libtar: add support for xattr extensions

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

5 files changed, 133 insertions, 1 deletions

diff --git a/lib/tar/base64.c b/lib/tar/base64.c
new file mode 100644
index 0000000..313e9f4
--- /dev/null
+++ b/lib/tar/base64.c
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "internal.h"
+
+static uint8_t convert(char in)
+{
+	if (isupper(in))
+		return in - 'A';
+	if (islower(in))
+		return in - 'a' + 26;
+	if (isdigit(in))
+		return in - '0' + 52;
+	if (in == '+')
+		return 62;
+	if (in == '/' || in == '-')
+		return 63;
+	return 0;
+}
+
+void base64_decode(uint8_t *out, const char *in)
+{
+	char temp[4];
+
+	while (*in != '\0' && *in != '=') {
+		temp[0] = *in == '\0' ? 0 : convert(*(in++));
+		temp[1] = *in == '\0' ? 0 : convert(*(in++));
+		temp[2] = *in == '\0' ? 0 : convert(*(in++));
+		temp[3] = *in == '\0' ? 0 : convert(*(in++));
+
+		*(out++) = ((temp[0] << 2) & 0xFC) | ((temp[1] >> 4) & 0x03);
+		*(out++) = ((temp[1] << 4) & 0xF0) | ((temp[2] >> 2) & 0x0F);
+		*(out++) = ((temp[2] << 6) & 0xC0) | ( temp[3]       & 0x3F);
+	}
+}
diff --git a/lib/tar/cleanup.c b/lib/tar/cleanup.c
index c4d1734..a34c28b 100644
--- a/lib/tar/cleanup.c
+++ b/lib/tar/cleanup.c
@@ -12,8 +12,20 @@ void free_sparse_list(sparse_map_t *sparse)
 	}
 }
 
+void free_xattr_list(tar_xattr_t *list)
+{
+	tar_xattr_t *old;
+
+	while (list != NULL) {
+		old = list;
+		list = list->next;
+		free(old);
+	}
+}
+
 void clear_header(tar_header_decoded_t *hdr)
 {
+	free_xattr_list(hdr->xattr);
 	free_sparse_list(hdr->sparse);
 	free(hdr->name);
 	free(hdr->link_target);
diff --git a/lib/tar/internal.h b/lib/tar/internal.h
index 3c0e27f..04a97d3 100644
--- a/lib/tar/internal.h
+++ b/lib/tar/internal.h
@@ -50,4 +50,10 @@ sparse_map_t *read_gnu_old_sparse(int fd, tar_header_t *hdr);
 
 void free_sparse_list(sparse_map_t *sparse);
 
+void free_xattr_list(tar_xattr_t *list);
+
+void base64_decode(uint8_t *out, const char *in);
+
+void urldecode(char *str);
+
 #endif /* INTERNAL_H */
diff --git a/lib/tar/read_header.c b/lib/tar/read_header.c
index db40d7d..94c4a69 100644
--- a/lib/tar/read_header.c
+++ b/lib/tar/read_header.c
@@ -60,12 +60,29 @@ fail:
 	return NULL;
 }
 
+static tar_xattr_t *mkxattr(const char *key, size_t keylen,
+			    const char *value, size_t valuelen)
+{
+	tar_xattr_t *xattr;
+
+	xattr = calloc(1, sizeof(*xattr) + keylen + 1 + valuelen + 1);
+	if (xattr == NULL)
+		return NULL;
+
+	xattr->key = xattr->data;
+	xattr->value = xattr->data + keylen + 1;
+	memcpy(xattr->key, key, keylen);
+	memcpy(xattr->value, value, valuelen);
+	return xattr;
+}
+
 static int read_pax_header(int fd, uint64_t entsize, unsigned int *set_by_pax,
 			   tar_header_decoded_t *out)
 {
 	sparse_map_t *sparse_last = NULL, *sparse;
 	uint64_t field, offset = 0, num_bytes = 0;
-	char *buffer, *line;
+	char *buffer, *line, *key, *ptr, *value;
+	tar_xattr_t *xattr;
 	uint64_t i;
 
 	buffer = record_to_memory(fd, entsize);
@@ -183,6 +200,39 @@ static int read_pax_header(int fd, uint64_t entsize, unsigned int *set_by_pax,
 				sparse_last->next = sparse;
 				sparse_last = sparse;
 			}
+		} else if (!strncmp(line, "SCHILY.xattr.", 13)) {
+			key = line + 13;
+
+			ptr = strrchr(key, '=');
+			if (ptr == NULL || ptr == key)
+				continue;
+
+			value = ptr + 1;
+
+			xattr = mkxattr(key, ptr - key, value, strlen(value));
+			if (xattr == NULL)
+				goto fail_errno;
+
+			xattr->next = out->xattr;
+			out->xattr = xattr;
+		} else if (!strncmp(line, "LIBARCHIVE.xattr.", 17)) {
+			key = line + 17;
+
+			ptr = strrchr(key, '=');
+			if (ptr == NULL || ptr == key)
+				continue;
+
+			value = ptr + 1;
+
+			xattr = mkxattr(key, ptr - key, value, strlen(value));
+			if (xattr == NULL)
+				goto fail_errno;
+
+			urldecode(xattr->key);
+			base64_decode((uint8_t *)xattr->value, value);
+
+			xattr->next = out->xattr;
+			out->xattr = xattr;
 		}
 	}
 
diff --git a/lib/tar/urldecode.c b/lib/tar/urldecode.c
new file mode 100644
index 0000000..ac03f10
--- /dev/null
+++ b/lib/tar/urldecode.c
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "internal.h"
+
+static int xdigit(int x)
+{
+	if (isupper(x))
+		return x - 'A' + 0x0A;
+	if (islower(x))
+		return x - 'a' + 0x0A;
+	return x - '0';
+}
+
+void urldecode(char *str)
+{
+	unsigned char *out = (unsigned char *)str;
+	char *in = str;
+	int x;
+
+	while (*in != '\0') {
+		x = *(in++);
+
+		if (x == '%' && isxdigit(in[0]) && isxdigit(in[1])) {
+			x = xdigit(*(in++)) << 4;
+			x |= xdigit(*(in++));
+		}
+
+		*(out++) = x;
+	}
+
+	*out = '\0';
+}