tar: handle tarfiles with (broken) checksums a-la Sun.

2 files changed, 16 insertions, 6 deletions

diff --git a/archival/libunarchive/get_header_tar.c b/archival/libunarchive/get_header_tar.c
index 622f09fa5..a9659181e 100644
--- a/archival/libunarchive/get_header_tar.c
+++ b/archival/libunarchive/get_header_tar.c
@@ -69,7 +69,7 @@ char get_header_tar(archive_handle_t *archive_handle)
                 char padding[12];   /* 500-512 */
         } tar;
         char *cp;
-        int sum, i;
+        int i, sum_u, sum_s, sum;
         int parse_names;
 
         if (sizeof(tar) != 512)
@@ -110,16 +110,23 @@ char get_header_tar(archive_handle_t *archive_handle)
 #endif
                         bb_error_msg_and_die("invalid tar magic");
         }
-        /* Do checksum on headers */
-        sum = ' ' * sizeof(tar.chksum);
+
+        /* Do checksum on headers.
+         * POSIX says that checksum is done on unsigned bytes, but
+         * Sun and HP-UX fucked it up... more details in
+         * GNU tar source. */
+        sum_s = sum_u = ' ' * sizeof(tar.chksum);
         for (i = 0; i < 148 ; i++) {
-                sum += ((char*)&tar)[i];
+                sum_u += ((unsigned char*)&tar)[i];
+                sum_s += ((signed char*)&tar)[i];
         }
         for (i = 156; i < 512 ; i++) {
-                sum += ((char*)&tar)[i];
+                sum_u += ((unsigned char*)&tar)[i];
+                sum_s += ((signed char*)&tar)[i];
         }
         /* This field does not need special treatment (getOctal) */
-        if (sum != xstrtoul(tar.chksum, 8)) {
+        sum = xstrtoul(tar.chksum, 8);
+        if (sum_u != sum && sum_s != sum) {
                 bb_error_msg_and_die("invalid tar header checksum");
         }
 
diff --git a/archival/tar.c b/archival/tar.c
index 1cdae296d..992128ef4 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -173,6 +173,9 @@ static void putOctal(char *cp, int len, off_t value)
 
 static void chksum_and_xwrite(int fd, struct TarHeader* hp)
 {
+        /* POSIX says that checksum is done on unsigned bytes
+         * (Sun and HP-UX fucked it up... more details in
+         * GNU tar source) */
         const unsigned char *cp;
         int chksum, size;