[PATCH kexec-tools] m68k: pass rng seed via BI_VIRT_RNG_SEED

[PATCH kexec-tools] m68k: pass rng seed via BI_VIRT_RNG_SEED

[Jason A. Donenfeld]

In order to pass fresh entropy to kexec'd kernels, use BI_VIRT_RNG_SEED
for passing a seed, with the same semantics that kexec-tools currently
uses for i386's setup_data.

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
Geert - I don't have a toolchain for testing this. Could you verify it
works, if you have a chance? -Jason

 kexec/arch/m68k/bootinfo.c       | 22 ++++++++++++++++++++++
 kexec/arch/m68k/bootinfo.h       |  6 ++++++
 kexec/arch/m68k/kexec-elf-m68k.c |  1 +
 3 files changed, 29 insertions(+)

diff --git a/kexec/arch/m68k/bootinfo.c b/kexec/arch/m68k/bootinfo.c
index 18bf226..74e65a0 100644
--- a/kexec/arch/m68k/bootinfo.c
+++ b/kexec/arch/m68k/bootinfo.c
@@ -135,40 +135,45 @@ void bootinfo_print(void)
 		size = bi->size;
 		switch (tag) {
 		case BI_MACHTYPE:
 			printf("BI_MACHTYPE: 0x%08x\n", bi->machtype);
 			break;
 
 		case BI_MEMCHUNK:
 			printf("BI_MEMCHUNK: 0x%08x bytes at 0x%08x\n",
 			       bi->mem_info.size, bi->mem_info.addr);
 			break;
 
 		case BI_RAMDISK:
 			printf("BI_RAMDISK: 0x%08x bytes at 0x%08x\n",
 			       bi->mem_info.size, bi->mem_info.addr);
 			break;
 
 		case BI_COMMAND_LINE:
 			printf("BI_COMMAND_LINE: %s\n", bi->string);
 			break;
 
+		case BI_VIRT_RNG_SEED:
+			/* These are secret, so never print them to the console */
+			printf("BI_VIRT_RNG_SEED: 0x%08x bytes\n", be16_to_cpu(bi->bytes.len));
+			break;
+
 		default:
 			printf("BI tag 0x%04x size %u\n", tag, size);
 			break;
 		}
 		bi = bi_next(bi, size);
 	}
 }
 
 int bootinfo_get_memory_ranges(struct memory_range **range)
 {
 	struct memory_range *ranges;
 	unsigned int i;
 	struct bi_rec *bi;
 
 	ranges = xmalloc(num_memchunks * sizeof(struct memory_range));
 	for (i = 0, bi = NULL;
 	     i < num_memchunks && (bi = bi_find(bi, BI_MEMCHUNK)); i++) {
 		ranges[i].start = bi->mem_info.addr;
 		ranges[i].end = bi->mem_info.addr + bi->mem_info.size - 1;
 		ranges[i].type = RANGE_RAM;
@@ -195,40 +200,57 @@ void bootinfo_set_cmdline(const char *cmdline)
 	memcpy(bi->string, cmdline, size);
 }
 
 void bootinfo_set_ramdisk(unsigned long ramdisk_addr,
 			  unsigned long ramdisk_size)
 {
 	struct bi_rec *bi;
 
 	/* Remove existing ramdisk records */
 	bi_remove(BI_RAMDISK);
 
 	if (!ramdisk_size)
 		return;
 
 	/* Add new ramdisk record */
 	bi = bi_add(BI_RAMDISK, sizeof(bi->mem_info));
 	bi->mem_info.addr = ramdisk_addr;
 	bi->mem_info.size = ramdisk_size;
 }
 
+void bootinfo_add_rng_seed(void)
+{
+	struct bi_rec *bi;
+	enum { RNG_SEED_LEN = 32 };
+
+	/* Remove existing rng seed records */
+	bi_remove(BI_VIRT_RNG_SEED);
+
+	/* Add new rng seed record */
+	bi = bi_add(BI_VIRT_RNG_SEED, sizeof(bi->bytes) + RNG_SEED_LEN);
+	if (getrandom(bi->bytes.data, RNG_SEED_LEN, GRND_NONBLOCK) != RNG_SEED_LEN) {
+		bi_remove(BI_VIRT_RNG_SEED);
+		return;
+	}
+	bi->bytes.len = cpu_to_be16(RNG_SEED_LEN);
+}
+
 
     /*
      * Check the bootinfo version in the kernel image
      * All failures are non-fatal, as kexec may be used to load
      * non-Linux images
      */
 
 void bootinfo_check_bootversion(const struct kexec_info *info)
 {
 	struct bi_rec *bi;
 	const struct bootversion *bv;
 	uint16_t major, minor;
 	unsigned int i;
 
 	bv = info->segment[0].buf;
 	if (bv->magic != BOOTINFOV_MAGIC) {
 		printf("WARNING: No bootversion in kernel image\n");
 		return;
 	}
 
diff --git a/kexec/arch/m68k/bootinfo.h b/kexec/arch/m68k/bootinfo.h
index b6f453d..6dff2ad 100644
--- a/kexec/arch/m68k/bootinfo.h
+++ b/kexec/arch/m68k/bootinfo.h
@@ -1,43 +1,49 @@
 #include <asm/bootinfo.h>
+#include <asm/bootinfo-virt.h>
 
 #define DEFAULT_BOOTINFO_FILE	"/proc/bootinfo"
 #define MAX_BOOTINFO_SIZE	1536
 
 
     /*
      *  Convenience overlay of several struct bi_record variants
      */
 
 struct bi_rec {
 	__be16 tag;
 	__be16 size;
 	union {
 		__be32 data[0];
 		/* shorthands for the types we use */
 		__be32 machtype;
 		struct {
 			__be32 addr;
 			__be32 size;
 		} mem_info;
 		char string[0];
+		struct {
+			__be16 len;
+			u8 data[0];
+		} bytes;
 	};
 };
 
 
     /*
      *  We only support the "new" tagged bootinfo (v2)
      */
 
 #define SUPPORTED_BOOTINFO_VERSION	2
 
 
 extern const char *bootinfo_file;
 
 extern void bootinfo_load(void);
 extern void bootinfo_print(void);
 extern int bootinfo_get_memory_ranges(struct memory_range **range);
 extern void bootinfo_set_cmdline(const char *cmdline);
 extern void bootinfo_set_ramdisk(unsigned long ramdisk_addr,
 				 unsigned long ramdisk_size);
+extern void bootinfo_add_rng_seed(void);
 extern void bootinfo_check_bootversion(const struct kexec_info *info);
 extern void add_bootinfo(struct kexec_info *info, unsigned long addr);
diff --git a/kexec/arch/m68k/kexec-elf-m68k.c b/kexec/arch/m68k/kexec-elf-m68k.c
index 8d00eb9..a2bf7ee 100644
--- a/kexec/arch/m68k/kexec-elf-m68k.c
+++ b/kexec/arch/m68k/kexec-elf-m68k.c
@@ -145,38 +145,39 @@ int elf_m68k_load(int argc, char **argv, const char *buf, off_t len,
 	bootinfo_addr = segment_end(info, info->nr_segments - 1) + 1;
 
 	/* Load ramdisk */
 	if (ramdisk_file) {
 		void *ramdisk = slurp_decompress_file(ramdisk_file,
 						      &ramdisk_size);
 		/* Store ramdisk at top of first memory chunk */
 		ramdisk_addr = _ALIGN_DOWN(info->memory_range[0].end -
 					   ramdisk_size + 1,
 					   PAGE_SIZE);
 		if (!buf)
 			die("Ramdisk load failed\n");
 		add_buffer(info, ramdisk, ramdisk_size, ramdisk_size,
 			   PAGE_SIZE, ramdisk_addr, info->memory_range[0].end,
 			   1);
 	}
 
 	/* Update and add bootinfo */
 	bootinfo_set_cmdline(cmdline);
 	bootinfo_set_ramdisk(ramdisk_addr, ramdisk_size);
+	bootinfo_add_rng_seed();
 	if (kexec_debug)
 		bootinfo_print();
 	add_bootinfo(info, bootinfo_addr);
 
 	/*
 	 * Check if the kernel (and bootinfo) exceed 4 MiB, as current kernels
 	 * don't support that.
 	 * As the segments are still unsorted, the bootinfo is located in the
 	 * last segment.
 	 */
 	if (segment_end(info, info->nr_segments - 1) >= virt_to_phys(4 MiB - 1))
 		printf("WARNING: Kernel is larger than 4 MiB\n");
 
 	/* Check struct bootversion at start of kernel */
 	bootinfo_check_bootversion(info);
 
 	return 0;
 }
-- 
2.37.3

Re: [PATCH kexec-tools] m68k: pass rng seed via BI_VIRT_RNG_SEED

[Jason A. Donenfeld]

On Fri, Sep 23, 2022 at 2:47 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> Geert - I don't have a toolchain for testing this. Could you verify it
> works, if you have a chance? -Jason
>
>  kexec/arch/m68k/bootinfo.c       | 22 ++++++++++++++++++++++
>  kexec/arch/m68k/bootinfo.h       |  6 ++++++
>  kexec/arch/m68k/kexec-elf-m68k.c |  1 +
>  3 files changed, 29 insertions(+)
>
> diff --git a/kexec/arch/m68k/bootinfo.c b/kexec/arch/m68k/bootinfo.c
> index 18bf226..74e65a0 100644
> --- a/kexec/arch/m68k/bootinfo.c
> +++ b/kexec/arch/m68k/bootinfo.c

I forgot to add `#include <sys/random.h>` I suspect.

Re: [PATCH kexec-tools] m68k: pass rng seed via BI_VIRT_RNG_SEED

[Geert Uytterhoeven]

Hi Jason,

On Fri, Sep 23, 2022 at 2:47 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> In order to pass fresh entropy to kexec'd kernels, use BI_VIRT_RNG_SEED
> for passing a seed, with the same semantics that kexec-tools currently
> uses for i386's setup_data.
>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Thanks for your patch!

> --- a/kexec/arch/m68k/bootinfo.c
> +++ b/kexec/arch/m68k/bootinfo.c
> @@ -135,40 +135,45 @@ void bootinfo_print(void)
>                 size = bi->size;
>                 switch (tag) {
>                 case BI_MACHTYPE:
>                         printf("BI_MACHTYPE: 0x%08x\n", bi->machtype);
>                         break;
>
>                 case BI_MEMCHUNK:
>                         printf("BI_MEMCHUNK: 0x%08x bytes at 0x%08x\n",
>                                bi->mem_info.size, bi->mem_info.addr);
>                         break;
>
>                 case BI_RAMDISK:
>                         printf("BI_RAMDISK: 0x%08x bytes at 0x%08x\n",
>                                bi->mem_info.size, bi->mem_info.addr);
>                         break;

Hmm, lots of context.

>
>                 case BI_COMMAND_LINE:
>                         printf("BI_COMMAND_LINE: %s\n", bi->string);
>                         break;
>
> +               case BI_VIRT_RNG_SEED:

This won't work as expected: BI_VIRT_* tags are only valid if the
machine type is MACH_VIRT.

Worse, this will trigger for other platform-specific tags using the same value:

    arch/m68k/include/uapi/asm/bootinfo-amiga.h:#define
BI_AMIGA_CHIPSET    0x8006  /* native chipset present (__be32) */
    arch/m68k/include/uapi/asm/bootinfo-mac.h:#define BI_MAC_SCCBASE
             0x8006  /* Mac SCC base address */
    arch/m68k/include/uapi/asm/bootinfo-virt.h:#define
BI_VIRT_RNG_SEED     0x8006

> +                       /* These are secret, so never print them to the console */
> +                       printf("BI_VIRT_RNG_SEED: 0x%08x bytes\n", be16_to_cpu(bi->bytes.len));
> +                       break;
> +
>                 default:
>                         printf("BI tag 0x%04x size %u\n", tag, size);
>                         break;
>                 }
>                 bi = bi_next(bi, size);
>         }
>  }

>  }
>
> +void bootinfo_add_rng_seed(void)
> +{
> +       struct bi_rec *bi;
> +       enum { RNG_SEED_LEN = 32 };
> +
> +       /* Remove existing rng seed records */
> +       bi_remove(BI_VIRT_RNG_SEED);
> +
> +       /* Add new rng seed record */
> +       bi = bi_add(BI_VIRT_RNG_SEED, sizeof(bi->bytes) + RNG_SEED_LEN);

Likewise, this will destroy existing BI_AMIGA_CHIPSET and BI_MAC_SCCBASE
tags, breaking Amiga and Mac.

> +       if (getrandom(bi->bytes.data, RNG_SEED_LEN, GRND_NONBLOCK) != RNG_SEED_LEN) {
> +               bi_remove(BI_VIRT_RNG_SEED);
> +               return;
> +       }
> +       bi->bytes.len = cpu_to_be16(RNG_SEED_LEN);
> +}
> +
>

As random seeds can now be generic, I think it makes sense to introduce
a machine-independent BI_RND_SEED.
In hindsight, we should have done this from the beginning...

> --- a/kexec/arch/m68k/bootinfo.h
> +++ b/kexec/arch/m68k/bootinfo.h
> @@ -1,43 +1,49 @@
>  #include <asm/bootinfo.h>
> +#include <asm/bootinfo-virt.h>
>
>  #define DEFAULT_BOOTINFO_FILE  "/proc/bootinfo"
>  #define MAX_BOOTINFO_SIZE      1536
>
>
>      /*
>       *  Convenience overlay of several struct bi_record variants
>       */
>
>  struct bi_rec {
>         __be16 tag;
>         __be16 size;
>         union {
>                 __be32 data[0];
>                 /* shorthands for the types we use */
>                 __be32 machtype;
>                 struct {
>                         __be32 addr;
>                         __be32 size;
>                 } mem_info;
>                 char string[0];
> +               struct {
> +                       __be16 len;
> +                       u8 data[0];
> +               } bytes;

I'd rather call this rng_seed, to avoid confusion between "data"
and "bytes",

>         };
>  };

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH kexec-tools] m68k: pass rng seed via BI_VIRT_RNG_SEED

[Jason A. Donenfeld]

Hi Geert,

On Fri, Sep 23, 2022 at 3:07 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> This won't work as expected: BI_VIRT_* tags are only valid if the
> machine type is MACH_VIRT.
> Worse, this will trigger for other platform-specific tags using the same value:
> Likewise, this will destroy existing BI_AMIGA_CHIPSET and BI_MAC_SCCBASE
> tags, breaking Amiga and Mac.
> As random seeds can now be generic, I think it makes sense to introduce
> a machine-independent BI_RND_SEED.
> In hindsight, we should have done this from the beginning...

Yes, I agree. I thought that would be rejected, though, which is why I
didn't do that before. I'll send a patch switching over to that.
There's no point in keeping the old one around, I don't think, so I'll
just move everything over to the new.

Jason

[PATCH v2] m68k: pass rng seed via BI_RNG_SEED

[Jason A. Donenfeld]

In order to pass fresh entropy to kexec'd kernels, use BI_RNG_SEED
for passing a seed, with the same semantics that kexec-tools currently
uses for i386's setup_data.

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
Geert - this hasn't been compile tested yet and also depends on changes
that haven't yet landed upstream. Posting this preliminarily now. -Jason

 kexec/arch/m68k/bootinfo.c       | 23 +++++++++++++++++++++++
 kexec/arch/m68k/bootinfo.h       |  5 +++++
 kexec/arch/m68k/kexec-elf-m68k.c |  1 +
 3 files changed, 29 insertions(+)

diff --git a/kexec/arch/m68k/bootinfo.c b/kexec/arch/m68k/bootinfo.c
index 18bf226..086a34b 100644
--- a/kexec/arch/m68k/bootinfo.c
+++ b/kexec/arch/m68k/bootinfo.c
@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/random.h>
 
 #include "../../kexec.h"
 
@@ -152,6 +153,11 @@ void bootinfo_print(void)
 			printf("BI_COMMAND_LINE: %s\n", bi->string);
 			break;
 
+		case BI_RNG_SEED:
+			/* These are secret, so never print them to the console */
+			printf("BI_RNG_SEED: 0x%08x bytes\n", be16_to_cpu(bi->rng_seed.len));
+			break;
+
 		default:
 			printf("BI tag 0x%04x size %u\n", tag, size);
 			break;
@@ -212,6 +218,23 @@ void bootinfo_set_ramdisk(unsigned long ramdisk_addr,
 	bi->mem_info.size = ramdisk_size;
 }
 
+void bootinfo_add_rng_seed(void)
+{
+	enum { RNG_SEED_LEN = 32 };
+	struct bi_rec *bi;
+
+	/* Remove existing rng seed records */
+	bi_remove(BI_RNG_SEED);
+
+	/* Add new rng seed record */
+	bi = bi_add(BI_RNG_SEED, sizeof(bi->rng_seed) + RNG_SEED_LEN);
+	if (getrandom(bi->rng_seed.data, RNG_SEED_LEN, GRND_NONBLOCK) != RNG_SEED_LEN) {
+		bi_remove(BI_RNG_SEED);
+		return;
+	}
+	bi->rng_seed.len = cpu_to_be16(RNG_SEED_LEN);
+}
+
 
     /*
      * Check the bootinfo version in the kernel image
diff --git a/kexec/arch/m68k/bootinfo.h b/kexec/arch/m68k/bootinfo.h
index b6f453d..90f75ad 100644
--- a/kexec/arch/m68k/bootinfo.h
+++ b/kexec/arch/m68k/bootinfo.h
@@ -20,6 +20,10 @@ struct bi_rec {
 			__be32 size;
 		} mem_info;
 		char string[0];
+		struct {
+			__be16 len;
+			u8 data[0];
+		} rng_seed;
 	};
 };
 
@@ -39,5 +43,6 @@ extern int bootinfo_get_memory_ranges(struct memory_range **range);
 extern void bootinfo_set_cmdline(const char *cmdline);
 extern void bootinfo_set_ramdisk(unsigned long ramdisk_addr,
 				 unsigned long ramdisk_size);
+extern void bootinfo_add_rng_seed(void);
 extern void bootinfo_check_bootversion(const struct kexec_info *info);
 extern void add_bootinfo(struct kexec_info *info, unsigned long addr);
diff --git a/kexec/arch/m68k/kexec-elf-m68k.c b/kexec/arch/m68k/kexec-elf-m68k.c
index 8d00eb9..a2bf7ee 100644
--- a/kexec/arch/m68k/kexec-elf-m68k.c
+++ b/kexec/arch/m68k/kexec-elf-m68k.c
@@ -162,6 +162,7 @@ int elf_m68k_load(int argc, char **argv, const char *buf, off_t len,
 	/* Update and add bootinfo */
 	bootinfo_set_cmdline(cmdline);
 	bootinfo_set_ramdisk(ramdisk_addr, ramdisk_size);
+	bootinfo_add_rng_seed();
 	if (kexec_debug)
 		bootinfo_print();
 	add_bootinfo(info, bootinfo_addr);
-- 
2.37.3

Re: [PATCH v2] m68k: pass rng seed via BI_RNG_SEED

[Jason A. Donenfeld]

On Fri, Sep 23, 2022 at 06:41:52PM +0200, Jason A. Donenfeld wrote:
> In order to pass fresh entropy to kexec'd kernels, use BI_RNG_SEED
> for passing a seed, with the same semantics that kexec-tools currently
> uses for i386's setup_data.
> 
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> Geert - this hasn't been compile tested yet and also depends on changes
> that haven't yet landed upstream. Posting this preliminarily now. -Jason

With [1] having landed, does this patch here suffice for kexec-tools?

[1] https://git.kernel.org/pub/scm/linux/kernel/git/geert/linux-m68k.git/commit/?id=f1bb20c8be1929743fdb313b4770601afc39c1b7

Jason