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openssh
openssh-8.1p1-use-openssl-kdf.patch
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File openssh-8.1p1-use-openssl-kdf.patch of Package openssh
Index: openssh-8.8p1/kex.c =================================================================== --- openssh-8.8p1.orig/kex.c +++ openssh-8.8p1/kex.c @@ -40,6 +40,7 @@ #ifdef WITH_OPENSSL #include <openssl/crypto.h> #include <openssl/dh.h> +#include <openssl/kdf.h> #endif #include "ssh.h" @@ -1115,8 +1116,93 @@ kex_choose_conf(struct ssh *ssh) return r; } +#ifdef WITH_OPENSSL + +static const EVP_MD * +get_openssl_md_for_hash_alg (int hash_alg) +{ + if (hash_alg < 0 || hash_alg >= SSH_DIGEST_MAX) + return NULL; + + switch (hash_alg) + { + case SSH_DIGEST_MD5: + return EVP_md5(); + case SSH_DIGEST_SHA1: + return EVP_sha1(); + case SSH_DIGEST_SHA256: + return EVP_sha256(); + case SSH_DIGEST_SHA384: + return EVP_sha384(); + case SSH_DIGEST_SHA512: + return EVP_sha512(); + default: + break; + } + + return NULL; +} + static int -derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, +derive_key_via_openssl(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, + const struct sshbuf *shared_secret, u_char **keyp) +{ + struct kex *kex = ssh->kex; + EVP_KDF_CTX *hashctx = NULL; + const EVP_MD *md = NULL; + u_char *digest = NULL; + int r = SSH_ERR_LIBCRYPTO_ERROR; + + hashctx = EVP_KDF_CTX_new_id (EVP_KDF_SSHKDF); + if (!hashctx) + goto out; + + md = get_openssl_md_for_hash_alg (kex->hash_alg); + if (!md) + goto out; + + if (EVP_KDF_ctrl (hashctx, EVP_KDF_CTRL_SET_MD, + md) != 1 + || EVP_KDF_ctrl (hashctx, EVP_KDF_CTRL_SET_KEY, + sshbuf_ptr(shared_secret), sshbuf_len(shared_secret)) != 1 + || EVP_KDF_ctrl (hashctx, EVP_KDF_CTRL_SET_SSHKDF_TYPE, + (int) id) != 1 + || EVP_KDF_ctrl (hashctx, EVP_KDF_CTRL_SET_SSHKDF_XCGHASH, + hash, (size_t) hashlen) != 1 + || EVP_KDF_ctrl (hashctx, EVP_KDF_CTRL_SET_SSHKDF_SESSION_ID, + sshbuf_ptr(kex->session_id), + (size_t) sshbuf_len(kex->session_id)) != 1) + goto out; + + digest = calloc (1, need); + if (!digest) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + + if (EVP_KDF_derive (hashctx, digest, need) != 1) + goto out; + + *keyp = digest; + digest = NULL; + r = 0; + + out: + if (hashctx) + EVP_KDF_CTX_free(hashctx); + + if (digest) + free(digest); + + return r; +} + +#else +# error This version of openssh must be built with openssl to benefit from FIPS certification. +#endif + +static int +derive_key_via_internal(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, const struct sshbuf *shared_secret, u_char **keyp) { struct kex *kex = ssh->kex; @@ -1179,6 +1265,50 @@ derive_key(struct ssh *ssh, int id, u_in return r; } +/* Belt and suspenders; we want the output from openssl because it's FIPS certified. However, + * if there's a bug in the implementation, we should not proceed. Minimize risk by requiring + * the implementations agree. */ +static int +derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen, + const struct sshbuf *shared_secret, u_char **keyp) +{ +#ifdef WITH_OPENSSL + + u_char *buf_openssl = NULL, *buf_internal = NULL; + int r; + + r = derive_key_via_openssl (ssh, id, need, hash, hashlen, shared_secret, &buf_openssl); + if (r != 0) + goto out; + + r = derive_key_via_internal (ssh, id, need, hash, hashlen, shared_secret, &buf_internal); + if (r != 0) + goto out; + + if (memcmp (buf_openssl, buf_internal, need)) + { + r = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } + + *keyp = buf_openssl; + buf_openssl = NULL; + + out: + if (buf_openssl) + free (buf_openssl); + if (buf_internal) + free (buf_internal); + + return r; + +#else + + return derive_key_via_internal (ssh, id, need, hash, hashlen, shared_secret, keyp); + +#endif +} + #define NKEYS 6 int kex_derive_keys(struct ssh *ssh, u_char *hash, u_int hashlen,
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