TLS Example Application

The folder hosts an example TLS application based on pigweed TLS modules. The example application connects to www.google.com:443, performs hanshake, verifies certificate, sends a https get request and listens for response. The application can be built into multiple variants using different TLS libraries and transport backends (impelmented in backends/). See BUILD.gn for examples.

Due to the use of TLS libraries, the binary size of the application can potentially be very big (300K ~ 600K+). Make sure that the target board has enough FLASH/RAM for running the application. For pigweed teensy41 target, it is recommended to modify the linker script to run all code from FLASH instead of ITCM. Specifically, in linker script arduino/cores/teensy/hardware/teensy/avr/cores/teensy4/imxrt1062_t41.ld make the following changes:

Move section (.text) from

...
.text.itcm : {
    . = .  32; /* MPU to trap NULL pointer deref */
    *(.fastrun)
    *(.text*)
    . = ALIGN(16);
} > ITCM  AT> FLASH
...

into segment .text.progmem. i.e.:

...
.text.progmem : {
    KEEP(*(.flashconfig))
    FILL(0xFF)
    . = ORIGIN(FLASH)  0x1000;
    KEEP(*(.ivt))
    KEEP(*(.bootdata))
    KEEP(*(.vectors))
    KEEP(*(.startup))
    *(.text*)
    *(.flashmem*)
    *(.progmem*)
            . = ALIGN(4);
            KEEP(*(.init))
            __preinit_array_start = .;
            KEEP (*(.preinit_array))
            __preinit_array_end = .;
            __init_array_start = .;
            KEEP (*(.init_array))
            __init_array_end = .;
    . = ALIGN(16);
} > FLASH
...

Place segment .ARM.exids in FLASH. i.e:

...
.ARM.exidx : {
    __exidx_start = .;
    *(.ARM.exidx* .gnu.linkonce.armexidx.*)
    __exidx_end = .;
} > FLASH
...

Before flashing the elf binary to the target board, consider stripping the binary to remove debug and symbol sections to make transfer faster. i.e.

arm-none-eabi-strip -s input.elf -o output.elf