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192 lines
6.1 KiB
192 lines
6.1 KiB
2 years ago
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Thu, 1 Oct 2020 20:23:48 +1000
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Subject: [PATCH] pgp: factor out rsa_pad
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rsa_pad does the PKCS#1 v1.5 padding for the RSA signature scheme.
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We want to use it in other RSA signature verification applications.
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I considered and rejected putting it in lib/crypto.c. That file doesn't
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currently require any MPI functions, but rsa_pad does. That's not so
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much of a problem for the grub kernel and modules, but crypto.c also
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gets built into all the grub utilities. So - despite the utils not
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using any asymmetric ciphers - we would need to built the entire MPI
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infrastructure in to them.
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A better and simpler solution is just to spin rsa_pad out into its own
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PKCS#1 v1.5 module.
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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---
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grub-core/Makefile.core.def | 8 ++++++
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grub-core/commands/pgp.c | 28 ++-------------------
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grub-core/lib/pkcs1_v15.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
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include/grub/pkcs1_v15.h | 27 +++++++++++++++++++++
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4 files changed, 96 insertions(+), 26 deletions(-)
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create mode 100644 grub-core/lib/pkcs1_v15.c
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create mode 100644 include/grub/pkcs1_v15.h
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diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
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index 809f11fea..99615c07b 100644
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--- a/grub-core/Makefile.core.def
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+++ b/grub-core/Makefile.core.def
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@@ -2387,6 +2387,14 @@ module = {
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cppflags = '$(CPPFLAGS_GCRY)';
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};
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+module = {
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+ name = pkcs1_v15;
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+ common = lib/pkcs1_v15.c;
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+
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+ cflags = '$(CFLAGS_GCRY) -Wno-redundant-decls -Wno-sign-compare';
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+ cppflags = '$(CPPFLAGS_GCRY)';
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+};
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+
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module = {
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name = all_video;
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common = lib/fake_module.c;
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diff --git a/grub-core/commands/pgp.c b/grub-core/commands/pgp.c
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index d39846d8c..bb6543819 100644
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--- a/grub-core/commands/pgp.c
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+++ b/grub-core/commands/pgp.c
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@@ -24,6 +24,7 @@
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#include <grub/file.h>
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#include <grub/command.h>
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#include <grub/crypto.h>
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+#include <grub/pkcs1_v15.h>
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#include <grub/i18n.h>
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#include <grub/gcrypt/gcrypt.h>
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#include <grub/pubkey.h>
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@@ -411,32 +412,7 @@ static int
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rsa_pad (gcry_mpi_t *hmpi, grub_uint8_t *hval,
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const gcry_md_spec_t *hash, struct grub_public_subkey *sk)
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{
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- grub_size_t tlen, emlen, fflen;
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- grub_uint8_t *em, *emptr;
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- unsigned nbits = gcry_mpi_get_nbits (sk->mpis[0]);
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- int ret;
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- tlen = hash->mdlen + hash->asnlen;
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- emlen = (nbits + 7) / 8;
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- if (emlen < tlen + 11)
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- return 1;
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-
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- em = grub_malloc (emlen);
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- if (!em)
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- return 1;
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-
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- em[0] = 0x00;
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- em[1] = 0x01;
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- fflen = emlen - tlen - 3;
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- for (emptr = em + 2; emptr < em + 2 + fflen; emptr++)
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- *emptr = 0xff;
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- *emptr++ = 0x00;
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- grub_memcpy (emptr, hash->asnoid, hash->asnlen);
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- emptr += hash->asnlen;
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- grub_memcpy (emptr, hval, hash->mdlen);
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-
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- ret = gcry_mpi_scan (hmpi, GCRYMPI_FMT_USG, em, emlen, 0);
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- grub_free (em);
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- return ret;
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+ return grub_crypto_rsa_pad(hmpi, hval, hash, sk->mpis[0]);
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}
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struct grub_pubkey_context
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diff --git a/grub-core/lib/pkcs1_v15.c b/grub-core/lib/pkcs1_v15.c
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new file mode 100644
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index 000000000..dbacd563d
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--- /dev/null
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+++ b/grub-core/lib/pkcs1_v15.c
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@@ -0,0 +1,59 @@
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+/*
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+ * GRUB -- GRand Unified Bootloader
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+ * Copyright (C) 2013 Free Software Foundation, Inc.
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+ *
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+ * GRUB is free software: you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation, either version 3 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * GRUB is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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+ */
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+
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+#include <grub/dl.h>
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+#include <grub/gcrypt/gcrypt.h>
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+
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+GRUB_MOD_LICENSE ("GPLv3+");
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+
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+/*
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+ * Given a hash value 'hval', of hash specification 'hash', perform
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+ * the EMSA-PKCS1-v1_5 padding suitable for a key with modulus 'mod'
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+ * (see RFC 8017 s 9.2) and place the result in 'hmpi'.
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+ */
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+gcry_err_code_t
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+grub_crypto_rsa_pad (gcry_mpi_t * hmpi, grub_uint8_t * hval,
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+ const gcry_md_spec_t * hash, gcry_mpi_t mod)
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+{
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+ grub_size_t tlen, emlen, fflen;
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+ grub_uint8_t *em, *emptr;
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+ unsigned nbits = gcry_mpi_get_nbits (mod);
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+ int ret;
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+ tlen = hash->mdlen + hash->asnlen;
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+ emlen = (nbits + 7) / 8;
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+ if (emlen < tlen + 11)
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+ return GPG_ERR_TOO_SHORT;
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+
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+ em = grub_malloc (emlen);
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+ if (!em)
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+ return 1;
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+
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+ em[0] = 0x00;
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+ em[1] = 0x01;
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+ fflen = emlen - tlen - 3;
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+ for (emptr = em + 2; emptr < em + 2 + fflen; emptr++)
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+ *emptr = 0xff;
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+ *emptr++ = 0x00;
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+ grub_memcpy (emptr, hash->asnoid, hash->asnlen);
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+ emptr += hash->asnlen;
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+ grub_memcpy (emptr, hval, hash->mdlen);
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+
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+ ret = gcry_mpi_scan (hmpi, GCRYMPI_FMT_USG, em, emlen, 0);
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+ grub_free (em);
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+ return ret;
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+}
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diff --git a/include/grub/pkcs1_v15.h b/include/grub/pkcs1_v15.h
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new file mode 100644
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index 000000000..5c338c84a
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--- /dev/null
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+++ b/include/grub/pkcs1_v15.h
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@@ -0,0 +1,27 @@
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+/*
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+ * GRUB -- GRand Unified Bootloader
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+ * Copyright (C) 2013 Free Software Foundation, Inc.
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+ *
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+ * GRUB is free software: you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation, either version 3 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * GRUB is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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+ */
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+
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+/*
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+ * Given a hash value 'hval', of hash specification 'hash', perform
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+ * the EMSA-PKCS1-v1_5 padding suitable for a key with modulus 'mod'
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+ * (See RFC 8017 s 9.2)
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+ */
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+gcry_err_code_t
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+grub_crypto_rsa_pad (gcry_mpi_t * hmpi, grub_uint8_t * hval,
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+ const gcry_md_spec_t * hash, gcry_mpi_t mod);
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+
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