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	tar: archive: improve fix for long names crashing - sbase - suckless unix tools
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	---
	commit 39a4c55378294437627421571a51b64bd5e09623
	parent 97629ab38692ee65250a882bb88eb31c71e51f00
	Author: Andrea Calligaris <[email protected]>
	Date: Wed, 26 Feb 2025 11:03:58 +0100

	tar: archive: improve fix for long names crashing

	As requested, I resend my old patch for fixing the crashing while
	archiving with names longer than 100 characters.

	Last patch dealing with the issue was [1], and the old patch was [2]. The
	code before this commit was not dealing correctly with multiple slashes,
	but use of basename(3) and dirname(3) needed a temporary buffer because
	otherwise we destroyed the path that was used later in several places.
	This solution does not modifies the path and use pointer arithmetic to
	solve the problem.

	[1] https://lists.suckless.org/hackers/2412/19213.html
	[2] https://lists.suckless.org/hackers/2402/19071.html

	Co-authored-by: Roberto E. Vargas Caballer <[email protected]>

	Diffstat:
	M tar.c \| 44 +++++++++++++++++------------…

	1 file changed, 24 insertions(+), 20 deletions(-)
	---
	diff --git a/tar.c b/tar.c
	@@ -180,11 +180,12 @@ static int
	archive(const char *path)
	{
	char b[BLKSIZ];
	+ const char base, p;
	struct group *gr;
	struct header *h;
	struct passwd *pw;
	struct stat st;
	- size_t chksum, i;
	+ size_t chksum, i, nlen, plen;
	ssize_t l, r;
	int fd = -1;

	@@ -202,27 +203,27 @@ archive(const char *path)
	h = (struct header *)b;
	memset(b, 0, sizeof(b));

	- if (strlen(path) > 255) {
	- const char *reason = "path exceeds 255 character limit";
	- eprintf("malformed tar archive: %s\n", reason);
	- } else if (strlen(path) >= 100) {
	- size_t prefix_len = 155;
	- const char *last_slash = strrchr(path, '/');
	-
	- if (last_slash && last_slash < path + prefix_len) {
	- prefix_len = last_slash - path + 1;
	- }
	-
	- /* strlcpy is fine here - for path ONLY -,
	- * since we're splitting the path.
	- * It's not an issue if the prefix can't hold
	- * the full path — name will take the rest. */
	- strlcpy(h->prefix, path, prefix_len);
	- estrlcpy(h->name, path + prefix_len, sizeof(h->name));
	- } else {
	- estrlcpy(h->name, path, sizeof(h->name));
	+ plen = 0;
	+ base = path;
	+ if ((nlen = strlen(base)) >= sizeof(h->name)) {
	+ /*
	+ * Cover case where path name is too long (in which case we
	+ * need to split it to prefix and name).
	+ */
	+ if ((base = strrchr(path, '/')) == NULL)
	+ goto too_long;
	+ for (p = base++; p > path && *p == '/'; --p)
	+ ;
	+
	+ nlen -= base - path;
	+ plen = p - path + 1;
	+ if (nlen >= sizeof(h->name) \|\| plen >= sizeof(h->prefix))
	+ goto too_long;
	}

	+ memcpy(h->name, base, nlen);
	+ memcpy(h->prefix, path, plen);
	+
	putoctal(h->mode, (unsigned)st.st_mode & 0777, sizeof(h->mode));
	putoctal(h->uid, (unsigned)st.st_uid, sizeof(h->uid));
	putoctal(h->gid, (unsigned)st.st_gid, sizeof(h->gid));
	@@ -270,6 +271,9 @@ archive(const char *path)
	}

	return 0;
	+
	+too_long:
	+ eprintf("filename too long: %s\n", path);
	}

	static int