| Message ID | 20231024162024.51260-2-david@sigma-star.at (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | DCP as trusted keys backend | expand |
On Tue Oct 24, 2023 at 7:20 PM EEST, David Gstir wrote: > DCP is capable of performing AES with two hardware-bound keys: > > - The one-time programmable (OTP) key which is burnt via on-chip fuses > - The unique key (UK) which is derived from the OTP key > > In addition to the two hardware-bound keys, DCP also supports > storing keys in 4 dedicated key slots within its secure memory area > (internal SRAM). > > These keys are not stored in main memory and are therefore > not directly accessible by the operating system. To use them > for AES operations, a one-byte key reference has to supplied > with the DCP operation descriptor in the control register. > > This adds support for using any of these 6 keys through the crypto API > via their key reference after they have been set up. The main purpose > is to add support for DCP-backed trusted keys. Other use cases are > possible too (see similar existing paes implementations), but these > should carefully be evaluated as e.g. enabling AF_ALG will give > userspace full access to use keys. In scenarios with untrustworthy > userspace, this will enable en-/decryption oracles. > > Co-developed-by: Richard Weinberger <richard@nod.at> > Signed-off-by: Richard Weinberger <richard@nod.at> > Co-developed-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> > Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> > Signed-off-by: David Gstir <david@sigma-star.at> > --- > drivers/crypto/mxs-dcp.c | 104 ++++++++++++++++++++++++++++++++++----- > include/soc/fsl/dcp.h | 17 +++++++ > 2 files changed, 110 insertions(+), 11 deletions(-) > create mode 100644 include/soc/fsl/dcp.h > > diff --git a/drivers/crypto/mxs-dcp.c b/drivers/crypto/mxs-dcp.c > index f6b7bce0e656..2dc664fb2faf 100644 > --- a/drivers/crypto/mxs-dcp.c > +++ b/drivers/crypto/mxs-dcp.c > @@ -15,6 +15,7 @@ > #include <linux/platform_device.h> > #include <linux/stmp_device.h> > #include <linux/clk.h> > +#include <soc/fsl/dcp.h> > > #include <crypto/aes.h> > #include <crypto/sha1.h> > @@ -101,6 +102,7 @@ struct dcp_async_ctx { > struct crypto_skcipher *fallback; > unsigned int key_len; > uint8_t key[AES_KEYSIZE_128]; > + bool key_referenced; > }; > > struct dcp_aes_req_ctx { > @@ -155,6 +157,7 @@ static struct dcp *global_sdcp; > #define MXS_DCP_CONTROL0_HASH_TERM (1 << 13) > #define MXS_DCP_CONTROL0_HASH_INIT (1 << 12) > #define MXS_DCP_CONTROL0_PAYLOAD_KEY (1 << 11) > +#define MXS_DCP_CONTROL0_OTP_KEY (1 << 10) > #define MXS_DCP_CONTROL0_CIPHER_ENCRYPT (1 << 8) > #define MXS_DCP_CONTROL0_CIPHER_INIT (1 << 9) > #define MXS_DCP_CONTROL0_ENABLE_HASH (1 << 6) > @@ -168,6 +171,8 @@ static struct dcp *global_sdcp; > #define MXS_DCP_CONTROL1_CIPHER_MODE_ECB (0 << 4) > #define MXS_DCP_CONTROL1_CIPHER_SELECT_AES128 (0 << 0) > > +#define MXS_DCP_CONTROL1_KEY_SELECT_SHIFT 8 > + > static int mxs_dcp_start_dma(struct dcp_async_ctx *actx) > { > int dma_err; > @@ -224,13 +229,16 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, > struct dcp *sdcp = global_sdcp; > struct dcp_dma_desc *desc = &sdcp->coh->desc[actx->chan]; > struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req); > + bool key_referenced = actx->key_referenced; > int ret; > > - key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key, > - 2 * AES_KEYSIZE_128, DMA_TO_DEVICE); > - ret = dma_mapping_error(sdcp->dev, key_phys); > - if (ret) > - return ret; > + if (!key_referenced) { > + key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key, > + 2 * AES_KEYSIZE_128, DMA_TO_DEVICE); > + ret = dma_mapping_error(sdcp->dev, key_phys); > + if (ret) > + return ret; > + } > > src_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_in_buf, > DCP_BUF_SZ, DMA_TO_DEVICE); > @@ -255,8 +263,12 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, > MXS_DCP_CONTROL0_INTERRUPT | > MXS_DCP_CONTROL0_ENABLE_CIPHER; > > - /* Payload contains the key. */ > - desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY; > + if (key_referenced) > + /* Set OTP key bit to select the key via KEY_SELECT. */ > + desc->control0 |= MXS_DCP_CONTROL0_OTP_KEY; > + else > + /* Payload contains the key. */ > + desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY; > > if (rctx->enc) > desc->control0 |= MXS_DCP_CONTROL0_CIPHER_ENCRYPT; > @@ -270,6 +282,9 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, > else > desc->control1 |= MXS_DCP_CONTROL1_CIPHER_MODE_CBC; > > + if (key_referenced) > + desc->control1 |= sdcp->coh->aes_key[0] << MXS_DCP_CONTROL1_KEY_SELECT_SHIFT; > + > desc->next_cmd_addr = 0; > desc->source = src_phys; > desc->destination = dst_phys; > @@ -284,9 +299,9 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, > err_dst: > dma_unmap_single(sdcp->dev, src_phys, DCP_BUF_SZ, DMA_TO_DEVICE); > err_src: > - dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128, > - DMA_TO_DEVICE); > - > + if (!key_referenced) > + dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128, > + DMA_TO_DEVICE); > return ret; > } > > @@ -453,7 +468,7 @@ static int mxs_dcp_aes_enqueue(struct skcipher_request *req, int enc, int ecb) > struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req); > int ret; > > - if (unlikely(actx->key_len != AES_KEYSIZE_128)) > + if (unlikely(actx->key_len != AES_KEYSIZE_128 && !actx->key_referenced)) > return mxs_dcp_block_fallback(req, enc); > > rctx->enc = enc; > @@ -500,6 +515,7 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key, > * there can still be an operation in progress. > */ > actx->key_len = len; > + actx->key_referenced = false; > if (len == AES_KEYSIZE_128) { > memcpy(actx->key, key, len); > return 0; > @@ -516,6 +532,32 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key, > return crypto_skcipher_setkey(actx->fallback, key, len); > } > > +static int mxs_dcp_aes_setrefkey(struct crypto_skcipher *tfm, const u8 *key, > + unsigned int len) > +{ > + struct dcp_async_ctx *actx = crypto_skcipher_ctx(tfm); > + > + if (len != DCP_PAES_KEYSIZE) > + return -EINVAL; > + > + switch (key[0]) { > + case DCP_PAES_KEY_SLOT0: > + case DCP_PAES_KEY_SLOT1: > + case DCP_PAES_KEY_SLOT2: > + case DCP_PAES_KEY_SLOT3: > + case DCP_PAES_KEY_UNIQUE: > + case DCP_PAES_KEY_OTP: > + memcpy(actx->key, key, len); > + actx->key_len = len; > + actx->key_referenced = true; > + break; > + default: > + return -EINVAL; > + } > + > + return 0; > +} > + > static int mxs_dcp_aes_fallback_init_tfm(struct crypto_skcipher *tfm) > { > const char *name = crypto_tfm_alg_name(crypto_skcipher_tfm(tfm)); > @@ -539,6 +581,13 @@ static void mxs_dcp_aes_fallback_exit_tfm(struct crypto_skcipher *tfm) > crypto_free_skcipher(actx->fallback); > } > > +static int mxs_dcp_paes_init_tfm(struct crypto_skcipher *tfm) > +{ > + crypto_skcipher_set_reqsize(tfm, sizeof(struct dcp_aes_req_ctx)); > + > + return 0; > +} > + > /* > * Hashing (SHA1/SHA256) > */ > @@ -889,6 +938,39 @@ static struct skcipher_alg dcp_aes_algs[] = { > .ivsize = AES_BLOCK_SIZE, > .init = mxs_dcp_aes_fallback_init_tfm, > .exit = mxs_dcp_aes_fallback_exit_tfm, > + }, { > + .base.cra_name = "ecb(paes)", > + .base.cra_driver_name = "ecb-paes-dcp", > + .base.cra_priority = 401, > + .base.cra_alignmask = 15, > + .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL, > + .base.cra_blocksize = AES_BLOCK_SIZE, > + .base.cra_ctxsize = sizeof(struct dcp_async_ctx), > + .base.cra_module = THIS_MODULE, > + > + .min_keysize = DCP_PAES_KEYSIZE, > + .max_keysize = DCP_PAES_KEYSIZE, > + .setkey = mxs_dcp_aes_setrefkey, > + .encrypt = mxs_dcp_aes_ecb_encrypt, > + .decrypt = mxs_dcp_aes_ecb_decrypt, > + .init = mxs_dcp_paes_init_tfm, > + }, { > + .base.cra_name = "cbc(paes)", > + .base.cra_driver_name = "cbc-paes-dcp", > + .base.cra_priority = 401, > + .base.cra_alignmask = 15, > + .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL, > + .base.cra_blocksize = AES_BLOCK_SIZE, > + .base.cra_ctxsize = sizeof(struct dcp_async_ctx), > + .base.cra_module = THIS_MODULE, > + > + .min_keysize = DCP_PAES_KEYSIZE, > + .max_keysize = DCP_PAES_KEYSIZE, > + .setkey = mxs_dcp_aes_setrefkey, > + .encrypt = mxs_dcp_aes_cbc_encrypt, > + .decrypt = mxs_dcp_aes_cbc_decrypt, > + .ivsize = AES_BLOCK_SIZE, > + .init = mxs_dcp_paes_init_tfm, > }, > }; > > diff --git a/include/soc/fsl/dcp.h b/include/soc/fsl/dcp.h > new file mode 100644 > index 000000000000..cda89e260c46 > --- /dev/null > +++ b/include/soc/fsl/dcp.h > @@ -0,0 +1,17 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2021 sigma star gmbh > + */ > + > +#ifndef MXS_DCP_H > +#define MXS_DCP_H > + > +#define DCP_PAES_KEYSIZE 1 > +#define DCP_PAES_KEY_SLOT0 0x00 > +#define DCP_PAES_KEY_SLOT1 0x01 > +#define DCP_PAES_KEY_SLOT2 0x02 > +#define DCP_PAES_KEY_SLOT3 0x03 > +#define DCP_PAES_KEY_UNIQUE 0xfe > +#define DCP_PAES_KEY_OTP 0xff > + > +#endif /* MXS_DCP_H */ For me this looks quite reasonable. BR, Jarkko
On Tue, Oct 24, 2023 at 06:20:15PM +0200, David Gstir wrote: > DCP is capable of performing AES with two hardware-bound keys: > > - The one-time programmable (OTP) key which is burnt via on-chip fuses > - The unique key (UK) which is derived from the OTP key > > In addition to the two hardware-bound keys, DCP also supports > storing keys in 4 dedicated key slots within its secure memory area > (internal SRAM). > > These keys are not stored in main memory and are therefore > not directly accessible by the operating system. To use them > for AES operations, a one-byte key reference has to supplied > with the DCP operation descriptor in the control register. > > This adds support for using any of these 6 keys through the crypto API > via their key reference after they have been set up. The main purpose > is to add support for DCP-backed trusted keys. Other use cases are > possible too (see similar existing paes implementations), but these > should carefully be evaluated as e.g. enabling AF_ALG will give > userspace full access to use keys. In scenarios with untrustworthy > userspace, this will enable en-/decryption oracles. > > Co-developed-by: Richard Weinberger <richard@nod.at> > Signed-off-by: Richard Weinberger <richard@nod.at> > Co-developed-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> > Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at> > Signed-off-by: David Gstir <david@sigma-star.at> > --- > drivers/crypto/mxs-dcp.c | 104 ++++++++++++++++++++++++++++++++++----- > include/soc/fsl/dcp.h | 17 +++++++ > 2 files changed, 110 insertions(+), 11 deletions(-) > create mode 100644 include/soc/fsl/dcp.h Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/drivers/crypto/mxs-dcp.c b/drivers/crypto/mxs-dcp.c index f6b7bce0e656..2dc664fb2faf 100644 --- a/drivers/crypto/mxs-dcp.c +++ b/drivers/crypto/mxs-dcp.c @@ -15,6 +15,7 @@ #include <linux/platform_device.h> #include <linux/stmp_device.h> #include <linux/clk.h> +#include <soc/fsl/dcp.h> #include <crypto/aes.h> #include <crypto/sha1.h> @@ -101,6 +102,7 @@ struct dcp_async_ctx { struct crypto_skcipher *fallback; unsigned int key_len; uint8_t key[AES_KEYSIZE_128]; + bool key_referenced; }; struct dcp_aes_req_ctx { @@ -155,6 +157,7 @@ static struct dcp *global_sdcp; #define MXS_DCP_CONTROL0_HASH_TERM (1 << 13) #define MXS_DCP_CONTROL0_HASH_INIT (1 << 12) #define MXS_DCP_CONTROL0_PAYLOAD_KEY (1 << 11) +#define MXS_DCP_CONTROL0_OTP_KEY (1 << 10) #define MXS_DCP_CONTROL0_CIPHER_ENCRYPT (1 << 8) #define MXS_DCP_CONTROL0_CIPHER_INIT (1 << 9) #define MXS_DCP_CONTROL0_ENABLE_HASH (1 << 6) @@ -168,6 +171,8 @@ static struct dcp *global_sdcp; #define MXS_DCP_CONTROL1_CIPHER_MODE_ECB (0 << 4) #define MXS_DCP_CONTROL1_CIPHER_SELECT_AES128 (0 << 0) +#define MXS_DCP_CONTROL1_KEY_SELECT_SHIFT 8 + static int mxs_dcp_start_dma(struct dcp_async_ctx *actx) { int dma_err; @@ -224,13 +229,16 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, struct dcp *sdcp = global_sdcp; struct dcp_dma_desc *desc = &sdcp->coh->desc[actx->chan]; struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req); + bool key_referenced = actx->key_referenced; int ret; - key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key, - 2 * AES_KEYSIZE_128, DMA_TO_DEVICE); - ret = dma_mapping_error(sdcp->dev, key_phys); - if (ret) - return ret; + if (!key_referenced) { + key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key, + 2 * AES_KEYSIZE_128, DMA_TO_DEVICE); + ret = dma_mapping_error(sdcp->dev, key_phys); + if (ret) + return ret; + } src_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_in_buf, DCP_BUF_SZ, DMA_TO_DEVICE); @@ -255,8 +263,12 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, MXS_DCP_CONTROL0_INTERRUPT | MXS_DCP_CONTROL0_ENABLE_CIPHER; - /* Payload contains the key. */ - desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY; + if (key_referenced) + /* Set OTP key bit to select the key via KEY_SELECT. */ + desc->control0 |= MXS_DCP_CONTROL0_OTP_KEY; + else + /* Payload contains the key. */ + desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY; if (rctx->enc) desc->control0 |= MXS_DCP_CONTROL0_CIPHER_ENCRYPT; @@ -270,6 +282,9 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, else desc->control1 |= MXS_DCP_CONTROL1_CIPHER_MODE_CBC; + if (key_referenced) + desc->control1 |= sdcp->coh->aes_key[0] << MXS_DCP_CONTROL1_KEY_SELECT_SHIFT; + desc->next_cmd_addr = 0; desc->source = src_phys; desc->destination = dst_phys; @@ -284,9 +299,9 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx, err_dst: dma_unmap_single(sdcp->dev, src_phys, DCP_BUF_SZ, DMA_TO_DEVICE); err_src: - dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128, - DMA_TO_DEVICE); - + if (!key_referenced) + dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128, + DMA_TO_DEVICE); return ret; } @@ -453,7 +468,7 @@ static int mxs_dcp_aes_enqueue(struct skcipher_request *req, int enc, int ecb) struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req); int ret; - if (unlikely(actx->key_len != AES_KEYSIZE_128)) + if (unlikely(actx->key_len != AES_KEYSIZE_128 && !actx->key_referenced)) return mxs_dcp_block_fallback(req, enc); rctx->enc = enc; @@ -500,6 +515,7 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key, * there can still be an operation in progress. */ actx->key_len = len; + actx->key_referenced = false; if (len == AES_KEYSIZE_128) { memcpy(actx->key, key, len); return 0; @@ -516,6 +532,32 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key, return crypto_skcipher_setkey(actx->fallback, key, len); } +static int mxs_dcp_aes_setrefkey(struct crypto_skcipher *tfm, const u8 *key, + unsigned int len) +{ + struct dcp_async_ctx *actx = crypto_skcipher_ctx(tfm); + + if (len != DCP_PAES_KEYSIZE) + return -EINVAL; + + switch (key[0]) { + case DCP_PAES_KEY_SLOT0: + case DCP_PAES_KEY_SLOT1: + case DCP_PAES_KEY_SLOT2: + case DCP_PAES_KEY_SLOT3: + case DCP_PAES_KEY_UNIQUE: + case DCP_PAES_KEY_OTP: + memcpy(actx->key, key, len); + actx->key_len = len; + actx->key_referenced = true; + break; + default: + return -EINVAL; + } + + return 0; +} + static int mxs_dcp_aes_fallback_init_tfm(struct crypto_skcipher *tfm) { const char *name = crypto_tfm_alg_name(crypto_skcipher_tfm(tfm)); @@ -539,6 +581,13 @@ static void mxs_dcp_aes_fallback_exit_tfm(struct crypto_skcipher *tfm) crypto_free_skcipher(actx->fallback); } +static int mxs_dcp_paes_init_tfm(struct crypto_skcipher *tfm) +{ + crypto_skcipher_set_reqsize(tfm, sizeof(struct dcp_aes_req_ctx)); + + return 0; +} + /* * Hashing (SHA1/SHA256) */ @@ -889,6 +938,39 @@ static struct skcipher_alg dcp_aes_algs[] = { .ivsize = AES_BLOCK_SIZE, .init = mxs_dcp_aes_fallback_init_tfm, .exit = mxs_dcp_aes_fallback_exit_tfm, + }, { + .base.cra_name = "ecb(paes)", + .base.cra_driver_name = "ecb-paes-dcp", + .base.cra_priority = 401, + .base.cra_alignmask = 15, + .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL, + .base.cra_blocksize = AES_BLOCK_SIZE, + .base.cra_ctxsize = sizeof(struct dcp_async_ctx), + .base.cra_module = THIS_MODULE, + + .min_keysize = DCP_PAES_KEYSIZE, + .max_keysize = DCP_PAES_KEYSIZE, + .setkey = mxs_dcp_aes_setrefkey, + .encrypt = mxs_dcp_aes_ecb_encrypt, + .decrypt = mxs_dcp_aes_ecb_decrypt, + .init = mxs_dcp_paes_init_tfm, + }, { + .base.cra_name = "cbc(paes)", + .base.cra_driver_name = "cbc-paes-dcp", + .base.cra_priority = 401, + .base.cra_alignmask = 15, + .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL, + .base.cra_blocksize = AES_BLOCK_SIZE, + .base.cra_ctxsize = sizeof(struct dcp_async_ctx), + .base.cra_module = THIS_MODULE, + + .min_keysize = DCP_PAES_KEYSIZE, + .max_keysize = DCP_PAES_KEYSIZE, + .setkey = mxs_dcp_aes_setrefkey, + .encrypt = mxs_dcp_aes_cbc_encrypt, + .decrypt = mxs_dcp_aes_cbc_decrypt, + .ivsize = AES_BLOCK_SIZE, + .init = mxs_dcp_paes_init_tfm, }, }; diff --git a/include/soc/fsl/dcp.h b/include/soc/fsl/dcp.h new file mode 100644 index 000000000000..cda89e260c46 --- /dev/null +++ b/include/soc/fsl/dcp.h @@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2021 sigma star gmbh + */ + +#ifndef MXS_DCP_H +#define MXS_DCP_H + +#define DCP_PAES_KEYSIZE 1 +#define DCP_PAES_KEY_SLOT0 0x00 +#define DCP_PAES_KEY_SLOT1 0x01 +#define DCP_PAES_KEY_SLOT2 0x02 +#define DCP_PAES_KEY_SLOT3 0x03 +#define DCP_PAES_KEY_UNIQUE 0xfe +#define DCP_PAES_KEY_OTP 0xff + +#endif /* MXS_DCP_H */