71 lines
1.9 KiB
Diff
71 lines
1.9 KiB
Diff
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From ca2afc9fb64d9a9b2f8930ba505d9ab6c8a57667 Mon Sep 17 00:00:00 2001
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From: Jakub Jelen <jjelen@redhat.com>
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Date: Thu, 12 May 2022 10:56:47 +0200
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Subject: [PATCH] cipher: Allow verification of small RSA signatures in FIPS
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mode
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* cipher/rsa.c (rsa_check_keysize): Formatting.
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(rsa_check_verify_keysize): New function.
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(rsa_verify): Allow using smaller keys for verification.
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--
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GnuPG-bug-id: 5975
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Signed-off-by: Jakub Jelen <jjelen@redhat.com>
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---
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cipher/rsa.c | 26 ++++++++++++++++++++++++--
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1 file changed, 24 insertions(+), 2 deletions(-)
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diff --git a/cipher/rsa.c b/cipher/rsa.c
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index c6319b67..9f2b36e8 100644
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--- a/cipher/rsa.c
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+++ b/cipher/rsa.c
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@@ -352,13 +352,35 @@ generate_std (RSA_secret_key *sk, unsigned int nbits, unsigned long use_e,
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static gpg_err_code_t
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rsa_check_keysize (unsigned int nbits)
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{
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- if (fips_mode() && nbits < 2048)
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+ if (fips_mode () && nbits < 2048)
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return GPG_ERR_INV_VALUE;
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return GPG_ERR_NO_ERROR;
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}
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+/* Check the RSA key length is acceptable for signature verification
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+ *
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+ * FIPS allows signature verification with RSA keys of size
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+ * 1024, 1280, 1536 and 1792 in legacy mode, but this is up to the
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+ * calling application to decide if the signature is legacy and
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+ * should be accepted.
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+ */
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+static gpg_err_code_t
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+rsa_check_verify_keysize (unsigned int nbits)
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+{
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+ if (fips_mode ())
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+ {
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+ if ((nbits >= 1024 && (nbits % 256) == 0) || nbits >= 2048)
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+ return GPG_ERR_NO_ERROR;
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+
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+ return GPG_ERR_INV_VALUE;
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+ }
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+
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+ return GPG_ERR_NO_ERROR;
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+}
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+
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+
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/****************
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* Generate a key pair with a key of size NBITS.
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* USE_E = 0 let Libcgrypt decide what exponent to use.
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@@ -1602,7 +1624,7 @@ rsa_verify (gcry_sexp_t s_sig, gcry_sexp_t s_data, gcry_sexp_t keyparms)
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gcry_mpi_t result = NULL;
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unsigned int nbits = rsa_get_nbits (keyparms);
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- rc = rsa_check_keysize (nbits);
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+ rc = rsa_check_verify_keysize (nbits);
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if (rc)
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return rc;
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--
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2.37.1
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