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[cloud] Add ability to retrieve Google Compute Engine metadata
For some unspecified "security" reason, the Google Compute Engine metadata server will refuse any requests that do not include the non-standard HTTP header "Metadata-Flavor: Google". Attempt to autodetect such requests (by comparing the hostname against "metadata.google.internal"), and add the "Metadata-Flavor: Google" header if applicable. Enable this feature in the CONFIG=cloud build, and include a sample embedded script allowing iPXE to boot from a script configured as metadata via e.g. # Create shared boot image make bin/ipxe.usb CONFIG=cloud EMBED=config/cloud/gce.ipxe # Configure per-instance boot script gcloud compute instances add-metadata <instance> \ --metadata-from-file ipxeboot=boot.ipxe Signed-off-by: Michael Brown <mcb30@ipxe.org>
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#!ipxe | ||
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echo Google Compute Engine - iPXE boot via metadata | ||
ifstat || | ||
dhcp || | ||
route || | ||
chain -ar http://metadata.google.internal/computeMetadata/v1/instance/attributes/ipxeboot |
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/* Allow retrieval of metadata (such as an iPXE boot script) from | ||
* Google Compute Engine metadata server. | ||
*/ | ||
#define HTTP_HACK_GCE |
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/* | ||
* Copyright (C) 2017 Michael Brown <mbrown@fensystems.co.uk>. | ||
* | ||
* This program is free software; you can redistribute it and/or | ||
* modify it under the terms of the GNU General Public License as | ||
* published by the Free Software Foundation; either version 2 of the | ||
* License, or any later version. | ||
* | ||
* This program is distributed in the hope that it will be useful, but | ||
* WITHOUT ANY WARRANTY; without even the implied warranty of | ||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
* General Public License for more details. | ||
* | ||
* You should have received a copy of the GNU General Public License | ||
* along with this program; if not, write to the Free Software | ||
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA | ||
* 02110-1301, USA. | ||
* | ||
* You can also choose to distribute this program under the terms of | ||
* the Unmodified Binary Distribution Licence (as given in the file | ||
* COPYING.UBDL), provided that you have satisfied its requirements. | ||
*/ | ||
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); | ||
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/** | ||
* @file | ||
* | ||
* Google Compute Engine (GCE) metadata retrieval | ||
* | ||
* For some unspecified "security" reason, the Google Compute Engine | ||
* metadata server will refuse any requests that do not include the | ||
* non-standard HTTP header "Metadata-Flavor: Google". | ||
*/ | ||
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#include <strings.h> | ||
#include <stdio.h> | ||
#include <ipxe/http.h> | ||
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/** Metadata host name | ||
* | ||
* This is used to identify metadata requests, in the absence of any | ||
* more robust mechanism. | ||
*/ | ||
#define GCE_METADATA_HOST_NAME "metadata.google.internal" | ||
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/** | ||
* Construct HTTP "Metadata-Flavor" header | ||
* | ||
* @v http HTTP transaction | ||
* @v buf Buffer | ||
* @v len Length of buffer | ||
* @ret len Length of header value, or negative error | ||
*/ | ||
static int http_format_metadata_flavor ( struct http_transaction *http, | ||
char *buf, size_t len ) { | ||
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/* Do nothing unless this appears to be a Google Compute | ||
* Engine metadata request. | ||
*/ | ||
if ( strcasecmp ( http->request.host, GCE_METADATA_HOST_NAME ) != 0 ) | ||
return 0; | ||
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/* Construct host URI */ | ||
return snprintf ( buf, len, "Google" ); | ||
} | ||
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/** HTTP "Metadata-Flavor" header */ | ||
struct http_request_header http_request_metadata_flavor __http_request_header ={ | ||
.name = "Metadata-Flavor", | ||
.format = http_format_metadata_flavor, | ||
}; |