diff options
| author | Michael Brown | 2012-03-18 21:02:25 +0100 |
|---|---|---|
| committer | Michael Brown | 2012-03-18 21:22:43 +0100 |
| commit | 3ec773cd2b9d32c5a4bb3a7a6ae86e49fd278c8f (patch) | |
| tree | 743d5b133e4469d9644319fd54f81c06822711c5 /src/crypto/rsa.c | |
| parent | [rng] Add Linux entropy source using /dev/random (diff) | |
| download | ipxe-3ec773cd2b9d32c5a4bb3a7a6ae86e49fd278c8f.tar.gz ipxe-3ec773cd2b9d32c5a4bb3a7a6ae86e49fd278c8f.tar.xz ipxe-3ec773cd2b9d32c5a4bb3a7a6ae86e49fd278c8f.zip | |
[crypto] Force caller to provide temporary storage for modular calculations
bigint_mod_multiply() and bigint_mod_exp() require a fixed amount of
temporary storage for intermediate results. (The amount of temporary
storage required depends upon the size of the integers involved.)
When performing calculations for 4096-bit RSA the amount of temporary
storage space required will exceed 2.5kB, which is too much to
allocate on the stack. Avoid this problem by forcing the caller to
allocate temporary storage.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Diffstat (limited to 'src/crypto/rsa.c')
| -rw-r--r-- | src/crypto/rsa.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/src/crypto/rsa.c b/src/crypto/rsa.c index 4aba5cc3..a0bf39eb 100644 --- a/src/crypto/rsa.c +++ b/src/crypto/rsa.c @@ -123,11 +123,15 @@ static int rsa_alloc ( struct rsa_context *context, size_t modulus_len, size_t exponent_len ) { unsigned int size = bigint_required_size ( modulus_len ); unsigned int exponent_size = bigint_required_size ( exponent_len ); + bigint_t ( size ) *modulus; + bigint_t ( exponent_size ) *exponent; + size_t tmp_len = bigint_mod_exp_tmp_len ( modulus, exponent ); struct { bigint_t ( size ) modulus; bigint_t ( exponent_size ) exponent; bigint_t ( size ) input; bigint_t ( size ) output; + uint8_t tmp[tmp_len]; } __attribute__ (( packed )) *dynamic; /* Free any existing dynamic storage */ @@ -147,6 +151,7 @@ static int rsa_alloc ( struct rsa_context *context, size_t modulus_len, context->exponent_size = exponent_size; context->input0 = &dynamic->input.element[0]; context->output0 = &dynamic->output.element[0]; + context->tmp = &dynamic->tmp; return 0; } @@ -309,7 +314,7 @@ static void rsa_cipher ( struct rsa_context *context, bigint_init ( input, in, context->max_len ); /* Perform modular exponentiation */ - bigint_mod_exp ( input, modulus, exponent, output ); + bigint_mod_exp ( input, modulus, exponent, output, context->tmp ); /* Copy out result */ bigint_done ( output, out, context->max_len ); |