From: Daniel Kahn Gillmor Date: Wed, 05 Feb 2025 18:03:42 -0500 Subject: gpg: Always support and default to using SHA-512. * g10/main.h (DEFAULT_DIGEST_ALGO): Use SHA512 instead of SHA256 in standard modes. Use SHA256 for PGP8, and SHA1 for archaic modes. * configure.ac: Do not allow disabling sha512. * g10/misc.c (map_md_openpgp_to_gcry): Always support SHA512. -- SHA512 is more performant on most 64-bit platforms than SHA256, and offers a better security margin. It is also widely implemented. RFC 4880 specifies SHA512, and any 4880-compatible client in the last 10 years supports it. According to doc/gpg.texi, PGP 8 supports SHA256. There's no clear reason to default to SHA1 for compatibility with those clients. (RFC 2440 and PGP7 don't support SHA256, so leave that alone) GnuPG-bug-id: 7516 Signed-off-by: Daniel Kahn Gillmor --- configure.ac | 2 +- g10/main.h | 2 +- g10/misc.c | 5 +---- 3 files changed, 3 insertions(+), 6 deletions(-) diff --git a/configure.ac b/configure.ac index c80bce1..42ef43b 100644 --- a/configure.ac +++ b/configure.ac @@ -339,7 +339,7 @@ GNUPG_GPG_DISABLE_ALGO([rmd160],[RIPE-MD160 hash]) GNUPG_GPG_DISABLE_ALGO([sha224],[SHA-224 hash]) # SHA256 is a MUST algorithm for GnuPG. GNUPG_GPG_DISABLE_ALGO([sha384],[SHA-384 hash]) -GNUPG_GPG_DISABLE_ALGO([sha512],[SHA-512 hash]) +# SHA512 is a MUST algorithm for GnuPG. # Allow disabling of zip support. diff --git a/g10/main.h b/g10/main.h index 2482fbd..f15d90f 100644 --- a/g10/main.h +++ b/g10/main.h @@ -41,7 +41,7 @@ # define DEFAULT_CIPHER_ALGO CIPHER_ALGO_3DES #endif -#define DEFAULT_DIGEST_ALGO ((GNUPG)? DIGEST_ALGO_SHA256:DIGEST_ALGO_SHA1) +#define DEFAULT_DIGEST_ALGO ((PGP7||RFC2440)?DIGEST_ALGO_SHA1:((PGP8)?DIGEST_ALGO_SHA256:DIGEST_ALGO_SHA512)) #define DEFAULT_S2K_DIGEST_ALGO DEFAULT_DIGEST_ALGO #ifdef HAVE_ZIP # define DEFAULT_COMPRESS_ALGO COMPRESS_ALGO_ZIP diff --git a/g10/misc.c b/g10/misc.c index 2f4b452..0e6d9d5 100644 --- a/g10/misc.c +++ b/g10/misc.c @@ -862,11 +862,8 @@ map_md_openpgp_to_gcry (digest_algo_t algo) case DIGEST_ALGO_SHA384: return 0; #endif -#ifdef GPG_USE_SHA512 case DIGEST_ALGO_SHA512: return GCRY_MD_SHA512; -#else - case DIGEST_ALGO_SHA512: return 0; -#endif + default: return 0; } }