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Commit 7118774e authored by Ethan Yonker's avatar Ethan Yonker Committed by Dees Troy
Browse files

libtar: backup and restore posix capabilities 

This patch also allows libtar to combine data from multiple extended
tar headers into a single header.

Change-Id: I82d13e89a3622ea665b60062b1904ddbedfa41b3
parent a083dc68

libtar/append.c

+22 −0
Original line number Diff line number Diff line
@@ -22,6 +22,10 @@ 
#include <sys/types.h>

#include <stdbool.h>



#include <sys/capability.h>

#include <sys/xattr.h>

#include <linux/xattr.h>



#ifdef STDC_HEADERS

# include <stdlib.h>

# include <string.h>
@@ -154,6 +158,24 @@ tar_append_file(TAR *t, const char *realname, const char *savename) 
	}

#endif



	/* get posix file capabilities */

	if (TH_ISREG(t) && t->options & TAR_STORE_POSIX_CAP)

	{

		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;

		}



		if (getxattr(realname, XATTR_NAME_CAPS, &t->th_buf.cap_data, sizeof(struct vfs_cap_data)) >= 0)

		{

			t->th_buf.has_cap_data = 1;

#if 1 //def DEBUG

			print_caps(&t->th_buf.cap_data);

#endif

		}

	}



	/* check if it's a hardlink */

#ifdef DEBUG

	puts("tar_append_file(): checking inode cache for hardlink...");

libtar/block.c

+115 −109
Original line number Diff line number Diff line
@@ -29,6 +29,10 @@ 
#define E4CRYPT_TAG "TWRP.security.e4crypt="

#define E4CRYPT_TAG_LEN 22



// Used to identify Posix capabilities in extended ('x')

#define CAPABILITIES_TAG "SCHILY.xattr.security.capability="

#define CAPABILITIES_TAG_LEN 33



/* 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
@@ -128,6 +132,11 @@ th_read(TAR *t) 
		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;

	}



	memset(&(t->th_buf), 0, sizeof(struct tar_header));
@@ -241,8 +250,8 @@ th_read(TAR *t) 
		}

	}



#ifdef HAVE_SELINUX

	if(TH_ISEXTHEADER(t))

	// Extended headers (selinux contexts, posix file capabilities, ext4 encryption policies)

	while(TH_ISEXTHEADER(t) || TH_ISPOLHEADER(t))

	{

		sz = th_get_size(t);
@@ -267,7 +276,19 @@ th_read(TAR *t) 
			buf[T_BLOCKSIZE-1] = 0;



			int len = strlen(buf);

			char *start = strstr(buf, SELINUX_TAG);

			// 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

#ifdef HAVE_SELINUX // selinux contexts

			start = strstr(buf, SELINUX_TAG);

			if(start && start+SELINUX_TAG_LEN < buf+len)

			{

				start += SELINUX_TAG_LEN;
@@ -280,6 +301,22 @@ th_read(TAR *t) 
#endif

				}

			}

#endif // HAVE_SELINUX

#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)

				{

				    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);
@@ -290,23 +327,34 @@ th_read(TAR *t) 
			return -1;

		}

	}

#endif



#ifdef HAVE_EXT4_CRYPT

	if(TH_ISPOLHEADER(t))

	return 0;

}



/* write an extended block */

static int

th_write_extended(TAR *t, char* buf, uint64_t sz)

{

		sz = th_get_size(t);

	char type2;

	uint64_t sz2;

	int i;



		if(sz >= T_BLOCKSIZE) // Not supported

	/* 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

	{

#ifdef DEBUG

			printf("    th_read(): Policy header is too long!\n");

#endif

		errno = EINVAL;

		return -1;

	}

		else

		{

			char buf[T_BLOCKSIZE];

			i = tar_block_read(t, buf);



	th_set_size(t, sz);

	th_finish(t);

	i = tar_block_write(t, &(t->th_buf));

	if (i != T_BLOCKSIZE)

	{

		if (i != -1)
@@ -314,46 +362,28 @@ th_read(TAR *t) 
		return -1;

	}



			// To be sure

			buf[T_BLOCKSIZE-1] = 0;



			int len = strlen(buf);

			char *start = strstr(buf, E4CRYPT_TAG);

			if(start && start+E4CRYPT_TAG_LEN < buf+len)

			{

				start += E4CRYPT_TAG_LEN;

				char *end = strchr(start, '\n');

				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

				}

			}

		}



		i = th_read_internal(t);

	i = tar_block_write(t, buf);

	if (i != T_BLOCKSIZE)

	{

		if (i != -1)

			errno = EINVAL;

		return -1;

	}

	}

#endif



	/* 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;

	uint64_t sz, sz2, total_sz = 0;

	char *ptr;

	char buf[T_BLOCKSIZE];
@@ -464,6 +494,8 @@ th_write(TAR *t) 
		th_set_size(t, sz2);

	}



	memset(buf, 0, T_BLOCKSIZE);

	ptr = buf;

#ifdef HAVE_SELINUX

	if((t->options & TAR_STORE_SELINUX) && t->th_buf.selinux_context != NULL)

	{
@@ -471,13 +503,6 @@ th_write(TAR *t) 
		printf("th_write(): using selinux_context (\"%s\")\n",

		       t->th_buf.selinux_context);

#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 = TH_EXT_TYPE;



		/* 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;
@@ -485,35 +510,9 @@ th_write(TAR *t) 
		if(sz >= 100) // another ascci digit for size

			++sz;



		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;

		}



		memset(buf, 0, T_BLOCKSIZE);

		snprintf(buf, T_BLOCKSIZE, "%d "SELINUX_TAG"%s\n", (int)sz, t->th_buf.selinux_context);

		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);

		total_sz += sz;

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

		ptr += sz;

	}

#endif
@@ -524,13 +523,6 @@ th_write(TAR *t) 
		printf("th_write(): using e4crypt_policy %s\n",

		       t->th_buf.e4crypt_policy);

#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 = TH_POL_TYPE;



		/* setup size - EXT header has format "*size of this whole tag as ascii numbers* *space* *content* *newline* */

		//                                                       size   newline

		sz = E4CRYPT_TAG_LEN + EXT4_KEY_DESCRIPTOR_HEX + 3  +    1;
@@ -538,37 +530,51 @@ th_write(TAR *t) 
		if(sz >= 100) // another ascci digit for size

			++sz;



		if(sz >= T_BLOCKSIZE) // impossible

		if (total_sz + sz >= T_BLOCKSIZE)

		{

			errno = EINVAL;

			if (th_write_extended(t, &buf, total_sz))

				return -1;

			ptr = buf;

			total_sz = sz;

		}

		else

			total_sz += sz;



		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;

		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



		memset(buf, 0, T_BLOCKSIZE);

		snprintf(buf, T_BLOCKSIZE, "%d "E4CRYPT_TAG"%s\n", (int)sz, t->th_buf.e4crypt_policy);

		i = tar_block_write(t, &buf);

		if (i != T_BLOCKSIZE)

	if((t->options & TAR_STORE_POSIX_CAP) && t->th_buf.has_cap_data)

	{

			if (i != -1)

				errno = EINVAL;

#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;



		/* reset type and size to original values */

		t->th_buf.typeflag = type2;

		th_set_size(t, sz2);

		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;

	}

#endif

	if (total_sz > 0 && th_write_extended(t, &buf, total_sz)) // write any outstanding tar extended header

		return -1;



	th_finish(t);

libtar/extract.c

+14 −0
Original line number Diff line number Diff line
@@ -20,6 +20,10 @@ 
#include <errno.h>

#include <utime.h>



#include <sys/capability.h>

#include <sys/xattr.h>

#include <linux/xattr.h>



#ifdef STDC_HEADERS

# include <stdlib.h>

#endif
@@ -166,6 +170,16 @@ tar_extract_file(TAR *t, const char *realname, const char *prefix, const int *pr 
	}

#endif



	if((t->options & TAR_STORE_POSIX_CAP) && t->th_buf.has_cap_data)

	{

#if 1 //def DEBUG

		printf("tar_extract_file(): restoring posix capabilities to file %s\n", realname);

		print_caps(&t->th_buf.cap_data);

#endif

		if (setxattr(realname, XATTR_NAME_CAPS, &t->th_buf.cap_data, sizeof(struct vfs_cap_data), 0) < 0)

			fprintf(stderr, "tar_extract_file(): failed to restore posix capabilities to file %s !!!\n", realname);

	}



#ifdef LIBTAR_FILE_HASH

	pn = th_get_pathname(t);

	pathname_len = strlen(pn) + 1;

libtar/libtar.h

+9 −2
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 


#include <sys/types.h>

#include <sys/stat.h>

#include <linux/capability.h>

#include "tar.h"



#include "libtar_listhash.h"
@@ -43,7 +44,7 @@ extern "C" 


/* extended metadata for next file - used to store selinux_context */

#define TH_EXT_TYPE		'x'

#define TH_POL_TYPE		'p'

#define TH_POL_TYPE_DO_NOT_USE		'p'



/* our version of the tar header structure */

struct tar_header
@@ -73,6 +74,8 @@ struct tar_header 
#ifdef HAVE_EXT4_CRYPT

	char *e4crypt_policy;

#endif

	int has_cap_data;

	struct vfs_cap_data cap_data;

};
@@ -118,6 +121,7 @@ TAR; 
#define TAR_STORE_SELINUX	128	/* store selinux context */

#define TAR_USE_NUMERIC_ID	256	/* favor numeric owner over names */

#define TAR_STORE_EXT4_POL	512	/* store ext4 crypto policy */

#define TAR_STORE_POSIX_CAP	1024	/* store posix file capabilities */



/* this is obsolete - it's here for backwards-compatibility only */

#define TAR_IGNORE_MAGIC	0
@@ -214,7 +218,7 @@ int th_write(TAR *t); 
#define TH_ISLONGNAME(t)	((t)->th_buf.typeflag == GNU_LONGNAME_TYPE)

#define TH_ISLONGLINK(t)	((t)->th_buf.typeflag == GNU_LONGLINK_TYPE)

#define TH_ISEXTHEADER(t)	((t)->th_buf.typeflag == TH_EXT_TYPE)

#define TH_ISPOLHEADER(t)	((t)->th_buf.typeflag == TH_POL_TYPE)

#define TH_ISPOLHEADER(t)	((t)->th_buf.typeflag == TH_POL_TYPE_DO_NOT_USE)



/* decode tar header info */

#define th_get_crc(t) oct_to_int((t)->th_buf.chksum, sizeof((t)->th_buf.chksum))
@@ -323,6 +327,9 @@ void int_to_oct(int64_t num, char *oct, size_t octlen); 
/* integer to string-octal conversion, or binary as necessary */

void int_to_oct_ex(int64_t num, char *oct, size_t octlen);



/* prints posix file capabilities */

void print_caps(struct vfs_cap_data *cap_data);





/***** wrapper.c **********************************************************/

libtar/util.c

+9 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <stdio.h>

#include <sys/param.h>

#include <errno.h>

#include <linux/capability.h>



#ifdef STDC_HEADERS

# include <string.h>
@@ -210,3 +211,11 @@ int_to_oct_ex(int64_t num, char *oct, size_t octlen) 
	}

	int_to_oct(num, oct, octlen);

}



void print_caps(struct vfs_cap_data *cap_data) {

	printf("     magic_etc=%u \n", cap_data->magic_etc);

	printf("     data[0].permitted=%u \n", cap_data->data[0].permitted);

	printf("     data[0].inheritable=%u \n", cap_data->data[0].inheritable);

	printf("     data[1].permitted=%u \n", cap_data->data[1].permitted);

	printf("     data[1].inheritable=%u \n", cap_data->data[1].inheritable);

}