Blame src/logic/tpax_init_ustar_header.c

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/**************************************************************/
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/*  tpax: a topological pax implementation                    */
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/*  Copyright (C) 2020--2021  SysDeer Technologies, LLC       */
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/*  Released under GPLv2 and GPLv3; see COPYING.TPAX.         */
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/**************************************************************/
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <grp.h>
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#include <pwd.h>
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#include <sys/stat.h>
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#include <tpax/tpax.h>
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#include <tpax/tpax_specs.h>
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#include "tpax_driver_impl.h"
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#ifndef ssizeof
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#define ssizeof(x) (ssize_t)(sizeof(x))
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#endif
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static void tpax_octal_write(char * ch, ssize_t len, uint64_t val)
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{
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	for (--len,--len; len>=0 ; len--) {
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		ch[len] = val % 8 + '0';
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		val /= 8;
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	}
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}
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int tpax_init_ustar_header(
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	const struct tpax_driver_ctx *  dctx,
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	const char *                    path,
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	const struct stat *             st,
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	const char *                    linkname,
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	struct tpax_ustar_header *      uhdr)
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{
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	size_t		len;
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	const char *	cap;
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	const char *	mark;
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	unsigned char *	uch;
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	unsigned char *	uchcap;
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	size_t		lnklen;
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	size_t		stsize;
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	int64_t		stmtim;
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	uint32_t	chksum;
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	char		typeflag;
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	struct group	grp;
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	struct group *	grpres;
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	struct passwd	pwd;
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	struct passwd *	pwdres;
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	char		pwdbuf[2048];
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	/* size & mtime validation */
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	stsize = S_ISREG(st->st_mode) ? st->st_size : 0;
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	stmtim = st->st_mtim.tv_sec;
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	if (stsize > 077777777777)
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		return -1;
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	if ((stmtim < 0) || (stmtim > 077777777777))
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		return -1;
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	/* linkname validation */
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	if (S_ISLNK(st->st_mode) && !linkname)
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		return -1;
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	lnklen = S_ISLNK(st->st_mode)
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		? strnlen(linkname,sizeof(uhdr->u_linkname) + 1)
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		: 0;
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	if (lnklen > sizeof(uhdr->u_linkname))
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		return -1;
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	/* typeflag validation */
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	if (S_ISREG(st->st_mode))
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		typeflag = TPAX_USTAR_TYPEFLAG_REGFILE;
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	else if (S_ISLNK(st->st_mode))
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		typeflag = TPAX_USTAR_TYPEFLAG_SYMLINK;
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	else if (S_ISDIR(st->st_mode))
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		typeflag = TPAX_USTAR_TYPEFLAG_DIRFILE;
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	else if (S_ISCHR(st->st_mode))
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		typeflag = TPAX_USTAR_TYPEFLAG_CHARDEV;
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	else if (S_ISBLK(st->st_mode))
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		typeflag = TPAX_USTAR_TYPEFLAG_BLKDEV;
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	else if (S_ISFIFO(st->st_mode))
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		typeflag = TPAX_USTAR_TYPEFLAG_FIFODEV;
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	else
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		return -1;
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	/* cap (without the trailing slash) */
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	mark = &path[strlen(path)];
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	cap  = mark;
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	for (--cap; (*cap == '/') && (cap > path); cap--)
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		(void)0;
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	cap = ((cap == path) && (path[0] == '/'))
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		? mark : &cap[1];
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	/* path solely consists of slash symbols? */
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	if ((cap == mark) && (path[0] =='/')) {
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		if ((cap - path) > (ssizeof(uhdr->u_prefix) + 1 + ssizeof(uhdr->u_name)))
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			return -1;
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		else if ((cap - path) <= ssizeof(uhdr->u_name))
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			mark = 0;
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		else
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			mark -= sizeof(uhdr->u_name);
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	/* path entirely fits in u_name? */
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	} else if ((cap - path) <= ssizeof(uhdr->u_name)) {
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		mark = 0;
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	/* split between u_prefix and u_name as needed */
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	} else {
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		mark = cap;
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		do {
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			for (--mark; (mark > path) && (*mark != '/'); mark--)
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				(void)0;
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		} while ((mark - path) > ssizeof(uhdr->u_prefix));
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	}
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	/* one shot */
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	memset(uhdr,0,sizeof(*uhdr));
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	/* u_name, u_prefix */
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	if (mark) {
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		memcpy(uhdr->u_prefix,path,mark-path);
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		memcpy(uhdr->u_name,&mark[1],cap - mark);
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	} else {
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		memcpy(uhdr->u_name,path,cap - path);
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	}
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	/* u_mode */
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	tpax_octal_write(uhdr->u_mode,ssizeof(uhdr->u_mode),st->st_mode & TPAX_USTAR_MODE_MASK);
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	/* u_uid, u_gid, u_uname, u_gname */
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	if (dctx->cctx->drvflags & TPAX_DRIVER_WRITE_FORMAT_RUSTAR) {
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		tpax_octal_write(uhdr->u_uid,ssizeof(uhdr->u_uid),0);
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		tpax_octal_write(uhdr->u_gid,ssizeof(uhdr->u_gid),0);
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	} else {
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		if ((uint64_t)st->st_uid <= 07777777)
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			tpax_octal_write(uhdr->u_uid,ssizeof(uhdr->u_uid),st->st_uid);
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		else
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			tpax_octal_write(uhdr->u_uid,ssizeof(uhdr->u_uid),0);
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		if ((uint64_t)st->st_gid <= 07777777)
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			tpax_octal_write(uhdr->u_gid,ssizeof(uhdr->u_gid),st->st_gid);
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		else
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			tpax_octal_write(uhdr->u_gid,ssizeof(uhdr->u_gid),0);
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		pwdres = 0;
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		grpres = 0;
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		getpwuid_r(
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			st->st_uid,&pwd,
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			pwdbuf,sizeof(pwdbuf),
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			&pwdres);
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		if (pwdres && pwd.pw_name)
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			if ((len = strlen(pwd.pw_name)) < sizeof(uhdr->u_uname))
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				memcpy(uhdr->u_uname,pwd.pw_name,len);
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		getgrgid_r(
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			st->st_gid,&grp,
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			pwdbuf,sizeof(pwdbuf),
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			&grpres);
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		if (grpres && grp.gr_name)
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			if ((len = strlen(grp.gr_name)) < sizeof(uhdr->u_gname))
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				memcpy(uhdr->u_gname,grp.gr_name,len);
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	}
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	/* u_size, u_mtime */
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	tpax_octal_write(uhdr->u_size,ssizeof(uhdr->u_size),stsize);
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	tpax_octal_write(uhdr->u_mtime,ssizeof(uhdr->u_mtime),stmtim);
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	/* u_typeflag */
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	uhdr->u_typeflag[0] = typeflag;
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	/* u_linkname */
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	if (lnklen)
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		memcpy(uhdr->u_linkname,linkname,lnklen);
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	/* u_magic */
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	uhdr->u_magic[0] = 'u';
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	uhdr->u_magic[1] = 's';
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	uhdr->u_magic[2] = 't';
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	uhdr->u_magic[3] = 'a';
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	uhdr->u_magic[4] = 'r';
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	/* u_version */
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	uhdr->u_version[0] = '0';
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	uhdr->u_version[1] = '0';
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	/* u_devmajor, u_devminor */
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	tpax_octal_write(uhdr->u_devmajor,ssizeof(uhdr->u_devmajor),0);
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	tpax_octal_write(uhdr->u_devminor,ssizeof(uhdr->u_devminor),0);
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	/* u_chksum */
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	uch    = (unsigned char *)uhdr->u_name;
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	uchcap = (unsigned char *)uhdr->u_pad;
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	for (chksum=0; uch
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		chksum += *uch;
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	chksum += sizeof(uhdr->u_chksum) * ' ';
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	tpax_octal_write(uhdr->u_chksum,ssizeof(uhdr->u_chksum),chksum);
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	/* all done; caller may now change REGFILE to HARDLINK */
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	return 0;
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}