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[crypto] Do not allow build-time cryptography settings to be overridden

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If a root certificate has been explicitly specified at build time
using TRUST=/path/to/cert then do not allow this to be overridden even
from a trustworthy settings source (such as VMware GuestInfo).

Similarly, if a client certificate (and private key) has been
explicitly specified at build time, then do not allow it to be
overridden at runtime.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2012-04-24 16:10:22 +01:00
parent 63d9cc28b9
commit bd16deaa87
2 changed files with 99 additions and 61 deletions
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93
src/crypto/clientcert.c
View File

@ -47,6 +47,13 @@ FILE_LICENCE ( GPL2_OR_LATER );
#warning "Attempting to embed private key with no corresponding certificate"
#endif
/* Allow client certificates to be overridden if not explicitly specified */
#ifdef CERTIFICATE
#define ALLOW_CERT_OVERRIDE 0
#else
#define ALLOW_CERT_OVERRIDE 1
#endif
/* Raw client certificate data */
extern char client_certificate_data[];
extern char client_certificate_len[];
@ -72,13 +79,19 @@ __asm__ ( ".section \".rodata\", \"a\", @progbits\n\t"
".previous\n\t" );
/** Client certificate */
struct client_certificate client_certificate;
struct client_certificate client_certificate = {
.data = client_certificate_data,
.len = ( ( size_t ) client_certificate_len ),
};
/** Client private key */
struct client_private_key client_private_key;
struct client_private_key client_private_key = {
.data = client_private_key_data,
.len = ( ( size_t ) client_private_key_len ),
};
/** Client certificate setting */
struct setting cert_setting __setting ( SETTING_CRYPTO ) = {
static struct setting cert_setting __setting ( SETTING_CRYPTO ) = {
.name = "cert",
.description = "Client certificate",
.tag = DHCP_EB_CERT,
@ -86,7 +99,7 @@ struct setting cert_setting __setting ( SETTING_CRYPTO ) = {
};
/** Client private key setting */
struct setting key_setting __setting ( SETTING_CRYPTO ) = {
static struct setting key_setting __setting ( SETTING_CRYPTO ) = {
.name = "key",
.description = "Client private key",
.tag = DHCP_EB_KEY,
@ -99,45 +112,51 @@ struct setting key_setting __setting ( SETTING_CRYPTO ) = {
* @ret rc Return status code
*/
static int clientcert_apply_settings ( void ) {
static void *cert;
static void *key;
static void *cert = NULL;
static void *key = NULL;
int len;
int rc;
/* Restore default client certificate */
client_certificate.data = client_certificate_data;
client_certificate.len = ( ( size_t ) client_certificate_len );
/* Allow client certificate to be overridden only if
* not explicitly specified at build time.
*/
if ( ALLOW_CERT_OVERRIDE ) {
/* Fetch new client certificate, if any */
free ( cert );
len = fetch_setting_copy ( NULL, &cert_setting, &cert );
if ( len < 0 ) {
rc = len;
DBGC ( &client_certificate, "CLIENTCERT cannot fetch client "
"certificate: %s\n", strerror ( rc ) );
return rc;
}
if ( cert ) {
client_certificate.data = cert;
client_certificate.len = len;
}
/* Restore default client certificate */
client_certificate.data = client_certificate_data;
client_certificate.len = ( ( size_t ) client_certificate_len );
/* Restore default client private key */
client_private_key.data = client_private_key_data;
client_private_key.len = ( ( size_t ) client_private_key_len );
/* Fetch new client certificate, if any */
free ( cert );
len = fetch_setting_copy ( NULL, &cert_setting, &cert );
if ( len < 0 ) {
rc = len;
DBGC ( &client_certificate, "CLIENTCERT cannot fetch "
"client certificate: %s\n", strerror ( rc ) );
return rc;
}
if ( cert ) {
client_certificate.data = cert;
client_certificate.len = len;
}
/* Fetch new client private key, if any */
free ( key );
len = fetch_setting_copy ( NULL, &key_setting, &key );
if ( len < 0 ) {
rc = len;
DBGC ( &client_certificate, "CLIENTCERT cannot fetch client "
"private key: %s\n", strerror ( rc ) );
return rc;
}
if ( key ) {
client_private_key.data = key;
client_private_key.len = len;
/* Restore default client private key */
client_private_key.data = client_private_key_data;
client_private_key.len = ( ( size_t ) client_private_key_len );
/* Fetch new client private key, if any */
free ( key );
len = fetch_setting_copy ( NULL, &key_setting, &key );
if ( len < 0 ) {
rc = len;
DBGC ( &client_certificate, "CLIENTCERT cannot fetch "
"client private key: %s\n", strerror ( rc ) );
return rc;
}
if ( key ) {
client_private_key.data = key;
client_private_key.len = len;
}
}
/* Debug */

67
src/crypto/rootcert.c
View File

@ -36,6 +36,13 @@ FILE_LICENCE ( GPL2_OR_LATER );
/** Length of a root certificate fingerprint */
#define FINGERPRINT_LEN SHA256_DIGEST_SIZE
/* Allow trusted certificates to be overridden if not explicitly specified */
#ifdef TRUSTED
#define ALLOW_TRUST_OVERRIDE 0
#else
#define ALLOW_TRUST_OVERRIDE 1
#endif
/* Use iPXE root CA if no trusted certificates are explicitly specified */
#ifndef TRUSTED
#define TRUSTED \
@ -50,9 +57,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
static const uint8_t fingerprints[] = { TRUSTED };
/** Root certificate fingerprint setting */
struct setting trust_setting __setting ( SETTING_CRYPTO ) = {
static struct setting trust_setting __setting ( SETTING_CRYPTO ) = {
.name = "trust",
.description = "Trusted root certificate fingerprint",
.description = "Trusted root certificate fingerprints",
.tag = DHCP_EB_TRUST,
.type = &setting_type_hex,
};
@ -67,38 +74,50 @@ struct x509_root root_certificates = {
/**
* Initialise root certificate
*
* We allow the list of trusted root certificate fingerprints to be
* overridden using the "trust" setting, but only at the point of iPXE
* The list of trusted root certificates can be specified at build
* time using the TRUST= build parameter. If no certificates are
* specified, then the default iPXE root CA certificate is trusted.
*
* If no certificates were explicitly specified, then we allow the
* list of trusted root certificate fingerprints to be overridden
* using the "trust" setting, but only at the point of iPXE
* initialisation. This prevents untrusted sources of settings
* (e.g. DHCP) from subverting the chain of trust, while allowing
* trustworthy sources (e.g. VMware GuestInfo or non-volatile stored
* options) to change the trusted root certificate without requiring a
* rebuild.
* options) to specify the trusted root certificate without requiring
* a rebuild.
*/
static void rootcert_init ( void ) {
void *external;
void *external = NULL;
int len;
int rc;
/* Fetch copy of "trust" setting, if it exists. This memory
* will never be freed.
/* Allow trusted root certificates to be overridden only if
* not explicitly specified at build time.
*/
len = fetch_setting_copy ( NULL, &trust_setting, &external );
if ( len < 0 ) {
rc = len;
DBGC ( &root_certificates, "ROOTCERT cannot fetch trusted "
"root certificate fingerprints: %s\n", strerror ( rc ) );
/* No way to prevent startup; fail safe by trusting no
* certificates.
*/
root_certificates.count = 0;
return;
}
if ( ALLOW_TRUST_OVERRIDE ) {
/* Use certificates from "trust" setting, if present */
if ( external ) {
root_certificates.fingerprints = external;
root_certificates.count = ( len / FINGERPRINT_LEN );
/* Fetch copy of "trust" setting, if it exists. This
* memory will never be freed.
*/
len = fetch_setting_copy ( NULL, &trust_setting, &external );
if ( len < 0 ) {
rc = len;
DBGC ( &root_certificates, "ROOTCERT cannot fetch "
"trusted root certificate fingerprints: %s\n",
strerror ( rc ) );
/* No way to prevent startup; fail safe by
* trusting no certificates.
*/
root_certificates.count = 0;
return;
}
/* Use certificates from "trust" setting, if present */
if ( external ) {
root_certificates.fingerprints = external;
root_certificates.count = ( len / FINGERPRINT_LEN );
}
}
DBGC ( &root_certificates, "ROOTCERT using %d %s certificate(s):\n",