Re: [PATCH] TPM: Fixup pubek sysfs file
From: Rajiv Andrade
Date: Mon Sep 14 2009 - 16:49:20 EST
I was about to suggest including some #defines here but the comment
section explaining the format already documents the offsets.
Thanks
Reviewed-by: Rajiv Andrade <srajiv@xxxxxxxxxxxxxxxxxx>
On Thu, 2009-09-03 at 22:52 -0600, Jason Gunthorpe wrote:
> tpm_show_pubek is utterly and completely wrong, all the offsets
> into the binary blob are wrong, the output is garbage. Do it again.
>
> Before:
> Algorithm: 00 0C 00 00
> Encscheme: 08 00
> Sigscheme: 00 00
> Parameters: 00 00 00 00 01 00 AF 6B 30 9B 0D B3
> Modulus length: -1266846667
> Modulus:
> 68 45 8D CA A5 EF A8 8A DD 0F D7 84 8E 8D 1F 40
> 22 92 09 CF 12 C8 9F 6E 55 57 6A 2C A8 0B 5E 45
> C7 5E 3D 56 DA 64 E6 E1 F7 8C DD 41 92 28 2E 06
> 41 02 3E 11 7D B2 C5 46 38 E5 8C 60 D2 96 EE 0C
> D6 3D F8 99 E3 02 3A 32 7A 02 C8 31 29 98 28 B9
> 1B EF 30 A1 A0 45 A0 C0 05 0E C5 96 95 FD 91 47
> 0A 35 E0 69 B0 8B 49 BD B9 F6 5D 25 21 25 79 1B
> 20 0D C3 C7 1F 87 5E 5F 41 4B DE 32 DF 55 F3 BD
> 7F CA D8 7D 3A B4 D5 0A EF CF 8E 72 20 52 15 FA
> FB C6 C0 2E C2 AB C6 07 D0 9D 96 6B 2E 30 F7 54
> C4 A5 CD 9B 13 54 A0 D1 71 66 91 97 06 12 B5 2D
> B2 33 62 FB 56 62 64 A8 AA E9 F2 F4 03 C3 F4 49
> 2A 09 0D 7D 75 99 6C F0 47 1E 7D D5 A5 CA CE EF
> 45 B2 DA 88 93 B4 EE EB FB B0 A6 A4 19 C4 B8 0D
> 04 46 AE BD C5 2E 30 84 49 57 25 34 78 E6 ED C4
> 50 AF 3B F6 86 43 54 0A D9 DB 54 9C 06 B3 50 7F
>
> After:
> Algorithm: 00 00 00 01
> Encscheme: 00 03
> Sigscheme: 00 01
> Parameters: 00 00 08 00 00 00 00 02 00 00 00 00
> Modulus length: 256
> Modulus:
> AF 6B 30 9B 0D B3 B4 7D 74 35 68 45 8D CA A5 EF
> A8 8A DD 0F D7 84 8E 8D 1F 40 22 92 09 CF 12 C8
> 9F 6E 55 57 6A 2C A8 0B 5E 45 C7 5E 3D 56 DA 64
> E6 E1 F7 8C DD 41 92 28 2E 06 41 02 3E 11 7D B2
> C5 46 38 E5 8C 60 D2 96 EE 0C D6 3D F8 99 E3 02
> 3A 32 7A 02 C8 31 29 98 28 B9 1B EF 30 A1 A0 45
> A0 C0 05 0E C5 96 95 FD 91 47 0A 35 E0 69 B0 8B
> 49 BD B9 F6 5D 25 21 25 79 1B 20 0D C3 C7 1F 87
> 5E 5F 41 4B DE 32 DF 55 F3 BD 7F CA D8 7D 3A B4
> D5 0A EF CF 8E 72 20 52 15 FA FB C6 C0 2E C2 AB
> C6 07 D0 9D 96 6B 2E 30 F7 54 C4 A5 CD 9B 13 54
> A0 D1 71 66 91 97 06 12 B5 2D B2 33 62 FB 56 62
> 64 A8 AA E9 F2 F4 03 C3 F4 49 2A 09 0D 7D 75 99
> 6C F0 47 1E 7D D5 A5 CA CE EF 45 B2 DA 88 93 B4
> EE EB FB B0 A6 A4 19 C4 B8 0D 04 46 AE BD C5 2E
> 30 84 49 57 25 34 78 E6 ED C4 50 AF 3B F6 86 43
>
> I've checked this decoded output in two different ways.
>
> Tested on a winbond WPCT200
>
> Signed-off-by: Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/char/tpm/tpm.c | 77 +++++++++++++++++++++++++++++++++---------------
> 1 files changed, 53 insertions(+), 24 deletions(-)
>
> Andrew: More testing found this too. In truth this file is probably
> fairly useless since it won't output anything once the TPM is owned,
> but if it is going to be there it may as well work right.
>
> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> index 5d5b324..196bc48 100644
> --- a/drivers/char/tpm/tpm.c
> +++ b/drivers/char/tpm/tpm.c
> @@ -460,6 +460,11 @@ static ssize_t transmit_cmd(struct tpm_chip *chip, struct tpm_cmd_t *cmd,
> dev_dbg(chip->dev, "A TPM error (%d) occurred %s\n", err, desc);
> return err;
> }
> + if (len != be32_to_cpu(cmd->header.out.length)) {
> + dev_dbg(chip->dev, "TPM returned the wrong length %x %x\n",
> + len, be32_to_cpu(cmd->header.out.length));
> + return -1;
> + }
> return 0;
> }
>
> @@ -811,43 +816,67 @@ ssize_t tpm_show_pubek(struct device *dev, struct device_attribute *attr,
> {
> u8 *data;
> struct tpm_cmd_t tpm_cmd;
> - ssize_t err;
> - int i, rc;
> + ssize_t len;
> + int i, rc, key_len;
> char *str = buf;
>
> struct tpm_chip *chip = dev_get_drvdata(dev);
>
> tpm_cmd.header.in = tpm_readpubek_header;
> - err = transmit_cmd(chip, &tpm_cmd, READ_PUBEK_RESULT_SIZE,
> - "attempting to read the PUBEK");
> - if (err)
> + if (transmit_cmd(chip, &tpm_cmd, READ_PUBEK_RESULT_SIZE,
> + "attempting to read the PUBEK"))
> + goto out;
> +
> + len = be32_to_cpu(tpm_cmd.header.out.length);
> + if (len <= 0)
> goto out;
>
> - /*
> - ignore header 10 bytes
> - algorithm 32 bits (1 == RSA )
> - encscheme 16 bits
> - sigscheme 16 bits
> - parameters (RSA 12->bytes: keybit, #primes, expbit)
> - keylenbytes 32 bits
> - 256 byte modulus
> - ignore checksum 20 bytes
> + /* Format (in bytes):
> + 10 RPC Header (tpm_cmd.header)
> + xx TPM_PUBKEY pubEK
> + xx TPM_KEY_PARMS
> + 4 algorithmID
> + 2 encScheme
> + 2 sigcScheme
> + 4 parmSize
> + xx parms (typically 12 bytes for a RSA key)
> + xx TPM_STORE_PUBKEY
> + 4 keyLength
> + xx key (typically 256 for a RSA key)
> + 20 TPM_DIGEST checksum
> */
> data = tpm_cmd.params.readpubek_out_buffer;
> + len -= 10;
> + if (len < 24)
> + goto out;
> str +=
> sprintf(str,
> "Algorithm: %02X %02X %02X %02X\nEncscheme: %02X %02X\n"
> "Sigscheme: %02X %02X\nParameters: %02X %02X %02X %02X"
> - " %02X %02X %02X %02X %02X %02X %02X %02X\n"
> - "Modulus length: %d\nModulus: \n",
> - data[10], data[11], data[12], data[13], data[14],
> - data[15], data[16], data[17], data[22], data[23],
> - data[24], data[25], data[26], data[27], data[28],
> - data[29], data[30], data[31], data[32], data[33],
> - be32_to_cpu(*((__be32 *) (data + 34))));
> -
> - for (i = 0; i < 256; i++) {
> - str += sprintf(str, "%02X ", data[i + 38]);
> + " %02X %02X %02X %02X %02X %02X %02X %02X\n",
> + data[0], data[1], data[2], data[3],
> + data[4], data[5],
> + data[6], data[7],
> + data[12], data[13], data[14], data[15], data[16], data[17],
> + data[18], data[19], data[20], data[21], data[22], data[23]);
> + /* Skip TPM_KEY_PARMS.parms and TPM_STORE_PBUKEY.keyLength */
> + i = 4 + 2 + 2 + 4 + be32_to_cpu(*((__be32 *) (data + 8))) + 4;
> + if (i > len)
> + goto out;
> + data += i;
> + len -= i;
> + key_len = be32_to_cpu(*((__be32 *) (data) - 1));
> +
> + /* Note: The value printed here is the TPM_STORE_PUBKEY. For RSA keys
> + this is a modulus, but it can vary for other key types. */
> + str += sprintf(str, "Modulus length: %d\nModulus: \n", key_len);
> +
> + /* len is bounded, so key_len is bounded, so sprintf is bounded, so
> + str doesn't overflow. Well, maybe. */
> + if (key_len > len)
> + goto out;
> + for (i = 0; i < key_len; i++) {
> + str += sprintf(str, "%02X ", data[i]);
> if ((i + 1) % 16 == 0)
> str += sprintf(str, "\n");
> }
--
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