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Subject[PATCH 3/9] pefile: Parse a PE binary and verify signature
Date
Parse a PE binary, find pkcs7 signature and verify signature.

v2:

Moved PE file parsing and signature verification in arch/x86/

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
arch/x86/Kconfig | 9 +++
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/pefile_parser.c | 145 ++++++++++++++++++++++++++++++++++++++++
arch/x86/kernel/pefile_parser.h | 31 +++++++++
4 files changed, 186 insertions(+)
create mode 100644 arch/x86/kernel/pefile_parser.c
create mode 100644 arch/x86/kernel/pefile_parser.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2cee2a6..29b9967 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1574,6 +1574,15 @@ config SECCOMP

source kernel/Kconfig.hz

+config SIGNED_PE_FILE_PARSER
+ bool "Signed PE binary parser"
+ depends on PKCS7_MESSAGE_PARSER=y
+ select ASN1
+ select OID_REGISTRY
+ ---help---
+ This option provides support for parsing signed PE
+ (Protable Executable) binaries.
+
config KEXEC
bool "kexec system call"
select BUILD_BIN2C
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index ece67cb..da7c6b3 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -106,6 +106,7 @@ obj-$(CONFIG_EFI) += sysfb_efi.o
obj-$(CONFIG_PERF_EVENTS) += perf_regs.o
obj-$(CONFIG_TRACING) += tracepoint.o
obj-$(CONFIG_IOSF_MBI) += iosf_mbi.o
+obj-$(CONFIG_SIGNED_PE_FILE_PARSER) += pefile_parser.o

###
# 64 bit specific files
diff --git a/arch/x86/kernel/pefile_parser.c b/arch/x86/kernel/pefile_parser.c
new file mode 100644
index 0000000..72bc2bb
--- /dev/null
+++ b/arch/x86/kernel/pefile_parser.c
@@ -0,0 +1,145 @@
+/* Parse a signed PE binary
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt) "PEFILE: "fmt
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/pe.h>
+#include <keys/asymmetric-subtype.h>
+#include <keys/asymmetric-parser.h>
+#include <crypto/hash.h>
+#include <crypto/pkcs7.h>
+#include "pefile_parser.h"
+
+#define kenter(FMT, ...) \
+ pr_devel("==> %s("FMT")\n", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) \
+ pr_devel("<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
+
+/*
+ * Parse a PE binary.
+ */
+static int pefile_parse_binary(const void *pebuf, unsigned int pelen,
+ struct pefile_context *ctx)
+{
+ const struct mz_hdr *mz = pebuf;
+ const struct pe_hdr *pe;
+ const struct pe32_opt_hdr *pe32;
+ const struct pe32plus_opt_hdr *pe64;
+ const struct data_directory *ddir;
+ const struct data_dirent *dde;
+ const struct section_header *secs, *sec;
+ size_t cursor, datalen = pelen;
+
+ kenter("");
+
+#define chkaddr(base, x, s) \
+ do { \
+ if ((x) < base || (s) >= datalen || (x) > datalen - (s)) \
+ return -ELIBBAD; \
+ } while (0)
+
+ chkaddr(0, 0, sizeof(*mz));
+ if (mz->magic != MZ_MAGIC)
+ return -ELIBBAD;
+ cursor = sizeof(*mz);
+
+ chkaddr(cursor, mz->peaddr, sizeof(*pe));
+ pe = pebuf + mz->peaddr;
+ if (pe->magic != PE_MAGIC)
+ return -ELIBBAD;
+ cursor = mz->peaddr + sizeof(*pe);
+
+ chkaddr(0, cursor, sizeof(pe32->magic));
+ pe32 = pebuf + cursor;
+ pe64 = pebuf + cursor;
+
+ switch (pe32->magic) {
+ case PE_OPT_MAGIC_PE32:
+ chkaddr(0, cursor, sizeof(*pe32));
+ ctx->image_checksum_offset =
+ (unsigned long)&pe32->csum - (unsigned long)pebuf;
+ ctx->header_size = pe32->header_size;
+ cursor += sizeof(*pe32);
+ ctx->n_data_dirents = pe32->data_dirs;
+ break;
+
+ case PE_OPT_MAGIC_PE32PLUS:
+ chkaddr(0, cursor, sizeof(*pe64));
+ ctx->image_checksum_offset =
+ (unsigned long)&pe64->csum - (unsigned long)pebuf;
+ ctx->header_size = pe64->header_size;
+ cursor += sizeof(*pe64);
+ ctx->n_data_dirents = pe64->data_dirs;
+ break;
+
+ default:
+ pr_debug("Unknown PEOPT magic = %04hx\n", pe32->magic);
+ return -ELIBBAD;
+ }
+
+ pr_debug("checksum @ %x\n", ctx->image_checksum_offset);
+ pr_debug("header size = %x\n", ctx->header_size);
+
+ if (cursor >= ctx->header_size || ctx->header_size >= datalen)
+ return -ELIBBAD;
+
+ if (ctx->n_data_dirents > (ctx->header_size - cursor) / sizeof(*dde))
+ return -ELIBBAD;
+
+ ddir = pebuf + cursor;
+ cursor += sizeof(*dde) * ctx->n_data_dirents;
+
+ ctx->cert_dirent_offset =
+ (unsigned long)&ddir->certs - (unsigned long)pebuf;
+ ctx->certs_size = ddir->certs.size;
+
+ if (!ddir->certs.virtual_address || !ddir->certs.size) {
+ pr_debug("Unsigned PE binary\n");
+ return -EKEYREJECTED;
+ }
+
+ chkaddr(ctx->header_size, ddir->certs.virtual_address,
+ ddir->certs.size);
+ ctx->sig_offset = ddir->certs.virtual_address;
+ ctx->sig_len = ddir->certs.size;
+ pr_debug("cert = %x @%x [%*ph]\n",
+ ctx->sig_len, ctx->sig_offset,
+ ctx->sig_len, pebuf + ctx->sig_offset);
+
+ ctx->n_sections = pe->sections;
+ if (ctx->n_sections > (ctx->header_size - cursor) / sizeof(*sec))
+ return -ELIBBAD;
+ ctx->secs = secs = pebuf + cursor;
+
+ return 0;
+}
+
+/*
+ * Parse a PE binary and verify PKCS7 signature.
+ */
+int pefile_parse_verify_sig(const void *pebuf, unsigned int pelen)
+{
+ struct pefile_context ctx;
+ int ret;
+
+ kenter("");
+
+ memset(&ctx, 0, sizeof(ctx));
+ ret = pefile_parse_binary(pebuf, pelen, &ctx);
+ if (ret < 0)
+ return ret;
+
+ /* Not yet complete */
+ return -ENOANO;
+}
diff --git a/arch/x86/kernel/pefile_parser.h b/arch/x86/kernel/pefile_parser.h
new file mode 100644
index 0000000..e28a7e1
--- /dev/null
+++ b/arch/x86/kernel/pefile_parser.h
@@ -0,0 +1,31 @@
+/* PE Binary parser bits
+ *
+ * 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.
+ */
+#include <crypto/hash_info.h>
+
+struct pefile_context {
+ unsigned header_size;
+ unsigned image_checksum_offset;
+ unsigned cert_dirent_offset;
+ unsigned n_data_dirents;
+ unsigned n_sections;
+ unsigned certs_size;
+ unsigned sig_offset;
+ unsigned sig_len;
+ const struct section_header *secs;
+ void *pkcs7;
+
+ /* PKCS#7 MS Individual Code Signing content */
+ const void *digest; /* Digest */
+ unsigned digest_len; /* Digest length */
+ enum hash_algo digest_algo; /* Digest algorithm */
+};
+
+extern int pefile_parse_verify_sig(const void *pebuf, unsigned int pelen);
--
1.9.0


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