查看“STM32 header for binary files”的源代码

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The STM32 header is a STMicroelectronics header needed for binaries loaded by [[:Category:ROM_code|ROM code]] and by [[TF-A_overview|TF-A]].

== Description ==
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[[File:STM32_header.png | right | |400px]]

Each binary image (signed or not) loaded by [[:Category:ROM_code|ROM code]] and by [[TF-A_overview|TF-A]] need to include a specific STM32 header added on top of the binary data. The header includes the authentication information.

{|
! Name !! Length !! Byte Offset !! Description
|-
| Magic number || 32 bits || 0 || 4 bytes in big endian:<br> 'S', 'T', 'M', 0x32 = 0x53544D32
|-
| Image signature || 512 bits || 4 || ECDSA signature for image authentication<ref group="Note">Signature is calculated from first byte of header version field to last byte of image given by image length field.</ref>
|-
| Image checksum || 32 bits || 68 || Checksum of the payload<ref group="Note">32-bit sum of all payload bytes accessed as 8-bit unsigned numbers, discarding any overflow bits. Used to check the downloaded image integrity when signature is not used (if b0=1 in Option flags).</ref>
|-
| Header version || 32 bits || 72 || Header version v1.0 = 0x00010000<br>    Byte0: reserved<br>    Byte1:major version = 0x01  <br>    Byte2: minor version = 0x00 <br>    Byte3: reserved
|-
| Image length || 32 bits || 76 || Length of image in bytes<ref group="Note">Length is the length of the built image, it does not include the length of the STM32 header.</ref>
|-
| Image entry  Point || 32 bits || 80 || Entry point of image
|-
| Reserved1 || 32 bits || 84 || Reserved
|-
| Load address || 32 bits || 88 || Load address of image<ref group="Note">This field is not used by ROM code.</ref>
|-
| Reserved2 || 32 bits || 92 || Reserved
|-
| Version number || 32 bits || 96 || Image Version (monotonic number)<ref group="Note">Image '''version number''' is an anti rollback monotonic counter. The ROM code checks that it is higher or equal to the monotonic counter stored in OTP.</ref>
|-
| Option flags || 32 bits || 100 || b0=1: no signature verification<ref group="Note">Enabling signature verification is mandatory on secure closed chips.</ref>
|-
| ECDSA algorithm || 32 bits || 104 || 1: P-256 NIST ; 2: brainpool 256
|-
| ECDSA public key || 512 bits || 108 || ECDSA public key to be used to verify the signature.<ref group="Note"> This field is an extract of PEM public key file that only kept the ECC Point coordinates ''x'' and ''y'' in a raw binary format  ([http://www.rfc-editor.org/info/rfc5480 RFC 5480]). This field will be hashed with SHA-256 and compared to the '''Hash of pubKey''' that is stored in OTP.</ref>
|-
| Padding || 83 Bytes || 172 || Reserved padding bytes<ref group="Note">This padding forces STM32 header size to 256 bytes (0x100).</ref>. Must all be set to 0
|-
| Binary type || 1 Byte || 255 || Used to check the binary type<br>0x00: U-Boot <br>0x10-0x1F: TF-A <br>0x20-0X2F: OPTEE <br>0x30: Copro
|}
<references group="Note"/>

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The OTP used for the '''Version number''' and the '''Hash of pubKey''' are defined in the chapter “OTP configuration“ of the [[: Category:ROM_code |ROM code overview]].

[[Category:ROM code|0]]
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