[PATCH 5/8] efi_loader: Make the pkcs7 header parsing function an extern
Akashi Takahiro
takahiro.akashi at linaro.org
Fri May 8 02:51:24 CEST 2020
On Thu, May 07, 2020 at 04:48:30PM +0530, Sughosh Ganu wrote:
> On Thu, 7 May 2020 at 13:04, Akashi Takahiro <takahiro.akashi at linaro.org>
> wrote:
>
> > On Thu, Apr 30, 2020 at 11:06:27PM +0530, Sughosh Ganu wrote:
> > > The pkcs7 header parsing functionality is pretty generic, and can be
> > > used by other features like capsule authentication. Make the function
> > > as an extern, also changing it's name to efi_parse_pkcs7_header.
> >
> > The patch itself is fine to me, but is "pkcs7 header" a common term?
> >
>
> I haven't come across it in any other code base. I used it since in the
> concept of a capsule, the signature is prepended to the capsule payload. If
> you can think of a better name, please suggest so. I will change it in the
> next version.
Simply, efi_parse_pkcs7_signature()?
In addition, please update the function description, which still
mentions "variable."
-Takahiro Akashi
> -sughosh
>
>
> >
> > -Takahiro Akashi
> >
> > >
> > > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > > ---
> > > include/efi_loader.h | 2 +
> > > lib/efi_loader/efi_signature.c | 78 ++++++++++++++++++++++++++++++++
> > > lib/efi_loader/efi_variable.c | 82 +---------------------------------
> > > 3 files changed, 82 insertions(+), 80 deletions(-)
> > >
> > > diff --git a/include/efi_loader.h b/include/efi_loader.h
> > > index b7638d5825..8d923451ce 100644
> > > --- a/include/efi_loader.h
> > > +++ b/include/efi_loader.h
> > > @@ -781,6 +781,8 @@ bool efi_secure_boot_enabled(void);
> > >
> > > bool efi_image_parse(void *efi, size_t len, struct efi_image_regions
> > **regp,
> > > WIN_CERTIFICATE **auth, size_t *auth_len);
> > > +struct pkcs7_message *efi_parse_pkcs7_header(const void *buf, size_t
> > buflen);
> > > +
> > > #endif /* CONFIG_EFI_SECURE_BOOT */
> > >
> > > #ifdef CONFIG_EFI_HAVE_CAPSULE_SUPPORT
> > > diff --git a/lib/efi_loader/efi_signature.c
> > b/lib/efi_loader/efi_signature.c
> > > index bf6f39aab2..9897f5418e 100644
> > > --- a/lib/efi_loader/efi_signature.c
> > > +++ b/lib/efi_loader/efi_signature.c
> > > @@ -25,6 +25,84 @@ const efi_guid_t efi_guid_cert_x509_sha256 =
> > EFI_CERT_X509_SHA256_GUID;
> > >
> > > #ifdef CONFIG_EFI_SECURE_BOOT
> > >
> > > +static u8 pkcs7_hdr[] = {
> > > + /* SEQUENCE */
> > > + 0x30, 0x82, 0x05, 0xc7,
> > > + /* OID: pkcs7-signedData */
> > > + 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x02,
> > > + /* Context Structured? */
> > > + 0xa0, 0x82, 0x05, 0xb8,
> > > +};
> > > +
> > > +/**
> > > + * efi_parse_pkcs7_header - parse a signature in variable
> > > + * @buf: Pointer to the payload's value
> > > + * @buflen: Length of @buf
> > > + *
> > > + * Parse a signature embedded in variable's value and instantiate
> > > + * a pkcs7_message structure. Since pkcs7_parse_message() accepts only
> > > + * pkcs7's signedData, some header needed be prepended for correctly
> > > + * parsing authentication data, particularly for variable's.
> > > + *
> > > + * Return: Pointer to pkcs7_message structure on success, NULL on
> > error
> > > + */
> > > +struct pkcs7_message *efi_parse_pkcs7_header(const void *buf, size_t
> > buflen)
> > > +{
> > > + u8 *ebuf;
> > > + size_t ebuflen, len;
> > > + struct pkcs7_message *msg;
> > > +
> > > + /*
> > > + * This is the best assumption to check if the binary is
> > > + * already in a form of pkcs7's signedData.
> > > + */
> > > + if (buflen > sizeof(pkcs7_hdr) &&
> > > + !memcmp(&((u8 *)buf)[4], &pkcs7_hdr[4], 11)) {
> > > + msg = pkcs7_parse_message(buf, buflen);
> > > + goto out;
> > > + }
> > > +
> > > + /*
> > > + * Otherwise, we should add a dummy prefix sequence for pkcs7
> > > + * message parser to be able to process.
> > > + * NOTE: EDK2 also uses similar hack in WrapPkcs7Data()
> > > + * in CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyCommon.c
> > > + * TODO:
> > > + * The header should be composed in a more refined manner.
> > > + */
> > > + debug("Makeshift prefix added to authentication data\n");
> > > + ebuflen = sizeof(pkcs7_hdr) + buflen;
> > > + if (ebuflen <= 0x7f) {
> > > + debug("Data is too short\n");
> > > + return NULL;
> > > + }
> > > +
> > > + ebuf = malloc(ebuflen);
> > > + if (!ebuf) {
> > > + debug("Out of memory\n");
> > > + return NULL;
> > > + }
> > > +
> > > + memcpy(ebuf, pkcs7_hdr, sizeof(pkcs7_hdr));
> > > + memcpy(ebuf + sizeof(pkcs7_hdr), buf, buflen);
> > > + len = ebuflen - 4;
> > > + ebuf[2] = (len >> 8) & 0xff;
> > > + ebuf[3] = len & 0xff;
> > > + len = ebuflen - 0x13;
> > > + ebuf[0x11] = (len >> 8) & 0xff;
> > > + ebuf[0x12] = len & 0xff;
> > > +
> > > + msg = pkcs7_parse_message(ebuf, ebuflen);
> > > +
> > > + free(ebuf);
> > > +
> > > +out:
> > > + if (IS_ERR(msg))
> > > + return NULL;
> > > +
> > > + return msg;
> > > +}
> > > +
> > > /**
> > > * efi_hash_regions - calculate a hash value
> > > * @regs: List of regions
> > > diff --git a/lib/efi_loader/efi_variable.c
> > b/lib/efi_loader/efi_variable.c
> > > index 6c2dd82306..be34a2cadd 100644
> > > --- a/lib/efi_loader/efi_variable.c
> > > +++ b/lib/efi_loader/efi_variable.c
> > > @@ -415,85 +415,7 @@ bool efi_secure_boot_enabled(void)
> > > return efi_secure_boot;
> > > }
> > >
> > > -#ifdef CONFIG_EFI_SECURE_BOOT
> > > -static u8 pkcs7_hdr[] = {
> > > - /* SEQUENCE */
> > > - 0x30, 0x82, 0x05, 0xc7,
> > > - /* OID: pkcs7-signedData */
> > > - 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x02,
> > > - /* Context Structured? */
> > > - 0xa0, 0x82, 0x05, 0xb8,
> > > -};
> > > -
> > > -/**
> > > - * efi_variable_parse_signature - parse a signature in variable
> > > - * @buf: Pointer to variable's value
> > > - * @buflen: Length of @buf
> > > - *
> > > - * Parse a signature embedded in variable's value and instantiate
> > > - * a pkcs7_message structure. Since pkcs7_parse_message() accepts only
> > > - * pkcs7's signedData, some header needed be prepended for correctly
> > > - * parsing authentication data, particularly for variable's.
> > > - *
> > > - * Return: Pointer to pkcs7_message structure on success, NULL on
> > error
> > > - */
> > > -static struct pkcs7_message *efi_variable_parse_signature(const void
> > *buf,
> > > - size_t buflen)
> > > -{
> > > - u8 *ebuf;
> > > - size_t ebuflen, len;
> > > - struct pkcs7_message *msg;
> > > -
> > > - /*
> > > - * This is the best assumption to check if the binary is
> > > - * already in a form of pkcs7's signedData.
> > > - */
> > > - if (buflen > sizeof(pkcs7_hdr) &&
> > > - !memcmp(&((u8 *)buf)[4], &pkcs7_hdr[4], 11)) {
> > > - msg = pkcs7_parse_message(buf, buflen);
> > > - goto out;
> > > - }
> > > -
> > > - /*
> > > - * Otherwise, we should add a dummy prefix sequence for pkcs7
> > > - * message parser to be able to process.
> > > - * NOTE: EDK2 also uses similar hack in WrapPkcs7Data()
> > > - * in CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyCommon.c
> > > - * TODO:
> > > - * The header should be composed in a more refined manner.
> > > - */
> > > - debug("Makeshift prefix added to authentication data\n");
> > > - ebuflen = sizeof(pkcs7_hdr) + buflen;
> > > - if (ebuflen <= 0x7f) {
> > > - debug("Data is too short\n");
> > > - return NULL;
> > > - }
> > > -
> > > - ebuf = malloc(ebuflen);
> > > - if (!ebuf) {
> > > - debug("Out of memory\n");
> > > - return NULL;
> > > - }
> > > -
> > > - memcpy(ebuf, pkcs7_hdr, sizeof(pkcs7_hdr));
> > > - memcpy(ebuf + sizeof(pkcs7_hdr), buf, buflen);
> > > - len = ebuflen - 4;
> > > - ebuf[2] = (len >> 8) & 0xff;
> > > - ebuf[3] = len & 0xff;
> > > - len = ebuflen - 0x13;
> > > - ebuf[0x11] = (len >> 8) & 0xff;
> > > - ebuf[0x12] = len & 0xff;
> > > -
> > > - msg = pkcs7_parse_message(ebuf, ebuflen);
> > > -
> > > - free(ebuf);
> > > -
> > > -out:
> > > - if (IS_ERR(msg))
> > > - return NULL;
> > > -
> > > - return msg;
> > > -}
> > > +#ifdef CONFIG_SECURE_BOOT
> > >
> > > /**
> > > * efi_variable_authenticate - authenticate a variable
> > > @@ -591,7 +513,7 @@ static efi_status_t efi_variable_authenticate(u16
> > *variable,
> > > /* variable's signature list */
> > > if (auth->auth_info.hdr.dwLength < sizeof(auth->auth_info))
> > > goto err;
> > > - var_sig = efi_variable_parse_signature(auth->auth_info.cert_data,
> > > + var_sig = efi_parse_pkcs7_header(auth->auth_info.cert_data,
> > > auth->auth_info.hdr.dwLength
> > > -
> > sizeof(auth->auth_info));
> > > if (IS_ERR(var_sig)) {
> > > --
> > > 2.17.1
> > >
> >
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