7zip: Introduce get_data_offset

Its functionality is split off from archive_read_format_7zip_bid
and returns offset to actual data, i.e. it handles self extracting
(SFX) files if offset 0 is not already a 7zip magic.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>

diff --git a/libarchive/archive_read_support_format_7zip.c b/libarchive/archive_read_support_format_7zip.c
index c98aa1256976a31fae8e3e3c2c5efdef65842ec8..8153d50506607d1073334be874a75cdc548ce660 100644 (file)
--- a/libarchive/archive_read_support_format_7zip.c
+++ b/libarchive/archive_read_support_format_7zip.c
@@ -450,6 +450,7 @@ static ssize_t      read_stream(struct archive_read *, const void **, size_t,
 static int     seek_pack(struct archive_read *);
 static int64_t skip_stream(struct archive_read *, size_t);
 static int     skip_sfx(struct archive_read *, const ssize_t);
+static int     get_data_offset(struct archive_read *, int64_t *);
 static ssize_t find_pe_overlay(struct archive_read *);
 static ssize_t find_elf_data_sec(struct archive_read *);
 static int     slurp_central_directory(struct archive_read *, struct _7zip *,
@@ -530,25 +531,22 @@ archive_read_format_7zip_has_encrypted_entries(struct archive_read *_a)
 }
 
 static int
-archive_read_format_7zip_bid(struct archive_read *a, int best_bid)
+get_data_offset(struct archive_read *a, int64_t *data_offset)
 {
        const unsigned char *p;
        ssize_t min_addr;
        ssize_t offset;
        ssize_t window;
 
-       /* If someone has already bid more than 32, then avoid
-          trashing the look-ahead buffers with a seek. */
-       if (best_bid > 32)
-               return (-1);
-
        if ((p = __archive_read_ahead(a, 6, NULL)) == NULL)
-               return (0);
+               return (ARCHIVE_FATAL);
 
        /* If first six bytes are the 7-Zip signature,
-        * return the bid right now. */
-       if (memcmp(p, _7ZIP_SIGNATURE, 6) == 0)
-               return (48);
+        * return the offset right now. */
+       if (memcmp(p, _7ZIP_SIGNATURE, 6) == 0) {
+               *data_offset = 0;
+               return (ARCHIVE_OK);
+       }
 
        /*
         * It may a 7-Zip SFX archive file. If first two bytes are
@@ -563,7 +561,7 @@ archive_read_format_7zip_bid(struct archive_read *a, int best_bid)
        else if (memcmp(p, "\x7F\x45LF", 4) == 0)
                min_addr = find_elf_data_sec(a);
        else
-               return (0);
+               return (ARCHIVE_FATAL);
 
        offset = min_addr;
        window = 4096;
@@ -575,19 +573,37 @@ archive_read_format_7zip_bid(struct archive_read *a, int best_bid)
                        /* Remaining bytes are less than window. */
                        window >>= 1;
                        if (window < 0x40)
-                               return (0);
+                               return (ARCHIVE_FATAL);
                        continue;
                }
                p = buff + offset;
                while (p + 32 < buff + bytes_avail) {
                        int step = check_7zip_header_in_sfx(p);
-                       if (step == 0)
-                               return (48);
+                       if (step == 0) {
+                               *data_offset = p - buff;
+                               return (ARCHIVE_OK);
+                       }
                        p += step;
                }
                offset = p - buff;
        }
-       return (0);
+       return (ARCHIVE_FATAL);
+}
+
+static int
+archive_read_format_7zip_bid(struct archive_read *a, int best_bid)
+{
+       int64_t data_offset;
+
+       /* If someone has already bid more than 32, then avoid
+          trashing the look-ahead buffers with a seek. */
+       if (best_bid > 32)
+               return (-1);
+
+       if (get_data_offset(a, &data_offset) < 0)
+               return (0);
+
+       return (48);
 }
 
 static int