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Added support for password-protected .zip files.
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To use: mount a .zip file as usual, open a file as usual, but append '$' plus
the password to the end of the path, like so:

    PHYSFS_File *f = PHYSFS_openRead("/path/to/my/file.txt$MyPassword");

Note that this is the "traditional" PKWARE crypto, like you might get from
PkZip 2.04g or Info-ZIP. They have more advanced cryptography in the modern
.zip spec, but that's not implemented here. If you've ever tried to unzip
an archive and were prompted for a password, you probably saw the traditional
crypto at work.

Note that this is NOT a secure thing: if you ship an app that contains a
password, someone with a debugger can retrieve it. Note also that this
password could be available to any code registered as a PHYSFS_Archiver, and
that due to how archives combine into a single file tree, the wrong archiver
can get the password, at a minimum causing it to fail because passwords don't
match.

In short: make sure you know what you're doing before you use this!
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@icculus
icculus committed Sep 12, 2016
1 parent ab7eb81 commit 66b7767
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Showing 3 changed files with 160 additions and 17 deletions.
173 changes: 157 additions & 16 deletions src/archiver_zip.c
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Expand Up @@ -63,11 +63,13 @@ typedef struct _ZIPentry
PHYSFS_uint64 offset; /* offset of data in archive */
PHYSFS_uint16 version; /* version made by */
PHYSFS_uint16 version_needed; /* version needed to extract */
PHYSFS_uint16 general_bits; /* general purpose bits */
PHYSFS_uint16 compression_method; /* compression method */
PHYSFS_uint32 crc; /* crc-32 */
PHYSFS_uint64 compressed_size; /* compressed size */
PHYSFS_uint64 uncompressed_size; /* uncompressed size */
PHYSFS_sint64 last_mod_time; /* last file mod time */
PHYSFS_uint32 dos_mod_time; /* original MS-DOS style mod time */
struct _ZIPentry *hashnext; /* next item in this hash bucket */
struct _ZIPentry *children; /* linked list of kids, if dir */
struct _ZIPentry *sibling; /* next item in same dir */
Expand All @@ -78,11 +80,12 @@ typedef struct _ZIPentry
*/
typedef struct
{
PHYSFS_Io *io; /* the i/o interface for this archive. */
ZIPentry root; /* root of directory tree. */
ZIPentry **hash; /* all entries hashed for fast lookup. */
size_t hashBuckets; /* number of buckets in hash. */
int zip64; /* non-zero if this is a Zip64 archive. */
PHYSFS_Io *io; /* the i/o interface for this archive. */
ZIPentry root; /* root of directory tree. */
ZIPentry **hash; /* all entries hashed for fast lookup. */
size_t hashBuckets; /* number of buckets in hash. */
int zip64; /* non-zero if this is a Zip64 archive. */
int has_crypto; /* non-zero if any entry uses encryption. */
} ZIPinfo;

/*
Expand All @@ -95,6 +98,8 @@ typedef struct
PHYSFS_uint32 compressed_position; /* offset in compressed data. */
PHYSFS_uint32 uncompressed_position; /* tell() position. */
PHYSFS_uint8 *buffer; /* decompression buffer. */
PHYSFS_uint32 crypto_keys[3]; /* for "traditional" crypto. */
PHYSFS_uint32 initial_crypto_keys[3]; /* for "traditional" crypto. */
z_stream stream; /* zlib stream state. */
} ZIPfileinfo;

Expand All @@ -115,6 +120,103 @@ typedef struct
#define UNIX_FILETYPE_MASK 0170000
#define UNIX_FILETYPE_SYMLINK 0120000

#define ZIP_GENERAL_BITS_TRADITIONAL_CRYPTO (1 << 0)
#define ZIP_GENERAL_BITS_IGNORE_LOCAL_HEADER (1 << 3)

/* support for "traditional" PKWARE encryption. */
static int zip_entry_is_tradional_crypto(const ZIPentry *entry)
{
return (entry->general_bits & ZIP_GENERAL_BITS_TRADITIONAL_CRYPTO) != 0;
} /* zip_entry_is_traditional_crypto */

static int zip_entry_ignore_local_header(const ZIPentry *entry)
{
return (entry->general_bits & ZIP_GENERAL_BITS_IGNORE_LOCAL_HEADER) != 0;
} /* zip_entry_is_traditional_crypto */

static PHYSFS_uint32 zip_crypto_crc32(const PHYSFS_uint32 crc, const PHYSFS_uint8 val)
{
int i;
PHYSFS_uint32 xorval = (crc ^ ((PHYSFS_uint32) val)) & 0xFF;
for (i = 0; i < 8; i++)
xorval = ((xorval & 1) ? (0xEDB88320 ^ (xorval >> 1)) : (xorval >> 1));
return xorval ^ (crc >> 8);
} /* zip_crc32 */

static void zip_update_crypto_keys(PHYSFS_uint32 *keys, const PHYSFS_uint8 val)
{
keys[0] = zip_crypto_crc32(keys[0], val);
keys[1] = keys[1] + (keys[0] & 0x000000FF);
keys[1] = (keys[1] * 134775813) + 1;
keys[2] = zip_crypto_crc32(keys[2], (PHYSFS_uint8) ((keys[1] >> 24) & 0xFF));
} /* zip_update_crypto_keys */

static PHYSFS_uint8 zip_decrypt_byte(const PHYSFS_uint32 *keys)
{
const PHYSFS_uint16 tmp = keys[2] | 2;
return (PHYSFS_uint8) ((tmp * (tmp ^ 1)) >> 8);
} /* zip_decrypt_byte */

static PHYSFS_sint64 zip_read_decrypt(ZIPfileinfo *finfo, void *buf, PHYSFS_uint64 len)
{
PHYSFS_Io *io = finfo->io;
const PHYSFS_sint64 br = io->read(io, buf, len);

/* Decompression the new data if necessary. */
if (zip_entry_is_tradional_crypto(finfo->entry) && (br > 0))
{
PHYSFS_uint32 *keys = finfo->crypto_keys;
PHYSFS_uint8 *ptr = (PHYSFS_uint8 *) buf;
PHYSFS_sint64 i;
for (i = 0; i < br; i++, ptr++)
{
const PHYSFS_uint8 ch = *ptr ^ zip_decrypt_byte(keys);
zip_update_crypto_keys(keys, ch);
*ptr = ch;
} /* for */
} /* if */

return br;
} /* zip_read_decrypt */

static int zip_prep_crypto_keys(ZIPfileinfo *finfo, const PHYSFS_uint8 *crypto_header, const PHYSFS_uint8 *password)
{
/* It doesn't appear to be documented in PKWare's APPNOTE.TXT, but you
need to use a different byte in the header to verify the password
if general purpose bit 3 is set. Discovered this from Info-Zip.
That's what the (verifier) value is doing, below. */

PHYSFS_uint32 *keys = finfo->crypto_keys;
const ZIPentry *entry = finfo->entry;
const int usedate = zip_entry_ignore_local_header(entry);
const PHYSFS_uint8 verifier = (PHYSFS_uint8) ((usedate ? (entry->dos_mod_time >> 8) : (entry->crc >> 24)) & 0xFF);
PHYSFS_uint8 finalbyte = 0;
int i = 0;

/* initialize vector with defaults, then password, then header. */
keys[0] = 305419896;
keys[1] = 591751049;
keys[2] = 878082192;

while (*password)
zip_update_crypto_keys(keys, *(password++));

for (i = 0; i < 12; i++)
{
const PHYSFS_uint8 c = crypto_header[i] ^ zip_decrypt_byte(keys);
zip_update_crypto_keys(keys, c);
finalbyte = c;
} /* for */

/* you have a 1/256 chance of passing this test incorrectly. :/ */
if (finalbyte != verifier)
BAIL_MACRO(PHYSFS_ERR_BAD_PASSWORD, 0);

/* save the initial vector for seeking purposes. Not secure!! */
memcpy(finfo->initial_crypto_keys, finfo->crypto_keys, 12);
return 1;
} /* zip_prep_crypto_keys */


/*
* Bridge physfs allocation functions to zlib's format...
Expand Down Expand Up @@ -213,7 +315,6 @@ static int readui16(PHYSFS_Io *io, PHYSFS_uint16 *val)
static PHYSFS_sint64 ZIP_read(PHYSFS_Io *_io, void *buf, PHYSFS_uint64 len)
{
ZIPfileinfo *finfo = (ZIPfileinfo *) _io->opaque;
PHYSFS_Io *io = finfo->io;
ZIPentry *entry = finfo->entry;
PHYSFS_sint64 retval = 0;
PHYSFS_sint64 maxread = (PHYSFS_sint64) len;
Expand All @@ -226,7 +327,7 @@ static PHYSFS_sint64 ZIP_read(PHYSFS_Io *_io, void *buf, PHYSFS_uint64 len)
BAIL_IF_MACRO(maxread == 0, ERRPASS, 0); /* quick rejection. */

if (entry->compression_method == COMPMETH_NONE)
retval = io->read(io, buf, maxread);
retval = zip_read_decrypt(finfo, buf, maxread);
else
{
finfo->stream.next_out = buf;
Expand All @@ -247,7 +348,7 @@ static PHYSFS_sint64 ZIP_read(PHYSFS_Io *_io, void *buf, PHYSFS_uint64 len)
if (br > ZIP_READBUFSIZE)
br = ZIP_READBUFSIZE;

br = io->read(io, finfo->buffer, (PHYSFS_uint64) br);
br = zip_read_decrypt(finfo, finfo->buffer, (PHYSFS_uint64) br);
if (br <= 0)
break;

Expand Down Expand Up @@ -289,12 +390,13 @@ static int ZIP_seek(PHYSFS_Io *_io, PHYSFS_uint64 offset)
ZIPfileinfo *finfo = (ZIPfileinfo *) _io->opaque;
ZIPentry *entry = finfo->entry;
PHYSFS_Io *io = finfo->io;
const int encrypted = zip_entry_is_tradional_crypto(entry);

BAIL_IF_MACRO(offset > entry->uncompressed_size, PHYSFS_ERR_PAST_EOF, 0);

if (entry->compression_method == COMPMETH_NONE)
if (!encrypted && (entry->compression_method == COMPMETH_NONE))
{
const PHYSFS_sint64 newpos = offset + entry->offset;
PHYSFS_sint64 newpos = offset + entry->offset;
BAIL_IF_MACRO(!io->seek(io, newpos), ERRPASS, 0);
finfo->uncompressed_position = (PHYSFS_uint32) offset;
} /* if */
Expand All @@ -315,12 +417,15 @@ static int ZIP_seek(PHYSFS_Io *_io, PHYSFS_uint64 offset)
if (zlib_err(inflateInit2(&str, -MAX_WBITS)) != Z_OK)
return 0;

if (!io->seek(io, entry->offset))
if (!io->seek(io, entry->offset + (encrypted ? 12 : 0)))
return 0;

inflateEnd(&finfo->stream);
memcpy(&finfo->stream, &str, sizeof (z_stream));
finfo->uncompressed_position = finfo->compressed_position = 0;

if (encrypted)
memcpy(finfo->crypto_keys, finfo->initial_crypto_keys, 12);
} /* if */

while (finfo->uncompressed_position != offset)
Expand Down Expand Up @@ -994,10 +1099,10 @@ static ZIPentry *zip_load_entry(PHYSFS_Io *io, const int zip64,
/* Get the pertinent parts of the record... */
if (!readui16(io, &entry.version)) return NULL;
if (!readui16(io, &entry.version_needed)) return NULL;
if (!readui16(io, &ui16)) return NULL; /* general bits */
if (!readui16(io, &entry.general_bits)) return NULL; /* general bits */
if (!readui16(io, &entry.compression_method)) return NULL;
if (!readui32(io, &ui32)) return NULL;
entry.last_mod_time = zip_dos_time_to_physfs_time(ui32);
if (!readui32(io, &entry.dos_mod_time)) return NULL;
entry.last_mod_time = zip_dos_time_to_physfs_time(entry.dos_mod_time);
if (!readui32(io, &entry.crc)) return NULL;
if (!readui32(io, &ui32)) return NULL;
entry.compressed_size = (PHYSFS_uint64) ui32;
Expand Down Expand Up @@ -1175,6 +1280,9 @@ static int zip_load_entries(ZIPinfo *info,
allocator.Free(entry);
return 0;
} /* if */

if (zip_entry_is_tradional_crypto(entry))
info->has_crypto = 1;
} /* for */

return 1;
Expand Down Expand Up @@ -1557,6 +1665,26 @@ static PHYSFS_Io *ZIP_openRead(void *opaque, const char *filename)
ZIPinfo *info = (ZIPinfo *) opaque;
ZIPentry *entry = zip_find_entry(info, filename);
ZIPfileinfo *finfo = NULL;
PHYSFS_Io *io = NULL;
PHYSFS_uint8 *password = NULL;
int i;

/* if not found, see if maybe "$PASSWORD" is appended. */
if ((!entry) && (info->has_crypto))
{
const char *ptr = strrchr(filename, '$');
if (ptr != NULL)
{
const PHYSFS_uint64 len = (PHYSFS_uint64) (ptr - filename);
char *str = (char *) __PHYSFS_smallAlloc(len + 1);
BAIL_IF_MACRO(!str, PHYSFS_ERR_OUT_OF_MEMORY, NULL);
memcpy(str, filename, len);
str[len] = '\0';
entry = zip_find_entry(info, str);
__PHYSFS_smallFree(str);
password = (PHYSFS_uint8 *) (ptr + 1);
} /* if */
} /* if */

BAIL_IF_MACRO(!entry, ERRPASS, NULL);

Expand All @@ -1567,8 +1695,9 @@ static PHYSFS_Io *ZIP_openRead(void *opaque, const char *filename)
GOTO_IF_MACRO(!finfo, PHYSFS_ERR_OUT_OF_MEMORY, ZIP_openRead_failed);
memset(finfo, '\0', sizeof (ZIPfileinfo));

finfo->io = zip_get_io(info->io, info, entry);
GOTO_IF_MACRO(!finfo->io, ERRPASS, ZIP_openRead_failed);
io = zip_get_io(info->io, info, entry);
GOTO_IF_MACRO(!io, ERRPASS, ZIP_openRead_failed);
finfo->io = io;
finfo->entry = ((entry->symlink != NULL) ? entry->symlink : entry);
initializeZStream(&finfo->stream);

Expand All @@ -1581,6 +1710,18 @@ static PHYSFS_Io *ZIP_openRead(void *opaque, const char *filename)
goto ZIP_openRead_failed;
} /* if */

if (!zip_entry_is_tradional_crypto(entry))
GOTO_IF_MACRO(password != NULL, PHYSFS_ERR_BAD_PASSWORD, ZIP_openRead_failed);
else
{
PHYSFS_uint8 crypto_header[12];
GOTO_IF_MACRO(password == NULL, PHYSFS_ERR_BAD_PASSWORD, ZIP_openRead_failed);
if (io->read(io, crypto_header, 12) != 12)
goto ZIP_openRead_failed;
else if (!zip_prep_crypto_keys(finfo, crypto_header, password))
goto ZIP_openRead_failed;
} /* if */

memcpy(retval, &ZIP_Io, sizeof (PHYSFS_Io));
retval->opaque = finfo;

Expand Down
1 change: 1 addition & 0 deletions src/physfs.c
View file
Expand Up @@ -701,6 +701,7 @@ PHYSFS_DECL const char *PHYSFS_getErrorByCode(PHYSFS_ErrorCode code)
case PHYSFS_ERR_DIR_NOT_EMPTY: return "directory isn't empty";
case PHYSFS_ERR_OS_ERROR: return "OS reported an error";
case PHYSFS_ERR_DUPLICATE: return "duplicate resource";
case PHYSFS_ERR_BAD_PASSWORD: return "bad password";
} /* switch */

return NULL; /* don't know this error code. */
Expand Down
3 changes: 2 additions & 1 deletion src/physfs.h
View file
Expand Up @@ -3153,7 +3153,8 @@ typedef enum PHYSFS_ErrorCode
PHYSFS_ERR_BUSY, /**< Tried to modify a file the OS needs. */
PHYSFS_ERR_DIR_NOT_EMPTY, /**< Tried to delete dir with files in it. */
PHYSFS_ERR_OS_ERROR, /**< Unspecified OS-level error. */
PHYSFS_ERR_DUPLICATE /**< Duplicate entry. */
PHYSFS_ERR_DUPLICATE, /**< Duplicate entry. */
PHYSFS_ERR_BAD_PASSWORD /**< Bad password. */
} PHYSFS_ErrorCode;


Expand Down

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