imx: hab: Check if CSF is valid before authenticating image

For proper authentication the HAB code must check if the CSF is valid.
Users must call the csf_is_valid() function to parse the CSF prior to
authenticating any additional images. The function will return a failure
if any of the following invalid conditions are met:

- CSF pointer is NULL
- CSF Header does not exist
- CSF does not lie within the image bounds
- CSF command length zero

Signed-off-by: Utkarsh Gupta <utkarsh.gupta@nxp.com>
Signed-off-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>

diff --git a/arch/arm/include/asm/mach-imx/hab.h b/arch/arm/include/asm/mach-imx/hab.h
index a0cb19db2fb9de96231966f4bdcde60cf1df479e..bb732030e97e931440d168d6e32f0badd8e1133c 100644 (file)
--- a/arch/arm/include/asm/mach-imx/hab.h
+++ b/arch/arm/include/asm/mach-imx/hab.h
@@ -38,6 +38,12 @@ struct ivt {
        uint32_t reserved2;     /* Reserved should be zero */
 };
 
+struct __packed hab_hdr {
+       u8 tag;              /* Tag field */
+       u8 len[2];           /* Length field in bytes (big-endian) */
+       u8 par;              /* Parameters field */
+};
+
 /* -------- start of HAB API updates ------------*/
 /* The following are taken from HAB4 SIS */
 
@@ -182,6 +188,8 @@ typedef void hapi_clock_init_t(void);
 #define HAB_CID_ROM 0 /**< ROM Caller ID */
 #define HAB_CID_UBOOT 1 /**< UBOOT Caller ID*/
 
+#define HAB_CMD_HDR          0xD4  /* CSF Header */
+
 #define IVT_SIZE                       0x20
 #define CSF_PAD_SIZE                   0x2000
 

diff --git a/arch/arm/mach-imx/hab.c b/arch/arm/mach-imx/hab.c
index ba6b31d49070a3eb19416a68c7712d95529e5f81..7f66965af56275c8923a1b60b3656d0b82ceb9db 100644 (file)
--- a/arch/arm/mach-imx/hab.c
+++ b/arch/arm/mach-imx/hab.c
@@ -453,6 +453,83 @@ U_BOOT_CMD(
 
 #endif /* !defined(CONFIG_SPL_BUILD) */
 
+/* Get CSF Header length */
+static int get_hab_hdr_len(struct hab_hdr *hdr)
+{
+       return (size_t)((hdr->len[0] << 8) + (hdr->len[1]));
+}
+
+/* Check whether addr lies between start and
+ * end and is within the length of the image
+ */
+static int chk_bounds(u8 *addr, size_t bytes, u8 *start, u8 *end)
+{
+       size_t csf_size = (size_t)((end + 1) - addr);
+
+       return (addr && (addr >= start) && (addr <= end) &&
+               (csf_size >= bytes));
+}
+
+/* Get Length of each command in CSF */
+static int get_csf_cmd_hdr_len(u8 *csf_hdr)
+{
+       if (*csf_hdr == HAB_CMD_HDR)
+               return sizeof(struct hab_hdr);
+
+       return get_hab_hdr_len((struct hab_hdr *)csf_hdr);
+}
+
+/* Check if CSF is valid */
+static bool csf_is_valid(struct ivt *ivt, ulong start_addr, size_t bytes)
+{
+       u8 *start = (u8 *)start_addr;
+       u8 *csf_hdr;
+       u8 *end;
+
+       size_t csf_hdr_len;
+       size_t cmd_hdr_len;
+       size_t offset = 0;
+
+       if (bytes != 0)
+               end = start + bytes - 1;
+       else
+               end = start;
+
+       /* Verify if CSF pointer content is zero */
+       if (!ivt->csf) {
+               puts("Error: CSF pointer is NULL\n");
+               return false;
+       }
+
+       csf_hdr = (u8 *)ivt->csf;
+
+       /* Verify if CSF Header exist */
+       if (*csf_hdr != HAB_CMD_HDR) {
+               puts("Error: CSF header command not found\n");
+               return false;
+       }
+
+       csf_hdr_len = get_hab_hdr_len((struct hab_hdr *)csf_hdr);
+
+       /* Check if the CSF lies within the image bounds */
+       if (!chk_bounds(csf_hdr, csf_hdr_len, start, end)) {
+               puts("Error: CSF lies outside the image bounds\n");
+               return false;
+       }
+
+       do {
+               cmd_hdr_len = get_csf_cmd_hdr_len(&csf_hdr[offset]);
+               if (!cmd_hdr_len) {
+                       puts("Error: Invalid command length\n");
+                       return false;
+               }
+               offset += cmd_hdr_len;
+
+       } while (offset < csf_hdr_len);
+
+       return true;
+}
+
 bool imx_hab_is_enabled(void)
 {
        struct imx_sec_config_fuse_t *fuse =
@@ -525,6 +602,10 @@ int imx_hab_authenticate_image(uint32_t ddr_start, uint32_t image_size,
        start = ddr_start;
        bytes = image_size;
 
+       /* Verify CSF */
+       if (!csf_is_valid(ivt, start, bytes))
+               goto hab_authentication_exit;
+
        if (hab_rvt_entry() != HAB_SUCCESS) {
                puts("hab entry function fail\n");
                goto hab_exit_failure_print_status;