Improve unzip's handling of stream ZIP files

Search harder for the ZIP magic numbers at the end of a file by checking
16 KiB from the end instead of just 1 KiB.  ZIP files with long comments
(such as certain cryptographically signed files) or those sitting in a
wrapper could have more than 1 KiB of data after the magic numbers, so
they couldn't be read.

Signed-off-by: Dan Fandrich <dan@coneharvesters.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/archival/unzip.c b/archival/unzip.c
index 1d3291a..84081c0 100644 (file)
--- a/archival/unzip.c
+++ b/archival/unzip.c
@@ -150,23 +150,26 @@ enum { zip_fd = 3 };
 
 
 #if ENABLE_DESKTOP
+
+#define PEEK_FROM_END 16384
+
 /* NB: does not preserve file position! */
 static uint32_t find_cdf_offset(void)
 {
-       unsigned char buf[1024];
        cde_header_t cde_header;
        unsigned char *p;
        off_t end;
+       unsigned char *buf = xzalloc(PEEK_FROM_END);
 
        end = xlseek(zip_fd, 0, SEEK_END);
-       end -= 1024;
+       end -= PEEK_FROM_END;
        if (end < 0)
                end = 0;
        xlseek(zip_fd, end, SEEK_SET);
-       full_read(zip_fd, buf, 1024);
+       full_read(zip_fd, buf, PEEK_FROM_END);
 
        p = buf;
-       while (p <= buf + 1024 - CDE_HEADER_LEN - 4) {
+       while (p <= buf + PEEK_FROM_END - CDE_HEADER_LEN - 4) {
                if (*p != 'P') {
                        p++;
                        continue;
@@ -180,8 +183,10 @@ static uint32_t find_cdf_offset(void)
                /* we found CDE! */
                memcpy(cde_header.raw, p + 1, CDE_HEADER_LEN);
                FIX_ENDIANNESS_CDE(cde_header);
+               free(buf);
                return cde_header.formatted.cdf_offset;
        }
+       //free(buf);
        bb_error_msg_and_die("can't find file table");
 };