library api: tpax_init_ustar_header(): initial implementation.

1 files changed, 216 insertions, 0 deletions

diff --git a/src/logic/tpax_init_ustar_header.c b/src/logic/tpax_init_ustar_header.c
new file mode 100644
index 0000000..a3ab120
--- /dev/null
+++ b/src/logic/tpax_init_ustar_header.c
@@ -0,0 +1,216 @@
+/******************************************************/
+/*  tpax: a topological pax implementation            */
+/*  Copyright (C) 2020  Z. Gilboa                     */
+/*  Released under GPLv2 and GPLv3; see COPYING.TPAX. */
+/******************************************************/
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <sys/stat.h>
+
+#include <tpax/tpax.h>
+#include <tpax/tpax_specs.h>
+#include "tpax_driver_impl.h"
+
+#ifndef ssizeof
+#define ssizeof(x) (ssize_t)(sizeof(x))
+#endif
+
+static void tpax_octal_write(char * ch, ssize_t len, uint64_t val)
+{
+	for (--len,--len; len>=0 ; len--) {
+		ch[len] = val % 8 + '0';
+		val /= 8;
+	}
+}
+
+int tpax_init_ustar_header(
+	const struct tpax_driver_ctx *  dctx,
+	const char *                    path,
+	const struct stat *             st,
+	const char *                    linkname,
+	struct tpax_ustar_header *      uhdr)
+{
+	size_t		len;
+	const char *	cap;
+	const char *	mark;
+	unsigned char *	uch;
+	unsigned char *	uchcap;
+	size_t		lnklen;
+	size_t		stsize;
+	int64_t		stmtim;
+	uint32_t	chksum;
+	char		typeflag;
+	struct group	grp;
+	struct group *	grpres;
+	struct passwd	pwd;
+	struct passwd *	pwdres;
+	char		pwdbuf[2048];
+
+	/* size & mtime validation */
+	stsize = S_ISREG(st->st_mode) ? st->st_size : 0;
+	stmtim = st->st_mtim.tv_sec;
+
+	if (stsize > 077777777777)
+		return -1;
+
+	if ((stmtim < 0) || (stmtim > 077777777777))
+		return -1;
+
+	/* linkname validation */
+	if (S_ISLNK(st->st_mode) && !linkname)
+		return -1;
+
+	lnklen = S_ISLNK(st->st_mode)
+		? strnlen(linkname,sizeof(uhdr->u_linkname) + 1)
+		: 0;
+
+	if (lnklen > sizeof(uhdr->u_linkname))
+		return -1;
+
+	/* typeflag validation */
+	if (S_ISREG(st->st_mode))
+		typeflag = TPAX_USTAR_TYPEFLAG_REGFILE;
+	else if (S_ISLNK(st->st_mode))
+		typeflag = TPAX_USTAR_TYPEFLAG_SYMLINK;
+	else if (S_ISCHR(st->st_mode))
+		typeflag = TPAX_USTAR_TYPEFLAG_CHARDEV;
+	else if (S_ISBLK(st->st_mode))
+		typeflag = TPAX_USTAR_TYPEFLAG_BLKDEV;
+	else if (S_ISFIFO(st->st_mode))
+		typeflag = TPAX_USTAR_TYPEFLAG_FIFODEV;
+	else
+		return -1;
+
+	/* cap (without the trailing slash) */
+	mark = &path[strlen(path)];
+	cap  = mark;
+
+	for (--cap; (*cap == '/') && (cap > path); cap--)
+		(void)0;
+
+	cap = ((cap == path) && (path[0] == '/'))
+		? mark : &cap[1];
+
+	/* path solely consists of slash symbols? */
+	if ((cap == mark) && (path[0] =='/')) {
+		if ((cap - path) > (ssizeof(uhdr->u_prefix) + 1 + ssizeof(uhdr->u_name)))
+			return -1;
+
+		else if ((cap - path) <= ssizeof(uhdr->u_name))
+			mark = 0;
+
+		else
+			mark -= sizeof(uhdr->u_name);
+
+	/* path entirely fits in u_name? */
+	} else if ((cap - path) <= ssizeof(uhdr->u_name)) {
+		mark = 0;
+
+	/* split between u_prefix and u_name as needed */
+	} else {
+		mark = cap;
+
+		do {
+			for (--mark; (mark > path) && (*mark != '/'); mark--)
+				(void)0;
+		} while ((mark - path) > ssizeof(uhdr->u_prefix));
+	}
+
+	/* one shot */
+	memset(uhdr,0,sizeof(*uhdr));
+
+	/* u_name, u_prefix */
+	if (mark) {
+		memcpy(uhdr->u_prefix,path,mark-path);
+		memcpy(uhdr->u_name,&mark[1],cap - mark);
+	} else {
+		memcpy(uhdr->u_name,path,cap - path);
+	}
+
+	/* u_mode */
+	tpax_octal_write(uhdr->u_mode,ssizeof(uhdr->u_mode),st->st_mode & TPAX_USTAR_MODE_MASK);
+
+	/* u_uid, u_gid, u_uname, u_gname */
+	if (dctx->cctx->drvflags & TPAX_DRIVER_WRITE_FORMAT_RUSTAR) {
+		tpax_octal_write(uhdr->u_uid,ssizeof(uhdr->u_uid),0);
+		tpax_octal_write(uhdr->u_gid,ssizeof(uhdr->u_gid),0);
+	} else {
+		if ((uint64_t)st->st_uid <= 07777777)
+			tpax_octal_write(uhdr->u_uid,ssizeof(uhdr->u_uid),st->st_uid);
+		else
+			tpax_octal_write(uhdr->u_uid,ssizeof(uhdr->u_uid),0);
+
+		if ((uint64_t)st->st_gid <= 07777777)
+			tpax_octal_write(uhdr->u_gid,ssizeof(uhdr->u_gid),st->st_gid);
+		else
+			tpax_octal_write(uhdr->u_gid,ssizeof(uhdr->u_gid),0);
+
+		pwdres = 0;
+		grpres = 0;
+
+		getpwuid_r(
+			st->st_uid,&pwd,
+			pwdbuf,sizeof(pwdbuf),
+			&pwdres);
+
+		if (pwdres && pwd.pw_name)
+			if ((len = strlen(pwd.pw_name)) < sizeof(uhdr->u_uname))
+				memcpy(uhdr->u_uname,pwd.pw_name,len);
+
+		getgrgid_r(
+			st->st_gid,&grp,
+			pwdbuf,sizeof(pwdbuf),
+			&grpres);
+
+		if (grpres && grp.gr_name)
+			if ((len = strlen(grp.gr_name)) < sizeof(uhdr->u_gname))
+				memcpy(uhdr->u_gname,grp.gr_name,len);
+	}
+
+	/* u_size, u_mtime */
+	tpax_octal_write(uhdr->u_size,ssizeof(uhdr->u_size),stsize);
+	tpax_octal_write(uhdr->u_mtime,ssizeof(uhdr->u_mtime),stmtim);
+
+	/* u_typeflag */
+	uhdr->u_typeflag[0] = typeflag;
+
+	/* u_linkname */
+	if (lnklen)
+		memcpy(uhdr->u_linkname,linkname,lnklen);
+
+	/* u_magic */
+	uhdr->u_magic[0] = 'u';
+	uhdr->u_magic[1] = 's';
+	uhdr->u_magic[2] = 't';
+	uhdr->u_magic[3] = 'a';
+	uhdr->u_magic[4] = 'r';
+
+	/* u_version */
+	uhdr->u_version[0] = '0';
+	uhdr->u_version[1] = '0';
+
+	/* u_devmajor, u_devminor */
+	tpax_octal_write(uhdr->u_devmajor,ssizeof(uhdr->u_devmajor),0);
+	tpax_octal_write(uhdr->u_devminor,ssizeof(uhdr->u_devminor),0);
+
+	/* u_chksum */
+	uch    = (unsigned char *)uhdr->u_name;
+	uchcap = (unsigned char *)uhdr->u_pad;
+
+	for (chksum=0; uch<uchcap; uch++)
+		chksum += *uch;
+
+	chksum += sizeof(uhdr->u_chksum) * ' ';
+
+	tpax_octal_write(uhdr->u_chksum,ssizeof(uhdr->u_chksum),chksum);
+
+	/* all done; caller may now change REGFILE to HARDLINK */
+	return 0;
+}