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(dynamic-2a00-1028-838d-271e-8e3b-4aff-fe4c-a100.ipv6.o2.cz. [2a00:1028:838d:271e:8e3b:4aff:fe4c:a100]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45eb6d4741bsm36462739f8f.22.2026.05.26.04.58.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 May 2026 04:58:31 -0700 (PDT) Message-ID: <885a7940-3fcd-4fc4-b80e-cd82a817defd@suse.com> Date: Tue, 26 May 2026 13:58:29 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 08/14] module: Move authentication logic into dedicated new file To: =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Nathan Chancellor , Nicolas Schier , Arnd Bergmann , Luis Chamberlain , Sami Tolvanen , Daniel Gomez , Paul Moore , James Morris , "Serge E. Hallyn" , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Naveen N Rao , Mimi Zohar , Roberto Sassu , Dmitry Kasatkin , Eric Snowberg , Nicolas Schier , Daniel Gomez , Aaron Tomlin , "Christophe Leroy (CS GROUP)" , Nicolas Bouchinet , Xiu Jianfeng , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , bpf@vger.kernel.org, =?UTF-8?Q?Fabian_Gr=C3=BCnbichler?= , Arnout Engelen , Mattia Rizzolo , kpcyrd , Christian Heusel , =?UTF-8?Q?C=C3=A2ju_Mihai-Drosi?= , Eric Biggers , Sebastian Andrzej Siewior , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-modules@vger.kernel.org, linux-security-module@vger.kernel.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-integrity@vger.kernel.org, debian-kernel@lists.debian.org References: <20260505-module-hashes-v5-0-e174a5a49fce@weissschuh.net> <20260505-module-hashes-v5-8-e174a5a49fce@weissschuh.net> Content-Language: en-US From: Petr Pavlu In-Reply-To: <20260505-module-hashes-v5-8-e174a5a49fce@weissschuh.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/5/26 11:05 AM, Thomas Weißschuh wrote: > The module authentication functionality will also be used by the > hash-based module authentication. To make it usable even if > CONFIG_MODULE_SIG is disabled, move it to a new file. > > Signed-off-by: Thomas Weißschuh > --- > [...] > diff --git a/kernel/module/auth.c b/kernel/module/auth.c > index 956ac63d9d33..831a13eb0c9b 100644 > --- a/kernel/module/auth.c > +++ b/kernel/module/auth.c > @@ -5,10 +5,16 @@ > * Written by David Howells (dhowells@redhat.com) > */ > > +#include > #include > #include > +#include > #include > +#include > +#include > #include > +#include > +#include "internal.h" > > #undef MODULE_PARAM_PREFIX > #define MODULE_PARAM_PREFIX "module." > @@ -30,3 +36,82 @@ void set_module_sig_enforced(void) > { > sig_enforce = true; > } > + > +static int mod_verify_sig(const void *mod, struct load_info *info) > +{ > + struct module_signature ms; > + size_t sig_len, modlen = info->len; > + int ret; > + > + if (modlen <= sizeof(ms)) > + return -EBADMSG; > + > + memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms)); > + > + ret = mod_check_sig(&ms, modlen, "module"); > + if (ret) > + return ret; > + > + sig_len = be32_to_cpu(ms.sig_len); > + modlen -= sig_len + sizeof(ms); > + info->len = modlen; > + > + return module_sig_check(mod, modlen, mod + modlen, sig_len); > +} > + > +int module_auth_check(struct load_info *info, int flags) > +{ > + int err = -ENODATA; > + const unsigned long markerlen = sizeof(MODULE_SIGNATURE_MARKER) - 1; > + const char *reason; > + const void *mod = info->hdr; > + bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS | > + MODULE_INIT_IGNORE_VERMAGIC); > + /* > + * Do not allow mangled modules as a module with version information > + * removed is no longer the module that was signed. > + */ > + if (!mangled_module && > + info->len > markerlen && > + memcmp(mod + info->len - markerlen, MODULE_SIGNATURE_MARKER, markerlen) == 0) { > + /* We truncate the module to discard the signature */ > + info->len -= markerlen; > + err = mod_verify_sig(mod, info); > + if (!err) { > + info->auth_ok = true; > + return 0; > + } > + } > + > + /* > + * We don't permit modules to be loaded into the trusted kernels > + * without a valid signature on them, but if we're not enforcing, > + * certain errors are non-fatal. > + */ > + switch (err) { > + case -ENODATA: > + reason = "unsigned module"; > + break; > + case -ENOPKG: > + reason = "module with unsupported crypto"; > + break; > + case -ENOKEY: > + reason = "module with unavailable key"; > + break; > + > + default: > + /* > + * All other errors are fatal, including lack of memory, > + * unparseable signatures, and signature check failures -- > + * even if signatures aren't required. > + */ > + return err; > + } > + > + if (is_module_sig_enforced()) { > + pr_notice("Loading of %s is rejected\n", reason); > + return -EKEYREJECTED; > + } > + > + return security_locked_down(LOCKDOWN_MODULE_SIGNATURE); > +} The resulting call chain of the module authentication/signature functions is as follows: ima_read_modsig() -----------------------------, v module_auth_check() -> mod_verify_sig() -> mod_check_sig() | |-> module_sig_check() '-> module_hash_check() I think this logic is quite hard to follow because mod_verify_sig(), mod_check_sig() and module_sig_check() have very similar names. The naming of module_auth_check(), module_sig_check() and module_hash_check() looks good to me, but I would prefer to rename mod_check_sig() and mod_verify_sig(). Perhaps mod_check_sig() could be renamed to mod_check_sig_header(), and mod_verify_sig() to mod_dispatch_auth_check()? Otherwise, the patch looks ok to me. Feel free to add: Reviewed-by: Petr Pavlu -- Thanks, Petr