From: Jonathan Dieter <jdieter@gmail.com>
Date: Sun, 29 Apr 2018 18:15:24 +0000 (+0300)
Subject: Revamp file structure one last (hopefully) time so we can check the header
X-Git-Tag: archive/raspbian/1.1.9+ds1-1+rpi1~1^2~299
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=054e890cc39e437858f3e3a257289f897b37ee53;p=zchunk.git

Revamp file structure one last (hopefully) time so we can check the header
checksum without reading the whole header into memory in one go

Signed-off-by: Jonathan Dieter <jdieter@gmail.com>
---

diff --git a/src/lib/compint.c b/src/lib/compint.c
index 4ee6bd8..89b9c7a 100644
--- a/src/lib/compint.c
+++ b/src/lib/compint.c
@@ -42,7 +42,8 @@ void compint_from_size(char *compint, size_t val, size_t *length) {
     return;
 }
 
-int compint_to_size(size_t *val, const char *compint, size_t *length) {
+int compint_to_size(size_t *val, const char *compint, size_t *length,
+                    size_t max_length) {
     *val = 0;
     size_t old_val = 0;
     const unsigned char *i = (unsigned char *)compint;
@@ -64,8 +65,12 @@ int compint_to_size(size_t *val, const char *compint, size_t *length) {
             break;
         i++;
         /* Make sure we're not overflowing and fail if we do */
-        if(count > MAX_COMP_SIZE || *val < old_val) {
-            zck_log(ZCK_LOG_ERROR, "Number too large\n");
+        if(count > MAX_COMP_SIZE || count+*length > max_length ||
+           *val < old_val) {
+            if(count > max_length)
+                zck_log(ZCK_LOG_ERROR, "Read past end of header\n");
+            else
+                zck_log(ZCK_LOG_ERROR, "Number too large\n");
             *length -= count;
             *val = 0;
             return False;
@@ -85,9 +90,10 @@ int compint_from_int(char *compint, int val, size_t *length) {
     return True;
 }
 
-int compint_to_int(int *val, const char *compint, size_t *length) {
+int compint_to_int(int *val, const char *compint, size_t *length,
+                   size_t max_length) {
     size_t new = (size_t)*val;
-    if(!compint_to_size(&new, compint, length))
+    if(!compint_to_size(&new, compint, length, max_length))
         return False;
     *val = (int)new;
     if(*val < 0) {
diff --git a/src/lib/dl/dl.c b/src/lib/dl/dl.c
index b7f6616..77cf781 100644
--- a/src/lib/dl/dl.c
+++ b/src/lib/dl/dl.c
@@ -443,50 +443,48 @@ int PUBLIC zck_dl_get_header(zckCtx *zck, zckDL *dl, char *url) {
     zck->fd = dl->dst_fd;
 
     /* Download first hundred bytes and read magic and hash type */
-    if(!zck_dl_bytes(dl, url, 100, start, &buffer_len))
+    if(!zck_dl_bytes(dl, url, 200, start, &buffer_len))
         return False;
-    if(!zck_read_initial(zck))
+    if(!read_lead_1(zck))
         return False;
     start = tell_data(dl->dst_fd);
 
-    /* If we haven't downloaded enough for the index hash plus a few others, do
-     * it now */
-    if(!zck_dl_bytes(dl, url, zck->hash_type.digest_size+start+MAX_COMP_SIZE*4,
+    if(!zck_dl_bytes(dl, url, zck->lead_size + zck->hash_type.digest_size,
                      start, &buffer_len))
         return False;
-    /* Read and store the index hash */
-    if(!zck_read_header_hash(zck))
+    if(!read_lead_2(zck))
         return False;
-    start += zck->hash_type.digest_size;
     zck_log(ZCK_LOG_DEBUG, "Header hash: (%s)",
             zck_hash_name_from_type(zck_get_full_hash_type(zck)));
     char *digest = zck_get_header_digest(zck);
     zck_log(ZCK_LOG_DEBUG, "%s\n", digest);
     free(digest);
+    start = tell_data(dl->dst_fd);
 
-    /* Read and store compression type and index size */
-    if(!zck_read_ct_is(zck))
+    /* If we haven't downloaded enough for the index hash plus a few others, do
+     * it now */
+    if(!zck_dl_bytes(dl, url, zck->lead_size + zck->header_length,
+                     start, &buffer_len))
         return False;
-    start = tell_data(dl->dst_fd);
-    zck_log(ZCK_LOG_DEBUG, "Index size: %llu\n", zck->index_size);
 
-    /* Download and read rest of index */
-    if(!zck_dl_bytes(dl, url, zck->index_size, start,
-                     &buffer_len))
+    /* Verify header checksum */
+    if(!validate_header(zck))
         return False;
-    if(!zck_header_hash(zck))
+    zck_hash_close(&(zck->check_full_hash));
+
+    /* Read the header */
+    if(!read_preface(zck))
         return False;
-    if(!zck_read_index(zck))
+    start += zck->preface_size;
+    zck_log(ZCK_LOG_DEBUG, "Index size: %llu\n", zck->index_size);
+
+    /* Read the index */
+    if(!read_index(zck))
         return False;
 
     /* Read signatures */
-    if(!zck_read_sig(zck))
+    if(!read_sig(zck))
         return False;
-    if(!close_read_header(zck))
-        return False;
-    if(!zck_validate_header(zck))
-        return False;
-    zck_hash_close(&(zck->check_full_hash));
 
     /* Write zeros to rest of file */
     zckIndex *info = &(dl->info.index);
diff --git a/src/lib/header.c b/src/lib/header.c
index 7e158fa..2b96aa5 100644
--- a/src/lib/header.c
+++ b/src/lib/header.c
@@ -32,6 +32,8 @@
 
 #include "zck_private.h"
 
+#define MAX_HEADER_IN_MEM 10*1024*1024
+
 #define VALIDATE(f)     if(!f) { \
                             zck_log(ZCK_LOG_ERROR, \
                                     "zckCtx not initialized\n"); \
@@ -52,12 +54,16 @@
                                 return False; \
                             }
 
-int check_flags(zckCtx *zck, char *header, size_t *length) {
-    zck->has_streams = header[8] & 0x01;
+int check_flags(zckCtx *zck, char *header, size_t *length, size_t max_length) {
+    if(max_length < 4) {
+        zck_log(ZCK_LOG_ERROR, "Read past end of header\n");
+        return False;
+    }
+    zck->has_streams = header[3] & 0x01;
     if(zck->has_streams)
         zck_log(ZCK_LOG_INFO, "Archive has streams\n");
-    if((header[8] & 0xfe) != 0 || header[7] != 0 || header[6] != 0 ||
-       header[5] != 0) {
+    if((header[3] & 0xfe) != 0 || header[2] != 0 || header[1] != 0 ||
+       header[0] != 0) {
         zck_log(ZCK_LOG_ERROR, "Unknown flags(s) set\n");
         return False;
     }
@@ -65,115 +71,198 @@ int check_flags(zckCtx *zck, char *header, size_t *length) {
     return True;
 }
 
-int add_to_header_string(zckCtx *zck, char *data, size_t length) {
-    VALIDATE(zck);
-
-    zck->header_string = realloc(zck->header_string, zck->header_size + length);
-    if(zck->header_string == NULL) {
-        zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
-                zck->header_size + length);
-        return False;
-    }
-    memcpy(zck->header_string + zck->header_size, data, length);
-    zck->header_size += length;
-    return True;
-}
+int read_lead_1(zckCtx *zck) {
+    VALIDATE_READ(zck);
 
-int add_to_sig_string(zckCtx *zck, char *data, size_t length) {
-    VALIDATE(zck);
+    int lead = 5 + 2*MAX_COMP_SIZE;
 
-    zck->sig_string = realloc(zck->sig_string, zck->sig_size + length);
-    if(zck->sig_string == NULL) {
-        zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
-                zck->sig_size + length);
+    char *header = zmalloc(lead);
+    if(header == NULL) {
+        zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n", lead);
         return False;
     }
-    memcpy(zck->sig_string + zck->sig_size, data, length);
-    zck->sig_size += length;
-    return True;
-}
-
-int zck_read_initial(zckCtx *zck) {
-    VALIDATE_READ(zck);
-
-    char *header = NULL;
     size_t length = 0;
 
-    zck_log(ZCK_LOG_DEBUG, "Reading magic, flags and hash type\n");
-    if(read_header(zck, &header, 9 + MAX_COMP_SIZE) < 9 + MAX_COMP_SIZE)
+    if(read_data(zck->fd, header, lead) < lead)
         return False;
 
     if(memcmp(header, "\0ZCK1", 5) != 0) {
         free(header);
         zck_log(ZCK_LOG_ERROR,
-                "Invalid header, perhaps this is not a zck file?\n");
+                "Invalid lead, perhaps this is not a zck file?\n");
         return False;
     }
     length += 5;
 
-    if(!check_flags(zck, header, &length))
-        return False;
+    /* Read hash type for header and full digest and initialize check hash */
     int hash_type = 0;
-    if(!compint_to_int(&hash_type, header+length, &length))
+    if(!compint_to_int(&hash_type, header+length, &length, lead))
+        return False;
+    if(zck->prep_hash_type > -1 && zck->prep_hash_type != hash_type) {
+        zck_log(ZCK_LOG_ERROR,
+                "Hash type (%i) doesn't match requested hash type "
+                "(%i)\n", hash_type, zck->prep_hash_type);
         return False;
+    }
     if(!zck_hash_setup(&(zck->hash_type), hash_type))
         return False;
+    zck_log(ZCK_LOG_DEBUG, "Setting header and full digest hash type to %s\n",
+            zck_hash_name_from_type(hash_type));
 
-    /* Return any unused bytes from read_header */
-    if(!read_header_unread(zck, 9 + MAX_COMP_SIZE - length))
+    /* Read header size */
+    size_t header_length = 0;
+    if(!compint_to_size(&header_length, header+length, &length, lead))
         return False;
+    if(zck->prep_hdr_size > -1 && (size_t)zck->prep_hdr_size != header_length) {
+        zck_log(ZCK_LOG_ERROR,
+                "Header length (%lu) doesn't match requested header length "
+                "(%lu)\n", header_length, zck->prep_hdr_size);
+        return False;
+    }
+    zck->header_length = header_length;
 
-    return add_to_header_string(zck, header, length);
+    zck->header = header;
+    zck->header_size = lead;
+    zck->lead_string = header;
+    zck->lead_size = length;
+    zck->hdr_digest_loc = length;
+    return True;
 }
 
-int zck_read_header_hash(zckCtx *zck) {
+int read_lead_2(zckCtx *zck) {
     VALIDATE_READ(zck);
 
-    if(zck->header_string == NULL) {
+    if(zck->lead_string == NULL || zck->lead_size == 0) {
         zck_log(ZCK_LOG_ERROR,
-                "Reading index hash before initial bytes are read\n");
+                "Reading lead step 2 before lead step 1 is read\n");
         return False;
     }
 
-    char *header = NULL;
+    char *header = zck->lead_string;
+    size_t length = zck->lead_size;
+    size_t lead = zck->header_size;
 
-    char *digest = zmalloc(zck->hash_type.digest_size);
-    if(digest == NULL) {
+    /* Read header digest */
+    zck_log(ZCK_LOG_DEBUG, "Reading header digest\n");
+    header = realloc(header, length + zck->hash_type.digest_size);
+    if(header == NULL) {
+        zck_log(ZCK_LOG_ERROR, "Unable to re-allocate %lu bytes\n",
+                length + zck->hash_type.digest_size);
+        return False;
+    }
+    size_t to_read = 0;
+    if(lead < length + zck->hash_type.digest_size)
+        to_read = length + zck->hash_type.digest_size - lead;
+    if(read_data(zck->fd, header + lead, to_read) < to_read)
+        return False;
+    lead += to_read;
+
+    if(zck->prep_digest &&
+       memcmp(zck->prep_digest, header + length, zck->hash_type.digest_size) != 0) {
+        zck_log(ZCK_LOG_ERROR,
+                "Header digest doesn't match requested header digest\n");
+        return False;
+    }
+    zck->header_digest = zmalloc(zck->hash_type.digest_size);
+    if(zck->header_digest == NULL) {
         zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
                 zck->hash_type.digest_size);
         return False;
     }
-    zck_log(ZCK_LOG_DEBUG, "Reading header hash\n");
-    if(read_header(zck, &header, zck->hash_type.digest_size)
-                                  < zck->hash_type.digest_size) {
-        free(digest);
+    memcpy(zck->header_digest, header + length, zck->hash_type.digest_size);
+    length += zck->hash_type.digest_size;
+
+    /* Store pre-header */
+    zck->header = header;
+    zck->header_size = lead;
+    zck->lead_string = header;
+    zck->lead_size = length;
+    zck_log(ZCK_LOG_DEBUG, "Parsed lead: %lu bytes\n", length);
+    return True;
+}
+
+int validate_header(zckCtx *zck) {
+    if(zck->header_length > MAX_HEADER_IN_MEM) {
+
+    }
+
+    /* Allocate header and store any extra bytes at beginning of header */
+    zck->header = realloc(zck->header, zck->lead_size + zck->header_length);
+    if(zck->header == NULL) {
+        zck_log(ZCK_LOG_ERROR, "Unable to reallocate %lu bytes\n",
+                zck->lead_size + zck->header_length);
+        return False;
+    }
+    zck->lead_string = zck->header;
+    char *header = zck->header + zck->lead_size;
+    size_t loaded = 0;
+
+    if(zck->header_length < zck->header_size - zck->lead_size) {
+        zck_log(ZCK_LOG_ERROR, "Header size is too small for actual data\n");
         return False;
     }
-    memcpy(digest, header, zck->hash_type.digest_size);
-    zck->header_digest = digest;
+    if(zck->lead_size < zck->header_size)
+        loaded = zck->header_size - zck->lead_size;
+
+    /* Read header from file */
+    zck_log(ZCK_LOG_DEBUG, "Reading the rest of the header: %lu bytes\n",
+            zck->header_length);
+    if(loaded < zck->header_length) {
+        if(!read_data(zck->fd, header + loaded, zck->header_length - loaded))
+            return False;
+        zck->header_size = zck->lead_size + zck->header_length;
+    }
+
+    if(!zck_hash_init(&(zck->check_full_hash), &(zck->hash_type)))
+        return False;
+    if(!zck_hash_update(&(zck->check_full_hash), zck->header,
+                        zck->hdr_digest_loc))
+        return False;
+    if(!zck_hash_update(&(zck->check_full_hash), header, zck->header_length))
+        return False;
+    if(!zck_validate_header(zck))
+        return False;
     return True;
 }
 
-int zck_read_ct_is(zckCtx *zck) {
+int read_preface(zckCtx *zck) {
     VALIDATE_READ(zck);
 
-    if(zck->header_string == NULL) {
+    if(zck->header_digest == NULL) {
         zck_log(ZCK_LOG_ERROR,
-                "Reading compression type before hash type is read\n");
+                "Reading preface before lead is read\n");
         return False;
     }
 
-    char *header = NULL;
+    char *header = zck->header + zck->lead_size;
     size_t length = 0;
+    size_t max_length = zck->header_length;
 
-    zck_log(ZCK_LOG_DEBUG, "Reading compression type and index size\n");
-    if(read_header(zck, &header, MAX_COMP_SIZE*2) < MAX_COMP_SIZE*2)
+    /* Read data digest */
+    zck_log(ZCK_LOG_DEBUG, "Reading data digest\n");
+    if(length + zck->hash_type.digest_size > max_length) {
+        zck_log(ZCK_LOG_ERROR, "Read past end of header\n");
         return False;
+    }
+    zck->full_hash_digest = zmalloc(zck->hash_type.digest_size);
+    if(!zck->full_hash_digest) {
+        zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
+                zck->hash_type.digest_size);
+        return False;
+    }
+    memcpy(zck->full_hash_digest, header+length, zck->hash_type.digest_size);
+    length += zck->hash_type.digest_size;
 
+    /* Read flags */
+    if(!check_flags(zck, header+length, &length, max_length-length))
+        return False;
+
+    /* Setup for reading compression type */
+    zck_log(ZCK_LOG_DEBUG, "Reading compression type and index size\n");
     int tmp = 0;
 
     /* Read and initialize compression type */
-    if(!compint_to_int(&tmp, header, &length))
+    if(!compint_to_int(&tmp, header+length, &length, max_length))
         return False;
     if(!zck_set_ioption(zck, ZCK_COMP_TYPE, tmp))
         return False;
@@ -181,59 +270,56 @@ int zck_read_ct_is(zckCtx *zck) {
         return False;
 
     /* Read and initialize index size */
-    if(!compint_to_int(&tmp, header + length, &length))
+    if(!compint_to_int(&tmp, header+length, &length, max_length))
         return False;
     zck->index_size = tmp;
 
-    /* Return any unused bytes from read_header */
-    if(!read_header_unread(zck, MAX_COMP_SIZE*2 - length))
-        return False;
-
-    return add_to_header_string(zck, header, length);
-}
-
-int zck_header_hash(zckCtx *zck) {
-    /* Calculate checksum to this point */
-    if(!zck_hash_init(&(zck->check_full_hash), &(zck->hash_type)))
-        return False;
-    if(!zck_hash_update(&(zck->check_full_hash), zck->header_string,
-                        zck->header_size))
-        return False;
+    zck->preface_string = header;
+    zck->preface_size = length;
     return True;
 }
 
-int zck_read_index(zckCtx *zck) {
+int read_index(zckCtx *zck) {
     VALIDATE_READ(zck);
 
+    if(zck->preface_string == NULL) {
+        zck_log(ZCK_LOG_ERROR,
+                "Reading index before preface is read\n");
+        return False;
+    }
+
     char *header = NULL;
     zck_log(ZCK_LOG_DEBUG, "Reading index\n");
-    if(!read_header(zck, &header, zck->index_size))
+    if(zck->lead_size + zck->preface_size + zck->index_size >
+       zck->header_size) {
+        zck_log(ZCK_LOG_ERROR, "Read past end of header\n");
         return False;
-
-    if(!zck_index_read(zck, header, zck->index_size))
+    }
+    header = zck->header + zck->lead_size + zck->preface_size;
+    int max_length = zck->header_size - (zck->lead_size + zck->preface_size);
+    if(!zck_index_read(zck, header, zck->index_size, max_length))
         return False;
 
+    zck->index_string = header;
     return True;
 }
 
-int zck_read_sig(zckCtx *zck) {
+int read_sig(zckCtx *zck) {
     VALIDATE_READ(zck);
 
-    if(zck->header_string == NULL) {
+    if(zck->index_string == NULL) {
         zck_log(ZCK_LOG_ERROR,
-                "Reading signatures before hash type is read\n");
+                "Reading signatures before index is read\n");
         return False;
     }
 
-    char *header = NULL;
+    char *header = zck->header + zck->lead_size + zck->preface_size +
+                   zck->index_size;
+    size_t max_length = zck->header_size - (zck->lead_size + zck->preface_size +
+                                            zck->index_size);
     size_t length = 0;
 
-    /* Get signature size */
-    ssize_t rd = read_header(zck, &header, MAX_COMP_SIZE);
-    if(rd < 0)
-        return False;
-
-    if(!compint_to_int(&(zck->sigs.count), header, &length))
+    if(!compint_to_int(&(zck->sigs.count), header, &length, max_length))
         return False;
 
     /* We don't actually support signatures yet, so bail if there is one */
@@ -243,75 +329,59 @@ int zck_read_sig(zckCtx *zck) {
         return False;
     }
 
-    if(!zck_hash_update(&(zck->check_full_hash), header,
-                        length))
-        return False;
+    /* Set data_offset */
+    zck->data_offset = zck->lead_size + zck->header_length;
 
-    /* Return any unused bytes from read_header */
-    if(!read_header_unread(zck, rd - length))
-        return False;
+    if(zck->header_size >
+       zck->lead_size + zck->preface_size + zck->index_size + length)
+        zck_log(ZCK_LOG_WARNING, "There are %lu unused bytes in the header\n");
 
-    zck->data_offset = zck->hdr_buf_size;
-    return add_to_sig_string(zck, header, length);
+    zck->sig_size = length;
+    zck->sig_string = header;
+    return True;
 }
 
 int zck_read_header(zckCtx *zck) {
     VALIDATE_READ(zck);
 
-    if(!zck_read_initial(zck))
-        return False;
-    if(!zck_read_header_hash(zck))
+    if(!read_lead_1(zck))
         return False;
-    if(!zck_read_ct_is(zck))
+    if(!read_lead_2(zck))
         return False;
-    if(!zck_header_hash(zck))
+    if(!validate_header(zck))
         return False;
-    if(!zck_read_index(zck))
+    if(!read_preface(zck))
         return False;
-    if(!zck_read_sig(zck))
+    if(!read_index(zck))
         return False;
-    if(!close_read_header(zck))
-        return False;
-    if(!zck_validate_header(zck))
+    if(!read_sig(zck))
         return False;
     if(!zck_import_dict(zck))
         return False;
     return True;
 }
 
-int zck_header_create(zckCtx *zck) {
-    int header_malloc = 9 + MAX_COMP_SIZE + zck->hash_type.digest_size +
-                        MAX_COMP_SIZE*2;
+int preface_create(zckCtx *zck) {
+    int header_malloc = zck->hash_type.digest_size + 4 + 2*MAX_COMP_SIZE;
 
     char *header = zmalloc(header_malloc);
     if(header == NULL) {
         zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n", header_malloc);
         return False;
     }
-    size_t start = 0;
     size_t length = 0;
-    memcpy(header, "\0ZCK1", 5);
-    length += 5;
-    /* First three bytes of flags are always 0 */
+
+    /* Write out the full data digest */
+    memcpy(header + length, zck->full_hash_digest, zck->hash_type.digest_size);
+    length += zck->hash_type.digest_size;
+
+    /* Write out flags */
+    memset(header + length, 0, 3);
     length += 3;
     /* Final byte for flags */
     if(zck->has_streams)
         header[length] &= 1;
     length += 1;
-    compint_from_size(header+length, zck->hash_type.type, &length);
-    if(!add_to_header_string(zck, header, length)) {
-        free(header);
-        return False;
-    }
-    start = length;
-
-    /* If we have the digest, write it in, otherwise write zeros */
-    if(zck->header_digest)
-        memcpy(header+length, zck->header_digest, zck->hash_type.digest_size);
-    else
-        memset(header+length, 0, zck->hash_type.digest_size);
-    length += zck->hash_type.digest_size;
-    start = length;
 
     /* Write out compression type and index size */
     if(!compint_from_int(header+length, zck->comp.type, &length)) {
@@ -319,11 +389,6 @@ int zck_header_create(zckCtx *zck) {
         return False;
     }
     compint_from_size(header+length, zck->index_size, &length);
-    if(!add_to_header_string(zck, header+start, length-start)) {
-        free(header);
-        return False;
-    }
-    start = length;
 
     /* Shrink header to actual size */
     header = realloc(header, length);
@@ -331,14 +396,14 @@ int zck_header_create(zckCtx *zck) {
         zck_log(ZCK_LOG_ERROR, "Unable to reallocate %lu bytes\n", length);
         return False;
     }
-    if(zck->hdr_buf)
-        free(zck->hdr_buf);
-    zck->hdr_buf = header;
-    zck->hdr_buf_size = length;
+
+    zck->preface_string = header;
+    zck->preface_size = length;
+    zck_log(ZCK_LOG_DEBUG, "Generated preface: %lu bytes\n", zck->preface_size);
     return True;
 }
 
-int zck_sig_create(zckCtx *zck) {
+int sig_create(zckCtx *zck) {
     char *header = zmalloc(MAX_COMP_SIZE);
     if(header == NULL) {
         zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n", MAX_COMP_SIZE);
@@ -358,22 +423,130 @@ int zck_sig_create(zckCtx *zck) {
     }
     zck->sig_string = header;
     zck->sig_size = length;
+    zck_log(ZCK_LOG_DEBUG, "Generated signatures: %lu bytes\n", zck->sig_size);
     return True;
 }
 
-int zck_write_header(zckCtx *zck) {
-    VALIDATE_WRITE(zck);
+int lead_create(zckCtx *zck) {
+    int phs = 5 + 2*MAX_COMP_SIZE + zck->hash_type.digest_size;
+    char *header = zmalloc(phs);
+    if(header == NULL) {
+        zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n", phs);
+        return False;
+    }
+    size_t length = 0;
+    memcpy(header, "\0ZCK1", 5);
+    length += 5;
+
+    /* Write out full data and header hash type */
+    compint_from_size(header + length, zck->hash_type.type, &length);
+    /* Write out header length */
+    zck->header_length = zck->preface_size + zck->index_size + zck->sig_size;
+    compint_from_size(header + length, zck->header_length, &length);
+    /* Skip header digest; we'll fill it in later */
+    zck->hdr_digest_loc = length;
+    length += zck->hash_type.digest_size;
 
-    if(!write_data(zck->fd, zck->hdr_buf, zck->hdr_buf_size))
+    header = realloc(header, length);
+    if(header == NULL) {
+        zck_log(ZCK_LOG_ERROR, "Unable to reallocate %lu bytes\n", length);
         return False;
+    }
+
+    zck->lead_string = header;
+    zck->lead_size = length;
+    zck_log(ZCK_LOG_DEBUG, "Generated lead: %lu bytes\n", zck->lead_size);
     return True;
 }
 
+int zck_header_create(zckCtx *zck) {
+    /* Rebuild header without header hash */
+    if(zck->header_digest) {
+        free(zck->header_digest);
+        zck->header_digest = NULL;
+    }
+
+    /* Generate index */
+    if(!index_create(zck))
+        return False;
 
-int zck_write_sigs(zckCtx *zck) {
+    /* Generate preface */
+    if(!preface_create(zck))
+        return False;
+
+    /* Rebuild signatures */
+    if(!sig_create(zck))
+        return False;
+
+    /* Rebuild pre-header */
+    if(!lead_create(zck))
+        return False;
+
+    /* Calculate data offset */
+    zck->data_offset = zck->lead_size + zck->preface_size +
+                       zck->index_size + zck->sig_size;
+
+    /* Merge everything into one large string */
+    zck_log(ZCK_LOG_DEBUG, "Merging into header: %lu bytes\n",
+            zck->data_offset);
+    zck->header = zmalloc(zck->data_offset);
+    if(zck->header == NULL) {
+        zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
+                zck->data_offset);
+        return False;
+    }
+    size_t offs = 0;
+    memcpy(zck->header + offs, zck->lead_string, zck->lead_size);
+    free(zck->lead_string);
+    zck->lead_string = zck->header + offs;
+    offs += zck->lead_size;
+    memcpy(zck->header + offs, zck->preface_string, zck->preface_size);
+    free(zck->preface_string);
+    zck->preface_string = zck->header + offs;
+    offs += zck->preface_size;
+    memcpy(zck->header + offs, zck->index_string, zck->index_size);
+    free(zck->index_string);
+    zck->index_string = zck->header + offs;
+    offs += zck->index_size;
+    memcpy(zck->header + offs, zck->sig_string, zck->sig_size);
+    free(zck->sig_string);
+    zck->sig_string = zck->header + offs;
+    zck->header_size = zck->data_offset;
+
+    zckHash header_hash = {0};
+
+    /* Calculate hash of header */
+    if(!zck_hash_init(&header_hash, &(zck->hash_type)))
+        return False;
+    zck_log(ZCK_LOG_DEBUG, "Hashing lead\n");
+    /* Hash lead up to header digest */
+    if(!zck_hash_update(&header_hash, zck->lead_string,
+                        zck->hdr_digest_loc))
+        return False;
+    zck_log(ZCK_LOG_DEBUG, "Hashing the rest\n");
+    /* Hash rest of header */
+    if(!zck_hash_update(&header_hash, zck->preface_string, zck->header_length))
+        return False;
+    zck->header_digest = zck_hash_finalize(&header_hash);
+    if(zck->header_digest == NULL) {
+        zck_log(ZCK_LOG_ERROR,
+                "Unable to calculate %s checksum for index\n",
+                zck_hash_name_from_type(zck->hash_type.type));
+        return False;
+    }
+    /* Write digest to header */
+    memcpy(zck->lead_string+zck->hdr_digest_loc, zck->header_digest,
+           zck->hash_type.digest_size);
+
+    return True;
+}
+
+int zck_write_header(zckCtx *zck) {
     VALIDATE_WRITE(zck);
 
-    if(!write_data(zck->fd, zck->sig_string, zck->sig_size))
+    zck_log(ZCK_LOG_DEBUG, "Writing header: %lu bytes\n",
+            zck->lead_size);
+    if(!write_data(zck->fd, zck->header, zck->header_size))
         return False;
     return True;
 }
diff --git a/src/lib/index/index_common.c b/src/lib/index/index_common.c
index 0fc081e..0484cd9 100644
--- a/src/lib/index/index_common.c
+++ b/src/lib/index/index_common.c
@@ -80,26 +80,14 @@ void zck_index_free(zckCtx *zck) {
         free(zck->full_hash.ctx);
         zck->full_hash.ctx = NULL;
     }
-    if(zck->index_string) {
-        free(zck->index_string);
-        zck->index_string = NULL;
-    }
-    if(zck->header_string) {
-        free(zck->header_string);
-        zck->header_string = NULL;
-    }
-    zck->header_size = 0;
-    if(zck->sig_string) {
-        free(zck->sig_string);
-        zck->sig_string = NULL;
-    }
+    zck->lead_string = NULL;
+    zck->lead_size = 0;
+    zck->preface_string = NULL;
+    zck->preface_size = 0;
+    zck->index_string = NULL;
+    zck->index_size = 0;
+    zck->sig_string = NULL;
     zck->sig_size = 0;
-    if(zck->hdr_buf) {
-        free(zck->hdr_buf);
-        zck->hdr_buf = NULL;
-    }
-    zck->hdr_buf_read = 0;
-    zck->hdr_buf_size = 0;
     if(zck->header_digest) {
         free(zck->header_digest);
         zck->header_digest = NULL;
diff --git a/src/lib/index/index_create.c b/src/lib/index/index_create.c
index a09fe97..1070881 100644
--- a/src/lib/index/index_create.c
+++ b/src/lib/index/index_create.c
@@ -36,10 +36,9 @@
                             return False; \
                         }
 
-int zck_index_finalize(zckCtx *zck) {
+int index_create(zckCtx *zck) {
     VALIDATE(zck);
 
-    zckHash index_hash;
     char *index;
     size_t index_malloc = 0;
     size_t index_size = 0;
@@ -49,8 +48,8 @@ int zck_index_finalize(zckCtx *zck) {
     if(zck->full_hash_digest == NULL)
         return False;
 
-    index_malloc  = MAX_COMP_SIZE * 2; // Chunk hash type and # of index entries
-    index_malloc += zck->hash_type.digest_size; // Full hash digest
+    /* Set initial malloc size */
+    index_malloc  = MAX_COMP_SIZE * 2;
 
     /* Add digest size + MAX_COMP_SIZE bytes for length of each entry in
      * index */
@@ -66,8 +65,6 @@ int zck_index_finalize(zckCtx *zck) {
     index = zmalloc(index_malloc);
     compint_from_size(index+index_size, zck->index.hash_type, &index_size);
     compint_from_size(index+index_size, zck->index.count, &index_size);
-    memcpy(index+index_size, zck->full_hash_digest, zck->hash_type.digest_size);
-    index_size += zck->hash_type.digest_size;
     if(zck->index.first) {
         zckIndexItem *tmp = zck->index.first;
         while(tmp) {
@@ -91,48 +88,7 @@ int zck_index_finalize(zckCtx *zck) {
     }
     zck->index_string = index;
     zck->index_size = index_size;
-
-    /* Rebuild header without index hash */
-    if(zck->header_digest) {
-        free(zck->header_digest);
-        zck->header_digest = NULL;
-    }
-    if(!zck_header_create(zck))
-        return False;
-
-    /* Rebuild signatures */
-    if(!zck_sig_create(zck))
-        return False;
-
-    /* Calculate hash of header */
-    if(!zck_hash_init(&index_hash, &(zck->hash_type))) {
-        free(index);
-        return False;
-    }
-    if(!zck_hash_update(&index_hash, zck->header_string, zck->header_size)) {
-        free(index);
-        return False;
-    }
-    if(!zck_hash_update(&index_hash, zck->index_string, zck->index_size)) {
-        free(index);
-        return False;
-    }
-    if(!zck_hash_update(&index_hash, zck->sig_string, zck->sig_size)) {
-        free(index);
-        return False;
-    }
-    zck->header_digest = zck_hash_finalize(&index_hash);
-    if(zck->header_digest == NULL) {
-        zck_log(ZCK_LOG_ERROR,
-                "Unable to calculate %s checksum for index\n",
-                zck_hash_name_from_type(zck->hash_type.type));
-        return False;
-    }
-
-    /* Rebuild header string with calculated index hash */
-    if(!zck_header_create(zck))
-        return False;
-
+    zck_log(ZCK_LOG_DEBUG, "Generated index: %lu bytes\n", zck->index_size);
     return True;
 }
 
@@ -255,7 +211,3 @@ int zck_index_finish_chunk(zckCtx *zck) {
     zck_hash_close(&(zck->work_index_hash));
     return True;
 }
-
-int zck_write_index(zckCtx *zck) {
-    return write_data(zck->fd, zck->index_string, zck->index_size);
-}
diff --git a/src/lib/index/index_read.c b/src/lib/index/index_read.c
index d50b337..e600f97 100644
--- a/src/lib/index/index_read.c
+++ b/src/lib/index/index_read.c
@@ -32,45 +32,31 @@
 
 #include "zck_private.h"
 
-int zck_index_read(zckCtx *zck, char *data, size_t size) {
+int zck_index_read(zckCtx *zck, char *data, size_t size, size_t max_length) {
     size_t length = 0;
 
-    /* Add index to checksum */
-    if(!zck_hash_update(&(zck->check_full_hash), data, size))
-        return False;
-
-    /* Make sure there's at least enough data for full digest and index count */
-    if(size < zck->hash_type.digest_size + MAX_COMP_SIZE*2) {
-        zck_log(ZCK_LOG_ERROR, "Index is too small to read\n");
-        return False;
-    }
 
     /* Read and configure hash type */
     int hash_type;
-    if(!compint_to_int(&hash_type, data + length, &length))
+    if(!compint_to_int(&hash_type, data + length, &length, max_length))
         return False;
     if(!zck_set_ioption(zck, ZCK_HASH_CHUNK_TYPE, hash_type))
         return False;
 
     /* Read number of index entries */
     size_t index_count;
-    if(!compint_to_size(&index_count, data + length, &length))
+    if(!compint_to_size(&index_count, data + length, &length, max_length))
         return False;
     zck->index.count = index_count;
 
-    /* Read full data hash */
-    zck->full_hash_digest = zmalloc(zck->hash_type.digest_size);
-    if(!zck->full_hash_digest) {
-        zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
-                zck->hash_type.digest_size);
-        return False;
-    }
-    memcpy(zck->full_hash_digest, data + length, zck->hash_type.digest_size);
-    length += zck->hash_type.digest_size;
-
     zckIndexItem *prev = zck->index.first;
     size_t idx_loc = 0;
     while(length < size) {
+        if(length + zck->index.digest_size > max_length) {
+            zck_log(ZCK_LOG_ERROR, "Read past end of header\n");
+            return False;
+        }
+
         zckIndexItem *new = zmalloc(sizeof(zckIndexItem));
         if(!new) {
             zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
@@ -91,14 +77,14 @@ int zck_index_read(zckCtx *zck, char *data, size_t size) {
 
         /* Read and store entry length */
         size_t chunk_length = 0;
-        if(!compint_to_size(&chunk_length, data+length, &length))
+        if(!compint_to_size(&chunk_length, data+length, &length, max_length))
             return False;
         new->start = idx_loc;
         new->comp_length = chunk_length;
 
         /* Read and store uncompressed entry length */
         chunk_length = 0;
-        if(!compint_to_size(&chunk_length, data+length, &length))
+        if(!compint_to_size(&chunk_length, data+length, &length, max_length))
             return False;
         new->length = chunk_length;
 
diff --git a/src/lib/io.c b/src/lib/io.c
index f841cf9..e9a70e6 100644
--- a/src/lib/io.c
+++ b/src/lib/io.c
@@ -33,57 +33,6 @@
 
 #include "zck_private.h"
 
-int read_header_unread(zckCtx *zck, size_t length) {
-    if(zck->hdr_buf_size < length) {
-        zck_log(ZCK_LOG_ERROR,
-                "Attempting to unread %lu bytes while only %lu were read\n",
-                length, zck->hdr_buf_size);
-        return False;
-    }
-    zck->hdr_buf_size -= length;
-    return True;
-}
-
-ssize_t read_header(zckCtx *zck, char **data, size_t length) {
-    while(zck->hdr_buf_size + length > zck->hdr_buf_read) {
-        zck->hdr_buf = realloc(zck->hdr_buf, zck->hdr_buf_size + length);
-        if(zck->hdr_buf == NULL) {
-            zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
-                    zck->hdr_buf_size + length);
-            return -1;
-        }
-        ssize_t rd = read_data(zck->fd, zck->hdr_buf + zck->hdr_buf_read,
-                               zck->hdr_buf_size + length - zck->hdr_buf_read);
-        if(rd < 0)
-            return -1;
-        zck->hdr_buf_read = zck->hdr_buf_read + rd;
-        length = zck->hdr_buf_read - zck->hdr_buf_size;
-    }
-    *data = zck->hdr_buf + zck->hdr_buf_size;
-    zck->hdr_buf_size += length;
-    return length;
-}
-
-int close_read_header(zckCtx *zck) {
-    if(zck->hdr_buf_read > zck->hdr_buf_size) {
-        zck->comp.data = zmalloc(zck->hdr_buf_read - zck->hdr_buf_size);
-        if(zck->comp.data == NULL) {
-            zck_log(ZCK_LOG_ERROR, "Unable to allocate %lu bytes\n",
-                    zck->hdr_buf_read - zck->hdr_buf_size);
-            return False;
-        }
-        memcpy(zck->comp.data, zck->hdr_buf + zck->hdr_buf_size,
-               zck->hdr_buf_read - zck->hdr_buf_size);
-        zck->comp.data_size = zck->hdr_buf_read - zck->hdr_buf_size;
-        zck->comp.data_loc = zck->comp.data_size;
-    }
-    free(zck->hdr_buf);
-    zck->hdr_buf = NULL;
-    zck->hdr_buf_read = 0;
-    zck->hdr_buf_size = 0;
-    return True;
-}
-
 ssize_t read_data(int fd, char *data, size_t length) {
     if(length == 0)
         return 0;
@@ -134,7 +83,7 @@ int read_comp_size(int fd, size_t *val, size_t *length) {
         *val = 0;
         return False;
     }
-    return !compint_to_size(val, data, length);
+    return !compint_to_size(val, data, length, MAX_COMP_SIZE);
 }
 
 int seek_data(int fd, off_t offset, int whence) {
diff --git a/src/lib/zck.c b/src/lib/zck.c
index 67f5930..8a92345 100644
--- a/src/lib/zck.c
+++ b/src/lib/zck.c
@@ -87,17 +87,10 @@ int PUBLIC zck_close(zckCtx *zck) {
     if(zck->mode == ZCK_MODE_WRITE) {
         if(zck_end_chunk(zck) < 0)
             return False;
-        if(!zck_index_finalize(zck))
+        if(!zck_header_create(zck))
             return False;
-        zck_log(ZCK_LOG_DEBUG, "Writing header\n");
         if(!zck_write_header(zck))
             return False;
-        zck_log(ZCK_LOG_DEBUG, "Writing index\n");
-        if(!zck_write_index(zck))
-            return False;
-        zck_log(ZCK_LOG_DEBUG, "Writing signatures\n");
-        if(!zck_write_sigs(zck))
-            return False;
         zck_log(ZCK_LOG_DEBUG, "Writing chunks\n");
         if(!chunks_from_temp(zck))
             return False;
@@ -129,6 +122,10 @@ void zck_clear(zckCtx *zck) {
     if(zck == NULL)
         return;
     zck_index_free(zck);
+    if(zck->header)
+        free(zck->header);
+    zck->header = NULL;
+    zck->header_size = 0;
     if(!zck_comp_close(zck))
         zck_log(ZCK_LOG_WARNING, "Unable to close compression\n");
     zck_hash_close(&(zck->full_hash));
@@ -164,6 +161,8 @@ zckCtx PUBLIC *zck_create() {
                 sizeof(zckCtx));
         return False;
     }
+    zck->prep_hash_type = -1;
+    zck->prep_hdr_size = -1;
     return zck;
 }
 
diff --git a/src/lib/zck_private.h b/src/lib/zck_private.h
index f12fd01..c29a94f 100644
--- a/src/lib/zck_private.h
+++ b/src/lib/zck_private.h
@@ -115,16 +115,26 @@ typedef struct zckCtx {
 
     char *full_hash_digest;
     char *header_digest;
-    char *hdr_buf;
-    size_t hdr_buf_size;
-    size_t hdr_buf_read;
-    char *header_string;
+    size_t data_offset;
+    size_t header_length;
+
+    char *header;
     size_t header_size;
-    char *sig_string;
-    size_t sig_size;
+    size_t hdr_digest_loc;
+    char *lead_string;
+    size_t lead_size;
+    char *preface_string;
+    size_t preface_size;
     char *index_string;
     size_t index_size;
-    size_t data_offset;
+    char *sig_string;
+    size_t sig_size;
+
+
+    char *prep_digest;
+    int prep_hash_type;
+    ssize_t prep_hdr_size;
+
     zckIndex index;
     zckIndexItem *work_index_item;
     zckHash work_index_hash;
@@ -180,9 +190,9 @@ int set_chunk_hash_type(zckCtx *zck, int hash_type)
     __attribute__ ((warn_unused_result));
 
 /* index/index.c */
-int zck_index_read(zckCtx *zck, char *data, size_t size)
+int zck_index_read(zckCtx *zck, char *data, size_t size, size_t max_length)
     __attribute__ ((warn_unused_result));
-int zck_index_finalize(zckCtx *zck)
+int index_create(zckCtx *zck)
     __attribute__ ((warn_unused_result));
 int zck_index_new_chunk(zckIndex *index, char *digest, int digest_size,
                         size_t comp_size, size_t orig_size, int finished)
@@ -215,25 +225,19 @@ int read_comp_size(int fd, size_t *val, size_t *length)
     __attribute__ ((warn_unused_result));
 int chunks_from_temp(zckCtx *zck)
     __attribute__ ((warn_unused_result));
-ssize_t read_header(zckCtx *zck, char **data, size_t length)
-    __attribute__ ((warn_unused_result));
-int read_header_unread(zckCtx *zck, size_t length)
-    __attribute__ ((warn_unused_result));
-int close_read_header(zckCtx *zck)
-    __attribute__ ((warn_unused_result));
 
 /* header.c */
-int zck_read_initial(zckCtx *zck)
+int read_lead_1(zckCtx *zck)
     __attribute__ ((warn_unused_result));
-int zck_read_header_hash(zckCtx *zck)
+int read_lead_2(zckCtx *zck)
     __attribute__ ((warn_unused_result));
-int zck_read_ct_is(zckCtx *zck)
+int validate_header(zckCtx *zck)
     __attribute__ ((warn_unused_result));
-int zck_header_hash(zckCtx *zck)
+int read_preface(zckCtx *zck)
     __attribute__ ((warn_unused_result));
-int zck_read_index(zckCtx *zck)
+int read_index(zckCtx *zck)
     __attribute__ ((warn_unused_result));
-int zck_read_sig(zckCtx *zck)
+int read_sig(zckCtx *zck)
     __attribute__ ((warn_unused_result));
 int zck_read_header(zckCtx *zck)
     __attribute__ ((warn_unused_result));
@@ -282,9 +286,11 @@ int zck_dl_range_chk_chunk(zckDL *dl, char *url, int is_chunk)
 int compint_from_int(char *compint, int val, size_t *length)
     __attribute__ ((warn_unused_result));
 void compint_from_size(char *compint, size_t val, size_t *length);
-int compint_to_int(int *val, const char *compint, size_t *length)
+int compint_to_int(int *val, const char *compint, size_t *length,
+                   size_t max_length)
     __attribute__ ((warn_unused_result));
-int compint_to_size(size_t *val, const char *compint, size_t *length)
+int compint_to_size(size_t *val, const char *compint, size_t *length,
+                    size_t max_length)
     __attribute__ ((warn_unused_result));
 
 
diff --git a/test/empty.c b/test/empty.c
index 23badd0..865f173 100644
--- a/test/empty.c
+++ b/test/empty.c
@@ -36,7 +36,7 @@
 #include "zck_private.h"
 #include "util.h"
 
-static char *checksum="42590fea6f55aca71e222ebe2d147ed89d17aac951a997fef8b980b2803a0412";
+static char *checksum="b09c9fd796877692c1ddf0a9a0201e9a901409a173061caceef80e7484a3ebca";
 
 int main (int argc, char *argv[]) {
     /* Create empty zchunk file */
diff --git a/zchunk_format.txt b/zchunk_format.txt
index dd12864..15b221a 100644
--- a/zchunk_format.txt
+++ b/zchunk_format.txt
@@ -1,19 +1,4 @@
-+-+-+-+-+-+-+-+-+-+====================+=================+
-|   ID    | Flags | Checksum type (ci) | Header checksum |
-+-+-+-+-+-+-+-+-+-+====================+=================+
-
-+========================+=================+=======+
-| Compression type (ci ) | Index size (ci) | Index |
-+========================+=================+=======+
-
-+======================+============+
-| Signature size (ci) | Signatures |
-+======================+============+
-
-+=================+===========+===========+
-| Compressed Dict |   Chunk   |   Chunk   | ==> More chunks
-+=================+===========+===========+
-
+Definitions:
 (ci)
  Compressed (unsigned) integer - An variable length little endian
  integer where the first seven bits of the number are stored in the
@@ -22,15 +7,14 @@
  the top bit of the final byte must be one, indicating the end of the
  number.
 
-ID
- '\0ZCK1', identifies file as zchunk version 1 file
+The lead:
 
-Flags
- 32 bits for flags.  All unused flags MUST be set to 0.  If a decoder sees
- a flag set that it doesn't recognize, it MUST exit with an error.  Flags
++-+-+-+-+-+====================+=================+==================+
+|   ID    | Checksum type (ci) | Header checksum | Header size (ci) |
++-+-+-+-+-+====================+=================+==================+
 
- Current flags are:
-  bit 0: File has data streams
+ID
+ '\0ZCK1', identifies file as zchunk version 1 file
 
 Checksum type
  This is an integer containing the type of checksum used to generate the
@@ -44,6 +28,33 @@ Header checksum
  This is the checksum of everything from the beginning of the file
  until the end of the index, ignoring the header checksum.
 
+Header size:
+ This is an integer containing the size of the header, not including the lead
+
+
+The preface:
+
++===============+-+-+-+-+========================+=================+=======+
+| Data checksum | Flags | Compression type (ci ) | Index size (ci) | Index |
++===============+-+-+-+-+========================+=================+=======+
+
++======================+============+
+| Signature count (ci) | Signatures |
++======================+============+
+
+Data checksum
+ This is the checksum of everything after the index, including the
+ compressed dict and all the compressed chunks.  This checksum is
+ generated using the overall checksum type, *not* the chunk checksum
+ type.
+
+Flags
+ 32 bits for flags.  All unused flags MUST be set to 0.  If a decoder sees
+ a flag set that it doesn't recognize, it MUST exit with an error.  Flags
+
+ Current flags are:
+  bit 0: File has data streams
+
 Compression type
  This is an integer containing the type of compression used to
  compress dict and chunks.
@@ -58,12 +69,20 @@ Index size
 Index
  This is the index, which is described in the next section.
 
-Signature size
- This is an integer countaining the size of the signature section.
+Signature count
+ This is an integer countaining the number of signatures.
 
 Signatures
  These are the signatures, described in a later section.
 
+
+The data:
+
++=================+===========+===========+
+| Compressed Dict |   Chunk   |   Chunk   | ==> More chunks
++=================+===========+===========+
+
+
 Compressed Dict (optional)
  This is a custom dictionary used when compressing each chunk.
  Because each chunk is compressed completely separately from the
@@ -78,9 +97,9 @@ Chunk
 
 The index:
 
-+==========================+==================+===============+
-| Chunk checksum type (ci) | Chunk count (ci) | Data checksum |
-+==========================+==================+===============+
++==========================+==================+
+| Chunk checksum type (ci) | Chunk count (ci) |
++==========================+==================+
 
 +==================+===============+==================+
 | Dict stream (ci) | Dict checksum | Dict length (ci) |
@@ -109,12 +128,6 @@ Chunk checksum type
 Chunk count
  This is a count of the number of chunks in the zchunk file.
 
-Checksum of all data
- This is the checksum of everything after the index, including the
- compressed dict and all the compressed chunks.  This checksum is
- generated using the overall checksum type, *not* the chunk checksum
- type.
-
 Dict stream
  If the data streams flag is set, this must always be 0, otherwise don't
  include this integer