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Ts'o" Subject: [PATCH v9 2/3] fdt: add support for rng-seed Date: Thu, 22 Aug 2019 15:15:22 +0800 Message-Id: <20190822071522.143986-3-hsinyi@chromium.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190822071522.143986-1-hsinyi@chromium.org> References: <20190822071522.143986-1-hsinyi@chromium.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190822_001646_356728_EC6FEB0C X-CRM114-Status: GOOD ( 21.78 ) X-Spam-Score: -0.2 (/) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-0.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:441 listed in] [list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kate Stewart , Peter Zijlstra , Catalin Marinas , Mukesh Ojha , Grzegorz Halat , "H . Peter Anvin" , Guenter Roeck , Will Deacon , Marek Szyprowski , Rob Herring , Daniel Thompson , Anders Roxell , Yury Norov , Marc Zyngier , Russell King , Aaro Koskinen , Ingo Molnar , Viresh Kumar , Waiman Long , "Paul E . McKenney" , Wei Li , Alexey Dobriyan , Julien Thierry , Len Brown , Kees Cook , Arnd Bergmann , Rik van Riel , Stephen Boyd , Shaokun Zhang , Mike Rapoport , Borislav Petkov , Josh Poimboeuf , Thomas Gleixner , Greg Kroah-Hartman , Marcelo Tosatti , linux-kernel@vger.kernel.org, Armijn Hemel , Jiri Kosina , Mathieu Desnoyers , Andrew Morton , Tim Chen , "David S . Miller" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Introducing a chosen node, rng-seed, which is an entropy that can be passed to kernel called very early to increase initial device randomness. Bootloader should provide this entropy and the value is read from /chosen/rng-seed in DT. Obtain of_fdt_crc32 for CRC check after early_init_dt_scan_nodes(), since early_init_dt_scan_chosen() would modify fdt to erase rng-seed. Add a new interface add_bootloader_randomness() for rng-seed use case. Depends on whether the seed is trustworthy, rng seed would be passed to add_hwgenerator_randomness(). Otherwise it would be passed to add_device_randomness(). Decision is controlled by kernel config RANDOM_TRUST_BOOTLOADER. Signed-off-by: Hsin-Yi Wang Reviewed-by: Stephen Boyd Reviewed-by: Rob Herring Reviewed-by: Theodore Ts'o --- Change from v8: * Add a new interface add_bootloader_randomness * Add a new kernel config --- drivers/char/Kconfig | 10 ++++++++++ drivers/char/random.c | 15 +++++++++++++++ drivers/of/fdt.c | 14 ++++++++++++-- include/linux/random.h | 1 + 4 files changed, 38 insertions(+), 2 deletions(-) diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig index 96156c729a31..5974a5906fd0 100644 --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -551,3 +551,13 @@ config RANDOM_TRUST_CPU has not installed a hidden back door to compromise the CPU's random number generation facilities. This can also be configured at boot with "random.trust_cpu=on/off". + +config RANDOM_TRUST_BOOTLOADER + bool "Trust the bootloader to initialize Linux's CRNG" + default n + help + Bootloader could provide rng-seed set in /chosen/rng-seed in DT to help + increase initial device randomness. Assume the entropy provided is + trustworthy, it would be regarded as true hardware RNGs and update the + entropy estimate. Otherwise it would be regarded as device input that + could help mix the entropy pool, but won't be added to actual entropy. \ No newline at end of file diff --git a/drivers/char/random.c b/drivers/char/random.c index 5d5ea4ce1442..29d3ff3de1e1 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -2445,3 +2445,18 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, credit_entropy_bits(poolp, entropy); } EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); + +/* Handle random seed passed by bootloader. + * If the seed is trustworthy, it would be regarded as hardware RNGs. Otherwise + * it would be regarded as device data. + * The decision is controlled by CONFIG_RANDOM_TRUST_BOOTLOADER. + */ +void add_bootloader_randomness(const void *buf, unsigned int size) +{ +#ifdef CONFIG_RANDOM_TRUST_BOOTLOADER + add_hwgenerator_randomness(buf, size, size * 8); +#else + add_device_randomness(buf, size); +#endif +} +EXPORT_SYMBOL_GPL(add_bootloader_randomness); \ No newline at end of file diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index 9cdf14b9aaab..7d97ab6d0e31 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -24,6 +24,7 @@ #include #include #include +#include #include /* for COMMAND_LINE_SIZE */ #include @@ -1044,6 +1045,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname, { int l; const char *p; + const void *rng_seed; pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname); @@ -1078,6 +1080,14 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname, pr_debug("Command line is: %s\n", (char*)data); + rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l); + if (rng_seed && l > 0) { + add_bootloader_randomness(rng_seed, l); + + /* try to clear seed so it won't be found. */ + fdt_nop_property(initial_boot_params, node, "rng-seed"); + } + /* break now */ return 1; } @@ -1166,8 +1176,6 @@ bool __init early_init_dt_verify(void *params) /* Setup flat device-tree pointer */ initial_boot_params = params; - of_fdt_crc32 = crc32_be(~0, initial_boot_params, - fdt_totalsize(initial_boot_params)); return true; } @@ -1197,6 +1205,8 @@ bool __init early_init_dt_scan(void *params) return false; early_init_dt_scan_nodes(); + of_fdt_crc32 = crc32_be(~0, initial_boot_params, + fdt_totalsize(initial_boot_params)); return true; } diff --git a/include/linux/random.h b/include/linux/random.h index 1f7dced2bba6..f189c927fdea 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -19,6 +19,7 @@ struct random_ready_callback { }; extern void add_device_randomness(const void *, unsigned int); +extern void add_bootloader_randomness(const void *, unsigned int); #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__) static inline void add_latent_entropy(void)