From 4c0b4b1d1ae0cbc86f150e2905a1c3d2a17b7c1e Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 1 Jul 2014 16:02:52 +0100 Subject: pefile: Parse the "Microsoft individual code signing" data blob The PKCS#7 certificate should contain a "Microsoft individual code signing" data blob as its signed content. This blob contains a digest of the signed content of the PE binary and the OID of the digest algorithm used (typically SHA256). Signed-off-by: David Howells Acked-by: Vivek Goyal Reviewed-by: Kees Cook --- crypto/asymmetric_keys/Makefile | 9 ++- crypto/asymmetric_keys/mscode.asn1 | 28 ++++++++ crypto/asymmetric_keys/mscode_parser.c | 120 +++++++++++++++++++++++++++++++++ crypto/asymmetric_keys/verify_pefile.c | 7 ++ crypto/asymmetric_keys/verify_pefile.h | 5 ++ 5 files changed, 168 insertions(+), 1 deletion(-) create mode 100644 crypto/asymmetric_keys/mscode.asn1 create mode 100644 crypto/asymmetric_keys/mscode_parser.c (limited to 'crypto') diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile index 3e4de5297015..e47fcd9ac5e8 100644 --- a/crypto/asymmetric_keys/Makefile +++ b/crypto/asymmetric_keys/Makefile @@ -54,4 +54,11 @@ pkcs7_test_key-y := \ obj-$(CONFIG_SIGNED_PE_FILE_VERIFICATION) += verify_signed_pefile.o verify_signed_pefile-y := \ - verify_pefile.o + verify_pefile.o \ + mscode_parser.o \ + mscode-asn1.o + +$(obj)/mscode_parser.o: $(obj)/mscode-asn1.h $(obj)/mscode-asn1.h +$(obj)/mscode-asn1.o: $(obj)/mscode-asn1.c $(obj)/mscode-asn1.h + +clean-files += mscode-asn1.c mscode-asn1.h diff --git a/crypto/asymmetric_keys/mscode.asn1 b/crypto/asymmetric_keys/mscode.asn1 new file mode 100644 index 000000000000..6d09ba48c41c --- /dev/null +++ b/crypto/asymmetric_keys/mscode.asn1 @@ -0,0 +1,28 @@ +--- Microsoft individual code signing data blob parser +--- +--- Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. +--- Written by David Howells (dhowells@redhat.com) +--- +--- 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. +--- + +MSCode ::= SEQUENCE { + type SEQUENCE { + contentType ContentType, + parameters ANY + }, + content SEQUENCE { + digestAlgorithm DigestAlgorithmIdentifier, + digest OCTET STRING ({ mscode_note_digest }) + } +} + +ContentType ::= OBJECT IDENTIFIER ({ mscode_note_content_type }) + +DigestAlgorithmIdentifier ::= SEQUENCE { + algorithm OBJECT IDENTIFIER ({ mscode_note_digest_algo }), + parameters ANY OPTIONAL +} diff --git a/crypto/asymmetric_keys/mscode_parser.c b/crypto/asymmetric_keys/mscode_parser.c new file mode 100644 index 000000000000..09336c32b3d4 --- /dev/null +++ b/crypto/asymmetric_keys/mscode_parser.c @@ -0,0 +1,120 @@ +/* Parse a Microsoft Individual Code Signing blob + * + * Copyright (C) 2014 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * 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) "MSCODE: "fmt +#include +#include +#include +#include +#include +#include "verify_pefile.h" +#include "mscode-asn1.h" + +/* + * Parse a Microsoft Individual Code Signing blob + */ +int mscode_parse(struct pefile_context *ctx) +{ + const void *content_data; + size_t data_len; + int ret; + + ret = pkcs7_get_content_data(ctx->pkcs7, &content_data, &data_len, 1); + + if (ret) { + pr_debug("PKCS#7 message does not contain data\n"); + return ret; + } + + pr_devel("Data: %zu [%*ph]\n", data_len, (unsigned)(data_len), + content_data); + + return asn1_ber_decoder(&mscode_decoder, ctx, content_data, data_len); +} + +/* + * Check the content type OID + */ +int mscode_note_content_type(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + enum OID oid; + + oid = look_up_OID(value, vlen); + if (oid == OID__NR) { + char buffer[50]; + + sprint_oid(value, vlen, buffer, sizeof(buffer)); + pr_err("Unknown OID: %s\n", buffer); + return -EBADMSG; + } + + if (oid != OID_msIndividualSPKeyPurpose) { + pr_err("Unexpected content type OID %u\n", oid); + return -EBADMSG; + } + + return 0; +} + +/* + * Note the digest algorithm OID + */ +int mscode_note_digest_algo(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct pefile_context *ctx = context; + char buffer[50]; + enum OID oid; + + oid = look_up_OID(value, vlen); + switch (oid) { + case OID_md4: + ctx->digest_algo = HASH_ALGO_MD4; + break; + case OID_md5: + ctx->digest_algo = HASH_ALGO_MD5; + break; + case OID_sha1: + ctx->digest_algo = HASH_ALGO_SHA1; + break; + case OID_sha256: + ctx->digest_algo = HASH_ALGO_SHA256; + break; + + case OID__NR: + sprint_oid(value, vlen, buffer, sizeof(buffer)); + pr_err("Unknown OID: %s\n", buffer); + return -EBADMSG; + + default: + pr_err("Unsupported content type: %u\n", oid); + return -ENOPKG; + } + + return 0; +} + +/* + * Note the digest we're guaranteeing with this certificate + */ +int mscode_note_digest(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct pefile_context *ctx = context; + + ctx->digest = value; + ctx->digest_len = vlen; + return 0; +} diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c index 13f3b44b5046..b975918e82d2 100644 --- a/crypto/asymmetric_keys/verify_pefile.c +++ b/crypto/asymmetric_keys/verify_pefile.c @@ -245,6 +245,13 @@ int verify_pefile_signature(const void *pebuf, unsigned pelen, goto error; } + ret = mscode_parse(&ctx); + if (ret < 0) + goto error; + + pr_debug("Digest: %u [%*ph]\n", + ctx.digest_len, ctx.digest_len, ctx.digest); + ret = -ENOANO; // Not yet complete error: diff --git a/crypto/asymmetric_keys/verify_pefile.h b/crypto/asymmetric_keys/verify_pefile.h index e165d23458d4..55d5f7ebc45a 100644 --- a/crypto/asymmetric_keys/verify_pefile.h +++ b/crypto/asymmetric_keys/verify_pefile.h @@ -35,3 +35,8 @@ struct pefile_context { pr_devel("==> %s("FMT")\n", __func__, ##__VA_ARGS__) #define kleave(FMT, ...) \ pr_devel("<== %s()"FMT"\n", __func__, ##__VA_ARGS__) + +/* + * mscode_parser.c + */ +extern int mscode_parse(struct pefile_context *ctx); -- cgit v1.2.3-59-g8ed1b