On Thu, 2018-11-29 at 15:27 +0300, Vitaly Chikunov wrote:
> If configured with "--with-kernel-headers=PATH" try to extract hash
> algorithms from "hash_info.h" from the kernel source tree or
> kernel-headers package located in the specified path. (Otherwise, it
> will be tried to get from the installed kernel.)
>
> This also introduces two algorithm lists, one is built-in and another is
> from the kernel source. (They should never contain conflicting algorithm
> IDs by their append-only nature.) If the digest is not found in the
> built-in list it will be searched in the list from kernel's
> "hash_info.h".
>
> This patch will allow evmctl to be just recompiled to work with digest
> algorithms introduced in the newer kernels.
>
> Suggested-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> Signed-off-by: Vitaly Chikunov <vt@xxxxxxxxxxxx>
> ---
> Changes since v1:
> - New patch.
> Changes since v2:
> - Mark PATH portion of "--with-kernel-headers=PATH" non-optional and
> change description to reflect correct behavior.
Defaulting to the currently running kernel build tree would have been
nice.
>
> configure.ac | 6 ++++++
> src/Makefile.am | 6 ++++++
> src/hash_info.gen | 43 +++++++++++++++++++++++++++++++++++++++++++
> src/libimaevm.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
> 4 files changed, 98 insertions(+), 1 deletion(-)
> create mode 100755 src/hash_info.gen
>
> diff --git a/configure.ac b/configure.ac
> index a5b4288..60f3684 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -27,12 +27,18 @@ AC_HEADER_STDC
> PKG_CHECK_MODULES(OPENSSL, [ openssl >= 0.9.8 ])
> AC_SUBST(OPENSSL_CFLAGS)
> AC_SUBST(OPENSSL_LIBS)
> +AC_SUBST(KERNEL_HEADERS)
> AC_CHECK_HEADER(unistd.h)
> AC_CHECK_HEADERS(openssl/conf.h)
>
> AC_CHECK_HEADERS(sys/xattr.h, , [AC_MSG_ERROR([sys/xattr.h header not found. You need the c-library development package.])])
> AC_CHECK_HEADERS(keyutils.h, , [AC_MSG_ERROR([keyutils.h header not found. You need the libkeyutils development package.])])
>
> +AC_ARG_WITH(kernel_headers, [AS_HELP_STRING([--with-kernel-headers=PATH],
> + [specifies the Linux kernel-headers package location or kernel root directory you want to use])],
> + [KERNEL_HEADERS="$withval"],
> + [KERNEL_HEADERS=/lib/modules/$(uname -r)/source])
> +
> #debug support - yes for a while
> PKG_ARG_ENABLE(debug, "yes", DEBUG, [Enable Debug support])
> if test $pkg_cv_enable_debug = yes; then
> diff --git a/src/Makefile.am b/src/Makefile.am
> index deb18fb..d74fc6f 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -9,6 +9,11 @@ libimaevm_la_LIBADD = $(OPENSSL_LIBS)
>
> include_HEADERS = imaevm.h
>
> +nodist_libimaevm_la_SOURCES = hash_info.h
> +BUILT_SOURCES = hash_info.h
> +hash_info.h: Makefile
> + ./hash_info.gen $(KERNEL_HEADERS) >$@
> +
> bin_PROGRAMS = evmctl
>
> evmctl_SOURCES = evmctl.c
> @@ -18,5 +23,6 @@ evmctl_LDADD = $(OPENSSL_LIBS) -lkeyutils libimaevm.la
>
> INCLUDES = -I$(top_srcdir) -include config.h
>
> +CLEANFILES = hash_info.h
> DISTCLEANFILES = @DISTCLEANFILES@
>
> diff --git a/src/hash_info.gen b/src/hash_info.gen
> new file mode 100755
> index 0000000..60fc750
> --- /dev/null
> +++ b/src/hash_info.gen
> @@ -0,0 +1,43 @@
> +#!/bin/sh
> +#
> +# Generate hash_info.h from kernel headers
> +#
> +# Copyright (C) 2018 <vt@xxxxxxxxxxxx>
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 2, or (at your option)
> +# any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +# GNU General Public License for more details.
> +
> +KERNEL_HEADERS=$1
> +HASH_INFO_H=uapi/linux/hash_info.h
> +HASH_INFO=$KERNEL_HEADERS/include/$HASH_INFO_H
> +
> +# Allow to specify kernel-headers past include/
> +if [ ! -e $HASH_INFO ]; then
> + HASH_INFO2=$KERNEL_HEADERS/$HASH_INFO_H
> + if [ -e $HASH_INFO2 ]; then
> + HASH_INFO=$HASH_INFO2
> + fi
> +fi
> +
> +if [ ! -e $HASH_INFO ]; then
> + echo "/* $HASH_INFO is not found */"
> + HASH_INFO=/dev/null
> +else
> + echo "/* $HASH_INFO is found */"
> +fi
> +
> +echo "enum hash_algo {"
> +grep HASH_ALGO_.*, $HASH_INFO
> +printf "\tHASH_ALGO__LAST\n"
> +echo "};"
> +
> +echo "const char *const hash_algo_name[HASH_ALGO__LAST] = {"
> +sed -n 's/HASH_ALGO_\(.*\),/[HASH_ALGO_\1] = "\L\1\E",/p' $HASH_INFO
> +echo "};"
Almost perfectly matches crypto/hash_crypto.c! Waiting to see if/how
the next patch addresses the differences...
> diff --git a/src/libimaevm.c b/src/libimaevm.c
> index 7b2b62c..cb4721b 100644
> --- a/src/libimaevm.c
> +++ b/src/libimaevm.c
> @@ -50,6 +50,7 @@
> #include <string.h>
> #include <stdio.h>
> #include <assert.h>
> +#include <ctype.h>
>
> #include <openssl/crypto.h>
> #include <openssl/pem.h>
> @@ -58,6 +59,7 @@
> #include <openssl/err.h>
>
> #include "imaevm.h"
> +#include "hash_info.h"
>
> const char *const pkey_hash_algo[PKEY_HASH__LAST] = {
> [PKEY_HASH_MD4] = "md4",
> @@ -153,6 +155,17 @@ void dump(const void *ptr, int len)
> do_dump(stdout, ptr, len, true);
> }
>
> +const char *get_hash_algo_by_id(int algo)
> +{
> + if (algo < PKEY_HASH__LAST)
> + return pkey_hash_algo[algo];
> + if (algo < HASH_ALGO__LAST)
> + return hash_algo_name[algo];
> +
> + log_err("digest %d not found\n", algo);
> + return "unknown";
> +}
> +
> int get_filesize(const char *filename)
> {
> struct stat stats;
> @@ -528,15 +541,44 @@ int verify_hash_v2(const char *file, const unsigned char *hash, int size,
> return 0;
> }
>
> +/* compare algo names case insensitively and ignoring separators */
> +static int algocmp(const char *a, const char *b)
> +{
> + while (*a && *b) {
> + int cha, chb;
> +
> + cha = tolower((unsigned char)*a++);
> + if (!isalnum(cha))
> + continue;
> + chb = tolower((unsigned char)*b++);
> + if (!isalnum(chb)) {
> + a--;
> + continue;
> + }
> + if (cha != chb)
> + return -1;
> + }
> + return *a || *b;
> +}
> +
> int get_hash_algo(const char *algo)
> {
> int i;
>
> + /* first iterate over builtin algorithms */
> for (i = 0; i < PKEY_HASH__LAST; i++)
> if (pkey_hash_algo[i] &&
> !strcmp(algo, pkey_hash_algo[i]))
> return i;
>
> + /* iterate over algorithms provided by kernel-headers */
> + for (i = 0; i < HASH_ALGO__LAST; i++) {
> + if (hash_algo_name[i] &&
> + !algocmp(algo, hash_algo_name[i]))
> + return i;
> + }
Assuming the two lists are in sync, which they should be, "i" could be
set to PKEY_HASH__LAST.
Mimi
> +
> + log_info("digest %s not found, fall back to sha1\n", algo);
> return PKEY_HASH_SHA1;
> }
>
> @@ -611,7 +653,7 @@ int ima_verify_signature(const char *file, unsigned char *sig, int siglen,
> return -1;
> }
> /* Use hash algorithm as retrieved from signature */
> - params.hash_algo = pkey_hash_algo[sig_hash_algo];
> + params.hash_algo = get_hash_algo_by_id(sig_hash_algo);
>
> /*
> * Validate the signature based on the digest included in the
