offset);
+ }
}
if (!dynamic) printf(", static");
@@ -134,6 +147,7 @@ static void do_elf_file(int fd, struct stat *sb)
// Notes are in program headers *and* section headers, but some files don't
// contain program headers, so we prefer to check here.
// (Note: fields got reordered for 64 bit)
+ if (shoff+i*shnum>TT.len) goto bad;
for (i = 0; i<shnum; i++) {
char *shdr = map+shoff+i*shsize;
int sh_type = elf_int(shdr+4, 4);
@@ -146,6 +160,8 @@ static void do_elf_file(int fd, struct stat *sb)
} else if (sh_type == 7 /*SHT_NOTE*/) {
char *note = map+sh_offset;
+ if (sh_offset+sh_size>TT.len) goto bad;
+
// An ELF note is a sequence of entries, each consisting of an
// ndhr followed by n_namesz+n_descsz bytes of data (each of those
// rounded up to the next 4 bytes, without this being reflected in
@@ -158,11 +174,13 @@ static void do_elf_file(int fd, struct stat *sb)
if (n_namesz==4 && !memcmp(note+12, "GNU", 4)) {
if (n_type==3 /*NT_GNU_BUILD_ID*/) {
+ if (n_descsz+16>sh_size) goto bad;
printf(", BuildID=");
for (j = 0; j < n_descsz; ++j) printf("%02x", note[16 + j]);
}
} else if (n_namesz==8 && !memcmp(note+12, "Android", 8)) {
if (n_type==1 /*.android.note.ident*/) {
+ if (n_descsz+24+64>sh_size) goto bad;
printf(", for Android %d", (int)elf_int(note+20, 4));
if (n_descsz > 24)
printf(", built by NDK %.64s (%.64s)", note+24, note+24+64);
@@ -175,20 +193,24 @@ static void do_elf_file(int fd, struct stat *sb)
}
}
printf(", %sstripped", stripped ? "" : "not ");
+bad:
xputc('\n');
- munmap(map, sb->st_size);
+ if (map && map != MAP_FAILED) munmap(map, TT.len);
}
-static void do_regular_file(int fd, char *name, struct stat *sb)
+static void do_regular_file(int fd, char *name)
{
char *s;
- int len = read(fd, s = toybuf, sizeof(toybuf)-256);
- int magic;
+ int len, magic;
- if (len<0) perror_msg("%s", name);
+ // zero through elf shnum, just in case
+ memset(toybuf, 0, 80);
+ if ((len = readall(fd, s = toybuf, sizeof(toybuf)))<0) perror_msg("%s", name);
- if (len>40 && strstart(&s, "\177ELF")) do_elf_file(fd, sb);
+ if (!len) xputs("empty");
+ // 45 bytes: https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html
+ else if (len>=45 && strstart(&s, "\177ELF")) do_elf_file(fd);
else if (len>=8 && strstart(&s, "!<arch>\n")) xprintf("ar archive\n");
else if (len>28 && strstart(&s, "\x89PNG\x0d\x0a\x1a\x0a")) {
// PNG is big-endian: https://www.w3.org/TR/PNG/#7Integers-and-byte-order
@@ -360,11 +382,14 @@ void file_main(void)
xprintf("%s: %*s", name, (int)(TT.max_name_len - strlen(name)), "");
+ sb.st_size = 0;
if (fd || !((toys.optflags & FLAG_L) ? stat : lstat)(name, &sb)) {
if (fd || S_ISREG(sb.st_mode)) {
- if (!sb.st_size) what = "empty";
+ TT.len = sb.st_size;
+ // This test identifies an empty file we don't have permission to read
+ if (!fd && !sb.st_size) what = "empty";
else if ((fd = openro(name, O_RDONLY)) != -1) {
- do_regular_file(fd, name, &sb);
+ do_regular_file(fd, name);
if (fd) close(fd);
continue;
}