cregit-Linux how code gets into the kernel

Release 4.10 crypto/asymmetric_keys/pkcs7_trust.c

/* Validate the trust chain of a PKCS#7 message.
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.

#define pr_fmt(fmt) "PKCS7: "fmt
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/asn1.h>
#include <linux/key.h>
#include <keys/asymmetric-type.h>
#include <crypto/public_key.h>
#include "pkcs7_parser.h"

 * Check the trust on one PKCS#7 SignedInfo block.

static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7, struct pkcs7_signed_info *sinfo, struct key *trust_keyring) { struct public_key_signature *sig = sinfo->sig; struct x509_certificate *x509, *last = NULL, *p; struct key *key; int ret; kenter(",%u,", sinfo->index); if (sinfo->unsupported_crypto) { kleave(" = -ENOPKG [cached]"); return -ENOPKG; } for (x509 = sinfo->signer; x509; x509 = x509->signer) { if (x509->seen) { if (x509->verified) goto verified; kleave(" = -ENOKEY [cached]"); return -ENOKEY; } x509->seen = true; /* Look to see if this certificate is present in the trusted * keys. */ key = find_asymmetric_key(trust_keyring, x509->id, x509->skid, false); if (!IS_ERR(key)) { /* One of the X.509 certificates in the PKCS#7 message * is apparently the same as one we already trust. * Verify that the trusted variant can also validate * the signature on the descendant. */ pr_devel("sinfo %u: Cert %u as key %x\n", sinfo->index, x509->index, key_serial(key)); goto matched; } if (key == ERR_PTR(-ENOMEM)) return -ENOMEM; /* Self-signed certificates form roots of their own, and if we * don't know them, then we can't accept them. */ if (x509->next == x509) { kleave(" = -ENOKEY [unknown self-signed]"); return -ENOKEY; } might_sleep(); last = x509; sig = last->sig; } /* No match - see if the root certificate has a signer amongst the * trusted keys. */ if (last && (last->sig->auth_ids[0] || last->sig->auth_ids[1])) { key = find_asymmetric_key(trust_keyring, last->sig->auth_ids[0], last->sig->auth_ids[1], false); if (!IS_ERR(key)) { x509 = last; pr_devel("sinfo %u: Root cert %u signer is key %x\n", sinfo->index, x509->index, key_serial(key)); goto matched; } if (PTR_ERR(key) != -ENOKEY) return PTR_ERR(key); } /* As a last resort, see if we have a trusted public key that matches * the signed info directly. */ key = find_asymmetric_key(trust_keyring, sinfo->sig->auth_ids[0], NULL, false); if (!IS_ERR(key)) { pr_devel("sinfo %u: Direct signer is key %x\n", sinfo->index, key_serial(key)); x509 = NULL; goto matched; } if (PTR_ERR(key) != -ENOKEY) return PTR_ERR(key); kleave(" = -ENOKEY [no backref]"); return -ENOKEY; matched: ret = verify_signature(key, sig); key_put(key); if (ret < 0) { if (ret == -ENOMEM) return ret; kleave(" = -EKEYREJECTED [verify %d]", ret); return -EKEYREJECTED; } verified: if (x509) { x509->verified = true; for (p = sinfo->signer; p != x509; p = p->signer) p->verified = true; } kleave(" = 0"); return 0; }


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/** * pkcs7_validate_trust - Validate PKCS#7 trust chain * @pkcs7: The PKCS#7 certificate to validate * @trust_keyring: Signing certificates to use as starting points * * Validate that the certificate chain inside the PKCS#7 message intersects * keys we already know and trust. * * Returns, in order of descending priority: * * (*) -EKEYREJECTED if a signature failed to match for which we have a valid * key, or: * * (*) 0 if at least one signature chain intersects with the keys in the trust * keyring, or: * * (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a * chain. * * (*) -ENOKEY if we couldn't find a match for any of the signature chains in * the message. * * May also return -ENOMEM. */
int pkcs7_validate_trust(struct pkcs7_message *pkcs7, struct key *trust_keyring) { struct pkcs7_signed_info *sinfo; struct x509_certificate *p; int cached_ret = -ENOKEY; int ret; for (p = pkcs7->certs; p; p = p->next) p->seen = false; for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring); switch (ret) { case -ENOKEY: continue; case -ENOPKG: if (cached_ret == -ENOKEY) cached_ret = -ENOPKG; continue; case 0: cached_ret = 0; continue; default: return ret; } } return cached_ret; }


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