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Sun, 18 Aug 2024 18:00:01 +0100 (CET) From: Roberto Sassu To: dhowells@redhat.com, dwmw2@infradead.org, herbert@gondor.apana.org.au, davem@davemloft.net Cc: linux-kernel@vger.kernel.org, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, zohar@linux.ibm.com, linux-integrity@vger.kernel.org, Roberto Sassu Subject: [PATCH v2 05/14] PGPLIB: Signature parser Date: Sun, 18 Aug 2024 18:57:47 +0200 Message-Id: <20240818165756.629203-6-roberto.sassu@huaweicloud.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240818165756.629203-1-roberto.sassu@huaweicloud.com> References: <20240818165756.629203-1-roberto.sassu@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: LxC2BwAXm4VpKMJm+zZxAQ--.21009S7 X-Coremail-Antispam: 1UD129KBjvJXoWxuFW8tryruF45Cw1rAF47urg_yoWDGry3pa 4Iy34ftrWUG3ZavrW8Ar47X3y5Cr40y347Ka9Yq3WYy39agrn8ZrWvkFyFkF98t3WkX3yx CrZ8ta98ur4kZw7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPSb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUAV Cq3wA2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0 rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWUCVW8JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267 AKxVWxJVW8Jr1l84ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIEc7CjxVAF wI0_Gr0_Gr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7 xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Y z7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAaw2 AFwI0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAq x4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r 43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_JFI_Gr1lIxAIcVC0I7IYx2IY6xkF 7I0E14v26F4j6r4UJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI 0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7I U1aLvJUUUUU== X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAQATBGbBWHEB+wAAsi From: David Howells Provide some PGP signature parsing helpers: (1) A function to parse V4 signature subpackets and pass the desired ones to a processor function: int pgp_parse_sig_subpkts(const u8 *data, size_t datalen, struct pgp_parse_sig_context *ctx); (2) A function to parse out basic signature parameters from any PGP signature such that the algorithms and public key can be selected: int pgp_parse_sig_params(const u8 **_data, size_t *_datalen, struct pgp_sig_parameters *p); Signed-off-by: David Howells Co-developed-by: Roberto Sassu Signed-off-by: Roberto Sassu --- crypto/asymmetric_keys/pgp_library.c | 284 +++++++++++++++++++++++++++ crypto/asymmetric_keys/pgplib.h | 25 +++ 2 files changed, 309 insertions(+) diff --git a/crypto/asymmetric_keys/pgp_library.c b/crypto/asymmetric_keys/pgp_library.c index 33ed01f67654..2fd3e7d55f6f 100644 --- a/crypto/asymmetric_keys/pgp_library.c +++ b/crypto/asymmetric_keys/pgp_library.c @@ -270,3 +270,287 @@ int pgp_parse_public_key(const u8 **_data, size_t *_datalen, return 0; } EXPORT_SYMBOL_GPL(pgp_parse_public_key); + +/** + * pgp_parse_sig_subpkt_header - Parse a PGP V4 signature subpacket header + * @_data: Start of the subpacket (updated to subpacket data) + * @_datalen: Amount of data remaining in buffer (decreased) + * @_type: Where the subpacket type will be returned + * + * Parse a PGP V4 signature subpacket header [RFC 4880: 5.2.3.1]. + * + * Return: packet data size on success; non-zero on error. If successful, + * *_data and *_datalen will have been updated and *_headerlen will be set to + * hold the length of the packet header. + */ +static ssize_t pgp_parse_sig_subpkt_header(const u8 **_data, size_t *_datalen, + enum pgp_sig_subpkt_type *_type) +{ + enum pgp_sig_subpkt_type type; + const u8 *data = *_data; + size_t size, datalen = *_datalen; + + pr_devel("-->%s(,%zu,,)\n", __func__, datalen); + + if (datalen < 2) + goto short_subpacket; + + pr_devel("subpkt hdr %02x, %02x\n", data[0], data[1]); + + switch (data[0]) { + case 0x00 ... 0xbf: + /* One-byte length */ + size = data[0]; + data++; + datalen--; + break; + case 0xc0 ... 0xfe: + /* Two-byte length */ + if (datalen < 3) + goto short_subpacket; + size = (data[0] - 192) * 256; + size += data[1] + 192; + data += 2; + datalen -= 2; + break; + case 0xff: + if (datalen < 6) + goto short_subpacket; + size = data[1] << 24; + size |= data[2] << 16; + size |= data[3] << 8; + size |= data[4]; + data += 5; + datalen -= 5; + break; + } + + /* The type octet is included in the size */ + pr_devel("datalen=%zu size=%zu\n", datalen, size); + if (datalen < size) + goto short_subpacket; + if (size == 0) + goto very_short_subpacket; + if (size > INT_MAX) + goto too_big; + + type = *data++ & ~PGP_SIG_SUBPKT_TYPE_CRITICAL_MASK; + datalen--; + size--; + + *_data = data; + *_datalen = datalen; + *_type = type; + pr_devel("Found subpkt type=%u size=%zd\n", type, size); + return size; + +very_short_subpacket: + pr_debug("Signature subpacket size can't be zero\n"); + return -EBADMSG; +short_subpacket: + pr_debug("Attempt to parse short signature subpacket\n"); + return -EBADMSG; +too_big: + pr_debug("Signature subpacket size >2G\n"); + return -EMSGSIZE; +} + +/** + * pgp_parse_sig_subpkts - Parse a set of PGP V4 signatute subpackets + * @data: Data to be parsed (updated) + * @datalen: Amount of data (updated) + * @ctx: Parsing context + * + * Parse a set of PGP signature subpackets [RFC 4880: 5.2.3]. + * + * Return: 0 on successful parsing, an error value otherwise + */ +static int pgp_parse_sig_subpkts(const u8 *data, size_t datalen, + struct pgp_parse_sig_context *ctx) +{ + enum pgp_sig_subpkt_type type; + ssize_t pktlen; + int ret; + + pr_devel("-->%s(,%zu,,)\n", __func__, datalen); + + while (datalen > 2) { + pktlen = pgp_parse_sig_subpkt_header(&data, &datalen, &type); + if (pktlen < 0) + return pktlen; + if (test_bit(type, ctx->types_of_interest)) { + ret = ctx->process_packet(ctx, type, data, pktlen); + if (ret < 0) + return ret; + } + data += pktlen; + datalen -= pktlen; + } + + if (datalen != 0) { + pr_debug("Excess octets in signature subpacket stream\n"); + return -EBADMSG; + } + + return 0; +} + +struct pgp_parse_sig_params_ctx { + struct pgp_parse_sig_context base; + struct pgp_sig_parameters *params; + bool got_the_issuer; +}; + +/* + * Process a V4 signature subpacket. + */ +static int pgp_process_sig_params_subpkt(struct pgp_parse_sig_context *context, + enum pgp_sig_subpkt_type type, + const u8 *data, + size_t datalen) +{ + struct pgp_parse_sig_params_ctx *ctx = + container_of(context, struct pgp_parse_sig_params_ctx, base); + + if (ctx->got_the_issuer) { + pr_debug("V4 signature packet has multiple issuers\n"); + return -EBADMSG; + } + + if (datalen != 8) { + pr_debug("V4 signature issuer subpkt not 8 long (%zu)\n", + datalen); + return -EBADMSG; + } + + memcpy(&ctx->params->issuer, data, 8); + ctx->got_the_issuer = true; + return 0; +} + +/** + * pgp_parse_sig_params - Parse basic parameters from a PGP signature packet + * @_data: Content of packet (updated) + * @_datalen: Length of packet remaining (updated) + * @p: The basic parameters + * + * Parse the basic parameters from a PGP signature packet [RFC 4880: 5.2] that + * are needed to start off a signature verification operation. The only ones + * actually necessary are the signature type (which affects how the data is + * transformed) and the hash algorithm. + * + * We also extract the public key algorithm and the issuer's key ID as we'll + * need those to determine if we actually have the public key available. If + * not, then we can't verify the signature anyway. + * + * Return: 0 if successful or a negative error code. *_data and *_datalen are + * updated to point to the 16-bit subset of the hash value and the set of MPIs. + */ +int pgp_parse_sig_params(const u8 **_data, size_t *_datalen, + struct pgp_sig_parameters *p) +{ + const u8 *data = *_data; + size_t datalen = *_datalen; + int ret; + + pr_devel("-->%s(,%zu,,)\n", __func__, datalen); + + if (datalen < 1) + return -EBADMSG; + p->version = *data; + + if (p->version == PGP_SIG_VERSION_3) { + const struct pgp_signature_v3_packet *v3 = (const void *)data; + + if (datalen < sizeof(*v3)) { + pr_debug("Short V3 signature packet\n"); + return -EBADMSG; + } + datalen -= sizeof(*v3); + data += sizeof(*v3); + + /* V3 has everything we need in the header */ + p->signature_type = v3->hashed.signature_type; + memcpy(&p->issuer, &v3->issuer, 8); + p->pubkey_algo = v3->pubkey_algo; + p->hash_algo = v3->hash_algo; + + } else if (p->version == PGP_SIG_VERSION_4) { + const struct pgp_signature_v4_packet *v4 = (const void *)data; + struct pgp_parse_sig_params_ctx ctx = { + .base.process_packet = pgp_process_sig_params_subpkt, + .params = p, + .got_the_issuer = false, + }; + size_t subdatalen; + + if (datalen < sizeof(*v4) + 2 + 2 + 2) { + pr_debug("Short V4 signature packet\n"); + return -EBADMSG; + } + datalen -= sizeof(*v4); + data += sizeof(*v4); + + /* V4 has most things in the header... */ + p->signature_type = v4->signature_type; + p->pubkey_algo = v4->pubkey_algo; + p->hash_algo = v4->hash_algo; + + /* + * ... but we have to get the key ID from the subpackets, of + * which there are two sets. + */ + __set_bit(PGP_SIG_ISSUER, ctx.base.types_of_interest); + + subdatalen = *data++ << 8; + subdatalen |= *data++; + datalen -= 2; + if (subdatalen) { + /* Hashed subpackets */ + pr_devel("hashed data: %zu (after %zu)\n", + subdatalen, sizeof(*v4)); + if (subdatalen > datalen + 2 + 2) { + pr_debug("Short V4 signature packet [hdata]\n"); + return -EBADMSG; + } + ret = pgp_parse_sig_subpkts(data, subdatalen, + &ctx.base); + if (ret < 0) + return ret; + data += subdatalen; + datalen -= subdatalen; + } + + subdatalen = *data++ << 8; + subdatalen |= *data++; + datalen -= 2; + if (subdatalen) { + /* Unhashed subpackets */ + pr_devel("unhashed data: %zu\n", subdatalen); + if (subdatalen > datalen + 2) { + pr_debug("Short V4 signature packet [udata]\n"); + return -EBADMSG; + } + ret = pgp_parse_sig_subpkts(data, subdatalen, + &ctx.base); + if (ret < 0) + return ret; + data += subdatalen; + datalen -= subdatalen; + } + + if (!ctx.got_the_issuer) { + pr_debug("V4 signature packet lacks issuer\n"); + return -EBADMSG; + } + } else { + pr_debug("Signature packet with unhandled version %d\n", + p->version); + return -EBADMSG; + } + + *_data = data; + *_datalen = datalen; + return 0; +} +EXPORT_SYMBOL_GPL(pgp_parse_sig_params); diff --git a/crypto/asymmetric_keys/pgplib.h b/crypto/asymmetric_keys/pgplib.h index d82b84179433..967e2853186d 100644 --- a/crypto/asymmetric_keys/pgplib.h +++ b/crypto/asymmetric_keys/pgplib.h @@ -31,3 +31,28 @@ struct pgp_parse_pubkey { extern int pgp_parse_public_key(const u8 **_data, size_t *_datalen, struct pgp_parse_pubkey *pk); + +struct pgp_parse_sig_context { + unsigned long types_of_interest[128 / BITS_PER_LONG]; + int (*process_packet)(struct pgp_parse_sig_context *context, + enum pgp_sig_subpkt_type type, + const u8 *data, + size_t datalen); +}; + +extern int pgp_parse_sig_packets(const u8 *data, size_t datalen, + struct pgp_parse_sig_context *ctx); + +struct pgp_sig_parameters { + enum pgp_signature_version version : 8; + enum pgp_signature_type signature_type : 8; + enum pgp_pubkey_algo pubkey_algo : 8; + enum pgp_hash_algo hash_algo : 8; + union { + struct pgp_key_ID issuer; + __be32 issuer32[2]; + }; +}; + +extern int pgp_parse_sig_params(const u8 **_data, size_t *_datalen, + struct pgp_sig_parameters *p);