libtar/block.c - android_bootable_recovery - Gitiles

 /*
 **  Copyright 1998-2003 University of Illinois Board of Trustees
 **  Copyright 1998-2003 Mark D. Roth
 **  All rights reserved.
 **
 **  block.c - libtar code to handle tar archive header blocks
 **
 **  Mark D. Roth <roth@uiuc.edu>
 **  Campus Information Technologies and Educational Services
 **  University of Illinois at Urbana-Champaign
 */

 #include <internal.h>
 #include <errno.h>

 #ifdef STDC_HEADERS
 # include <string.h>
 # include <stdlib.h>
 #endif

 #define BIT_ISSET(bitmask, bit) ((bitmask) & (bit))

 // Used to identify selinux_context in extended ('x')
 // metadata. From RedHat implementation.
 #define SELINUX_TAG "RHT.security.selinux="
 #define SELINUX_TAG_LEN strlen(SELINUX_TAG)

 // Used to identify e4crypt_policy in extended ('x')
 #define E4CRYPT_TAG "TWRP.security.e4crypt="
 #define E4CRYPT_TAG_LEN strlen(E4CRYPT_TAG)

 // Used to identify Posix capabilities in extended ('x')
 #define CAPABILITIES_TAG "SCHILY.xattr.security.capability="
 #define CAPABILITIES_TAG_LEN strlen(CAPABILITIES_TAG)

 // Used to identify Android user.default xattr in extended ('x')
 #define ANDROID_USER_DEFAULT_TAG "ANDROID.user.default"
 #define ANDROID_USER_DEFAULT_TAG_LEN strlen(ANDROID_USER_DEFAULT_TAG)

 // Used to identify Android user.inode_cache xattr in extended ('x')
 #define ANDROID_USER_CACHE_TAG "ANDROID.user.inode_cache"
 #define ANDROID_USER_CACHE_TAG_LEN strlen(ANDROID_USER_CACHE_TAG)

 // Used to identify Android user.inode_code_cache xattr in extended ('x')
 #define ANDROID_USER_CODE_CACHE_TAG "ANDROID.user.inode_code_cache"
 #define ANDROID_USER_CODE_CACHE_TAG_LEN strlen(ANDROID_USER_CODE_CACHE_TAG)

 /* read a header block */
 /* FIXME: the return value of this function should match the return value
 	  of tar_block_read(), which is a macro which references a prototype
 	  that returns a ssize_t.  So far, this is safe, since tar_block_read()
 	  only ever reads 512 (T_BLOCKSIZE) bytes at a time, so any difference
 	  in size of ssize_t and int is of negligible risk.  BUT, if
 	  T_BLOCKSIZE ever changes, or ever becomes a variable parameter
 	  controllable by the user, all the code that calls it,
 	  including this function and all code that calls it, should be
 	  fixed for security reasons.
 	  Thanks to Chris Palmer for the critique.
 */
 int
 th_read_internal(TAR *t)
 {
 	int i;
 	int num_zero_blocks = 0;

 #ifdef DEBUG
 	printf("==> th_read_internal(TAR=\"%s\")\n", t->pathname);
 #endif

 	while ((i = tar_block_read(t, &(t->th_buf))) == T_BLOCKSIZE)
 	{
 		/* two all-zero blocks mark EOF */
 		if (t->th_buf.name[0] == '\0')
 		{
 			num_zero_blocks++;
 			if (!BIT_ISSET(t->options, TAR_IGNORE_EOT)
 			    && num_zero_blocks >= 2)
 				return 0;	/* EOF */
 			else
 				continue;
 		}

 		/* verify magic and version */
 		if (BIT_ISSET(t->options, TAR_CHECK_MAGIC)
 		    && strncmp(t->th_buf.magic, TMAGIC, TMAGLEN - 1) != 0)
 		{
 #ifdef DEBUG
 			puts("!!! unknown magic value in tar header");
 #endif
 			return -2;
 		}

 		if (BIT_ISSET(t->options, TAR_CHECK_VERSION)
 		    && strncmp(t->th_buf.version, TVERSION, TVERSLEN) != 0)
 		{
 #ifdef DEBUG
 			puts("!!! unknown version value in tar header");
 #endif
 			return -2;
 		}

 		/* check chksum */
 		if (!BIT_ISSET(t->options, TAR_IGNORE_CRC)
 		    && !th_crc_ok(t))
 		{
 #ifdef DEBUG
 			puts("!!! tar header checksum error");
 #endif
 			return -2;
 		}

 		break;
 	}

 #ifdef DEBUG
 	printf("<== th_read_internal(): returning %d\n", i);
 #endif
 	return i;
 }


 /* wrapper function for th_read_internal() to handle GNU extensions */
 int
 th_read(TAR *t)
 {
 	int i;
 	size_t sz, j, blocks;
 	char *ptr;

 #ifdef DEBUG
 	printf("==> th_read(t=0x%lx)\n", t);
 #endif

 	if (t->th_buf.gnu_longname != NULL)
 		free(t->th_buf.gnu_longname);
 	if (t->th_buf.gnu_longlink != NULL)
 		free(t->th_buf.gnu_longlink);
 	if (t->th_buf.selinux_context != NULL)
 		free(t->th_buf.selinux_context);
 #ifdef HAVE_EXT4_CRYPT
 	if (t->th_buf.e4crypt_policy != NULL) {
 		free(t->th_buf.e4crypt_policy);
 	}
 #endif
 	if (t->th_buf.has_cap_data)
 	{
 		memset(&t->th_buf.cap_data, 0, sizeof(struct vfs_cap_data));
 		t->th_buf.has_cap_data = 0;
 	}
 	t->th_buf.has_user_default = 0;
 	t->th_buf.has_user_cache = 0;
 	t->th_buf.has_user_code_cache = 0;

 	memset(&(t->th_buf), 0, sizeof(struct tar_header));

 	i = th_read_internal(t);
 	if (i == 0)
 		return 1;
 	else if (i != T_BLOCKSIZE)
 	{
 		if (i != -1)
 			errno = EINVAL;
 		return -1;
 	}

 	/* check for GNU long link extention */
 	if (TH_ISLONGLINK(t))
 	{
 		sz = th_get_size(t);
 		blocks = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0);
 		if (blocks > ((size_t)-1 / T_BLOCKSIZE))
 		{
 			errno = E2BIG;
 			return -1;
 		}
 #ifdef DEBUG
 		printf("    th_read(): GNU long linkname detected "
 		       "(%ld bytes, %d blocks)\n", sz, blocks);
 #endif
 		t->th_buf.gnu_longlink = (char *)malloc(blocks * T_BLOCKSIZE);
 		if (t->th_buf.gnu_longlink == NULL)
 			return -1;

 		for (j = 0, ptr = t->th_buf.gnu_longlink; j < blocks;
 		     j++, ptr += T_BLOCKSIZE)
 		{
 #ifdef DEBUG
 			printf("    th_read(): reading long linkname "
 			       "(%d blocks left, ptr == %ld)\n", blocks-j, ptr);
 #endif
 			i = tar_block_read(t, ptr);
 			if (i != T_BLOCKSIZE)
 			{
 				if (i != -1)
 					errno = EINVAL;
 				return -1;
 			}
 #ifdef DEBUG
 			printf("    th_read(): read block == \"%s\"\n", ptr);
 #endif
 		}
 #ifdef DEBUG
 		printf("    th_read(): t->th_buf.gnu_longlink == \"%s\"\n",
 		       t->th_buf.gnu_longlink);
 #endif

 		i = th_read_internal(t);
 		if (i != T_BLOCKSIZE)
 		{
 			if (i != -1)
 				errno = EINVAL;
 			return -1;
 		}
 	}

 	/* check for GNU long name extention */
 	if (TH_ISLONGNAME(t))
 	{
 		sz = th_get_size(t);
 		blocks = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0);
 		if (blocks > ((size_t)-1 / T_BLOCKSIZE))
 		{
 			errno = E2BIG;
 			return -1;
 		}
 #ifdef DEBUG
 		printf("    th_read(): GNU long filename detected "
 		       "(%ld bytes, %d blocks)\n", sz, blocks);
 #endif
 		t->th_buf.gnu_longname = (char *)malloc(blocks * T_BLOCKSIZE);
 		if (t->th_buf.gnu_longname == NULL)
 			return -1;

 		for (j = 0, ptr = t->th_buf.gnu_longname; j < blocks;
 		     j++, ptr += T_BLOCKSIZE)
 		{
 #ifdef DEBUG
 			printf("    th_read(): reading long filename "
 			       "(%d blocks left, ptr == %ld)\n", blocks-j, ptr);
 #endif
 			i = tar_block_read(t, ptr);
 			if (i != T_BLOCKSIZE)
 			{
 				if (i != -1)
 					errno = EINVAL;
 				return -1;
 			}
 #ifdef DEBUG
 			printf("    th_read(): read block == \"%s\"\n", ptr);
 #endif
 		}
 #ifdef DEBUG
 		printf("    th_read(): t->th_buf.gnu_longname == \"%s\"\n",
 		       t->th_buf.gnu_longname);
 #endif

 		i = th_read_internal(t);
 		if (i != T_BLOCKSIZE)
 		{
 			if (i != -1)
 				errno = EINVAL;
 			return -1;
 		}
 	}

 	// Extended headers (selinux contexts, posix file capabilities, ext4 encryption policies)
 	while(TH_ISEXTHEADER(t) || TH_ISPOLHEADER(t))
 	{
 		sz = th_get_size(t);

 		if(sz >= T_BLOCKSIZE) // Not supported
 		{
 #ifdef DEBUG
 			printf("    th_read(): Extended header is too long!\n");
 #endif
 		}
 		else
 		{
 			char buf[T_BLOCKSIZE];
 			i = tar_block_read(t, buf);
 			if (i != T_BLOCKSIZE)
 			{
 				if (i != -1)
 					errno = EINVAL;
 				return -1;
 			}

 			// To be sure
 			buf[T_BLOCKSIZE-1] = 0;

 			int len = strlen(buf);
 			// posix capabilities
 			char *start = strstr(buf, CAPABILITIES_TAG);
 			if (start && start+CAPABILITIES_TAG_LEN < buf+len)
 			{
 				start += CAPABILITIES_TAG_LEN;
 				memcpy(&t->th_buf.cap_data, start, sizeof(struct vfs_cap_data));
 				t->th_buf.has_cap_data = 1;
 #ifdef DEBUG
 				printf("    th_read(): Posix capabilities detected\n");
 #endif
 			} // end posix capabilities
 			// selinux contexts
 			start = strstr(buf, SELINUX_TAG);
 			if (start && start+SELINUX_TAG_LEN < buf+len)
 			{
 				start += SELINUX_TAG_LEN;
 				char *end = strchr(start, '\n');
 				if(end)
 				{
 					t->th_buf.selinux_context = strndup(start, end-start);
 #ifdef DEBUG
 					printf("    th_read(): SELinux context xattr detected: %s\n", t->th_buf.selinux_context);
 #endif
 				}
 			} // end selinux contexts
 			// android user.default xattr
 			start = strstr(buf, ANDROID_USER_DEFAULT_TAG);
 			if (start)
 			{
 				t->th_buf.has_user_default = 1;
 #ifdef DEBUG
 				printf("    th_read(): android user.default xattr detected\n");
 #endif
 			} // end android user.default xattr
 			// android user.inode_cache xattr
 			start = strstr(buf, ANDROID_USER_CACHE_TAG);
 			if (start)
 			{
 				t->th_buf.has_user_cache = 1;
 #ifdef DEBUG
 				printf("    th_read(): android user.inode_cache xattr detected\n");
 #endif
 			} // end android user.inode_cache xattr
 			// android user.inode_code_cache xattr
 			start = strstr(buf, ANDROID_USER_CODE_CACHE_TAG);
 			if (start)
 			{
 				t->th_buf.has_user_code_cache = 1;
 #ifdef DEBUG
 				printf("    th_read(): android user.inode_code_cache xattr detected\n");
 #endif
 			} // end android user.inode_code_cache xattr
 #ifdef HAVE_EXT4_CRYPT
 			start = strstr(buf, E4CRYPT_TAG);
 			if (start && start+E4CRYPT_TAG_LEN < buf+len)
 			{
 				start += E4CRYPT_TAG_LEN;
 				char *end = strchr(start, '\n');
 				if(!end)
 					end = strchr(start, '\0');
 				if(end)
 				{
 					t->th_buf.e4crypt_policy = strndup(start, end-start);
 #ifdef DEBUG
 					printf("    th_read(): E4Crypt policy detected: %s\n", t->th_buf.e4crypt_policy);
 #endif
 				}
 			}
 #endif // HAVE_EXT4_CRYPT
 		}

 		i = th_read_internal(t);
 		if (i != T_BLOCKSIZE)
 		{
 			if (i != -1)
 				errno = EINVAL;
 			return -1;
 		}
 	}

 	return 0;
 }

 /* write an extended block */
 static int
 th_write_extended(TAR *t, char* buf, uint64_t sz)
 {
 	char type2;
 	uint64_t sz2;
 	int i;

 	/* save old size and type */
 	type2 = t->th_buf.typeflag;
 	sz2 = th_get_size(t);

 	/* write out initial header block with fake size and type */
 	t->th_buf.typeflag = TH_EXT_TYPE;

 	if(sz >= T_BLOCKSIZE) // impossible
 	{
 		errno = EINVAL;
 		return -1;
 	}

 	th_set_size(t, sz);
 	th_finish(t);
 	i = tar_block_write(t, &(t->th_buf));
 	if (i != T_BLOCKSIZE)
 	{
 		if (i != -1)
 			errno = EINVAL;
 		return -1;
 	}

 	i = tar_block_write(t, buf);
 	if (i != T_BLOCKSIZE)
 	{
 		if (i != -1)
 			errno = EINVAL;
 		return -1;
 	}

 	/* reset type and size to original values */
 	t->th_buf.typeflag = type2;
 	th_set_size(t, sz2);
 	memset(buf, 0, T_BLOCKSIZE);
 	return 0;
 }

 /* write a header block */
 int
 th_write(TAR *t)
 {
 	int i, j;
 	char type2;
 	uint64_t sz, sz2, total_sz = 0;
 	char *ptr;
 	char buf[T_BLOCKSIZE];

 #ifdef DEBUG
 	printf("==> th_write(TAR=\"%s\")\n", t->pathname);
 	th_print(t);
 #endif

 	if ((t->options & TAR_GNU) && t->th_buf.gnu_longlink != NULL)
 	{
 #ifdef DEBUG
 		printf("th_write(): using gnu_longlink (\"%s\")\n",
 		       t->th_buf.gnu_longlink);
 #endif
 		/* save old size and type */
 		type2 = t->th_buf.typeflag;
 		sz2 = th_get_size(t);

 		/* write out initial header block with fake size and type */
 		t->th_buf.typeflag = GNU_LONGLINK_TYPE;
 		sz = strlen(t->th_buf.gnu_longlink);
 		th_set_size(t, sz);
 		th_finish(t);
 		i = tar_block_write(t, &(t->th_buf));
 		if (i != T_BLOCKSIZE)
 		{
 			if (i != -1)
 				errno = EINVAL;
 			return -1;
 		}

 		/* write out extra blocks containing long name */
 		for (j = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0),
 		     ptr = t->th_buf.gnu_longlink; j > 1;
 		     j--, ptr += T_BLOCKSIZE)
 		{
 			i = tar_block_write(t, ptr);
 			if (i != T_BLOCKSIZE)
 			{
 				if (i != -1)
 					errno = EINVAL;
 				return -1;
 			}
 		}
 		memset(buf, 0, T_BLOCKSIZE);
 		strncpy(buf, ptr, T_BLOCKSIZE);
 		i = tar_block_write(t, &buf);
 		if (i != T_BLOCKSIZE)
 		{
 			if (i != -1)
 				errno = EINVAL;
 			return -1;
 		}

 		/* reset type and size to original values */
 		t->th_buf.typeflag = type2;
 		th_set_size(t, sz2);
 	}

 	if ((t->options & TAR_GNU) && t->th_buf.gnu_longname != NULL)
 	{
 #ifdef DEBUG
 		printf("th_write(): using gnu_longname (\"%s\")\n",
 		       t->th_buf.gnu_longname);
 #endif
 		/* save old size and type */
 		type2 = t->th_buf.typeflag;
 		sz2 = th_get_size(t);

 		/* write out initial header block with fake size and type */
 		t->th_buf.typeflag = GNU_LONGNAME_TYPE;
 		sz = strlen(t->th_buf.gnu_longname);
 		th_set_size(t, sz);
 		th_finish(t);
 		i = tar_block_write(t, &(t->th_buf));
 		if (i != T_BLOCKSIZE)
 		{
 			if (i != -1)
 				errno = EINVAL;
 			return -1;
 		}

 		/* write out extra blocks containing long name */
 		for (j = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0),
 		     ptr = t->th_buf.gnu_longname; j > 1;
 		     j--, ptr += T_BLOCKSIZE)
 		{
 			i = tar_block_write(t, ptr);
 			if (i != T_BLOCKSIZE)
 			{
 				if (i != -1)
 					errno = EINVAL;
 				return -1;
 			}
 		}
 		memset(buf, 0, T_BLOCKSIZE);
 		strncpy(buf, ptr, T_BLOCKSIZE);
 		i = tar_block_write(t, &buf);
 		if (i != T_BLOCKSIZE)
 		{
 			if (i != -1)
 				errno = EINVAL;
 			return -1;
 		}

 		/* reset type and size to original values */
 		t->th_buf.typeflag = type2;
 		th_set_size(t, sz2);
 	}

 	memset(buf, 0, T_BLOCKSIZE);
 	ptr = buf;

 	if((t->options & TAR_STORE_SELINUX) && t->th_buf.selinux_context != NULL)
 	{
 #ifdef DEBUG
 		printf("th_write(): using selinux_context (\"%s\")\n",
 		       t->th_buf.selinux_context);
 #endif
 		/* setup size - EXT header has format "*size of this whole tag as ascii numbers* *space* *content* *newline* */
 		//                                                       size   newline
 		sz = SELINUX_TAG_LEN + strlen(t->th_buf.selinux_context) + 3  +    1;

 		if(sz >= 100) // another ascci digit for size
 			++sz;

 		total_sz += sz;
 		snprintf(ptr, T_BLOCKSIZE, "%d "SELINUX_TAG"%s\n", (int)sz, t->th_buf.selinux_context);
 		ptr += sz;
 	}

 #ifdef HAVE_EXT4_CRYPT
 	if((t->options & TAR_STORE_EXT4_POL) && t->th_buf.e4crypt_policy != NULL)
 	{
 #ifdef DEBUG
 		printf("th_write(): using e4crypt_policy %s\n",
 		       t->th_buf.e4crypt_policy);
 #endif
 		/* setup size - EXT header has format "*size of this whole tag as ascii numbers* *space* *content* *newline* */
 		//                                                       size   newline
 		sz = E4CRYPT_TAG_LEN + strlen(t->th_buf.e4crypt_policy) + 3  +    1;

 		if(sz >= 100) // another ascci digit for size
 			++sz;

 		if (total_sz + sz >= T_BLOCKSIZE)
 		{
 			if (th_write_extended(t, &buf, total_sz))
 				return -1;
 			ptr = buf;
 			total_sz = sz;
 		}
 		else
 			total_sz += sz;

 		snprintf(ptr, T_BLOCKSIZE, "%d "E4CRYPT_TAG"%s", (int)sz, t->th_buf.e4crypt_policy);
 		char *nlptr = ptr + sz - 1;
 		*nlptr = '\n';
 		ptr += sz;
 	}
 #endif

 	if((t->options & TAR_STORE_POSIX_CAP) && t->th_buf.has_cap_data)
 	{
 #ifdef DEBUG
 		printf("th_write(): has a posix capability\n");
 #endif
 		sz = CAPABILITIES_TAG_LEN + sizeof(struct vfs_cap_data) + 3 + 1;

 		if(sz >= 100) // another ascci digit for size
 			++sz;

 		if (total_sz + sz >= T_BLOCKSIZE)
 		{
 			if (th_write_extended(t, &buf, total_sz))
 				return -1;
 			ptr = buf;
 			total_sz = sz;
 		}
 		else
 			total_sz += sz;

 		snprintf(ptr, T_BLOCKSIZE, "%d "CAPABILITIES_TAG, (int)sz);
 		memcpy(ptr + CAPABILITIES_TAG_LEN + 3, &t->th_buf.cap_data, sizeof(struct vfs_cap_data));
 		char *nlptr = ptr + sz - 1;
 		*nlptr = '\n';
 		ptr += sz;
 	}
 	if (t->options & TAR_STORE_ANDROID_USER_XATTR)
 	{
 		if (t->th_buf.has_user_default) {
 #ifdef DEBUG
 			printf("th_write(): has android user.default xattr\n");
 #endif
 			sz = ANDROID_USER_DEFAULT_TAG_LEN + 3 + 1;

 			if (total_sz + sz >= T_BLOCKSIZE)
 			{
 				if (th_write_extended(t, &buf, total_sz))
 					return -1;
 				ptr = buf;
 				total_sz = sz;
 			}
 			else
 				total_sz += sz;

 			snprintf(ptr, T_BLOCKSIZE, "%d "ANDROID_USER_DEFAULT_TAG, (int)sz);
 			char *nlptr = ptr + sz - 1;
 			*nlptr = '\n';
 			ptr += sz;
 		}
 		if (t->th_buf.has_user_cache) {
 #ifdef DEBUG
 			printf("th_write(): has android user.inode_cache xattr\n");
 #endif
 			sz = ANDROID_USER_CACHE_TAG_LEN + 3 + 1;

 			if (total_sz + sz >= T_BLOCKSIZE)
 			{
 				if (th_write_extended(t, &buf, total_sz))
 					return -1;
 				ptr = buf;
 				total_sz = sz;
 			}
 			else
 				total_sz += sz;

 			snprintf(ptr, T_BLOCKSIZE, "%d "ANDROID_USER_CACHE_TAG, (int)sz);
 			char *nlptr = ptr + sz - 1;
 			*nlptr = '\n';
 			ptr += sz;
 		}
 		if (t->th_buf.has_user_code_cache) {
 #ifdef DEBUG
 			printf("th_write(): has android user.inode_code_cache xattr\n");
 #endif
 			sz = ANDROID_USER_CODE_CACHE_TAG_LEN + 3 + 1;

 			if (total_sz + sz >= T_BLOCKSIZE)
 			{
 				if (th_write_extended(t, &buf, total_sz))
 					return -1;
 				ptr = buf;
 				total_sz = sz;
 			}
 			else
 				total_sz += sz;

 			snprintf(ptr, T_BLOCKSIZE, "%d "ANDROID_USER_CODE_CACHE_TAG, (int)sz);
 			char *nlptr = ptr + sz - 1;
 			*nlptr = '\n';
 			ptr += sz;
 		}
 	}
 	if (total_sz > 0 && th_write_extended(t, &buf, total_sz)) // write any outstanding tar extended header
 		return -1;

 	th_finish(t);

 #ifdef DEBUG
 	/* print tar header */
 	th_print(t);
 #endif

 	i = tar_block_write(t, &(t->th_buf));
 	if (i != T_BLOCKSIZE)
 	{
 		if (i != -1)
 			errno = EINVAL;
 		return -1;
 	}

 #ifdef DEBUG
 	puts("th_write(): returning 0");
 #endif
 	return 0;
 }
	/*
	** Copyright 1998-2003 University of Illinois Board of Trustees
	** Copyright 1998-2003 Mark D. Roth
	** All rights reserved.
	**
	** block.c - libtar code to handle tar archive header blocks
	**
	** Mark D. Roth <roth@uiuc.edu>
	** Campus Information Technologies and Educational Services
	** University of Illinois at Urbana-Champaign
	*/

	#include <internal.h>
	#include <errno.h>

	#ifdef STDC_HEADERS
	# include <string.h>
	# include <stdlib.h>
	#endif

	#define BIT_ISSET(bitmask, bit) ((bitmask) & (bit))

	// Used to identify selinux_context in extended ('x')
	// metadata. From RedHat implementation.
	#define SELINUX_TAG "RHT.security.selinux="
	#define SELINUX_TAG_LEN strlen(SELINUX_TAG)

	// Used to identify e4crypt_policy in extended ('x')
	#define E4CRYPT_TAG "TWRP.security.e4crypt="
	#define E4CRYPT_TAG_LEN strlen(E4CRYPT_TAG)

	// Used to identify Posix capabilities in extended ('x')
	#define CAPABILITIES_TAG "SCHILY.xattr.security.capability="
	#define CAPABILITIES_TAG_LEN strlen(CAPABILITIES_TAG)

	// Used to identify Android user.default xattr in extended ('x')
	#define ANDROID_USER_DEFAULT_TAG "ANDROID.user.default"
	#define ANDROID_USER_DEFAULT_TAG_LEN strlen(ANDROID_USER_DEFAULT_TAG)

	// Used to identify Android user.inode_cache xattr in extended ('x')
	#define ANDROID_USER_CACHE_TAG "ANDROID.user.inode_cache"
	#define ANDROID_USER_CACHE_TAG_LEN strlen(ANDROID_USER_CACHE_TAG)

	// Used to identify Android user.inode_code_cache xattr in extended ('x')
	#define ANDROID_USER_CODE_CACHE_TAG "ANDROID.user.inode_code_cache"
	#define ANDROID_USER_CODE_CACHE_TAG_LEN strlen(ANDROID_USER_CODE_CACHE_TAG)

	/* read a header block */
	/* FIXME: the return value of this function should match the return value
	of tar_block_read(), which is a macro which references a prototype
	that returns a ssize_t. So far, this is safe, since tar_block_read()
	only ever reads 512 (T_BLOCKSIZE) bytes at a time, so any difference
	in size of ssize_t and int is of negligible risk. BUT, if
	T_BLOCKSIZE ever changes, or ever becomes a variable parameter
	controllable by the user, all the code that calls it,
	including this function and all code that calls it, should be
	fixed for security reasons.
	Thanks to Chris Palmer for the critique.
	*/
	int
	th_read_internal(TAR *t)
	{
	int i;
	int num_zero_blocks = 0;

	#ifdef DEBUG
	printf("==> th_read_internal(TAR=\"%s\")\n", t->pathname);
	#endif

	while ((i = tar_block_read(t, &(t->th_buf))) == T_BLOCKSIZE)
	{
	/* two all-zero blocks mark EOF */
	if (t->th_buf.name[0] == '\0')
	{
	num_zero_blocks++;
	if (!BIT_ISSET(t->options, TAR_IGNORE_EOT)
	&& num_zero_blocks >= 2)
	return 0; /* EOF */
	else
	continue;
	}

	/* verify magic and version */
	if (BIT_ISSET(t->options, TAR_CHECK_MAGIC)
	&& strncmp(t->th_buf.magic, TMAGIC, TMAGLEN - 1) != 0)
	{
	#ifdef DEBUG
	puts("!!! unknown magic value in tar header");
	#endif
	return -2;
	}

	if (BIT_ISSET(t->options, TAR_CHECK_VERSION)
	&& strncmp(t->th_buf.version, TVERSION, TVERSLEN) != 0)
	{
	#ifdef DEBUG
	puts("!!! unknown version value in tar header");
	#endif
	return -2;
	}

	/* check chksum */
	if (!BIT_ISSET(t->options, TAR_IGNORE_CRC)
	&& !th_crc_ok(t))
	{
	#ifdef DEBUG
	puts("!!! tar header checksum error");
	#endif
	return -2;
	}

	break;
	}

	#ifdef DEBUG
	printf("<== th_read_internal(): returning %d\n", i);
	#endif
	return i;
	}


	/* wrapper function for th_read_internal() to handle GNU extensions */
	int
	th_read(TAR *t)
	{
	int i;
	size_t sz, j, blocks;
	char *ptr;

	#ifdef DEBUG
	printf("==> th_read(t=0x%lx)\n", t);
	#endif

	if (t->th_buf.gnu_longname != NULL)
	free(t->th_buf.gnu_longname);
	if (t->th_buf.gnu_longlink != NULL)
	free(t->th_buf.gnu_longlink);
	if (t->th_buf.selinux_context != NULL)
	free(t->th_buf.selinux_context);
	#ifdef HAVE_EXT4_CRYPT
	if (t->th_buf.e4crypt_policy != NULL) {
	free(t->th_buf.e4crypt_policy);
	}
	#endif
	if (t->th_buf.has_cap_data)
	{
	memset(&t->th_buf.cap_data, 0, sizeof(struct vfs_cap_data));
	t->th_buf.has_cap_data = 0;
	}
	t->th_buf.has_user_default = 0;
	t->th_buf.has_user_cache = 0;
	t->th_buf.has_user_code_cache = 0;

	memset(&(t->th_buf), 0, sizeof(struct tar_header));

	i = th_read_internal(t);
	if (i == 0)
	return 1;
	else if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	/* check for GNU long link extention */
	if (TH_ISLONGLINK(t))
	{
	sz = th_get_size(t);
	blocks = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0);
	if (blocks > ((size_t)-1 / T_BLOCKSIZE))
	{
	errno = E2BIG;
	return -1;
	}
	#ifdef DEBUG
	printf(" th_read(): GNU long linkname detected "
	"(%ld bytes, %d blocks)\n", sz, blocks);
	#endif
	t->th_buf.gnu_longlink = (char )malloc(blocks T_BLOCKSIZE);
	if (t->th_buf.gnu_longlink == NULL)
	return -1;

	for (j = 0, ptr = t->th_buf.gnu_longlink; j < blocks;
	j++, ptr += T_BLOCKSIZE)
	{
	#ifdef DEBUG
	printf(" th_read(): reading long linkname "
	"(%d blocks left, ptr == %ld)\n", blocks-j, ptr);
	#endif
	i = tar_block_read(t, ptr);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}
	#ifdef DEBUG
	printf(" th_read(): read block == \"%s\"\n", ptr);
	#endif
	}
	#ifdef DEBUG
	printf(" th_read(): t->th_buf.gnu_longlink == \"%s\"\n",
	t->th_buf.gnu_longlink);
	#endif

	i = th_read_internal(t);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}
	}

	/* check for GNU long name extention */
	if (TH_ISLONGNAME(t))
	{
	sz = th_get_size(t);
	blocks = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0);
	if (blocks > ((size_t)-1 / T_BLOCKSIZE))
	{
	errno = E2BIG;
	return -1;
	}
	#ifdef DEBUG
	printf(" th_read(): GNU long filename detected "
	"(%ld bytes, %d blocks)\n", sz, blocks);
	#endif
	t->th_buf.gnu_longname = (char )malloc(blocks T_BLOCKSIZE);
	if (t->th_buf.gnu_longname == NULL)
	return -1;

	for (j = 0, ptr = t->th_buf.gnu_longname; j < blocks;
	j++, ptr += T_BLOCKSIZE)
	{
	#ifdef DEBUG
	printf(" th_read(): reading long filename "
	"(%d blocks left, ptr == %ld)\n", blocks-j, ptr);
	#endif
	i = tar_block_read(t, ptr);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}
	#ifdef DEBUG
	printf(" th_read(): read block == \"%s\"\n", ptr);
	#endif
	}
	#ifdef DEBUG
	printf(" th_read(): t->th_buf.gnu_longname == \"%s\"\n",
	t->th_buf.gnu_longname);
	#endif

	i = th_read_internal(t);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}
	}

	// Extended headers (selinux contexts, posix file capabilities, ext4 encryption policies)
	while(TH_ISEXTHEADER(t) \|\| TH_ISPOLHEADER(t))
	{
	sz = th_get_size(t);

	if(sz >= T_BLOCKSIZE) // Not supported
	{
	#ifdef DEBUG
	printf(" th_read(): Extended header is too long!\n");
	#endif
	}
	else
	{
	char buf[T_BLOCKSIZE];
	i = tar_block_read(t, buf);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	// To be sure
	buf[T_BLOCKSIZE-1] = 0;

	int len = strlen(buf);
	// posix capabilities
	char *start = strstr(buf, CAPABILITIES_TAG);
	if (start && start+CAPABILITIES_TAG_LEN < buf+len)
	{
	start += CAPABILITIES_TAG_LEN;
	memcpy(&t->th_buf.cap_data, start, sizeof(struct vfs_cap_data));
	t->th_buf.has_cap_data = 1;
	#ifdef DEBUG
	printf(" th_read(): Posix capabilities detected\n");
	#endif
	} // end posix capabilities
	// selinux contexts
	start = strstr(buf, SELINUX_TAG);
	if (start && start+SELINUX_TAG_LEN < buf+len)
	{
	start += SELINUX_TAG_LEN;
	char *end = strchr(start, '\n');
	if(end)
	{
	t->th_buf.selinux_context = strndup(start, end-start);
	#ifdef DEBUG
	printf(" th_read(): SELinux context xattr detected: %s\n", t->th_buf.selinux_context);
	#endif
	}
	} // end selinux contexts
	// android user.default xattr
	start = strstr(buf, ANDROID_USER_DEFAULT_TAG);
	if (start)
	{
	t->th_buf.has_user_default = 1;
	#ifdef DEBUG
	printf(" th_read(): android user.default xattr detected\n");
	#endif
	} // end android user.default xattr
	// android user.inode_cache xattr
	start = strstr(buf, ANDROID_USER_CACHE_TAG);
	if (start)
	{
	t->th_buf.has_user_cache = 1;
	#ifdef DEBUG
	printf(" th_read(): android user.inode_cache xattr detected\n");
	#endif
	} // end android user.inode_cache xattr
	// android user.inode_code_cache xattr
	start = strstr(buf, ANDROID_USER_CODE_CACHE_TAG);
	if (start)
	{
	t->th_buf.has_user_code_cache = 1;
	#ifdef DEBUG
	printf(" th_read(): android user.inode_code_cache xattr detected\n");
	#endif
	} // end android user.inode_code_cache xattr
	#ifdef HAVE_EXT4_CRYPT
	start = strstr(buf, E4CRYPT_TAG);
	if (start && start+E4CRYPT_TAG_LEN < buf+len)
	{
	start += E4CRYPT_TAG_LEN;
	char *end = strchr(start, '\n');
	if(!end)
	end = strchr(start, '\0');
	if(end)
	{
	t->th_buf.e4crypt_policy = strndup(start, end-start);
	#ifdef DEBUG
	printf(" th_read(): E4Crypt policy detected: %s\n", t->th_buf.e4crypt_policy);
	#endif
	}
	}
	#endif // HAVE_EXT4_CRYPT
	}

	i = th_read_internal(t);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}
	}

	return 0;
	}

	/* write an extended block */
	static int
	th_write_extended(TAR t, char buf, uint64_t sz)
	{
	char type2;
	uint64_t sz2;
	int i;

	/* save old size and type */
	type2 = t->th_buf.typeflag;
	sz2 = th_get_size(t);

	/* write out initial header block with fake size and type */
	t->th_buf.typeflag = TH_EXT_TYPE;

	if(sz >= T_BLOCKSIZE) // impossible
	{
	errno = EINVAL;
	return -1;
	}

	th_set_size(t, sz);
	th_finish(t);
	i = tar_block_write(t, &(t->th_buf));
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	i = tar_block_write(t, buf);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	/* reset type and size to original values */
	t->th_buf.typeflag = type2;
	th_set_size(t, sz2);
	memset(buf, 0, T_BLOCKSIZE);
	return 0;
	}

	/* write a header block */
	int
	th_write(TAR *t)
	{
	int i, j;
	char type2;
	uint64_t sz, sz2, total_sz = 0;
	char *ptr;
	char buf[T_BLOCKSIZE];

	#ifdef DEBUG
	printf("==> th_write(TAR=\"%s\")\n", t->pathname);
	th_print(t);
	#endif

	if ((t->options & TAR_GNU) && t->th_buf.gnu_longlink != NULL)
	{
	#ifdef DEBUG
	printf("th_write(): using gnu_longlink (\"%s\")\n",
	t->th_buf.gnu_longlink);
	#endif
	/* save old size and type */
	type2 = t->th_buf.typeflag;
	sz2 = th_get_size(t);

	/* write out initial header block with fake size and type */
	t->th_buf.typeflag = GNU_LONGLINK_TYPE;
	sz = strlen(t->th_buf.gnu_longlink);
	th_set_size(t, sz);
	th_finish(t);
	i = tar_block_write(t, &(t->th_buf));
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	/* write out extra blocks containing long name */
	for (j = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0),
	ptr = t->th_buf.gnu_longlink; j > 1;
	j--, ptr += T_BLOCKSIZE)
	{
	i = tar_block_write(t, ptr);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}
	}
	memset(buf, 0, T_BLOCKSIZE);
	strncpy(buf, ptr, T_BLOCKSIZE);
	i = tar_block_write(t, &buf);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	/* reset type and size to original values */
	t->th_buf.typeflag = type2;
	th_set_size(t, sz2);
	}

	if ((t->options & TAR_GNU) && t->th_buf.gnu_longname != NULL)
	{
	#ifdef DEBUG
	printf("th_write(): using gnu_longname (\"%s\")\n",
	t->th_buf.gnu_longname);
	#endif
	/* save old size and type */
	type2 = t->th_buf.typeflag;
	sz2 = th_get_size(t);

	/* write out initial header block with fake size and type */
	t->th_buf.typeflag = GNU_LONGNAME_TYPE;
	sz = strlen(t->th_buf.gnu_longname);
	th_set_size(t, sz);
	th_finish(t);
	i = tar_block_write(t, &(t->th_buf));
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	/* write out extra blocks containing long name */
	for (j = (sz / T_BLOCKSIZE) + (sz % T_BLOCKSIZE ? 1 : 0),
	ptr = t->th_buf.gnu_longname; j > 1;
	j--, ptr += T_BLOCKSIZE)
	{
	i = tar_block_write(t, ptr);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}
	}
	memset(buf, 0, T_BLOCKSIZE);
	strncpy(buf, ptr, T_BLOCKSIZE);
	i = tar_block_write(t, &buf);
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	/* reset type and size to original values */
	t->th_buf.typeflag = type2;
	th_set_size(t, sz2);
	}

	memset(buf, 0, T_BLOCKSIZE);
	ptr = buf;

	if((t->options & TAR_STORE_SELINUX) && t->th_buf.selinux_context != NULL)
	{
	#ifdef DEBUG
	printf("th_write(): using selinux_context (\"%s\")\n",
	t->th_buf.selinux_context);
	#endif
	/* setup size - EXT header has format "size of this whole tag as ascii numbers space content newline */
	// size newline
	sz = SELINUX_TAG_LEN + strlen(t->th_buf.selinux_context) + 3 + 1;

	if(sz >= 100) // another ascci digit for size
	++sz;

	total_sz += sz;
	snprintf(ptr, T_BLOCKSIZE, "%d "SELINUX_TAG"%s\n", (int)sz, t->th_buf.selinux_context);
	ptr += sz;
	}

	#ifdef HAVE_EXT4_CRYPT
	if((t->options & TAR_STORE_EXT4_POL) && t->th_buf.e4crypt_policy != NULL)
	{
	#ifdef DEBUG
	printf("th_write(): using e4crypt_policy %s\n",
	t->th_buf.e4crypt_policy);
	#endif
	/* setup size - EXT header has format "size of this whole tag as ascii numbers space content newline */
	// size newline
	sz = E4CRYPT_TAG_LEN + strlen(t->th_buf.e4crypt_policy) + 3 + 1;

	if(sz >= 100) // another ascci digit for size
	++sz;

	if (total_sz + sz >= T_BLOCKSIZE)
	{
	if (th_write_extended(t, &buf, total_sz))
	return -1;
	ptr = buf;
	total_sz = sz;
	}
	else
	total_sz += sz;

	snprintf(ptr, T_BLOCKSIZE, "%d "E4CRYPT_TAG"%s", (int)sz, t->th_buf.e4crypt_policy);
	char *nlptr = ptr + sz - 1;
	*nlptr = '\n';
	ptr += sz;
	}
	#endif

	if((t->options & TAR_STORE_POSIX_CAP) && t->th_buf.has_cap_data)
	{
	#ifdef DEBUG
	printf("th_write(): has a posix capability\n");
	#endif
	sz = CAPABILITIES_TAG_LEN + sizeof(struct vfs_cap_data) + 3 + 1;

	if(sz >= 100) // another ascci digit for size
	++sz;

	if (total_sz + sz >= T_BLOCKSIZE)
	{
	if (th_write_extended(t, &buf, total_sz))
	return -1;
	ptr = buf;
	total_sz = sz;
	}
	else
	total_sz += sz;

	snprintf(ptr, T_BLOCKSIZE, "%d "CAPABILITIES_TAG, (int)sz);
	memcpy(ptr + CAPABILITIES_TAG_LEN + 3, &t->th_buf.cap_data, sizeof(struct vfs_cap_data));
	char *nlptr = ptr + sz - 1;
	*nlptr = '\n';
	ptr += sz;
	}
	if (t->options & TAR_STORE_ANDROID_USER_XATTR)
	{
	if (t->th_buf.has_user_default) {
	#ifdef DEBUG
	printf("th_write(): has android user.default xattr\n");
	#endif
	sz = ANDROID_USER_DEFAULT_TAG_LEN + 3 + 1;

	if (total_sz + sz >= T_BLOCKSIZE)
	{
	if (th_write_extended(t, &buf, total_sz))
	return -1;
	ptr = buf;
	total_sz = sz;
	}
	else
	total_sz += sz;

	snprintf(ptr, T_BLOCKSIZE, "%d "ANDROID_USER_DEFAULT_TAG, (int)sz);
	char *nlptr = ptr + sz - 1;
	*nlptr = '\n';
	ptr += sz;
	}
	if (t->th_buf.has_user_cache) {
	#ifdef DEBUG
	printf("th_write(): has android user.inode_cache xattr\n");
	#endif
	sz = ANDROID_USER_CACHE_TAG_LEN + 3 + 1;

	if (total_sz + sz >= T_BLOCKSIZE)
	{
	if (th_write_extended(t, &buf, total_sz))
	return -1;
	ptr = buf;
	total_sz = sz;
	}
	else
	total_sz += sz;

	snprintf(ptr, T_BLOCKSIZE, "%d "ANDROID_USER_CACHE_TAG, (int)sz);
	char *nlptr = ptr + sz - 1;
	*nlptr = '\n';
	ptr += sz;
	}
	if (t->th_buf.has_user_code_cache) {
	#ifdef DEBUG
	printf("th_write(): has android user.inode_code_cache xattr\n");
	#endif
	sz = ANDROID_USER_CODE_CACHE_TAG_LEN + 3 + 1;

	if (total_sz + sz >= T_BLOCKSIZE)
	{
	if (th_write_extended(t, &buf, total_sz))
	return -1;
	ptr = buf;
	total_sz = sz;
	}
	else
	total_sz += sz;

	snprintf(ptr, T_BLOCKSIZE, "%d "ANDROID_USER_CODE_CACHE_TAG, (int)sz);
	char *nlptr = ptr + sz - 1;
	*nlptr = '\n';
	ptr += sz;
	}
	}
	if (total_sz > 0 && th_write_extended(t, &buf, total_sz)) // write any outstanding tar extended header
	return -1;

	th_finish(t);

	#ifdef DEBUG
	/* print tar header */
	th_print(t);
	#endif

	i = tar_block_write(t, &(t->th_buf));
	if (i != T_BLOCKSIZE)
	{
	if (i != -1)
	errno = EINVAL;
	return -1;
	}

	#ifdef DEBUG
	puts("th_write(): returning 0");
	#endif
	return 0;
	}