Command to set FP context

Needed for successful fingerprint template uploading on many Chromebooks

crosec/src/commands/fp_set_context.rs

@@ -0,0 +1,67 @@
+use std::{os::fd::AsRawFd, thread::sleep, time::Duration};
+
+use bytemuck::{Pod, Zeroable};
+use num::ToPrimitive;
+use num_derive::ToPrimitive;
+
+use crate::{ec_command::ec_command_bytemuck, EcCmdResult};
+
+use super::CrosEcCmd;
+
+pub type UserId = [u8; 32];
+
+/* Version 1 of the command is "asynchronous". */
+#[repr(C, align(4))]
+#[derive(Pod, Zeroable, Clone, Copy, Debug)]
+struct EcParamsFpContextV1 {
+    /**< enum fp_context_action */
+    action: u8,
+    reserved: [u8; 3],
+    user_id: UserId,
+}
+
+#[repr(u8)]
+#[derive(ToPrimitive)]
+enum FpContextAction {
+    Async = 0,
+    GetResult = 1,
+}
+
+/// Make sure that the fp mode is Reset before setting the context
+/// Related: https://chromium.googlesource.com/chromiumos/platform2/+/HEAD/biod/cros_fp_device.cc#660
+pub fn fp_set_context<File: AsRawFd>(file: &mut File, user_id: UserId) -> EcCmdResult<()> {
+    // From testing, it seems that this can be anything besides all zeroes, but we're going to use these numbers in honor of CoolStar - https://github.com/coolstar/crosfingerprint/blob/5e77307d7542218e173f24eb657b426565ed361a/fingerprint_adapter/eccmd.cpp#L140
+    ec_command_bytemuck(
+        CrosEcCmd::FpContext,
+        1,
+        &EcParamsFpContextV1 {
+            action: FpContextAction::Async.to_u8().unwrap(),
+            reserved: Default::default(),
+            user_id,
+        },
+        file.as_raw_fd(),
+    )?;
+    let mut tries = 20;
+    let delay = Duration::from_millis(100);
+    loop {
+        sleep(delay);
+        let result = ec_command_bytemuck(
+            CrosEcCmd::FpContext,
+            1,
+            &EcParamsFpContextV1 {
+                action: FpContextAction::GetResult.to_u8().unwrap(),
+                reserved: Default::default(),
+                user_id,
+            },
+            file.as_raw_fd(),
+        );
+        if result.is_ok() {
+            break result;
+        } else {
+            tries -= 1;
+            if tries == 0 {
+                break result;
+            }
+        }
+    }
+}

crosec/src/commands/mod.rs

@@ -21,6 +21,7 @@ pub enum CrosEcCmd {
     FpInfo = 0x0403,
     FpFrame = 0x0404,
     FpTemplate = 0x0405,
+    FpContext = 0x0406,
     FpStats = 0x0407,
     FpSetSeed = 0x0408,
     FpGetEncryptionStatus = 0x0409,
@@ -35,6 +36,7 @@ pub mod fp_download;
 pub mod fp_get_encryption_status;
 pub mod fp_info;
 pub mod fp_mode;
+pub mod fp_set_context;
 pub mod fp_set_seed;
 pub mod fp_stats;
 pub mod fp_upload_template;

ectool/Cargo.toml

@@ -14,3 +14,4 @@ num-traits = "0.2.19"
 image = "0.25.1"
 strum = "0.26.3"
 uom = "0.36.0"
+hex = "0.4.3"

ectool/src/check_user_id.rs

@@ -0,0 +1,7 @@
+use crosec::commands::fp_set_context::UserId;
+
+pub fn check_user_id(user_id_str: &str) -> Result<UserId, String> {
+    let mut user_id = UserId::default();
+    hex::decode_to_slice(user_id_str.as_bytes(), &mut user_id).map_err(|e| e.to_string())?;
+    Ok(user_id)
+}

ectool/src/fp_set_context_command.rs

@@ -0,0 +1,11 @@
+use crosec::commands::fp_set_context::{fp_set_context, UserId};
+use crosec::CROS_FP_PATH;
+use std::fs::File;
+
+pub fn fp_context_command(user_id: UserId) -> color_eyre::Result<()> {
+    let mut file = File::open(CROS_FP_PATH)?;
+    fp_set_context(&mut file, user_id)?;
+    let user_id_str = hex::encode(user_id);
+    println!("Set FP context to user id: 0x{user_id_str}");
+    Ok(())
+}

ectool/src/main.rs

@@ -5,15 +5,18 @@ use std::fs::File;
 use charge_control_subcommand::{charge_control_subcommand, ChargeControlSubcommand};
 use charge_current_limit_subcommand::charge_current_limit_subcommand;
 use check_seed::check_seed;
+use check_user_id::check_user_id;
 use clap::{Parser, Subcommand, ValueEnum};
 use color_eyre::eyre::Result;
 use crosec::commands::fp_info::fp_info;
 use crosec::commands::fp_mode::{fp_mode, FpMode};
+use crosec::commands::fp_set_context::UserId;
 use crosec::commands::fp_set_seed::{fp_set_seed, FP_CONTEXT_TPM_BYTES};
 use crosec::commands::fp_stats::fp_stats;
 use crosec::commands::get_protocol_info::get_protocol_info;
 use crosec::wait_event::{event::EcMkbpEventType, wait_event_sync};
 use fp_download_subcommand::{fp_download_subcommand, FpDownloadSubcommand};
+use fp_set_context_command::fp_context_command;
 use fp_upload_template_command::fp_upload_template_command;
 use get_uptime_info_command::get_uptime_info_commnad;
 use num_traits::cast::FromPrimitive;
@@ -39,8 +42,10 @@ use crosec::{
 mod charge_control_subcommand;
 mod charge_current_limit_subcommand;
 mod check_seed;
+mod check_user_id;
 mod fp_download_subcommand;
 mod fp_get_encryption_status_command;
+mod fp_set_context_command;
 mod fp_upload_template_command;
 mod get_uptime_info_command;
 
@@ -139,6 +144,11 @@ enum Commands {
         #[arg()]
         limit: u32,
     },
+    FpSetContext {
+        /// A 32 byte hex string
+        #[arg(value_parser = check_user_id)]
+        user_id: UserId,
+    },
 }
 
 fn main() -> Result<()> {
@@ -294,6 +304,7 @@ fn main() -> Result<()> {
         Commands::FpGetEncryptionStatus => fp_get_encryption_status_command()?,
         Commands::GetUptimeInfo { device } => get_uptime_info_commnad(device)?,
         Commands::ChargeCurrentLimit { limit } => charge_current_limit_subcommand(limit)?,
+        Commands::FpSetContext { user_id } => fp_context_command(user_id)?,
     }
 
     Ok(())