[hail patch 2/3] chunkd: checksum data prior to returning via GET

[Jeff Garzik <jeff@xxxxxxxxxx>]

commit 38d60bba8f9fe40017ec7c0be49c9848c82ce322
Author: Jeff Garzik <jeff@xxxxxxxxxx>
Date:   Thu Aug 5 17:55:32 2010 -0400

    [chunkd] checksum data prior to returning via GET
    
    When reading a file off disk, checksum the data after reading from
    disk, prior to sending across network to client.  Fail read, if
    checksum fails.
    
    This guarantees we will never send corrupted data to a client.
    
    Signed-off-by: Jeff Garzik <jgarzik@xxxxxxxxxx>

 chunkd/be-fs.c |   51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/chunkd/be-fs.c b/chunkd/be-fs.c
index d714e7c..24baad7 100644
--- a/chunkd/be-fs.c
+++ b/chunkd/be-fs.c
@@ -52,8 +52,12 @@ struct fs_obj {
 
 	int			in_fd;
 	char			*in_fn;
+	off_t			in_pos;
 	off_t			sendfile_ofs;
 
+	off_t			tail_pos;
+	size_t			tail_len;
+
 	size_t			checked_bytes;
 	SHA_CTX			checksum;
 	unsigned int		csum_idx;
@@ -368,6 +372,8 @@ struct backend_obj *fs_obj_new(uint32_t table_id,
 	if (!obj->csum_tbl)
 		goto err_out;
 	obj->csum_tbl_sz = csum_bytes;
+	obj->tail_pos = data_len & ~(CHUNK_BLK_SZ - 1);
+	obj->tail_len = data_len & (CHUNK_BLK_SZ - 1);
 
 	/* build local fs pathname */
 	fn = fs_obj_pathname(table_id, key, key_len);
@@ -492,6 +498,8 @@ struct backend_obj *fs_obj_open(uint32_t table_id, const char *user,
 	value_len = GUINT64_FROM_LE(hdr.value_len);
 	obj->n_blk = GUINT32_FROM_LE(hdr.n_blk);
 	csum_bytes = obj->n_blk * CHD_CSUM_SZ;
+	obj->tail_pos = value_len & ~(CHUNK_BLK_SZ - 1);
+	obj->tail_len = value_len & (CHUNK_BLK_SZ - 1);
 
 	/* verify file size large enough to contain value */
 	tmp64 = value_len + sizeof(hdr) + key_len + csum_bytes;
@@ -575,15 +583,56 @@ void fs_obj_free(struct backend_obj *bo)
 	free(obj);
 }
 
+static bool can_csum_blk(struct fs_obj *obj, size_t len)
+{
+	if (obj->in_pos & (CHUNK_BLK_SZ - 1))
+		return false;
+
+	if (obj->in_pos == obj->tail_pos && len == obj->tail_len)
+		return true;
+	if (len == CHUNK_BLK_SZ)
+		return true;
+
+	return false;
+}
+
 ssize_t fs_obj_read(struct backend_obj *bo, void *ptr, size_t len)
 {
 	struct fs_obj *obj = bo->private;
 	ssize_t rc;
 
 	rc = read(obj->in_fd, ptr, len);
-	if (rc < 0)
+	if (rc < 0) {
 		applog(LOG_ERR, "obj read(%s) failed: %s",
 		       obj->in_fn, strerror(errno));
+		return -errno;
+	}
+
+	if (can_csum_blk(obj, rc)) {
+		unsigned char md[CHD_CSUM_SZ];
+		unsigned int blk_pos;
+		int cmprc;
+
+		SHA1(ptr, rc, md);
+
+		blk_pos = (unsigned int) (obj->in_pos >> CHUNK_BLK_ORDER);
+		cmprc = memcmp(md, obj->csum_tbl + (blk_pos * CHD_CSUM_SZ),
+			       CHD_CSUM_SZ);
+
+		if (cmprc) {
+			applog(LOG_WARNING, "obj(%s) csum failed @ 0x%llx",
+			       obj->in_fn,
+			       (unsigned long long) obj->in_pos);
+			return -EIO;
+		}
+	} else {
+		applog(LOG_INFO, "obj(%s) unaligned read, 0x%x @ 0x%llx",
+		       obj->in_fn, len,
+		       (unsigned long long) obj->in_pos);
+		
+	}
+
+	obj->in_pos += rc;
 
 	return rc;
 }
--
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