pccrr.c File Reference

Peer Content Caching and Retrieval: Retrieval Protocol [MS-PCCRR]. More...

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <ipxe/uri.h>
#include <ipxe/open.h>
#include <ipxe/http.h>
#include <ipxe/base16.h>
#include <ipxe/pccrc.h>
#include <ipxe/pccrr.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
	FILE_SECBOOT (PERMITTED)
static int	peerdist_open_post (struct interface *xfer, const char *location, size_t digestsize, const uint8_t *id, unsigned int block)
	Open retrieval protocol connection using HTTP POST.
static int	peerdist_open_get (struct interface *xfer, const char *location, size_t digestsize, const uint8_t *id, unsigned int block)
	Open retrieval protocol connection using HTTP GET or local file.

Variables
struct peerdist_retrieval	peerdist_post
	PeerDist retrieval protocol using HTTP POST.
struct peerdist_retrieval	peerdist_get
	PeerDist retrieval protocol using HTTP GET or local file.

Detailed Description

Peer Content Caching and Retrieval: Retrieval Protocol [MS-PCCRR].

The MS-PCCRR specification defines an HTTP POST request/response pair for retrieving an encrypted block from a peer (with the decryption keys provided separately via the content information).

The HTTP POST request parameters serve only to identify the block: the actual response body is effectively a static encrypted blob.

We define an additional (non-standard) retrieval protocol in which the block is identified solely using the request URI, with the response being the same content that would be returned as the HTTP POST response body. This allows for encrypted blocks to be retrieved from a static source such as AWS S3 or a local FAT filesystem, without requiring a peer that can understand the retrieval protocol HTTP POST request format.

We define the static request URI format as:

<base>/xx/xxyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy-b.blk

where

• xxyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy is the segment ID (HoHoDK) as a lower-case hexadecimal string
• xx is the first two characters (i.e. the first byte) of the segment ID
• b is the block index within the segment (which will always be zero when using MS-PCCRC version 2 content information), as an unpadded decimal string
• the extension .blk represents a block file

This path format is designed to allow for efficient storage in a local FAT filesystem (by limiting both the number of directories and the number of entries within each directory).

Definition in file pccrr.c.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

FILE_SECBOOT()

FILE_SECBOOT

(

PERMITTED

)

peerdist_open_post()

int peerdist_open_post ( struct interface * xfer, const char * location, size_t digestsize, const uint8_t * id, unsigned int block )

static

Open retrieval protocol connection using HTTP POST.

Parameters

xfer	Data transfer interface
location	Peer location
digestsize	Digest size
id	Segment identifier
block	Block index

Return values

rc	Return status code

Definition at line 90 of file pccrr.c.

                                                     {
        char uri_string[ 7 /* "http://" */ + strlen ( location ) +
                         sizeof ( PEERDIST_MAGIC_PATH /* includes NUL */ ) ];
        peerdist_msg_getblks_t ( digestsize, 1, 0 ) req;
        struct http_request_content content;
        struct uri *uri;
        int rc;
 
        /* Construct block fetch request */
        memset ( &req, 0, sizeof ( req ) );
        req.getblks.hdr.version.raw = htonl ( PEERDIST_MSG_GETBLKS_VERSION );
        req.getblks.hdr.type = htonl ( PEERDIST_MSG_GETBLKS_TYPE );
        req.getblks.hdr.len = htonl ( sizeof ( req ) );
        req.getblks.hdr.algorithm = htonl ( PEERDIST_MSG_AES_128_CBC );
        req.segment.segment.digestsize = htonl ( digestsize );
        memcpy ( req.segment.id, id, digestsize );
        req.ranges.ranges.count = htonl ( 1 );
        req.ranges.range[0].first = htonl ( block );
        req.ranges.range[0].count = htonl ( 1 );
 
        /* Construct POST request content */
        memset ( &content, 0, sizeof ( content ) );
        content.data = &req;
        content.len = sizeof ( req );
 
        /* Construct URI string */
        snprintf ( uri_string, sizeof ( uri_string ),
                   ( "http://%s" PEERDIST_MAGIC_PATH ), location );
 
        /* Parse URI */
        uri = parse_uri ( uri_string );
        if ( ! uri ) {
                rc = -ENOMEM;
                goto err_uri;
        }
 
        /* Initiate HTTP POST to retrieve block */
        if ( ( rc = http_open ( xfer, &http_post, uri, NULL,
                                &content ) ) != 0 ) {
                DBGC ( xfer, "PCCRR %p could not open %s: %s\n",
                       xfer, uri_string, strerror ( rc ) );
                goto err_open;
        }
 
 err_open:
        uri_put ( uri );
 err_uri:
        return rc;
}

References block, http_request_content::data, DBGC, digestsize, ENOMEM, htonl, http_open(), http_request_content::len, memcpy(), memset(), NULL, parse_uri(), PEERDIST_MAGIC_PATH, PEERDIST_MSG_AES_128_CBC, peerdist_msg_getblks_t, PEERDIST_MSG_GETBLKS_TYPE, PEERDIST_MSG_GETBLKS_VERSION, rc, snprintf(), strerror(), strlen(), and uri_put().

peerdist_open_get()

int peerdist_open_get ( struct interface * xfer, const char * location, size_t digestsize, const uint8_t * id, unsigned int block )

static

Open retrieval protocol connection using HTTP GET or local file.

Parameters

xfer	Data transfer interface
location	Peer location
digestsize	Digest size
id	Segment identifier
block	Block index

Return values

rc	Return status code

Definition at line 158 of file pccrr.c.

                                                    {
        char uri_string[ strlen ( location ) + 4 /* "/xx/" */ +
                         ( 2 * PEERDIST_DIGEST_MAX_SIZE ) + 1 /* "-" */ +
                         10 /* block number */ + 4 /* ".blk" */ +
                         1 /* NUL */ ];
        size_t len;
        int rc;
 
        /* Construct URI string */
        assert ( digestsize <= PEERDIST_DIGEST_MAX_SIZE );
        len = snprintf ( uri_string, sizeof ( uri_string ), "%s/%02x/",
                         location, id[0] );
        assert ( len < sizeof ( uri_string ) );
        len += base16_encode ( id, digestsize, ( uri_string + len ),
                               ( sizeof ( uri_string ) - len ) );
        assert ( len < sizeof ( uri_string ) );
        snprintf ( ( uri_string + len ), ( sizeof ( uri_string ) - len ),
                   "-%d.blk", block );
 
        /* Open URI */
        if ( ( rc = xfer_open_uri_string ( xfer, uri_string ) ) != 0 ) {
                DBGC ( xfer, "PCCRR %p could not open %s: %s\n",
                       xfer, uri_string, strerror ( rc ) );
                return rc;
        }
 
        return 0;
}

References assert, block, DBGC, digestsize, len, PEERDIST_DIGEST_MAX_SIZE, rc, snprintf(), strerror(), strlen(), and xfer_open_uri_string().

Variable Documentation

peerdist_post

struct peerdist_retrieval peerdist_post

Initial value:

                        = {
        .name = "POST",
        .open = peerdist_open_post,
}

PeerDist retrieval protocol using HTTP POST.

Definition at line 143 of file pccrr.c.

                                        {
        .name = "POST",
        .open = peerdist_open_post,
};

Referenced by peerdisc_create(), and peerdisc_socket_rx().

peerdist_get

struct peerdist_retrieval peerdist_get

Initial value:

                        = {
        .name = "GET",
        .open = peerdist_open_get,
}

PeerDist retrieval protocol using HTTP GET or local file.

Definition at line 190 of file pccrr.c.

                                       {
        .name = "GET",
        .open = peerdist_open_get,
};

Referenced by peerdisc_create().