7zip: Extend support for filtered input

The 7-ZIP archives written by libarchive can be streamed. Support such
archives by using a fallback if seek is not supported: As long as the
target position is somewhere ahead in stream, consume bytes until the
position is reached.

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 5995618730cc18ee45fa3497a87d4b9f3f812887..112fd2ef2606244b5e3aeafb408d93f3e04ab81b 100644 (file)
--- a/libarchive/archive_read_support_format_7zip.c
+++ b/libarchive/archive_read_support_format_7zip.c
@@ -450,9 +450,9 @@ static ssize_t      read_stream(struct archive_read *, const void **, size_t,
                    size_t);
 static int     seek_pack(struct archive_read *);
 static int64_t skip_stream(struct archive_read *, size_t);
-static int     get_data_offset(struct archive_read *, int64_t *);
+static int     get_data_offset(struct archive_read *, int64_t *, int);
 static int     get_pe_sfx_offset(struct archive_read *, int64_t *);
-static int     get_elf_sfx_offset(struct archive_read *, int64_t *);
+static int     get_elf_sfx_offset(struct archive_read *, int64_t *, int);
 static int     slurp_central_directory(struct archive_read *, struct _7zip *,
                    struct _7z_header_info *);
 static int     setup_decode_folder(struct archive_read *, struct _7z_folder *,
@@ -465,6 +465,7 @@ static size_t       arm64_Convert(struct _7zip *, uint8_t *, size_t);
 static ssize_t         Bcj2_Decode(struct _7zip *, uint8_t *, size_t);
 static size_t  sparc_Convert(struct _7zip *, uint8_t *, size_t);
 static size_t  powerpc_Convert(struct _7zip *, uint8_t *, size_t);
+static int64_t seek_compat(struct archive_read *, int64_t, int, int);
 
 
 int
@@ -531,7 +532,7 @@ archive_read_format_7zip_has_encrypted_entries(struct archive_read *_a)
 }
 
 static int
-get_data_offset(struct archive_read *a, int64_t *data_offset)
+get_data_offset(struct archive_read *a, int64_t *data_offset, int compat)
 {
        const unsigned char *p;
        int64_t offset, sfx_offset;
@@ -561,7 +562,7 @@ get_data_offset(struct archive_read *a, int64_t *data_offset)
        if ((p[0] == 'M' && p[1] == 'Z'))
                r = get_pe_sfx_offset(a, &sfx_offset);
        else if (memcmp(p, "\x7F\x45LF", 4) == 0)
-               r = get_elf_sfx_offset(a, &sfx_offset);
+               r = get_elf_sfx_offset(a, &sfx_offset, compat);
        else
                r = ARCHIVE_FATAL;
        if (r < ARCHIVE_WARN || sfx_offset > SFX_MAX_SEEK)
@@ -607,7 +608,7 @@ archive_read_format_7zip_bid(struct archive_read *a, int best_bid)
        if (best_bid > 32)
                return (-1);
 
-       if (get_data_offset(a, &data_offset) < 0)
+       if (get_data_offset(a, &data_offset, 0) < 0)
                return (0);
 
        return (48);
@@ -730,7 +731,7 @@ get_pe_sfx_offset(struct archive_read *a, int64_t *sfx_offset)
 }
 
 static int
-get_elf_sfx_offset(struct archive_read *a, int64_t *sfx_offset)
+get_elf_sfx_offset(struct archive_read *a, int64_t *sfx_offset, int compat)
 {
        int64_t r;
        const char *h;
@@ -798,7 +799,7 @@ get_elf_sfx_offset(struct archive_read *a, int64_t *sfx_offset)
                /*
                 * Reading the section table to find strtab section
                 */
-               if (__archive_read_seek(a, e_shoff, SEEK_SET) < 0) {
+               if (seek_compat(a, e_shoff, SEEK_SET, compat) < 0) {
                        archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC, "Seek error");
                        return (ARCHIVE_FATAL);
                }
@@ -832,7 +833,7 @@ get_elf_sfx_offset(struct archive_read *a, int64_t *sfx_offset)
                /*
                 * Read the STRTAB section to find the .data offset
                 */
-               if (__archive_read_seek(a, strtab_offset, SEEK_SET) < 0) {
+               if (seek_compat(a, strtab_offset, SEEK_SET, compat) < 0) {
                        archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC, "Seek error");
                        return (ARCHIVE_FATAL);
                }
@@ -854,7 +855,7 @@ get_elf_sfx_offset(struct archive_read *a, int64_t *sfx_offset)
                /*
                 * Find the section with the .data name
                 */
-               if (__archive_read_seek(a, e_shoff, SEEK_SET) < 0) {
+               if (seek_compat(a, e_shoff, SEEK_SET, compat) < 0) {
                        archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC, "Seek error");
                        return (ARCHIVE_FATAL);
                }
@@ -887,7 +888,7 @@ get_elf_sfx_offset(struct archive_read *a, int64_t *sfx_offset)
                break;
        }
 
-       r = __archive_read_seek(a, 0, SEEK_SET);
+       r = seek_compat(a, 0, SEEK_SET, compat);
        if (r < 0)
                archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC, "Seek error");
        return (int)r;
@@ -3269,7 +3270,7 @@ slurp_central_directory(struct archive_read *a, struct _7zip *zip,
        int64_t data_offset;
        int check_header_crc, r;
 
-       if (get_data_offset(a, &data_offset) < 0)
+       if (get_data_offset(a, &data_offset, 1) < 0)
                return (ARCHIVE_FATAL);
        if (__archive_read_consume(a, data_offset) < 0) {
                archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC, "Seek error");
@@ -3313,8 +3314,8 @@ slurp_central_directory(struct archive_read *a, struct _7zip *zip,
        if (next_header_offset != 0) {
                if (bytes_avail >= (ssize_t)next_header_offset)
                        __archive_read_consume(a, next_header_offset);
-               else if (__archive_read_seek(a,
-                   next_header_offset + zip->seek_base, SEEK_SET) < 0) {
+               else if (seek_compat(a,
+                   next_header_offset + zip->seek_base, SEEK_SET, 1) < 0) {
                        archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC, "Seek error");
                        return (ARCHIVE_FATAL);
                }
@@ -3653,8 +3654,8 @@ seek_pack(struct archive_read *a)
            zip->si.pi.sizes[zip->pack_stream_index];
        pack_offset = zip->si.pi.positions[zip->pack_stream_index];
        if (zip->stream_offset != pack_offset) {
-               if (0 > __archive_read_seek(a, pack_offset + zip->seek_base,
-                   SEEK_SET)) {
+               if (0 > seek_compat(a, pack_offset + zip->seek_base,
+                   SEEK_SET, 1)) {
                        archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC, "Seek error");
                        return (ARCHIVE_FATAL);
                }
@@ -4595,3 +4596,34 @@ Bcj2_Decode(struct _7zip *zip, uint8_t *outBuf, size_t outSize)
 
        return ((ssize_t)outPos);
 }
+
+/*
+ * Perform a seek to given position. If seeking is not supported,
+ * target position is in front of current position, and compat is requested,
+ * try to consume bytes until position is reached.
+ */
+int64_t
+seek_compat(struct archive_read *a, int64_t offset, int whence, int compat)
+{
+       int64_t ret = ARCHIVE_FAILED;
+
+       if (a->filter->can_seek)
+               ret = __archive_read_seek(a, offset, whence);
+       else if (compat) {
+               switch (whence) {
+               case SEEK_CUR:
+                       ret = __archive_read_consume(a, offset);
+                       break;
+               case SEEK_SET:
+                       if (a->filter->position > offset)
+                               break;
+                       ret = __archive_read_consume(a,
+                           offset - a->filter->position);
+                       break;
+               default:
+                       break;
+               }
+       }
+
+       return (ret);
+}