| 1 | /* Module signature checker |
| 2 | * |
| 3 | * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. |
| 4 | * Written by David Howells (dhowells@redhat.com) |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public Licence |
| 8 | * as published by the Free Software Foundation; either version |
| 9 | * 2 of the Licence, or (at your option) any later version. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/kernel.h> |
| 13 | #include <keys/system_keyring.h> |
| 14 | #include <crypto/public_key.h> |
| 15 | #include "module-internal.h" |
| 16 | |
| 17 | /* |
| 18 | * Module signature information block. |
| 19 | * |
| 20 | * The constituents of the signature section are, in order: |
| 21 | * |
| 22 | * - Signer's name |
| 23 | * - Key identifier |
| 24 | * - Signature data |
| 25 | * - Information block |
| 26 | */ |
| 27 | struct module_signature { |
| 28 | u8 algo; /* Public-key crypto algorithm [0] */ |
| 29 | u8 hash; /* Digest algorithm [0] */ |
| 30 | u8 id_type; /* Key identifier type [PKEY_ID_PKCS7] */ |
| 31 | u8 signer_len; /* Length of signer's name [0] */ |
| 32 | u8 key_id_len; /* Length of key identifier [0] */ |
| 33 | u8 __pad[3]; |
| 34 | __be32 sig_len; /* Length of signature data */ |
| 35 | }; |
| 36 | |
| 37 | /* |
| 38 | * Verify the signature on a module. |
| 39 | */ |
| 40 | int mod_verify_sig(const void *mod, unsigned long *_modlen) |
| 41 | { |
| 42 | struct module_signature ms; |
| 43 | size_t modlen = *_modlen, sig_len; |
| 44 | |
| 45 | pr_devel("==>%s(,%zu)\n", __func__, modlen); |
| 46 | |
| 47 | if (modlen <= sizeof(ms)) |
| 48 | return -EBADMSG; |
| 49 | |
| 50 | memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms)); |
| 51 | modlen -= sizeof(ms); |
| 52 | |
| 53 | sig_len = be32_to_cpu(ms.sig_len); |
| 54 | if (sig_len >= modlen) |
| 55 | return -EBADMSG; |
| 56 | modlen -= sig_len; |
| 57 | *_modlen = modlen; |
| 58 | |
| 59 | if (ms.id_type != PKEY_ID_PKCS7) { |
| 60 | pr_err("Module is not signed with expected PKCS#7 message\n"); |
| 61 | return -ENOPKG; |
| 62 | } |
| 63 | |
| 64 | if (ms.algo != 0 || |
| 65 | ms.hash != 0 || |
| 66 | ms.signer_len != 0 || |
| 67 | ms.key_id_len != 0 || |
| 68 | ms.__pad[0] != 0 || |
| 69 | ms.__pad[1] != 0 || |
| 70 | ms.__pad[2] != 0) { |
| 71 | pr_err("PKCS#7 signature info has unexpected non-zero params\n"); |
| 72 | return -EBADMSG; |
| 73 | } |
| 74 | |
| 75 | return system_verify_data(mod, modlen, mod + modlen, sig_len, |
| 76 | VERIFYING_MODULE_SIGNATURE); |
| 77 | } |