From patchwork Fri Nov 15 13:35:32 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Christian_G=C3=B6ttsche?= X-Patchwork-Id: 13876265 Received: from server02.seltendoof.de (server02.seltendoof.de [168.119.48.163]) (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 AAEAB1CDA09; Fri, 15 Nov 2024 13:37:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=168.119.48.163 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731677833; cv=none; b=rhhOSQIP4g05A+bLY+glez0uHjsA/DU9obgFIRe+cN17TYZtLaPDpXNGpKyjB1K2BDVWOw5tnzzfkfb7q0piXzhaftsmipKu59Zt5Ye2qgFPQb70MmhHGg0JO2AFdWA9RkGcno22cbfZL1+PFEC0Tkaf6Le7lrxaD1ywKR5OoMw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731677833; c=relaxed/simple; bh=wbZeP+FqrGHfxL8k2FfPz/C2u93Wbv/O5/Sm2nOrQSg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=jRadhXt1qrlC9v5eVw+FlOKhxTAR6Gft7TnkIxE2cXYsNhnOJUVzjZyYQUaaUUKRnup6+Ylp24TArkCjBMDMm/bsCAlocO0nAOBcK1Lb74h7yWROUw9IsY57NM5x8IfKevEj0LOzhfi0ZKPOsmYquY7n+Kq/AXdGYFyY9Vi63mE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=seltendoof.de; spf=pass smtp.mailfrom=seltendoof.de; dkim=pass (2048-bit key) header.d=seltendoof.de header.i=@seltendoof.de header.b=CS9awf2R; arc=none smtp.client-ip=168.119.48.163 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=seltendoof.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=seltendoof.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=seltendoof.de header.i=@seltendoof.de header.b="CS9awf2R" From: =?utf-8?q?Christian_G=C3=B6ttsche?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=seltendoof.de; s=2023072701; t=1731677829; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NNe8CasdOqHvzGa8GCttK8HX6bCvp4pEw3d94J1Ra9E=; b=CS9awf2RoaagJnJBZq/a9g7JaemxTgRXpvsJdf9eu9TFwtvifeg6/SK8yRJRNozbQNPAau ASo2kG0r0vH5k6aJDflys5AbFl5y1RuidGJu3Y1FH5G1zUp2gpJiL72kLnqJqKE2SD2t4R SVPjamMfvn6VGO6TILl4SVTVYC6VHS42FmbIk9OJ6FTS4Bpzqr+/F9aWuPwqFtDLXyUW+g W83Y2i53YwllTiGypLzgZ5EganlQTsrc2DAyNfFB/Qnu9Mdeyj4BmjZhL9GVKDfjUOKsLT lAATwLpwM9XGBo66a2BuZ+e+yjADXE2pkZf3aJvvCgxvaszxdt1J//V6yzycCA== To: selinux@vger.kernel.org Cc: =?utf-8?q?Christian_G=C3=B6ttsche?= , Paul Moore , Stephen Smalley , Ondrej Mosnacek , Casey Schaufler , Canfeng Guo , Mimi Zohar , GUO Zihua , =?utf-8?q?Thi=C3=A9baud_Weksteen?= , linux-kernel@vger.kernel.org Subject: [RFC PATCH 13/22] selinux: validate constraints Date: Fri, 15 Nov 2024 14:35:32 +0100 Message-ID: <20241115133619.114393-13-cgoettsche@seltendoof.de> In-Reply-To: <20241115133619.114393-1-cgoettsche@seltendoof.de> References: <20241115133619.114393-1-cgoettsche@seltendoof.de> Reply-To: cgzones@googlemail.com Precedence: bulk X-Mailing-List: selinux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Christian Göttsche Validate constraint expressions during reading the policy. Avoid the usage of BUG() on constraint evaluation, to mitigate malformed policies halting the system. Closes: https://github.com/SELinuxProject/selinux-testsuite/issues/76 Signed-off-by: Christian Göttsche --- security/selinux/ss/policydb.c | 61 ++++++++++++++++++++++++++++++++-- security/selinux/ss/services.c | 55 +++++++++++++++--------------- 2 files changed, 88 insertions(+), 28 deletions(-) diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c index 5ba1e8d483fb..5d99e1498b55 100644 --- a/security/selinux/ss/policydb.c +++ b/security/selinux/ss/policydb.c @@ -1251,6 +1251,8 @@ static int read_cons_helper(struct policydb *p, struct constraint_node **nodep, return rc; c->permissions = le32_to_cpu(buf[0]); nexpr = le32_to_cpu(buf[1]); + if (nexpr == 0) + return -EINVAL; le = NULL; depth = -1; for (j = 0; j < nexpr; j++) { @@ -1282,15 +1284,70 @@ static int read_cons_helper(struct policydb *p, struct constraint_node **nodep, depth--; break; case CEXPR_ATTR: - if (depth == (CEXPR_MAXDEPTH - 1)) + if (depth >= (CEXPR_MAXDEPTH - 1)) return -EINVAL; depth++; break; + + switch (e->op) { + case CEXPR_EQ: + case CEXPR_NEQ: + break; + case CEXPR_DOM: + case CEXPR_DOMBY: + case CEXPR_INCOMP: + if ((e->attr & CEXPR_USER) || (e->attr & CEXPR_TYPE)) + return -EINVAL; + break; + default: + return -EINVAL; + } + + switch (e->attr) { + case CEXPR_USER: + case CEXPR_ROLE: + case CEXPR_TYPE: + case CEXPR_L1L2: + case CEXPR_L1H2: + case CEXPR_H1L2: + case CEXPR_H1H2: + case CEXPR_L1H1: + case CEXPR_L2H2: + break; + default: + return -EINVAL; + } + + break; case CEXPR_NAMES: if (!allowxtarget && (e->attr & CEXPR_XTARGET)) return -EINVAL; - if (depth == (CEXPR_MAXDEPTH - 1)) + if (depth >= (CEXPR_MAXDEPTH - 1)) + return -EINVAL; + + switch (e->op) { + case CEXPR_EQ: + case CEXPR_NEQ: + break; + default: + return -EINVAL; + } + + switch (e->attr) { + case CEXPR_USER: + case CEXPR_USER | CEXPR_TARGET: + case CEXPR_USER | CEXPR_XTARGET: + case CEXPR_ROLE: + case CEXPR_ROLE | CEXPR_TARGET: + case CEXPR_ROLE | CEXPR_XTARGET: + case CEXPR_TYPE: + case CEXPR_TYPE | CEXPR_TARGET: + case CEXPR_TYPE | CEXPR_XTARGET: + break; + default: return -EINVAL; + } + depth++; rc = ebitmap_read(&e->names, fp); if (rc) diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c index d8b5fb98adb9..b1b90f802328 100644 --- a/security/selinux/ss/services.c +++ b/security/selinux/ss/services.c @@ -278,22 +278,25 @@ static int constraint_expr_eval(struct policydb *policydb, for (e = cexpr; e; e = e->next) { switch (e->expr_type) { case CEXPR_NOT: - BUG_ON(sp < 0); + if (unlikely(sp < 0)) + goto invalid; s[sp] = !s[sp]; break; case CEXPR_AND: - BUG_ON(sp < 1); + if (unlikely(sp < 1)) + goto invalid; sp--; s[sp] &= s[sp + 1]; break; case CEXPR_OR: - BUG_ON(sp < 1); + if (unlikely(sp < 1)) + goto invalid; sp--; s[sp] |= s[sp + 1]; break; case CEXPR_ATTR: - if (sp == (CEXPR_MAXDEPTH - 1)) - return 0; + if (unlikely(sp >= (CEXPR_MAXDEPTH - 1))) + goto invalid; switch (e->attr) { case CEXPR_USER: val1 = scontext->user; @@ -369,13 +372,11 @@ static int constraint_expr_eval(struct policydb *policydb, s[++sp] = mls_level_incomp(l2, l1); continue; default: - BUG(); - return 0; + goto invalid; } break; default: - BUG(); - return 0; + goto invalid; } switch (e->op) { @@ -386,22 +387,19 @@ static int constraint_expr_eval(struct policydb *policydb, s[++sp] = (val1 != val2); break; default: - BUG(); - return 0; + goto invalid; } break; case CEXPR_NAMES: - if (sp == (CEXPR_MAXDEPTH-1)) - return 0; + if (unlikely(sp >= (CEXPR_MAXDEPTH-1))) + goto invalid; c = scontext; if (e->attr & CEXPR_TARGET) c = tcontext; else if (e->attr & CEXPR_XTARGET) { c = xcontext; - if (!c) { - BUG(); - return 0; - } + if (unlikely(!c)) + goto invalid; } if (e->attr & CEXPR_USER) val1 = c->user; @@ -409,10 +407,8 @@ static int constraint_expr_eval(struct policydb *policydb, val1 = c->role; else if (e->attr & CEXPR_TYPE) val1 = c->type; - else { - BUG(); - return 0; - } + else + goto invalid; switch (e->op) { case CEXPR_EQ: @@ -422,18 +418,25 @@ static int constraint_expr_eval(struct policydb *policydb, s[++sp] = !ebitmap_get_bit(&e->names, val1 - 1); break; default: - BUG(); - return 0; + goto invalid; } break; default: - BUG(); - return 0; + goto invalid; } } - BUG_ON(sp != 0); + if (unlikely(sp != 0)) + goto invalid; + return s[0]; + +invalid: + /* Should *never* be reached, cause malformed constraints should + * have been filtered by read_cons_helper(). + */ + WARN_ONCE(true, "SELinux: invalid constraint passed validation\n"); + return 0; } /*