| Message ID | 20211124150858.496805-3-ruchika.gupta@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v5,1/3] efi_loader: Add check for event log passed from firmware | expand |
On Wed, 24 Nov 2021 at 17:09, Ruchika Gupta <ruchika.gupta@linaro.org> wrote: > > Firmwares before U-Boot may be capable of doing tpm measurements > and passing them to U-Boot in the form of eventlog. However there > may be scenarios where the firmwares don't have TPM driver and > are not capable of extending the measurements in the PCRs. > Based on TCG spec, if previous firnware has extended PCR's, PCR0 > would not be 0. So, read the PCR0 to determine if the PCR's need > to be extended as eventlog is parsed or not. > > Signed-off-by: Ruchika Gupta <ruchika.gupta@linaro.org> > Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org> > --- > v5 : No change > > v4 : No change > > v3 : > Rebase changes on top of changes made in first patch of series > > v2 : > Removed check for PCR0 in eventlog > > lib/efi_loader/efi_tcg2.c | 75 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 75 insertions(+) > > diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c > index a789c44660..b44eed0ec9 100644 > --- a/lib/efi_loader/efi_tcg2.c > +++ b/lib/efi_loader/efi_tcg2.c > @@ -199,6 +199,43 @@ static efi_status_t tcg2_pcr_extend(struct udevice *dev, u32 pcr_index, > return EFI_SUCCESS; > } > > +/* tcg2_pcr_read - Read PCRs for a TPM2 device for a given tpml_digest_values > + * > + * @dev: device > + * @digest_list: list of digest algorithms to extend > + * > + * @Return: status code > + */ > +static efi_status_t tcg2_pcr_read(struct udevice *dev, u32 pcr_index, > + struct tpml_digest_values *digest_list) > +{ > + struct tpm_chip_priv *priv; > + unsigned int updates, pcr_select_min; > + u32 rc; > + size_t i; > + > + priv = dev_get_uclass_priv(dev); > + if (!priv) > + return EFI_DEVICE_ERROR; > + > + pcr_select_min = priv->pcr_select_min; > + > + for (i = 0; i < digest_list->count; i++) { > + u16 hash_alg = digest_list->digests[i].hash_alg; > + u8 *digest = (u8 *)&digest_list->digests[i].digest; > + > + rc = tpm2_pcr_read(dev, pcr_index, pcr_select_min, > + hash_alg, digest, alg_to_len(hash_alg), > + &updates); > + if (rc) { > + EFI_PRINT("Failed to read PCR\n"); > + return EFI_DEVICE_ERROR; > + } > + } > + > + return EFI_SUCCESS; > +} > + > /* put_event - Append an agile event to an eventlog > * > * @pcr_index: PCR index > @@ -1428,6 +1465,8 @@ efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer, > u32 pcr, pos; > u64 base; > u32 sz; > + bool extend_pcr = false; > + int i; > > ret = platform_get_eventlog(dev, &base, &sz); > if (ret != EFI_SUCCESS) > @@ -1449,6 +1488,26 @@ efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer, > return EFI_COMPROMISED_DATA; > } > > + ret = tcg2_pcr_read(dev, 0, &digest_list); > + if (ret) { > + log_err("Error reading PCR 0\n"); > + return ret; > + } > + > + /* > + * If PCR0 is 0, previous firmware didn't have the capability > + * to extend the PCR. In this scenario, extend the PCR as > + * the eventlog is parsed. > + */ > + for (i = 0; i < digest_list.count; i++) { > + u8 buffer[TPM2_DIGEST_LEN] = { 0 }; > + u16 hash_alg = digest_list.digests[i].hash_alg; > + > + if (!memcmp((u8 *)&digest_list.digests[i].digest, buffer, > + alg_to_len(hash_alg))) > + extend_pcr = true; > + } > + > while (pos < sz) { > ret = tcg2_parse_event(dev, buffer, sz, &pos, &digest_list, > &pcr); > @@ -1456,6 +1515,22 @@ efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer, > log_err("Error parsing event\n"); > return ret; > } > + if (extend_pcr) { > + ret = tcg2_pcr_extend(dev, pcr, &digest_list); > + if (ret != EFI_SUCCESS) { > + log_err("Error in extending PCR\n"); > + return ret; > + } > + > + /* Clear the digest for next event */ > + for (i = 0; i < digest_list.count; i++) { > + u16 hash_alg = digest_list.digests[i].hash_alg; > + u8 *digest = > + (u8 *)&digest_list.digests[i].digest; > + > + memset(digest, 0, alg_to_len(hash_alg)); > + } > + } > } > > memcpy(log_buffer, buffer, sz); > -- > 2.25.1 > Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Hi Ruchika, I just noticed the TPM_DIGEST_LEN usage [...] > > + * If PCR0 is 0, previous firmware didn't have the capability > > + * to extend the PCR. In this scenario, extend the PCR as > > + * the eventlog is parsed. > > + */ > > + for (i = 0; i < digest_list.count; i++) { > > + u8 buffer[TPM2_DIGEST_LEN] = { 0 }; This is only 32 bytes, you need TPM2_SHA512_DIGEST_SIZE to fit all digests > > + u16 hash_alg = digest_list.digests[i].hash_alg; [...] Regards /Ilias
diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c index a789c44660..b44eed0ec9 100644 --- a/lib/efi_loader/efi_tcg2.c +++ b/lib/efi_loader/efi_tcg2.c @@ -199,6 +199,43 @@ static efi_status_t tcg2_pcr_extend(struct udevice *dev, u32 pcr_index, return EFI_SUCCESS; } +/* tcg2_pcr_read - Read PCRs for a TPM2 device for a given tpml_digest_values + * + * @dev: device + * @digest_list: list of digest algorithms to extend + * + * @Return: status code + */ +static efi_status_t tcg2_pcr_read(struct udevice *dev, u32 pcr_index, + struct tpml_digest_values *digest_list) +{ + struct tpm_chip_priv *priv; + unsigned int updates, pcr_select_min; + u32 rc; + size_t i; + + priv = dev_get_uclass_priv(dev); + if (!priv) + return EFI_DEVICE_ERROR; + + pcr_select_min = priv->pcr_select_min; + + for (i = 0; i < digest_list->count; i++) { + u16 hash_alg = digest_list->digests[i].hash_alg; + u8 *digest = (u8 *)&digest_list->digests[i].digest; + + rc = tpm2_pcr_read(dev, pcr_index, pcr_select_min, + hash_alg, digest, alg_to_len(hash_alg), + &updates); + if (rc) { + EFI_PRINT("Failed to read PCR\n"); + return EFI_DEVICE_ERROR; + } + } + + return EFI_SUCCESS; +} + /* put_event - Append an agile event to an eventlog * * @pcr_index: PCR index @@ -1428,6 +1465,8 @@ efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer, u32 pcr, pos; u64 base; u32 sz; + bool extend_pcr = false; + int i; ret = platform_get_eventlog(dev, &base, &sz); if (ret != EFI_SUCCESS) @@ -1449,6 +1488,26 @@ efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer, return EFI_COMPROMISED_DATA; } + ret = tcg2_pcr_read(dev, 0, &digest_list); + if (ret) { + log_err("Error reading PCR 0\n"); + return ret; + } + + /* + * If PCR0 is 0, previous firmware didn't have the capability + * to extend the PCR. In this scenario, extend the PCR as + * the eventlog is parsed. + */ + for (i = 0; i < digest_list.count; i++) { + u8 buffer[TPM2_DIGEST_LEN] = { 0 }; + u16 hash_alg = digest_list.digests[i].hash_alg; + + if (!memcmp((u8 *)&digest_list.digests[i].digest, buffer, + alg_to_len(hash_alg))) + extend_pcr = true; + } + while (pos < sz) { ret = tcg2_parse_event(dev, buffer, sz, &pos, &digest_list, &pcr); @@ -1456,6 +1515,22 @@ efi_status_t tcg2_get_fw_eventlog(struct udevice *dev, void *log_buffer, log_err("Error parsing event\n"); return ret; } + if (extend_pcr) { + ret = tcg2_pcr_extend(dev, pcr, &digest_list); + if (ret != EFI_SUCCESS) { + log_err("Error in extending PCR\n"); + return ret; + } + + /* Clear the digest for next event */ + for (i = 0; i < digest_list.count; i++) { + u16 hash_alg = digest_list.digests[i].hash_alg; + u8 *digest = + (u8 *)&digest_list.digests[i].digest; + + memset(digest, 0, alg_to_len(hash_alg)); + } + } } memcpy(log_buffer, buffer, sz);