linux-kernel - Re: [PATCH v6 06/14] x86: Add early SHA support for Secure Launch early measurements

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Date:   Mon, 15 May 2023 20:50:13 -0400
From:   "Daniel P. Smith" <dpsmith@...rtussolutions.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        Ross Philipson <ross.philipson@...cle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-crypto@...r.kernel.org, iommu@...ts.linux-foundation.org,
        kexec@...ts.infradead.org, linux-efi@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        ardb@...nel.org, mjg59@...f.ucam.org,
        James.Bottomley@...senpartnership.com, luto@...capital.net,
        nivedita@...m.mit.edu, kanth.ghatraju@...cle.com,
        trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v6 06/14] x86: Add early SHA support for Secure Launch
 early measurements

On 5/10/23 23:33, Herbert Xu wrote:
> Ross Philipson <ross.philipson@...cle.com> wrote:
>>
>> +static void __sha_transform(u32 *digest, const char *data)
>> +{
>> +       u32 ws[SHA1_WORKSPACE_WORDS];
>> +
>> +       sha1_transform(digest, data, ws);
>> +
>> +       memzero_explicit(ws, sizeof(ws));
>> +}
>> +
>> +void early_sha1_init(struct sha1_state *sctx)
>> +{
>> +       sha1_init(sctx->state);
>> +       sctx->count = 0;
>> +}
>> +
>> +void early_sha1_update(struct sha1_state *sctx,
>> +                      const u8 *data,
>> +                      unsigned int len)
>> +{
>> +       unsigned int partial = sctx->count % SHA1_BLOCK_SIZE;
>> +
>> +       sctx->count += len;
>> +
>> +       if (likely((partial + len) >= SHA1_BLOCK_SIZE)) {
>> +               int blocks;
>> +
>> +               if (partial) {
>> +                       int p = SHA1_BLOCK_SIZE - partial;
>> +
>> +                       memcpy(sctx->buffer + partial, data, p);
>> +                       data += p;
>> +                       len -= p;
>> +
>> +                       __sha_transform(sctx->state, sctx->buffer);
>> +               }
>> +
>> +               blocks = len / SHA1_BLOCK_SIZE;
>> +               len %= SHA1_BLOCK_SIZE;
>> +
>> +               if (blocks) {
>> +                       while (blocks--) {
>> +                               __sha_transform(sctx->state, data);
>> +                               data += SHA1_BLOCK_SIZE;
>> +                       }
>> +               }
>> +               partial = 0;
>> +       }
>> +
>> +       if (len)
>> +               memcpy(sctx->buffer + partial, data, len);
>> +}
>> +
>> +void early_sha1_final(struct sha1_state *sctx, u8 *out)
>> +{
>> +       const int bit_offset = SHA1_BLOCK_SIZE - sizeof(__be64);
>> +       unsigned int partial = sctx->count % SHA1_BLOCK_SIZE;
>> +       __be64 *bits = (__be64 *)(sctx->buffer + bit_offset);
>> +       __be32 *digest = (__be32 *)out;
>> +       int i;
>> +
>> +       sctx->buffer[partial++] = 0x80;
>> +       if (partial > bit_offset) {
>> +               memset(sctx->buffer + partial, 0x0, SHA1_BLOCK_SIZE - partial);
>> +               partial = 0;
>> +
>> +               __sha_transform(sctx->state, sctx->buffer);
>> +       }
>> +
>> +       memset(sctx->buffer + partial, 0x0, bit_offset - partial);
>> +       *bits = cpu_to_be64(sctx->count << 3);
>> +       __sha_transform(sctx->state, sctx->buffer);
>> +
>> +       for (i = 0; i < SHA1_DIGEST_SIZE / sizeof(__be32); i++)
>> +               put_unaligned_be32(sctx->state[i], digest++);
>> +
>> +       *sctx = (struct sha1_state){};
>> +}
> 
> If we're going to add SHA1 then this should go into lib/crypto
> just like SHA2.

As mentioned before, this patch mimicked an early version for SHA2. We 
were remiss in not keeping it aligned with how the SHA2 evolved. I will 
take a closer look, but these wrappers may be able to go away and be 
reduced to just an include as SHA2 does these days.

v/r,
dps