Date: Wed, 15 Apr 2020 03:59:26 +0000 (UTC) From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r359953 - in head/sys: kern sys Message-ID: <202004150359.03F3xQnK077710@repo.freebsd.org>
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Author: kevans Date: Wed Apr 15 03:59:26 2020 New Revision: 359953 URL: https://svnweb.freebsd.org/changeset/base/359953 Log: kern uuid: break format validation out into a separate KPI This new KPI, validate_uuid, strictly validates the formatting of the input UUID and, optionally, populates a given struct uuid. As noted in the header, the key differences are that the new KPI won't recognize an empty string as a nil UUID and it won't do any kind of semantic validation on it. Also key is that populating a struct uuid is optional, so the caller doesn't necessarily need to allocate a bogus one on the stack just to validate the string. This KPI has specifically been broken out in support of D24288, which will preload /etc/hostid in loader so that early boot hostuuid users (e.g. anything that calls ether_gen_addr) can have a valid hostuuid to work with once it's been stashed in /etc/hostid. Modified: head/sys/kern/kern_uuid.c head/sys/sys/uuid.h Modified: head/sys/kern/kern_uuid.c ============================================================================== --- head/sys/kern/kern_uuid.c Wed Apr 15 03:40:33 2020 (r359952) +++ head/sys/kern/kern_uuid.c Wed Apr 15 03:59:26 2020 (r359953) @@ -382,19 +382,16 @@ be_uuid_dec(void const *buf, struct uuid *uuid) } int -parse_uuid(const char *str, struct uuid *uuid) +validate_uuid(const char *str, size_t size, struct uuid *uuid) { u_int c[11]; int n; - /* An empty string represents a nil UUID. */ - if (*str == '\0') { - bzero(uuid, sizeof(*uuid)); - return (0); - } + if (size == 0 || *str == '\0') + return (EINVAL); /* The UUID string representation has a fixed length. */ - if (strlen(str) != 36) + if (size != 36) return (EINVAL); /* @@ -406,25 +403,48 @@ parse_uuid(const char *str, struct uuid *uuid) if (str[8] != '-') return (EINVAL); + /* Now check the format. */ n = sscanf(str, "%8x-%4x-%4x-%2x%2x-%2x%2x%2x%2x%2x%2x", c + 0, c + 1, c + 2, c + 3, c + 4, c + 5, c + 6, c + 7, c + 8, c + 9, c + 10); /* Make sure we have all conversions. */ if (n != 11) return (EINVAL); - /* Successful scan. Build the UUID. */ - uuid->time_low = c[0]; - uuid->time_mid = c[1]; - uuid->time_hi_and_version = c[2]; - uuid->clock_seq_hi_and_reserved = c[3]; - uuid->clock_seq_low = c[4]; - for (n = 0; n < 6; n++) - uuid->node[n] = c[n + 5]; + /* Successful scan. Build the UUID if requested. */ + if (uuid != NULL) { + uuid->time_low = c[0]; + uuid->time_mid = c[1]; + uuid->time_hi_and_version = c[2]; + uuid->clock_seq_hi_and_reserved = c[3]; + uuid->clock_seq_low = c[4]; + for (n = 0; n < 6; n++) + uuid->node[n] = c[n + 5]; + } + return (0); +} + +int +parse_uuid(const char *str, struct uuid *uuid) +{ + unsigned int clock_seq; + int ret; + + /* An empty string represents a nil UUID. */ + if (*str == '\0') { + bzero(uuid, sizeof(*uuid)); + return (0); + } + + ret = validate_uuid(str, strlen(str), uuid); + if (ret != 0) + return (ret); + /* Check semantics... */ - return (((c[3] & 0x80) != 0x00 && /* variant 0? */ - (c[3] & 0xc0) != 0x80 && /* variant 1? */ - (c[3] & 0xe0) != 0xc0) ? EINVAL : 0); /* variant 2? */ + clock_seq = uuid->clock_seq_hi_and_reserved; + return (((clock_seq & 0x80) != 0x00 && /* variant 0? */ + (clock_seq & 0xc0) != 0x80 && /* variant 1? */ + (clock_seq & 0xe0) != 0xc0) ? EINVAL : 0); /* variant 2? */ } int Modified: head/sys/sys/uuid.h ============================================================================== --- head/sys/sys/uuid.h Wed Apr 15 03:40:33 2020 (r359952) +++ head/sys/sys/uuid.h Wed Apr 15 03:59:26 2020 (r359953) @@ -66,6 +66,21 @@ int uuid_ether_del(const uint8_t *); int snprintf_uuid(char *, size_t, struct uuid *); int printf_uuid(struct uuid *); int sbuf_printf_uuid(struct sbuf *, struct uuid *); + +/* + * There are a few key differences between validate_uuid and parse_uuid: + * + * - The struct uuid * parameter to validate_uuid is optional, so the caller + * can simply validate UUID format without doing anything with the result. + * - validate_uuid will not pass an empty string as a valid UUID, as it doesn't + * strictly meet the formatting requirements. parse_uuid will accept an + * empty string and zero out the uuid struct accordingly. + * - parse_uuid does additional semantic checks on clock_seq_hi_and_reserved + * that validate_uuid will not do. + * + * validate_uuid is intended to strictly check that it's a well-formed uuid. + */ +int validate_uuid(const char *, size_t, struct uuid *); int parse_uuid(const char *, struct uuid *); int uuidcmp(const struct uuid *, const struct uuid *);
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