Posix tarballs use extended headers to represent paths and values that do
not fit in the original ustar header format. This patch implements parsing
and handling of a subset of these extended headers. The motivating
tarball was the gcc source code, which exceeds the original path limit.
---
tar.c | 171 +++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 153 insertions(+), 18 deletions(-)
diff --git a/tar.c b/tar.c
index b74c134..31592c0 100644
--- a/tar.c
+++ b/tar.c
@@ -33,6 +33,19 @@ enum Type {
RESERVED = '7'
};
+struct xheader {
+ int valid : 1;
+ int has_atime : 1;
+ int has_ctime : 1;
+ int has_mtime : 1;
+ struct timespec atime;
+ struct timespec ctime;
+ struct timespec mtime;
+ char *path;
+ char *linkpath;
+ char *buf; /* Backing buffer during read. */
+};
+
struct header {
char name[100];
char mode[8];
@@ -252,9 +265,9 @@ archive(const char *path)
}
static int
-unarchive(char *fname, ssize_t l, char b[BLKSIZ])
+unarchive(char *fname, ssize_t l, char b[BLKSIZ], struct xheader *xhdr)
{
- char lname[101], *tmp, *p;
+ char linkbuf[101], *linkpath, *tmp, *p;
long mode, major, minor, type, mtime, uid, gid;
struct header *h = (struct header *)b;
int fd = -1;
@@ -281,12 +294,17 @@ unarchive(char *fname, ssize_t l, char b[BLKSIZ])
break;
case HARDLINK:
case SYMLINK:
- snprintf(lname, sizeof(lname), "%.*s", (int)sizeof(h->linkname),
- h->linkname);
- if (((h->type == HARDLINK) ? link : symlink)(lname, fname) < 0)
+ if (xhdr && xhdr->linkpath) {
+ linkpath = xhdr->linkpath;
+ } else {
+ snprintf(linkbuf, sizeof(linkbuf), "%.*s",
(int)sizeof(h->linkname),
+ h->linkname);
+ linkpath = linkbuf;
+ }
+ if (((h->type == HARDLINK) ? link : symlink)(linkpath, fname) <
0)
eprintf("%s %s -> %s:",
(h->type == HARDLINK) ? "link" : "symlink",
- fname, lname);
+ fname, linkpath);
break;
case DIRECTORY:
if ((mode = strtol(h->mode, &p, 8)) < 0 || *p != '\0')
@@ -334,6 +352,13 @@ unarchive(char *fname, ssize_t l, char b[BLKSIZ])
times[0].tv_sec = times[1].tv_sec = mtime;
times[0].tv_nsec = times[1].tv_nsec = 0;
+ if (xhdr && xhdr->has_mtime) {
+ times[0] = times[1] = xhdr->mtime;
+ }
+ if (xhdr && xhdr->has_atime) {
+ times[0] = xhdr->atime;
+ }
+
if (!mflag && utimensat(AT_FDCWD, fname, times, AT_SYMLINK_NOFOLLOW) <
0)
weprintf("utimensat %s:", fname);
if (h->type == SYMLINK) {
@@ -359,8 +384,104 @@ skipblk(ssize_t l)
break;
}
+static void
+xhdrtime(struct timespec *t, char *s)
+{
+ size_t i;
+ char *pns, *pdot;
+
+ t->tv_sec = strtoul(s, NULL, 10);
+ t->tv_nsec = 0;
+ if ((pdot = strchr(s, '.'))) {
+ pns = pdot+1;
+ for (i = 0; i < 9 && pns[i]; i++) {
+ t->tv_nsec *= 10;
+ t->tv_nsec += pns[i] - '0';
+ }
+ for (; i < 9; i++) {
+ t->tv_nsec *= 10;
+ }
+ }
+
+}
+
+static void
+readxhdr(struct xheader *xhdr , ssize_t l)
+{
+ char b[BLKSIZ];
+ char *reason, *buf;
+ char *p, *pend, *lenstr, *k, *v, *vend;
+
+ buf = xhdr->buf;
+ memset(xhdr, 0, sizeof(struct xheader));
+ xhdr->valid = 1;
+ xhdr->buf = erealloc(buf, l);
+
+ if (!eread(tarfd, xhdr->buf, l)) {
+ reason = "truncated";
+ goto bad;
+ }
+ if (l % BLKSIZ)
+ eread(tarfd, b, BLKSIZ-(l % BLKSIZ));
+
+ p = xhdr->buf;
+ pend = p + l;
+
+ while (p < pend) {
+ lenstr = p;
+ while (p < pend && (*p >= '0' && *p <= '9')) {
+ p++;
+ }
+ if (p >= pend || *p != ' ') {
+ reason = "corrupt length";
+ goto bad;
+ }
+ *p++ = 0;
+ k = p;
+ while (p < pend && *p != '=') {
+ p++;
+ }
+ if (p >= pend) {
+ reason = "corrupt keyword";
+ goto bad;
+ }
+ *p++ = 0;
+ v = p;
+ vend = lenstr + strtoul(lenstr, NULL, 10) - 1;
+ if (vend >= pend || vend <= p || *vend != '\n') {
+ reason = "length mismatch";
+ goto bad;
+ }
+ *vend = 0;
+ p = vend + 1;
+ if (strcmp(k, "path") == 0) {
+ xhdr->path = v;
+ } else if (strcmp(k, "linkpath") == 0) {
+ xhdr->linkpath = v;
+ } else if (k[0] && strcmp(k+1, "time") == 0) {
+ if (k[0] == 'a') {
+ xhdr->has_atime = 1;
+ xhdrtime(&xhdr->atime, v);
+ } else if (k[0] == 'c') {
+ xhdr->has_ctime = 1;
+ xhdrtime(&xhdr->ctime, v);
+ } else if (k[0] == 'm') {
+ xhdr->has_mtime = 1;
+ xhdrtime(&xhdr->mtime, v);
+ } else {
+ weprintf("unknown time header '%s'\n", k);
+ }
+ } else {
+ weprintf("ignoring unsupported pax header keyword
'%s'\n", k);
+ }
+ }
+ return;
+bad:
+ eprintf("malformed pax header: %s\n", reason);
+}
+
static int
-print(char *fname, ssize_t l, char b[BLKSIZ])
+print(char *fname, ssize_t l, char b[BLKSIZ], struct xheader *xhdr)
{
puts(fname);
skipblk(l);
@@ -445,13 +566,15 @@ bad:
static void
xt(int argc, char *argv[], int mode)
{
- char b[BLKSIZ], fname[256 + 1], *p;
+ struct xheader xhdr = {0};
+ char *fname;
+ char b[BLKSIZ], namebuf[256 + 1], *p;
struct timespec times[2];
struct header *h = (struct header *)b;
struct dirtime *dirtime;
long size;
int i, n;
- int (*fn)(char *, ssize_t, char[BLKSIZ]) = (mode == 'x') ? unarchive :
print;
+ int (*fn)(char *, ssize_t, char[BLKSIZ], struct xheader *) = (mode ==
'x') ? unarchive : print;
while (eread(tarfd, b, BLKSIZ) > 0 && h->name[0]) {
chktar(h);
@@ -459,14 +582,28 @@ xt(int argc, char *argv[], int mode)
/* small dance around non-null terminated fields */
if (h->prefix[0])
- n = snprintf(fname, sizeof(fname), "%.*s/",
+ n = snprintf(namebuf, sizeof(namebuf), "%.*s/",
(int)sizeof(h->prefix), h->prefix);
- snprintf(fname + n, sizeof(fname) - n, "%.*s",
+ snprintf(namebuf + n, sizeof(namebuf) - n, "%.*s",
(int)sizeof(h->name), h->name);
if ((size = strtol(h->size, &p, 8)) < 0 || *p != '\0')
eprintf("strtol %s: invalid number\n", h->size);
+ /* ignore global pax header craziness */
+ if (h->type == 'g') {
+ weprintf("ignoring global pax header\n");
+ skipblk(size);
+ continue;
+ }
+
+ if (h->type == 'x') {
+ readxhdr(&xhdr, size);
+ continue;
+ }
+
+ fname = (xhdr.valid && xhdr.path) ? xhdr.path : namebuf;
+
if (argc) {
/* only extract the given files */
for (i = 0; i < argc; i++)
@@ -478,17 +615,15 @@ xt(int argc, char *argv[], int mode)
}
}
- /* ignore global pax header craziness */
- if (h->type == 'g' || h->type == 'x') {
- skipblk(size);
- continue;
- }
-
- fn(fname, size, b);
+ fn(fname, size, b, xhdr.valid ? &xhdr : NULL);
if (vflag && mode != 't')
puts(fname);
+
+ xhdr.valid = 0;
}
+ free(xhdr.buf);
+
if (mode == 'x' && !mflag) {
while ((dirtime = popdirtime())) {
times[0].tv_sec = times[1].tv_sec = dirtime->mtime;
--
2.33.1
