X-Git-Url: https://git.hcoop.net/hcoop/debian/exim4.git/blobdiff_plain/188b6fee0dfdf699a1a302e16b70d17b4f325bcd..2ea97746a3f65eeffb434b8e4e18815e03b61532:/src/pdkim/signing.c?ds=sidebyside diff --git a/src/pdkim/signing.c b/src/pdkim/signing.c new file mode 100644 index 0000000..a47f824 --- /dev/null +++ b/src/pdkim/signing.c @@ -0,0 +1,891 @@ +/* + * PDKIM - a RFC4871 (DKIM) implementation + * + * Copyright (C) 1995 - 2018 Exim maintainers + * + * signing/verification interface + */ + +#include "../exim.h" +#include "crypt_ver.h" +#include "signing.h" + + +#ifdef MACRO_PREDEF +# include "../macro_predef.h" + +void +features_crypto(void) +{ +# ifdef SIGN_HAVE_ED25519 + builtin_macro_create(US"_CRYPTO_SIGN_ED25519"); +# endif +# ifdef EXIM_HAVE_SHA3 + builtin_macro_create(US"_CRYPTO_HASH_SHA3"); +# endif +} +#else + +#ifndef DISABLE_DKIM /* rest of file */ + +#ifndef SUPPORT_TLS +# error Need SUPPORT_TLS for DKIM +#endif + + +/******************************************************************************/ +#ifdef SIGN_GNUTLS +# define EXIM_GNUTLS_LIBRARY_LOG_LEVEL 3 + + +/* Logging function which can be registered with + * gnutls_global_set_log_function() + * gnutls_global_set_log_level() 0..9 + */ +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +static void +exim_gnutls_logger_cb(int level, const char *message) +{ +size_t len = strlen(message); +if (len < 1) + { + DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); + return; + } +DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, + message[len-1] == '\n' ? "" : "\n"); +} +#endif + + + +void +exim_dkim_init(void) +{ +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +DEBUG(D_tls) + { + gnutls_global_set_log_function(exim_gnutls_logger_cb); + /* arbitrarily chosen level; bump upto 9 for more */ + gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); + } +#endif +} + + +/* accumulate data (gnutls-only). String to be appended must be nul-terminated. */ +gstring * +exim_dkim_data_append(gstring * g, uschar * s) +{ +return string_cat(g, s); +} + + + +/* import private key from PEM string in memory. +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) +{ +gnutls_datum_t k = { .data = (void *)privkey_pem, .size = Ustrlen(privkey_pem) }; +gnutls_x509_privkey_t x509_key; +const uschar * where; +int rc; + +if ( (where = US"internal init", rc = gnutls_x509_privkey_init(&x509_key)) + || (rc = gnutls_privkey_init(&sign_ctx->key)) + || (where = US"privkey PEM-block import", + rc = gnutls_x509_privkey_import(x509_key, &k, GNUTLS_X509_FMT_PEM)) + || (where = US"internal privkey transfer", + rc = gnutls_privkey_import_x509(sign_ctx->key, x509_key, 0)) + ) + return string_sprintf("%s: %s", where, gnutls_strerror(rc)); + +switch (rc = gnutls_privkey_get_pk_algorithm(sign_ctx->key, NULL)) + { + case GNUTLS_PK_RSA: sign_ctx->keytype = KEYTYPE_RSA; break; +#ifdef SIGN_HAVE_ED25519 + case GNUTLS_PK_EDDSA_ED25519: sign_ctx->keytype = KEYTYPE_ED25519; break; +#endif + default: return rc < 0 + ? CUS gnutls_strerror(rc) + : string_sprintf("Unhandled key type: %d '%s'", rc, gnutls_pk_get_name(rc)); + } + +return NULL; +} + + + +/* allocate mem for signature (when signing) */ +/* hash & sign data. No way to do incremental. + +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) +{ +gnutls_datum_t k_data = { .data = data->data, .size = data->len }; +gnutls_digest_algorithm_t dig; +gnutls_datum_t k_sig; +int rc; + +switch (hash) + { + case HASH_SHA1: dig = GNUTLS_DIG_SHA1; break; + case HASH_SHA2_256: dig = GNUTLS_DIG_SHA256; break; + case HASH_SHA2_512: dig = GNUTLS_DIG_SHA512; break; + default: return US"nonhandled hash type"; + } + +if ((rc = gnutls_privkey_sign_data(sign_ctx->key, dig, 0, &k_data, &k_sig))) + return CUS gnutls_strerror(rc); + +/* Don't care about deinit for the key; shortlived process */ + +sig->data = k_sig.data; +sig->len = k_sig.size; +return NULL; +} + + + +/* import public key (from blob in memory) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) +{ +gnutls_datum_t k; +int rc; +const uschar * ret = NULL; + +gnutls_pubkey_init(&verify_ctx->key); +k.data = pubkey->data; +k.size = pubkey->len; + +switch(fmt) + { + case KEYFMT_DER: + if ((rc = gnutls_pubkey_import(verify_ctx->key, &k, GNUTLS_X509_FMT_DER))) + ret = US gnutls_strerror(rc); + break; +#ifdef SIGN_HAVE_ED25519 + case KEYFMT_ED25519_BARE: + if ((rc = gnutls_pubkey_import_ecc_raw(verify_ctx->key, + GNUTLS_ECC_CURVE_ED25519, &k, NULL))) + ret = US gnutls_strerror(rc); + break; +#endif + default: + ret = US"pubkey format not handled"; + break; + } +return ret; +} + + +/* verify signature (of hash if RSA sig, of data if EC sig. No way to do incremental) +(given pubkey & alleged sig) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) +{ +gnutls_datum_t k = { .data = data_hash->data, .size = data_hash->len }; +gnutls_datum_t s = { .data = sig->data, .size = sig->len }; +int rc; +const uschar * ret = NULL; + +#ifdef SIGN_HAVE_ED25519 +if (verify_ctx->keytype == KEYTYPE_ED25519) + { + if ((rc = gnutls_pubkey_verify_data2(verify_ctx->key, + GNUTLS_SIGN_EDDSA_ED25519, 0, &k, &s)) < 0) + ret = US gnutls_strerror(rc); + } +else +#endif + { + gnutls_sign_algorithm_t algo; + switch (hash) + { + case HASH_SHA1: algo = GNUTLS_SIGN_RSA_SHA1; break; + case HASH_SHA2_256: algo = GNUTLS_SIGN_RSA_SHA256; break; + case HASH_SHA2_512: algo = GNUTLS_SIGN_RSA_SHA512; break; + default: return US"nonhandled hash type"; + } + + if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->key, algo, 0, &k, &s)) < 0) + ret = US gnutls_strerror(rc); + } + +gnutls_pubkey_deinit(verify_ctx->key); +return ret; +} + + + + +#elif defined(SIGN_GCRYPT) +/******************************************************************************/ +/* This variant is used under pre-3.0.0 GnuTLS. Only rsa-sha1 and rsa-sha256 */ + + +/* Internal service routine: +Read and move past an asn.1 header, checking class & tag, +optionally returning the data-length */ + +static int +as_tag(blob * der, uschar req_cls, long req_tag, long * alen) +{ +int rc; +uschar tag_class; +int taglen; +long tag, len; + +debug_printf_indent("as_tag: %02x %02x %02x %02x\n", + der->data[0], der->data[1], der->data[2], der->data[3]); + +if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag)) + != ASN1_SUCCESS) + return rc; + +if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND; + +if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0) + return ASN1_DER_ERROR; +if (alen) *alen = len; + +/* debug_printf_indent("as_tag: tlen %d dlen %d\n", taglen, (int)len); */ + +der->data += taglen; +der->len -= taglen; +return rc; +} + +/* Internal service routine: +Read and move over an asn.1 integer, setting an MPI to the value +*/ + +static uschar * +as_mpi(blob * der, gcry_mpi_t * mpi) +{ +long alen; +int rc; +gcry_error_t gerr; + +debug_printf_indent("%s\n", __FUNCTION__); + +/* integer; move past the header */ +if ((rc = as_tag(der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) + return US asn1_strerror(rc); + +/* read to an MPI */ +if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL))) + return US gcry_strerror(gerr); + +/* move over the data */ +der->data += alen; der->len -= alen; +return NULL; +} + + + +void +exim_dkim_init(void) +{ +/* Version check should be the very first call because it +makes sure that important subsystems are initialized. */ +if (!gcry_check_version (GCRYPT_VERSION)) + { + fputs ("libgcrypt version mismatch\n", stderr); + exit (2); + } + +/* We don't want to see any warnings, e.g. because we have not yet +parsed program options which might be used to suppress such +warnings. */ +gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN); + +/* ... If required, other initialization goes here. Note that the +process might still be running with increased privileges and that +the secure memory has not been initialized. */ + +/* Allocate a pool of 16k secure memory. This make the secure memory +available and also drops privileges where needed. */ +gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0); + +/* It is now okay to let Libgcrypt complain when there was/is +a problem with the secure memory. */ +gcry_control (GCRYCTL_RESUME_SECMEM_WARN); + +/* ... If required, other initialization goes here. */ + +/* Tell Libgcrypt that initialization has completed. */ +gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0); + +return; +} + + + + +/* Accumulate data (gnutls-only). +String to be appended must be nul-terminated. */ + +gstring * +exim_dkim_data_append(gstring * g, uschar * s) +{ +return g; /*dummy*/ +} + + + +/* import private key from PEM string in memory. +Only handles RSA keys. +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) +{ +uschar * s1, * s2; +blob der; +long alen; +int rc; + +/*XXX will need extension to _spot_ as well as handle a +non-RSA key? I think... +So... this is not a PrivateKeyInfo - which would have a field +identifying the keytype - PrivateKeyAlgorithmIdentifier - +but a plain RSAPrivateKey (wrapped in PEM-headers. Can we +use those as a type tag? What forms are there? "BEGIN EC PRIVATE KEY" (cf. ec(1ssl)) + +How does OpenSSL PEM_read_bio_PrivateKey() deal with it? +gnutls_x509_privkey_import() ? +*/ + +/* + * RSAPrivateKey ::= SEQUENCE + * version Version, + * modulus INTEGER, -- n + * publicExponent INTEGER, -- e + * privateExponent INTEGER, -- d + * prime1 INTEGER, -- p + * prime2 INTEGER, -- q + * exponent1 INTEGER, -- d mod (p-1) + * exponent2 INTEGER, -- d mod (q-1) + * coefficient INTEGER, -- (inverse of q) mod p + * otherPrimeInfos OtherPrimeInfos OPTIONAL + + * ECPrivateKey ::= SEQUENCE { + * version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1), + * privateKey OCTET STRING, + * parameters [0] ECParameters {{ NamedCurve }} OPTIONAL, + * publicKey [1] BIT STRING OPTIONAL + * } + * Hmm, only 1 useful item, and not even an integer? Wonder how we might use it... + +- actually, gnutls_x509_privkey_import() appears to require a curve name parameter + value for that is an OID? a local-only integer (it's an enum in GnuTLS)? + + +Useful cmds: + ssh-keygen -t ecdsa -f foo.privkey + ssh-keygen -t ecdsa -b384 -f foo.privkey + ssh-keygen -t ecdsa -b521 -f foo.privkey + ssh-keygen -t ed25519 -f foo.privkey + + < foo openssl pkcs8 -in /dev/stdin -inform PEM -nocrypt -topk8 -outform DER | od -x + + openssl asn1parse -in foo -inform PEM -dump + openssl asn1parse -in foo -inform PEM -dump -stroffset 24 (??) +(not good for ed25519) + + */ + +if ( !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----")) + || !(s2 = Ustrstr(CS (s1+=31), "-----END RSA PRIVATE KEY-----" )) + ) + return US"Bad PEM wrapper"; + +*s2 = '\0'; + +if ((der.len = b64decode(s1, &der.data)) < 0) + return US"Bad PEM-DER b64 decode"; + +/* untangle asn.1 */ + +/* sequence; just move past the header */ +if ((rc = as_tag(&der, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) + != ASN1_SUCCESS) goto asn_err; + +/* integer version; move past the header, check is zero */ +if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) + goto asn_err; +if (alen != 1 || *der.data != 0) + return US"Bad version number"; +der.data++; der.len--; + +if ( (s1 = as_mpi(&der, &sign_ctx->n)) + || (s1 = as_mpi(&der, &sign_ctx->e)) + || (s1 = as_mpi(&der, &sign_ctx->d)) + || (s1 = as_mpi(&der, &sign_ctx->p)) + || (s1 = as_mpi(&der, &sign_ctx->q)) + || (s1 = as_mpi(&der, &sign_ctx->dp)) + || (s1 = as_mpi(&der, &sign_ctx->dq)) + || (s1 = as_mpi(&der, &sign_ctx->qp)) + ) + return s1; + +#ifdef extreme_debug +DEBUG(D_acl) debug_printf_indent("rsa_signing_init:\n"); + { + uschar * s; + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->n); + debug_printf_indent(" N : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->e); + debug_printf_indent(" E : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->d); + debug_printf_indent(" D : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->p); + debug_printf_indent(" P : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->q); + debug_printf_indent(" Q : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dp); + debug_printf_indent(" DP: %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dq); + debug_printf_indent(" DQ: %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->qp); + debug_printf_indent(" QP: %s\n", s); + } +#endif + +sign_ctx->keytype = KEYTYPE_RSA; +return NULL; + +asn_err: return US asn1_strerror(rc); +} + + + +/* allocate mem for signature (when signing) */ +/* sign already-hashed data. + +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) +{ +char * sexp_hash; +gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL; +gcry_mpi_t m_sig; +uschar * errstr; +gcry_error_t gerr; + +/*XXX will need extension for hash types (though, possibly, should +be re-specced to not rehash but take an already-hashed value? Actually +current impl looks WRONG - it _is_ given a hash so should not be +re-hashing. Has this been tested? + +Will need extension for non-RSA sugning algos. */ + +switch (hash) + { + case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; + case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; + default: return US"nonhandled hash type"; + } + +#define SIGSPACE 128 +sig->data = store_get(SIGSPACE); + +if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0) + { + gcry_mpi_swap (sign_ctx->p, sign_ctx->q); + gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q); + } + +if ( (gerr = gcry_sexp_build (&s_key, NULL, + "(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))", + sign_ctx->n, sign_ctx->e, + sign_ctx->d, sign_ctx->p, + sign_ctx->q, sign_ctx->qp)) + || (gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, + (int) data->len, CS data->data)) + || (gerr = gcry_pk_sign (&s_sig, s_hash, s_key)) + ) + return US gcry_strerror(gerr); + +/* gcry_sexp_dump(s_sig); */ + +if ( !(s_sig = gcry_sexp_find_token(s_sig, "s", 0)) + ) + return US"no sig result"; + +m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG); + +#ifdef extreme_debug +DEBUG(D_acl) + { + uschar * s; + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig); + debug_printf_indent(" SG: %s\n", s); + } +#endif + +gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig); +if (gerr) + { + debug_printf_indent("signature conversion from MPI to buffer failed\n"); + return US gcry_strerror(gerr); + } +#undef SIGSPACE + +return NULL; +} + + +/* import public key (from blob in memory) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) +{ +/* +in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi() +*/ +uschar tag_class; +int taglen; +long alen; +int rc; +uschar * errstr; +gcry_error_t gerr; +uschar * stage = US"S1"; + +if (fmt != KEYFMT_DER) return US"pubkey format not handled"; + +/* +sequence + sequence + OBJECT:rsaEncryption + NULL + BIT STRING:RSAPublicKey + sequence + INTEGER:Public modulus + INTEGER:Public exponent + +openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head; +openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump; +openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22; +*/ + +/* sequence; just move past the header */ +if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) + != ASN1_SUCCESS) goto asn_err; + +/* sequence; skip the entire thing */ +DEBUG(D_acl) stage = US"S2"; +if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, &alen)) + != ASN1_SUCCESS) goto asn_err; +pubkey->data += alen; pubkey->len -= alen; + + +/* bitstring: limit range to size of bitstring; +move over header + content wrapper */ +DEBUG(D_acl) stage = US"BS"; +if ((rc = as_tag(pubkey, 0, ASN1_TAG_BIT_STRING, &alen)) != ASN1_SUCCESS) + goto asn_err; +pubkey->len = alen; +pubkey->data++; pubkey->len--; + +/* sequence; just move past the header */ +DEBUG(D_acl) stage = US"S3"; +if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) + != ASN1_SUCCESS) goto asn_err; + +/* read two integers */ +DEBUG(D_acl) stage = US"MPI"; +if ( (errstr = as_mpi(pubkey, &verify_ctx->n)) + || (errstr = as_mpi(pubkey, &verify_ctx->e)) + ) + return errstr; + +#ifdef extreme_debug +DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n"); + { + uschar * s; + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->n); + debug_printf_indent(" N : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->e); + debug_printf_indent(" E : %s\n", s); + } + +#endif +return NULL; + +asn_err: +DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc)); + return US asn1_strerror(rc); +} + + +/* verify signature (of hash) +XXX though we appear to be doing a hash, too! +(given pubkey & alleged sig) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) +{ +/* +cf. libgnutls 2.8.5 _wrap_gcry_pk_verify() +*/ +char * sexp_hash; +gcry_mpi_t m_sig; +gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL; +gcry_error_t gerr; +uschar * stage; + +/*XXX needs extension for SHA512 */ +switch (hash) + { + case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; + case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; + default: return US"nonhandled hash type"; + } + +if ( (stage = US"pkey sexp build", + gerr = gcry_sexp_build (&s_pkey, NULL, "(public-key(rsa(n%m)(e%m)))", + verify_ctx->n, verify_ctx->e)) + || (stage = US"data sexp build", + gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, + (int) data_hash->len, CS data_hash->data)) + || (stage = US"sig mpi scan", + gerr = gcry_mpi_scan(&m_sig, GCRYMPI_FMT_USG, sig->data, sig->len, NULL)) + || (stage = US"sig sexp build", + gerr = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%m)))", m_sig)) + || (stage = US"verify", + gerr = gcry_pk_verify (s_sig, s_hash, s_pkey)) + ) + { + DEBUG(D_acl) debug_printf_indent("verify: error in stage '%s'\n", stage); + return US gcry_strerror(gerr); + } + +if (s_sig) gcry_sexp_release (s_sig); +if (s_hash) gcry_sexp_release (s_hash); +if (s_pkey) gcry_sexp_release (s_pkey); +gcry_mpi_release (m_sig); +gcry_mpi_release (verify_ctx->n); +gcry_mpi_release (verify_ctx->e); + +return NULL; +} + + + + +#elif defined(SIGN_OPENSSL) +/******************************************************************************/ + +void +exim_dkim_init(void) +{ +ERR_load_crypto_strings(); +} + + +/* accumulate data (was gnutls-only but now needed for OpenSSL non-EC too +because now using hash-and-sign interface) */ +gstring * +exim_dkim_data_append(gstring * g, uschar * s) +{ +return string_cat(g, s); +} + + +/* import private key from PEM string in memory. +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) +{ +BIO * bp = BIO_new_mem_buf(privkey_pem, -1); + +if (!(sign_ctx->key = PEM_read_bio_PrivateKey(bp, NULL, NULL, NULL))) + return string_sprintf("privkey PEM-block import: %s", + ERR_error_string(ERR_get_error(), NULL)); + +sign_ctx->keytype = +#ifdef SIGN_HAVE_ED25519 + EVP_PKEY_type(EVP_PKEY_id(sign_ctx->key)) == EVP_PKEY_ED25519 + ? KEYTYPE_ED25519 : KEYTYPE_RSA; +#else + KEYTYPE_RSA; +#endif +return NULL; +} + + + +/* allocate mem for signature (when signing) */ +/* hash & sign data. Incremental not supported. + +Return: NULL for success with the signaature in the sig blob, or an error string */ + +const uschar * +exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) +{ +const EVP_MD * md; +EVP_MD_CTX * ctx; +size_t siglen; + +switch (hash) + { + case HASH_NULL: md = NULL; break; /* Ed25519 signing */ + case HASH_SHA1: md = EVP_sha1(); break; + case HASH_SHA2_256: md = EVP_sha256(); break; + case HASH_SHA2_512: md = EVP_sha512(); break; + default: return US"nonhandled hash type"; + } + +#ifdef SIGN_HAVE_ED25519 +if ( (ctx = EVP_MD_CTX_new()) + && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0 + && EVP_DigestSign(ctx, NULL, &siglen, NULL, 0) > 0 + && (sig->data = store_get(siglen)) + + /* Obtain the signature (slen could change here!) */ + && EVP_DigestSign(ctx, sig->data, &siglen, data->data, data->len) > 0 + ) + { + EVP_MD_CTX_destroy(ctx); + sig->len = siglen; + return NULL; + } +#else +/*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */ +if ( (ctx = EVP_MD_CTX_create()) + && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0 + && EVP_DigestSignUpdate(ctx, data->data, data->len) > 0 + && EVP_DigestSignFinal(ctx, NULL, &siglen) > 0 + && (sig->data = store_get(siglen)) + + /* Obtain the signature (slen could change here!) */ + && EVP_DigestSignFinal(ctx, sig->data, &siglen) > 0 + ) + { + EVP_MD_CTX_destroy(ctx); + sig->len = siglen; + return NULL; + } +#endif + +if (ctx) EVP_MD_CTX_destroy(ctx); +return US ERR_error_string(ERR_get_error(), NULL); +} + + + +/* import public key (from blob in memory) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) +{ +const uschar * s = pubkey->data; +uschar * ret = NULL; + +switch(fmt) + { + case KEYFMT_DER: + /*XXX hmm, we never free this */ + if (!(verify_ctx->key = d2i_PUBKEY(NULL, &s, pubkey->len))) + ret = US ERR_error_string(ERR_get_error(), NULL); + break; +#ifdef SIGN_HAVE_ED25519 + case KEYFMT_ED25519_BARE: + if (!(verify_ctx->key = EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, NULL, + s, pubkey->len))) + ret = US ERR_error_string(ERR_get_error(), NULL); + break; +#endif + default: + ret = US"pubkey format not handled"; + break; + } + +return ret; +} + + + + +/* verify signature (of hash, except Ed25519 where of-data) +(given pubkey & alleged sig) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig) +{ +const EVP_MD * md; + +switch (hash) + { + case HASH_NULL: md = NULL; break; + case HASH_SHA1: md = EVP_sha1(); break; + case HASH_SHA2_256: md = EVP_sha256(); break; + case HASH_SHA2_512: md = EVP_sha512(); break; + default: return US"nonhandled hash type"; + } + +#ifdef SIGN_HAVE_ED25519 +if (!md) + { + EVP_MD_CTX * ctx; + + if ((ctx = EVP_MD_CTX_new())) + { + if ( EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0 + && EVP_DigestVerify(ctx, sig->data, sig->len, data->data, data->len) > 0 + ) + { EVP_MD_CTX_free(ctx); return NULL; } + EVP_MD_CTX_free(ctx); + } + } +else +#endif + { + EVP_PKEY_CTX * ctx; + + if ((ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL))) + { + if ( EVP_PKEY_verify_init(ctx) > 0 + && EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0 + && EVP_PKEY_CTX_set_signature_md(ctx, md) > 0 + && EVP_PKEY_verify(ctx, sig->data, sig->len, + data->data, data->len) == 1 + ) + { EVP_PKEY_CTX_free(ctx); return NULL; } + EVP_PKEY_CTX_free(ctx); + + DEBUG(D_tls) + if (Ustrcmp(ERR_reason_error_string(ERR_peek_error()), "wrong signature length") == 0) + debug_printf("sig len (from msg hdr): %d, expected (from dns pubkey) %d\n", + (int) sig->len, EVP_PKEY_size(verify_ctx->key)); + } + } + +return US ERR_error_string(ERR_get_error(), NULL); +} + + + +#endif +/******************************************************************************/ + +#endif /*DISABLE_DKIM*/ +#endif /*MACRO_PREDEF*/ +/* End of File */