From f542ef8f9e645bf30e11e196dd768fac4f957eac Mon Sep 17 00:00:00 2001 From: Guus Sliepen Date: Sat, 19 Dec 2009 22:17:39 +0100 Subject: [PATCH] Fix alignment of results of RSA operations when using libgcrypt. If the result of an RSA encryption or decryption operation can be represented in less bytes than given, gcry_mpi_print() will not add leading zero bytes. Fix this by adding those ourself. --- src/gcrypt/rsa.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/gcrypt/rsa.c b/src/gcrypt/rsa.c index 5e4ba41..a729591 100644 --- a/src/gcrypt/rsa.c +++ b/src/gcrypt/rsa.c @@ -276,6 +276,10 @@ bool rsa_public_encrypt(rsa_t *rsa, void *in, size_t len, void *out) { gcry_mpi_t outmpi = gcry_mpi_new(len * 8); gcry_mpi_powm(outmpi, inmpi, rsa->e, rsa->n); + int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8; + while(pad--) + *(char *)out++ = 0; + check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi)); return true; @@ -288,6 +292,10 @@ bool rsa_private_decrypt(rsa_t *rsa, void *in, size_t len, void *out) { gcry_mpi_t outmpi = gcry_mpi_new(len * 8); gcry_mpi_powm(outmpi, inmpi, rsa->d, rsa->n); + int pad = len - (gcry_mpi_get_nbits(outmpi) + 7) / 8; + while(pad--) + *(char *)out++ = 0; + check(gcry_mpi_print(GCRYMPI_FMT_USG, out,len, NULL, outmpi)); return true; -- 2.25.1