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feat: add seeded flag generation

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Michael
2026-05-16 17:56:41 +02:00
parent 46bb5768d1
commit ff791d8f8c
4 changed files with 17 additions and 5 deletions
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1
.env.example
View File

@@ -1,5 +1,6 @@
FLAG_LEN=32 FLAG_LEN=32
FLAG_FORMAT=ctf{FLAG_GOES_HERE} FLAG_FORMAT=ctf{FLAG_GOES_HERE}
FLAG_SEED=false
ENCRYPTOR_VENDOR_ID=GenuineIntel ENCRYPTOR_VENDOR_ID=GenuineIntel
ENCRYPTOR_MODEL_NAME=Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz ENCRYPTOR_MODEL_NAME=Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz
ENCRYPTOR_OS_VERSION=7.0.3-arch1-2 ENCRYPTOR_OS_VERSION=7.0.3-arch1-2

3
Makefile
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@@ -8,6 +8,7 @@ endif
# Default configuration # Default configuration
FLAG_LEN ?= 32 FLAG_LEN ?= 32
FLAG_FORMAT ?= ctf{FLAG_GOES_HERE} FLAG_FORMAT ?= ctf{FLAG_GOES_HERE}
FLAG_SEED ?= false
# Compilation variables # Compilation variables
RISCV_CC ?= riscv64-unknown-elf-gcc RISCV_CC ?= riscv64-unknown-elf-gcc
@@ -105,7 +106,7 @@ endif
$(GENERATED): .FORCE $(GENERATED): .FORCE
mkdir -p $(dir $@) mkdir -p $(dir $@)
python codegen/generate.py $(FLAG_FORMAT) $(FLAG_LEN) > $@ python codegen/generate.py $(FLAG_FORMAT) $(FLAG_LEN) $(FLAG_SEED) > $@
build: build:

1
README.md
View File

@@ -27,6 +27,7 @@ The provided `.env.example` file contains a sample configuration.
- `FLAG_LEN`: Number, the length of the flag - `FLAG_LEN`: Number, the length of the flag
- `FLAG_FORMAT`: String, containing the constant `FLAG_GOES_HERE` to be replaced by the flag - `FLAG_FORMAT`: String, containing the constant `FLAG_GOES_HERE` to be replaced by the flag
- `FLAG_SEED`: String, the seed used to generate the flag, or `false` if it should be random
- `ENCRYPTOR_VENDOR_ID`: String, overwrite CPU vendor id. Will use system information if unset - `ENCRYPTOR_VENDOR_ID`: String, overwrite CPU vendor id. Will use system information if unset
- `ENCRYPTOR_MODEL_NAME`: String, overwrite CPU model name. Will use system information if unset - `ENCRYPTOR_MODEL_NAME`: String, overwrite CPU model name. Will use system information if unset
- `ENCRYPTOR_OS_VERSION`: String, overwrite OS version. Will use system information if unset - `ENCRYPTOR_OS_VERSION`: String, overwrite OS version. Will use system information if unset

17
codegen/generate.py
View File

@@ -1,7 +1,10 @@
import random import random
import secrets
import sys import sys
def generate_flag(length):
characters = list("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
return "".join([random.choice(characters) for _ in range(length)])
def eprint(*args, **kwargs): def eprint(*args, **kwargs):
print("[Codegen]", *args, file=sys.stderr, **kwargs) print("[Codegen]", *args, file=sys.stderr, **kwargs)
@@ -47,16 +50,22 @@ def get_check_code(flag_part, user_part, c_mangler):
return random.choice(variations) return random.choice(variations)
def main(): def main():
if len(sys.argv) != 3: if len(sys.argv) != 3 and len(sys.argv) != 4:
eprint(f"Usage: {sys.argv[0]} <flag_format> <flag_length>") eprint(f"Usage: {sys.argv[0]} <flag_format> <flag_length> [flag_seed]")
exit(1) exit(1)
# Flag prefix is not used, currently the flag is just used as-is # Flag prefix is not used, currently the flag is just used as-is
flag_format = sys.argv[1] flag_format = sys.argv[1]
flag_len = int(sys.argv[2]) flag_len = int(sys.argv[2])
if len(sys.argv) >= 4:
# We might have a seed
flag_seed = sys.argv[3]
if flag_seed.lower() != "false":
random.seed(flag_seed)
# Generate a secret # Generate a secret
secret = secrets.token_urlsafe(flag_len) secret = generate_flag(flag_len)
secret = flag_format.replace("FLAG_GOES_HERE", secret) secret = flag_format.replace("FLAG_GOES_HERE", secret)
eprint(f"Generated Flag: {secret}") eprint(f"Generated Flag: {secret}")