From 8c449c503f4c37f72089a0dc50e00631a22ed12a Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Sat, 29 Jun 2019 02:26:11 +0200
Subject: Add support for reading old style GNU sparse tar file format

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
 lib/tar/read_header.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)

(limited to 'lib')

diff --git a/lib/tar/read_header.c b/lib/tar/read_header.c
index 76634e1..44a38f9 100644
--- a/lib/tar/read_header.c
+++ b/lib/tar/read_header.c
@@ -390,6 +390,7 @@ static int decode_header(const tar_header_t *hdr, unsigned int set_by_pax,
 	switch (hdr->typeflag) {
 	case '\0':
 	case TAR_TYPE_FILE:
+	case TAR_TYPE_GNU_SPARSE:
 		out->sb.st_mode |= S_IFREG;
 		break;
 	case TAR_TYPE_LINK:
@@ -450,6 +451,104 @@ fail:
 	return NULL;
 }
 
+static void free_sparse_list(tar_sparse_data_t *sparse)
+{
+	tar_sparse_data_t *old;
+
+	while (sparse != NULL) {
+		old = sparse;
+		sparse = sparse->next;
+		free(old);
+	}
+}
+
+static tar_sparse_data_t *read_gnu_old_sparse(int fd, tar_header_t *hdr)
+{
+	tar_sparse_data_t *list = NULL, *end = NULL, *node;
+	gnu_sparse_t sph;
+	uint64_t off, sz;
+	ssize_t ret;
+	int i;
+
+	for (i = 0; i < 4; ++i) {
+		if (!isdigit(hdr->tail.gnu.sparse[i].offset[0]))
+			break;
+		if (!isdigit(hdr->tail.gnu.sparse[i].numbytes[0]))
+			break;
+
+		if (read_octal(hdr->tail.gnu.sparse[i].offset,
+			       sizeof(hdr->tail.gnu.sparse[i].offset), &off))
+			goto fail;
+		if (read_octal(hdr->tail.gnu.sparse[i].numbytes,
+			       sizeof(hdr->tail.gnu.sparse[i].numbytes), &sz))
+			goto fail;
+
+		node = calloc(1, sizeof(*node));
+		if (node == NULL)
+			goto fail_errno;
+
+		node->offset = off;
+		node->count = sz;
+
+		if (list == NULL) {
+			list = end = node;
+		} else {
+			end->next = node;
+			end = node;
+		}
+	}
+
+	if (hdr->tail.gnu.isextended == 0)
+		return list;
+
+	do {
+		ret = read_retry(fd, &sph, sizeof(sph));
+		if (ret < 0)
+			goto fail_errno;
+		if ((size_t)ret < sizeof(sph))
+			goto fail_eof;
+
+		for (i = 0; i < 21; ++i) {
+			if (!isdigit(sph.sparse[i].offset[0]))
+				break;
+			if (!isdigit(sph.sparse[i].numbytes[0]))
+				break;
+
+			if (read_octal(sph.sparse[i].offset,
+				       sizeof(sph.sparse[i].offset), &off))
+				goto fail;
+			if (read_octal(sph.sparse[i].numbytes,
+				       sizeof(sph.sparse[i].numbytes), &sz))
+				goto fail;
+
+			node = calloc(1, sizeof(*node));
+			if (node == NULL)
+				goto fail_errno;
+
+			node->offset = off;
+			node->count = sz;
+
+			if (list == NULL) {
+				list = end = node;
+			} else {
+				end->next = node;
+				end = node;
+			}
+		}
+	} while (sph.isextended != 0);
+
+	return list;
+fail_eof:
+	fputs("parsing GNU sparse header: unexpected end of file", stderr);
+	goto fail;
+fail_errno:
+	perror("parsing GNU sparse header");
+	goto fail;
+fail:
+	free_sparse_list(list);
+	return NULL;
+}
+
 int read_header(int fd, tar_header_decoded_t *out)
 {
 	unsigned int set_by_pax = 0;
@@ -513,6 +612,22 @@ int read_header(int fd, tar_header_decoded_t *out)
 			if (read_pax_header(fd, pax_size, &set_by_pax, out))
 				goto fail;
 			continue;
+		case TAR_TYPE_GNU_SPARSE:
+			if (!(set_by_pax & PAX_SIZE)) {
+				if (read_number(hdr.tail.gnu.realsize,
+						sizeof(hdr.tail.gnu.realsize),
+						&pax_size))
+					goto fail;
+
+				out->sb.st_size = pax_size;
+				set_by_pax |= PAX_SIZE;
+			}
+
+			free_sparse_list(out->sparse);
+			out->sparse = read_gnu_old_sparse(fd, &hdr);
+			if (out->sparse == NULL)
+				goto fail;
+			break;
 		}
 		break;
 	}
@@ -543,6 +658,7 @@ fail:
 
 void clear_header(tar_header_decoded_t *hdr)
 {
+	free_sparse_list(hdr->sparse);
 	free(hdr->name);
 	free(hdr->link_target);
 	memset(hdr, 0, sizeof(*hdr));
-- 
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