| Message ID | 20250430090350.30023-2-ssrish@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Enhancements to the secvar interface in static key management mode | expand |
On 4/30/25 5:03 AM, Srish Srinivasan wrote: > On a PLPKS enabled PowerVM LPAR, the secvar format property for static > key management is misrepresented as "ibm,plpks-sb-unknown", creating > reason for confusion. > > Static key management mode uses fixed, built-in keys. Dynamic key > management mode allows keys to be updated in production to handle > security updates without firmware rebuilds. > > Define a function named plpks_get_sb_keymgmt_mode() to retrieve the > key management mode based on the existence of the SB_VERSION property > in the firmware. > > Set the secvar format property to either "ibm,plpks-sb-v1" or > "ibm,plpks-sb-v0" based on the key management mode, and return the > length of the secvar format property. Reviewed-by: Nayna Jain <nayna@linux.ibm.com> Thanks & Regards, - Nayna > > Co-developed-by: Souradeep <soura@imap.linux.ibm.com> > Signed-off-by: Souradeep <soura@imap.linux.ibm.com> > Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com> > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> > Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> > --- > arch/powerpc/platforms/pseries/plpks-secvar.c | 70 +++++++++++-------- > 1 file changed, 40 insertions(+), 30 deletions(-) > > diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c b/arch/powerpc/platforms/pseries/plpks-secvar.c > index 257fd1f8bc19..d57067a733ab 100644 > --- a/arch/powerpc/platforms/pseries/plpks-secvar.c > +++ b/arch/powerpc/platforms/pseries/plpks-secvar.c > @@ -152,39 +152,49 @@ static int plpks_set_variable(const char *key, u64 key_len, u8 *data, > return rc; > } > > -// PLPKS dynamic secure boot doesn't give us a format string in the same way OPAL does. > -// Instead, report the format using the SB_VERSION variable in the keystore. > -// The string is made up by us, and takes the form "ibm,plpks-sb-v<n>" (or "ibm,plpks-sb-unknown" > -// if the SB_VERSION variable doesn't exist). Hypervisor defines the SB_VERSION variable as a > -// "1 byte unsigned integer value". > -static ssize_t plpks_secvar_format(char *buf, size_t bufsize) > +/* > + * Return the key management mode. > + * > + * SB_VERSION is defined as a "1 byte unsigned integer value". It is owned by > + * the Partition Firmware and its presence indicates that the key management > + * mode is dynamic. Only signed variables have null bytes in their names. > + * SB_VERSION does not. > + * > + * Return 1 to indicate that the key management mode is dynamic. Otherwise > + * return 0, indicating that the key management mode is static. > + */ > +static u8 plpks_get_sb_keymgmt_mode(void) > { > - struct plpks_var var = {0}; > - ssize_t ret; > - u8 version; > - > - var.component = NULL; > - // Only the signed variables have null bytes in their names, this one doesn't > - var.name = "SB_VERSION"; > - var.namelen = strlen(var.name); > - var.datalen = 1; > - var.data = &version; > - > - // Unlike the other vars, SB_VERSION is owned by firmware instead of the OS > - ret = plpks_read_fw_var(&var); > - if (ret) { > - if (ret == -ENOENT) { > - ret = snprintf(buf, bufsize, "ibm,plpks-sb-unknown"); > - } else { > - pr_err("Error %ld reading SB_VERSION from firmware\n", ret); > - ret = -EIO; > - } > - goto err; > + u8 mode; > + ssize_t rc; > + struct plpks_var var = { > + .component = NULL, > + .name = "SB_VERSION", > + .namelen = 10, > + .datalen = 1, > + .data = &mode, > + }; > + > + rc = plpks_read_fw_var(&var); > + if (rc) { > + pr_info("Error %ld reading SB_VERSION from firmware\n", rc); > + mode = 0; > } > + return mode; > +} > > - ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version); > -err: > - return ret; > +// PLPKS dynamic secure boot doesn't give us a format string in the same way > +// OPAL does. Instead, report the format using the SB_VERSION variable in the > +// keystore. The string, made up by us, takes the form "ibm,plpks-sb-v<n>".Set > +// the secvar format property to either "ibm,plpks-sb-v1" or "ibm,plpks-sb-v0", > +// based on the key management mode, and return the length of the secvar format > +// property. > +static ssize_t plpks_secvar_format(char *buf, size_t bufsize) > +{ > + u8 mode; > + > + mode = plpks_get_sb_keymgmt_mode(); > + return snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", mode); > } > > static int plpks_max_size(u64 *max_size)
On Wed, 2025-04-30 at 14:33 +0530, Srish Srinivasan wrote: > On a PLPKS enabled PowerVM LPAR, the secvar format property for > static > key management is misrepresented as "ibm,plpks-sb-unknown", creating > reason for confusion. > > Static key management mode uses fixed, built-in keys. Dynamic key > management mode allows keys to be updated in production to handle > security updates without firmware rebuilds. > > Define a function named plpks_get_sb_keymgmt_mode() to retrieve the > key management mode based on the existence of the SB_VERSION property > in the firmware. > > Set the secvar format property to either "ibm,plpks-sb-v1" or > "ibm,plpks-sb-v0" based on the key management mode, and return the > length of the secvar format property. > > Co-developed-by: Souradeep <soura@imap.linux.ibm.com> > Signed-off-by: Souradeep <soura@imap.linux.ibm.com> > Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com> > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> > Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> > --- > arch/powerpc/platforms/pseries/plpks-secvar.c | 70 +++++++++++------ > -- > 1 file changed, 40 insertions(+), 30 deletions(-) > > diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c > b/arch/powerpc/platforms/pseries/plpks-secvar.c > index 257fd1f8bc19..d57067a733ab 100644 > --- a/arch/powerpc/platforms/pseries/plpks-secvar.c > +++ b/arch/powerpc/platforms/pseries/plpks-secvar.c > @@ -152,39 +152,49 @@ static int plpks_set_variable(const char *key, > u64 key_len, u8 *data, > return rc; > } > > -// PLPKS dynamic secure boot doesn't give us a format string in the > same way OPAL does. > -// Instead, report the format using the SB_VERSION variable in the > keystore. > -// The string is made up by us, and takes the form "ibm,plpks-sb- > v<n>" (or "ibm,plpks-sb-unknown" > -// if the SB_VERSION variable doesn't exist). Hypervisor defines the > SB_VERSION variable as a > -// "1 byte unsigned integer value". > -static ssize_t plpks_secvar_format(char *buf, size_t bufsize) > +/* > + * Return the key management mode. > + * > + * SB_VERSION is defined as a "1 byte unsigned integer value". It is > owned by > + * the Partition Firmware and its presence indicates that the key > management > + * mode is dynamic. Only signed variables have null bytes in their > names. > + * SB_VERSION does not. > + * > + * Return 1 to indicate that the key management mode is dynamic. > Otherwise > + * return 0, indicating that the key management mode is static. > + */ This description isn't accurate. For dynamic mode, it doesn't return 1, it returns whatever version is defined in SB_VERSION, which could be 1, or could at some later point be a higher version. Which makes the function name a bit of a misnomer too - it is returning the version number, just the version number can now be zero. > +static u8 plpks_get_sb_keymgmt_mode(void) > { > - struct plpks_var var = {0}; > - ssize_t ret; > - u8 version; > - > - var.component = NULL; > - // Only the signed variables have null bytes in their names, > this one doesn't > - var.name = "SB_VERSION"; > - var.namelen = strlen(var.name); > - var.datalen = 1; > - var.data = &version; > - > - // Unlike the other vars, SB_VERSION is owned by firmware > instead of the OS > - ret = plpks_read_fw_var(&var); > - if (ret) { > - if (ret == -ENOENT) { > - ret = snprintf(buf, bufsize, "ibm,plpks-sb- > unknown"); > - } else { > - pr_err("Error %ld reading SB_VERSION from > firmware\n", ret); > - ret = -EIO; > - } > - goto err; > + u8 mode; > + ssize_t rc; > + struct plpks_var var = { > + .component = NULL, > + .name = "SB_VERSION", > + .namelen = 10, > + .datalen = 1, > + .data = &mode, > + }; > + > + rc = plpks_read_fw_var(&var); > + if (rc) { > + pr_info("Error %ld reading SB_VERSION from > firmware\n", rc); We need to check for -ENOENT, otherwise this message is going to be printed every time you boot a machine in static mode. I think you should handle this as the existing code does: if it's ENOENT, return 0, and for other codes print an error and return -EIO. > + mode = 0; > } > + return mode; > +} > > - ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version); > -err: > - return ret; > +// PLPKS dynamic secure boot doesn't give us a format string in the > same way > +// OPAL does. Instead, report the format using the SB_VERSION > variable in the > +// keystore. The string, made up by us, takes the form "ibm,plpks- > sb-v<n>".Set > +// the secvar format property to either "ibm,plpks-sb-v1" or > "ibm,plpks-sb-v0", > +// based on the key management mode, and return the length of the > secvar format > +// property. > +static ssize_t plpks_secvar_format(char *buf, size_t bufsize) > +{ > + u8 mode; > + > + mode = plpks_get_sb_keymgmt_mode(); > + return snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", mode); It might be better to use something like "ibm,plpks-sb-static" in place of "ibm,plpks-sb-v0" to make it instantly clear that static mode doesn't use the same version numbering scheme as dynamic mode. > } > > static int plpks_max_size(u64 *max_size)
On 5/5/25 2:06 PM, Andrew Donnellan wrote: > On Wed, 2025-04-30 at 14:33 +0530, Srish Srinivasan wrote: >> On a PLPKS enabled PowerVM LPAR, the secvar format property for >> static >> key management is misrepresented as "ibm,plpks-sb-unknown", creating >> reason for confusion. >> >> Static key management mode uses fixed, built-in keys. Dynamic key >> management mode allows keys to be updated in production to handle >> security updates without firmware rebuilds. >> >> Define a function named plpks_get_sb_keymgmt_mode() to retrieve the >> key management mode based on the existence of the SB_VERSION property >> in the firmware. >> >> Set the secvar format property to either "ibm,plpks-sb-v1" or >> "ibm,plpks-sb-v0" based on the key management mode, and return the >> length of the secvar format property. >> >> Co-developed-by: Souradeep <soura@imap.linux.ibm.com> >> Signed-off-by: Souradeep <soura@imap.linux.ibm.com> >> Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com> >> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> >> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> >> --- >> arch/powerpc/platforms/pseries/plpks-secvar.c | 70 +++++++++++------ >> -- >> 1 file changed, 40 insertions(+), 30 deletions(-) >> >> diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c >> b/arch/powerpc/platforms/pseries/plpks-secvar.c >> index 257fd1f8bc19..d57067a733ab 100644 >> --- a/arch/powerpc/platforms/pseries/plpks-secvar.c >> +++ b/arch/powerpc/platforms/pseries/plpks-secvar.c >> @@ -152,39 +152,49 @@ static int plpks_set_variable(const char *key, >> u64 key_len, u8 *data, >> return rc; >> } >> >> -// PLPKS dynamic secure boot doesn't give us a format string in the >> same way OPAL does. >> -// Instead, report the format using the SB_VERSION variable in the >> keystore. >> -// The string is made up by us, and takes the form "ibm,plpks-sb- >> v<n>" (or "ibm,plpks-sb-unknown" >> -// if the SB_VERSION variable doesn't exist). Hypervisor defines the >> SB_VERSION variable as a >> -// "1 byte unsigned integer value". >> -static ssize_t plpks_secvar_format(char *buf, size_t bufsize) >> +/* >> + * Return the key management mode. >> + * >> + * SB_VERSION is defined as a "1 byte unsigned integer value". It is >> owned by >> + * the Partition Firmware and its presence indicates that the key >> management >> + * mode is dynamic. Only signed variables have null bytes in their >> names. >> + * SB_VERSION does not. >> + * >> + * Return 1 to indicate that the key management mode is dynamic. >> Otherwise >> + * return 0, indicating that the key management mode is static. >> + */ > This description isn't accurate. > > For dynamic mode, it doesn't return 1, it returns whatever version is > defined in SB_VERSION, which could be 1, or could at some later point be > a higher version. > > Which makes the function name a bit of a misnomer too - it is returning > the version number, just the version number can now be zero. Hi Andrew, Thanks a lot for your feedback. Thanks for noticing this. Yes, will fix it. > >> +static u8 plpks_get_sb_keymgmt_mode(void) >> { >> - struct plpks_var var = {0}; >> - ssize_t ret; >> - u8 version; >> - >> - var.component = NULL; >> - // Only the signed variables have null bytes in their names, >> this one doesn't >> - var.name = "SB_VERSION"; >> - var.namelen = strlen(var.name); >> - var.datalen = 1; >> - var.data = &version; >> - >> - // Unlike the other vars, SB_VERSION is owned by firmware >> instead of the OS >> - ret = plpks_read_fw_var(&var); >> - if (ret) { >> - if (ret == -ENOENT) { >> - ret = snprintf(buf, bufsize, "ibm,plpks-sb- >> unknown"); >> - } else { >> - pr_err("Error %ld reading SB_VERSION from >> firmware\n", ret); >> - ret = -EIO; >> - } >> - goto err; >> + u8 mode; >> + ssize_t rc; >> + struct plpks_var var = { >> + .component = NULL, >> + .name = "SB_VERSION", >> + .namelen = 10, >> + .datalen = 1, >> + .data = &mode, >> + }; >> + >> + rc = plpks_read_fw_var(&var); >> + if (rc) { >> + pr_info("Error %ld reading SB_VERSION from >> firmware\n", rc); > We need to check for -ENOENT, otherwise this message is going to be > printed every time you boot a machine in static mode. Yes, I agree with your concern. I just want to add that, as per my understanding, we need to check for both -ENOENT and -EPERM, as explained below: As per H_PKS_READ_OBJECT semantics described in the PAPR v10.60 (https://files.openpower.foundation/s/XFgfMaqLMD5Bcm8), * If the object is not world readable, verify that the consumer password matches the stored value in the hypervisor. Else return H_AUTHORITY. * Verify if the object exists, else return H_NOT_FOUND. * Verify if the policy for the object is met, else return H_AUTHORITY. So, the hypervisor returns H_NOT_FOUND only for the authenticated consumer. For unauthenticated consumers, which is the case here, it would return H_AUTHORITY. > I think you should handle this as the existing code does: if it's > ENOENT, return 0, and for other codes print an error and return -EIO. Currently, the other layers in the boot stack assume static key mode for any failure in reading SB_VERSION. We added the same interpretation in the kernel to keep it consistent with the other layers, and represent the same to the user. This is the reason for not parsing the error codes when trying to read SB_VERSION, and defaulting to the static key management mode. However, we want the exact error code to be logged for debugging purposes. And, it does make sense to have logging only for error codes other than -ENOENT and -EPERM, as you suggested. Does this sound okay? > >> + mode = 0; >> } >> + return mode; >> +} >> >> - ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version); >> -err: >> - return ret; >> +// PLPKS dynamic secure boot doesn't give us a format string in the >> same way >> +// OPAL does. Instead, report the format using the SB_VERSION >> variable in the >> +// keystore. The string, made up by us, takes the form "ibm,plpks- >> sb-v<n>".Set >> +// the secvar format property to either "ibm,plpks-sb-v1" or >> "ibm,plpks-sb-v0", >> +// based on the key management mode, and return the length of the >> secvar format >> +// property. >> +static ssize_t plpks_secvar_format(char *buf, size_t bufsize) >> +{ >> + u8 mode; >> + >> + mode = plpks_get_sb_keymgmt_mode(); >> + return snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", mode); > It might be better to use something like "ibm,plpks-sb-static" in place > of "ibm,plpks-sb-v0" to make it instantly clear that static mode > doesn't use the same version numbering scheme as dynamic mode. Sure. Thanks and Regards, Srish > >> } >> >> static int plpks_max_size(u64 *max_size)
On 5/5/25 4:36 AM, Andrew Donnellan wrote: > On Wed, 2025-04-30 at 14:33 +0530, Srish Srinivasan wrote: >> On a PLPKS enabled PowerVM LPAR, the secvar format property for >> static >> key management is misrepresented as "ibm,plpks-sb-unknown", creating >> reason for confusion. >> >> Static key management mode uses fixed, built-in keys. Dynamic key >> management mode allows keys to be updated in production to handle >> security updates without firmware rebuilds. >> >> Define a function named plpks_get_sb_keymgmt_mode() to retrieve the >> key management mode based on the existence of the SB_VERSION property >> in the firmware. >> >> Set the secvar format property to either "ibm,plpks-sb-v1" or >> "ibm,plpks-sb-v0" based on the key management mode, and return the >> length of the secvar format property. >> >> Co-developed-by: Souradeep <soura@imap.linux.ibm.com> >> Signed-off-by: Souradeep <soura@imap.linux.ibm.com> >> Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com> >> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> >> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com> >> --- >> arch/powerpc/platforms/pseries/plpks-secvar.c | 70 +++++++++++------ >> -- >> 1 file changed, 40 insertions(+), 30 deletions(-) >> >> diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c >> b/arch/powerpc/platforms/pseries/plpks-secvar.c >> index 257fd1f8bc19..d57067a733ab 100644 >> --- a/arch/powerpc/platforms/pseries/plpks-secvar.c >> +++ b/arch/powerpc/platforms/pseries/plpks-secvar.c >> @@ -152,39 +152,49 @@ static int plpks_set_variable(const char *key, >> u64 key_len, u8 *data, >> return rc; >> } >> >> -// PLPKS dynamic secure boot doesn't give us a format string in the >> same way OPAL does. >> -// Instead, report the format using the SB_VERSION variable in the >> keystore. >> -// The string is made up by us, and takes the form "ibm,plpks-sb- >> v<n>" (or "ibm,plpks-sb-unknown" >> -// if the SB_VERSION variable doesn't exist). Hypervisor defines the >> SB_VERSION variable as a >> -// "1 byte unsigned integer value". >> -static ssize_t plpks_secvar_format(char *buf, size_t bufsize) >> +/* >> + * Return the key management mode. >> + * >> + * SB_VERSION is defined as a "1 byte unsigned integer value". It is >> owned by >> + * the Partition Firmware and its presence indicates that the key >> management >> + * mode is dynamic. Only signed variables have null bytes in their >> names. >> + * SB_VERSION does not. >> + * >> + * Return 1 to indicate that the key management mode is dynamic. >> Otherwise >> + * return 0, indicating that the key management mode is static. >> + */ > This description isn't accurate. > > For dynamic mode, it doesn't return 1, it returns whatever version is > defined in SB_VERSION, which could be 1, or could at some later point be > a higher version. > > Which makes the function name a bit of a misnomer too - it is returning > the version number, just the version number can now be zero. > >> +static u8 plpks_get_sb_keymgmt_mode(void) >> { >> - struct plpks_var var = {0}; >> - ssize_t ret; >> - u8 version; >> - >> - var.component = NULL; >> - // Only the signed variables have null bytes in their names, >> this one doesn't >> - var.name = "SB_VERSION"; >> - var.namelen = strlen(var.name); >> - var.datalen = 1; >> - var.data = &version; >> - >> - // Unlike the other vars, SB_VERSION is owned by firmware >> instead of the OS >> - ret = plpks_read_fw_var(&var); >> - if (ret) { >> - if (ret == -ENOENT) { >> - ret = snprintf(buf, bufsize, "ibm,plpks-sb- >> unknown"); >> - } else { >> - pr_err("Error %ld reading SB_VERSION from >> firmware\n", ret); >> - ret = -EIO; >> - } >> - goto err; >> + u8 mode; >> + ssize_t rc; >> + struct plpks_var var = { >> + .component = NULL, >> + .name = "SB_VERSION", >> + .namelen = 10, >> + .datalen = 1, >> + .data = &mode, >> + }; >> + >> + rc = plpks_read_fw_var(&var); >> + if (rc) { >> + pr_info("Error %ld reading SB_VERSION from >> firmware\n", rc); > We need to check for -ENOENT, otherwise this message is going to be > printed every time you boot a machine in static mode. > > I think you should handle this as the existing code does: if it's > ENOENT, return 0, and for other codes print an error and return -EIO. > >> + mode = 0; >> } >> + return mode; >> +} >> >> - ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version); >> -err: >> - return ret; >> +// PLPKS dynamic secure boot doesn't give us a format string in the >> same way >> +// OPAL does. Instead, report the format using the SB_VERSION >> variable in the >> +// keystore. The string, made up by us, takes the form "ibm,plpks- >> sb-v<n>".Set >> +// the secvar format property to either "ibm,plpks-sb-v1" or >> "ibm,plpks-sb-v0", >> +// based on the key management mode, and return the length of the >> secvar format >> +// property. >> +static ssize_t plpks_secvar_format(char *buf, size_t bufsize) >> +{ >> + u8 mode; >> + >> + mode = plpks_get_sb_keymgmt_mode(); >> + return snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", mode); > It might be better to use something like "ibm,plpks-sb-static" in place > of "ibm,plpks-sb-v0" to make it instantly clear that static mode > doesn't use the same version numbering scheme as dynamic mode. Yes, "ibm,plpks-sb-static" is more clear compared to "ibm,plpks-sb-v0". However, I am not sure why "static mode doesn't use the same version numbering scheme as dynamic mode". Infact, as per my understanding, it is part of same versioning system. "0 represent static, 1 represent dynamic and anything beyond 1 would mean dynamic with additional features". Also, wouldn't having "ibm,pkpks-sb-static" and then "ibm,pkpk-sb-v1" for dynamic would be bit confusing? I mean being static is clear, but what they relate v1 to? Or did you mean to have "ibm,plpks-sb-static" and "ibm,plpks-sb-dynamic" for the two modes? Thanks & Regards, - Nayna
On Tue, 2025-05-06 at 15:27 -0400, Nayna Jain wrote: > > > It might be better to use something like "ibm,plpks-sb-static" in > > place > > of "ibm,plpks-sb-v0" to make it instantly clear that static mode > > doesn't use the same version numbering scheme as dynamic mode. > > Yes, "ibm,plpks-sb-static" is more clear compared to "ibm,plpks-sb- > v0". > However, I am not sure why "static mode doesn't use the same version > numbering scheme as dynamic mode". Infact, as per my understanding, > it > is part of same versioning system. "0 represent static, 1 represent > dynamic and anything beyond 1 would mean dynamic with additional > features". > > Also, wouldn't having "ibm,pkpks-sb-static" and then "ibm,pkpk-sb-v1" > for dynamic would be bit confusing? I mean being static is clear, but > what they relate v1 to? Or did you mean to have "ibm,plpks-sb-static" > and "ibm,plpks-sb-dynamic" for the two modes? > I don't feel strongly about this, as long as it's well documented.
On Wed, 2025-05-07 at 00:29 +0530, Srish Srinivasan wrote: > > > + rc = plpks_read_fw_var(&var); > > > + if (rc) { > > > + pr_info("Error %ld reading SB_VERSION from > > > firmware\n", rc); > > We need to check for -ENOENT, otherwise this message is going to be > > printed every time you boot a machine in static mode. > Yes, I agree with your concern. I just want to add that, as per my > understanding, we need to check for both -ENOENT and -EPERM, > as explained below: > > As per H_PKS_READ_OBJECT semantics described in the PAPR v10.60 > (https://files.openpower.foundation/s/XFgfMaqLMD5Bcm8), > > * If the object is not world readable, verify that the consumer > password > matches the stored value in the hypervisor. Else return H_AUTHORITY. > * Verify if the object exists, else return H_NOT_FOUND. > * Verify if the policy for the object is met, else return > H_AUTHORITY. > > So, the hypervisor returns H_NOT_FOUND only for the authenticated > consumer. For unauthenticated consumers, which is the case here, > it would return H_AUTHORITY. We expect SB_VERSION to always be world-readable, I think? In which case it shouldn't return H_AUTHORITY / -EPERM, ever, and if it does that's an error which should be handled as an error. Or am I misinterpreting the spec here?
On 5/7/25 11:47 AM, Andrew Donnellan wrote: > On Wed, 2025-05-07 at 00:29 +0530, Srish Srinivasan wrote: >>>> + rc = plpks_read_fw_var(&var); >>>> + if (rc) { >>>> + pr_info("Error %ld reading SB_VERSION from >>>> firmware\n", rc); >>> We need to check for -ENOENT, otherwise this message is going to be >>> printed every time you boot a machine in static mode. >> Yes, I agree with your concern. I just want to add that, as per my >> understanding, we need to check for both -ENOENT and -EPERM, >> as explained below: >> >> As per H_PKS_READ_OBJECT semantics described in the PAPR v10.60 >> (https://files.openpower.foundation/s/XFgfMaqLMD5Bcm8), >> >> * If the object is not world readable, verify that the consumer >> password >> matches the stored value in the hypervisor. Else return H_AUTHORITY. >> * Verify if the object exists, else return H_NOT_FOUND. >> * Verify if the policy for the object is met, else return >> H_AUTHORITY. >> >> So, the hypervisor returns H_NOT_FOUND only for the authenticated >> consumer. For unauthenticated consumers, which is the case here, >> it would return H_AUTHORITY. > We expect SB_VERSION to always be world-readable, I think? In which > case it shouldn't return H_AUTHORITY / -EPERM, ever, and if it does > that's an error which should be handled as an error. Or am I > misinterpreting the spec here? Yes, SB_VERSION is world-readable and should not return H_AUTHORITY in the case of dynamic key management mode. However, in the case of static key management mode, when SB_VERSION does not exist, the hypervisor tries to authenticate the consumer. If the authentication is successful, H_NOT_FOUND is returned, else H_AUTHORITY is returned. The intention behind authenticating the consumer when the object is not found is to ensure that a non-authenticated consumer is unable to conclude on the absence of the object. Here, when the kernel tries to read the non-existent SB_VERSION, it fails the authentication check and therefore, gets the H_AUTHORITY error code. > >
On Wed, 2025-05-07 at 21:18 +0530, Srish Srinivasan wrote: > > We expect SB_VERSION to always be world-readable, I think? In which > > case it shouldn't return H_AUTHORITY / -EPERM, ever, and if it does > > that's an error which should be handled as an error. Or am I > > misinterpreting the spec here? > > Yes, SB_VERSION is world-readable and should not return H_AUTHORITY > in > the case of dynamic key management mode. However, in > the case of static key management mode, when SB_VERSION does not > exist, > the hypervisor tries to authenticate the consumer. If the > authentication is successful, H_NOT_FOUND is returned, else > H_AUTHORITY > is returned. The intention behind authenticating the > consumer when the object is not found is to ensure that a > non-authenticated consumer is unable to conclude on the absence of > the object. Here, when the kernel tries to read the non-existent > SB_VERSION, it fails the authentication check and therefore, > gets the H_AUTHORITY error code. Ah, I see my confusion: if the object *doesn't exist*, then it obviously can't be a world-readable object, thus triggering the password verification. In which case, we do need to catch -EPERM. Thanks for correcting me!
On Wed, 2025-05-07 at 00:29 +0530, Srish Srinivasan wrote: > > I think you should handle this as the existing code does: if it's > > ENOENT, return 0, and for other codes print an error and return - > > EIO. > Currently, the other layers in the boot stack assume static key mode > for > any failure in reading SB_VERSION. We added the same interpretation > in the kernel to keep it consistent with the other layers, and > represent > the same to the user. This is the reason for not parsing the error > codes > when trying to read SB_VERSION, and defaulting to the static key > management mode. However, we want the exact error code to be logged > for debugging purposes. And, it does make sense to have logging only > for > error codes other than -ENOENT and -EPERM, as you suggested. > Does this sound okay? Okay, maybe document explicitly in a comment that we default to static mode in the event of any weird errors.
On 5/12/25 3:25 PM, Andrew Donnellan wrote: > On Wed, 2025-05-07 at 00:29 +0530, Srish Srinivasan wrote: >>> I think you should handle this as the existing code does: if it's >>> ENOENT, return 0, and for other codes print an error and return - >>> EIO. >> Currently, the other layers in the boot stack assume static key mode >> for >> any failure in reading SB_VERSION. We added the same interpretation >> in the kernel to keep it consistent with the other layers, and >> represent >> the same to the user. This is the reason for not parsing the error >> codes >> when trying to read SB_VERSION, and defaulting to the static key >> management mode. However, we want the exact error code to be logged >> for debugging purposes. And, it does make sense to have logging only >> for >> error codes other than -ENOENT and -EPERM, as you suggested. >> Does this sound okay? > Okay, maybe document explicitly in a comment that we default to static > mode in the event of any weird errors. Sure, will do that. Thank You. >
diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c b/arch/powerpc/platforms/pseries/plpks-secvar.c index 257fd1f8bc19..d57067a733ab 100644 --- a/arch/powerpc/platforms/pseries/plpks-secvar.c +++ b/arch/powerpc/platforms/pseries/plpks-secvar.c @@ -152,39 +152,49 @@ static int plpks_set_variable(const char *key, u64 key_len, u8 *data, return rc; } -// PLPKS dynamic secure boot doesn't give us a format string in the same way OPAL does. -// Instead, report the format using the SB_VERSION variable in the keystore. -// The string is made up by us, and takes the form "ibm,plpks-sb-v<n>" (or "ibm,plpks-sb-unknown" -// if the SB_VERSION variable doesn't exist). Hypervisor defines the SB_VERSION variable as a -// "1 byte unsigned integer value". -static ssize_t plpks_secvar_format(char *buf, size_t bufsize) +/* + * Return the key management mode. + * + * SB_VERSION is defined as a "1 byte unsigned integer value". It is owned by + * the Partition Firmware and its presence indicates that the key management + * mode is dynamic. Only signed variables have null bytes in their names. + * SB_VERSION does not. + * + * Return 1 to indicate that the key management mode is dynamic. Otherwise + * return 0, indicating that the key management mode is static. + */ +static u8 plpks_get_sb_keymgmt_mode(void) { - struct plpks_var var = {0}; - ssize_t ret; - u8 version; - - var.component = NULL; - // Only the signed variables have null bytes in their names, this one doesn't - var.name = "SB_VERSION"; - var.namelen = strlen(var.name); - var.datalen = 1; - var.data = &version; - - // Unlike the other vars, SB_VERSION is owned by firmware instead of the OS - ret = plpks_read_fw_var(&var); - if (ret) { - if (ret == -ENOENT) { - ret = snprintf(buf, bufsize, "ibm,plpks-sb-unknown"); - } else { - pr_err("Error %ld reading SB_VERSION from firmware\n", ret); - ret = -EIO; - } - goto err; + u8 mode; + ssize_t rc; + struct plpks_var var = { + .component = NULL, + .name = "SB_VERSION", + .namelen = 10, + .datalen = 1, + .data = &mode, + }; + + rc = plpks_read_fw_var(&var); + if (rc) { + pr_info("Error %ld reading SB_VERSION from firmware\n", rc); + mode = 0; } + return mode; +} - ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version); -err: - return ret; +// PLPKS dynamic secure boot doesn't give us a format string in the same way +// OPAL does. Instead, report the format using the SB_VERSION variable in the +// keystore. The string, made up by us, takes the form "ibm,plpks-sb-v<n>".Set +// the secvar format property to either "ibm,plpks-sb-v1" or "ibm,plpks-sb-v0", +// based on the key management mode, and return the length of the secvar format +// property. +static ssize_t plpks_secvar_format(char *buf, size_t bufsize) +{ + u8 mode; + + mode = plpks_get_sb_keymgmt_mode(); + return snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", mode); } static int plpks_max_size(u64 *max_size)