From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F1A502749DA for ; Mon, 15 Sep 2025 05:55:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757915738; cv=none; b=AD9Pze9AcR9L8s8sCAWUy13gh3mNkPzSsKms6Pl1/jMEDrzWxGwRWlyagMp+9OcTCIJNt057mjDJiMu3hDWh0NM1jwDqMJEOQMPJ48SsxS7O2WodptZvmnxtyl0XszsSRHiAJ1Eaf+v1DH8Vq5kp2fsv0PZqhfA0+50Ss5BYOAw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757915738; c=relaxed/simple; bh=DbYsO7UJQJRjzTAl4hsAi+uv5Z0ebRu1GjxF1gpkvJY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TLldUDgBW4pP2H4lGKbFnX+gZTZtqLX9kMUsPBENIYnQIo2H8Z3KntwvNOUPhVCUK9pahK5LIkjq1earEd6++U1zJ3Uj5fp562/sVep2xjwKZUEoEbD/F1fjXLWIe44AOqbArgdArp7aYMu9w1/7LD8Rsojg16LwdxMIyryoeQE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Ey9+Pde3; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ey9+Pde3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1757915735; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PgzCsQOKmacoCjP/GBUfHiLtpkuIZsT3t9XMSe2iV7U=; b=Ey9+Pde3xvjEz/agHISwelVwUa2YRJmsIhgi6foc9d2dBPqSqD/57r9dzzx9L046IX8NCP 8wWpEoFBYUbaYZrmbvhO2wxuQemmFxP2bhz+0LYBwdjVd313ZbsIgM6ccxwz5ncC17NM0x Npw6D6lQOXaO1+3WnPbQh+tMN4iS96c= Received: from mail-pg1-f199.google.com (mail-pg1-f199.google.com [209.85.215.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-556-vWixbYKUMCOzgwGipdjsoQ-1; Mon, 15 Sep 2025 01:55:34 -0400 X-MC-Unique: vWixbYKUMCOzgwGipdjsoQ-1 X-Mimecast-MFC-AGG-ID: vWixbYKUMCOzgwGipdjsoQ_1757915733 Received: by mail-pg1-f199.google.com with SMTP id 41be03b00d2f7-b54d0ffd172so350245a12.0 for ; Sun, 14 Sep 2025 22:55:34 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757915733; x=1758520533; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=PgzCsQOKmacoCjP/GBUfHiLtpkuIZsT3t9XMSe2iV7U=; b=UtxUxi7d2w9axvjN3vzT3nH0hUfQJouiA2AhG5To/T3xnWlpm4So9DNV+rzFtoaTCO d33UiMlRNbdoykJMrsRPrWChC25hiudA9nlxgb8GMyRQJE6iQD/YtVdkOP6umillPS/6 s6IoPFSBrMogaq301UtIONDK9laFahtobLXOBSOS+1EZL2diB9bqtqzdYLw53dGdsX9f FzfOODkP+t5YTvLMSw3cqrhFBM5j43AOAcx5SpJldLVVmn7j4L9mDw7vQhZcTWso/zo8 Dt/J3Hlkb+v9PcW2DzB3TQ+Iw2kcNBWQIVubBTr2mUXH7JhmjGCSxzlDhtYMXgqBd+K4 DcSg== X-Gm-Message-State: AOJu0Ywl3iSMI5b8/4XOX551VkKLsyGhqqZ9BYgr2LGUeT7eLhktydY7 iwYr8Lf3vrVMzHKluvKSf1p75cpfxrpxHmKHMw75mbGUITg74/MPKInKdKm4UXz0/4oQrXCaySl 9YJ4GK3Yp8eInkD5v476I7YYmsyjgYq07bpQmnKyFUA1YgFslYaY2ax0aMSVn3fgKUkYoErpgI+ 2DrRTDKXZEVDWFKItW+vStL67PkjwfKv1dkqJDUxV6nILkNMeCXh9eTg== X-Gm-Gg: ASbGnctlELolelha0liSph1fjaULR5rDrxCI9KG0Aiqf0YuN4Yh8nJTT55vZ3h5CcEP 4YcMJ2Yg/1MI5eHAFZuQrHMs3n28xeItR+hfNCdLwvbhTguM9HzolNLqyV0LA60GBVp5Tig4Fhe Y0EKTTTYAIhmb2Y3tDa9FVxxy5pwdcgVIm4gyCff19yWa6bz1uoSDC7dcf/MWVfxc0h/m7k1zUD mYFasoaEunQTlr9AwD8Pt/HB5NGqiFyFatQ3+0p2d23bqBtRXPO7rTuHIItIJZm4l93SXNFv7m5 8SpZLEW3+9iF2FhyefdLrZvM4isguAI= X-Received: by 2002:a05:6a20:548d:b0:248:7e43:b6b8 with SMTP id adf61e73a8af0-26027c23f44mr12880585637.3.1757915733175; Sun, 14 Sep 2025 22:55:33 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGmcsBuNESqmUSaUAZsD1y3Jo2f26HFzeSrkABroCjauRovq1uR/BneKn5f+6zwo9yQ8EBy3Q== X-Received: by 2002:a05:6a20:548d:b0:248:7e43:b6b8 with SMTP id adf61e73a8af0-26027c23f44mr12880551637.3.1757915732593; Sun, 14 Sep 2025 22:55:32 -0700 (PDT) Received: from localhost ([209.132.188.88]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-77618a7feefsm8575003b3a.58.2025.09.14.22.55.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 14 Sep 2025 22:55:32 -0700 (PDT) From: Coiby Xu To: linux-integrity@vger.kernel.org, Mimi Zohar Cc: Roberto Sassu , Dmitry Kasatkin , Eric Snowberg , Paul Moore , James Morris , "Serge E. Hallyn" , linux-security-module@vger.kernel.org (open list:SECURITY SUBSYSTEM), linux-kernel@vger.kernel.org (open list) Subject: [PATCH v3] ima: don't clear IMA_DIGSIG flag when setting or removing non-IMA xattr Date: Mon, 15 Sep 2025 13:55:23 +0800 Message-ID: <20250915055524.2187783-1-coxu@redhat.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250902042515.759750-1-coxu@redhat.com> References: <20250902042515.759750-1-coxu@redhat.com> Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently when both IMA and EVM are in fix mode, the IMA signature will be reset to IMA hash if a program first stores IMA signature in security.ima and then writes/removes some other security xattr for the file. For example, on Fedora, after booting the kernel with "ima_appraise=fix evm=fix ima_policy=appraise_tcb" and installing rpm-plugin-ima, installing/reinstalling a package will not make good reference IMA signature generated. Instead IMA hash is generated, # getfattr -m - -d -e hex /usr/bin/bash # file: usr/bin/bash security.ima=0x0404... This happens because when setting security.selinux, the IMA_DIGSIG flag that had been set early was cleared. As a result, IMA hash is generated when the file is closed. Similarly, IMA signature can be cleared on file close after removing security xattr like security.evm or setting/removing ACL. Prevent replacing the IMA file signature with a file hash, by preventing the IMA_DIGSIG flag from being reset. Here's a minimal C reproducer which sets security.selinux as the last step which can also replaced by removing security.evm or setting ACL, #include #include #include #include #include #include int main() { const char* file_path = "/usr/sbin/test_binary"; const char* hex_string = "030204d33204490066306402304"; int length = strlen(hex_string); char* ima_attr_value; int fd; fd = open(file_path, O_WRONLY|O_CREAT|O_EXCL, 0644); if (fd == -1) { perror("Error opening file"); return 1; } ima_attr_value = (char*)malloc(length / 2 ); for (int i = 0, j = 0; i < length; i += 2, j++) { sscanf(hex_string + i, "%2hhx", &ima_attr_value[j]); } if (fsetxattr(fd, "security.ima", ima_attr_value, length/2, 0) == -1) { perror("Error setting extended attribute"); close(fd); return 1; } const char* selinux_value= "system_u:object_r:bin_t:s0"; if (fsetxattr(fd, "security.selinux", selinux_value, strlen(selinux_value), 0) == -1) { perror("Error setting extended attribute"); close(fd); return 1; } close(fd); return 0; } Signed-off-by: Coiby Xu --- security/integrity/ima/ima_appraise.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index f435eff4667f..5149ff4fd50d 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -694,6 +694,15 @@ static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, return 0; } +/* + * ima_reset_appraise_flags - reset ima_iint_cache flags + * + * @digsig: whether to clear/set IMA_DIGSIG flag, tristate values + * 0: clear IMA_DIGSIG + * 1: set IMA_DIGSIG + * -1: don't change IMA_DIGSIG + * + */ static void ima_reset_appraise_flags(struct inode *inode, int digsig) { struct ima_iint_cache *iint; @@ -706,9 +715,9 @@ static void ima_reset_appraise_flags(struct inode *inode, int digsig) return; iint->measured_pcrs = 0; set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); - if (digsig) + if (digsig == 1) set_bit(IMA_DIGSIG, &iint->atomic_flags); - else + else if (digsig == 0) clear_bit(IMA_DIGSIG, &iint->atomic_flags); } @@ -794,6 +803,8 @@ static int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG); } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) { digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG); + } else { + digsig = -1; } if (result == 1 || evm_revalidate_status(xattr_name)) { ima_reset_appraise_flags(d_backing_inode(dentry), digsig); @@ -807,7 +818,7 @@ static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, const char *acl_name, struct posix_acl *kacl) { if (evm_revalidate_status(acl_name)) - ima_reset_appraise_flags(d_backing_inode(dentry), 0); + ima_reset_appraise_flags(d_backing_inode(dentry), -1); return 0; } @@ -815,11 +826,13 @@ static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, static int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry, const char *xattr_name) { - int result; + int result, digsig = -1; result = ima_protect_xattr(dentry, xattr_name, NULL, 0); if (result == 1 || evm_revalidate_status(xattr_name)) { - ima_reset_appraise_flags(d_backing_inode(dentry), 0); + if (!strcmp(xattr_name, XATTR_NAME_IMA)) + digsig = 0; + ima_reset_appraise_flags(d_backing_inode(dentry), digsig); if (result == 1) result = 0; } base-commit: 7aac71907bdea16e2754a782b9d9155449a9d49d -- 2.51.0