Re: [PATCH v5 1/6] lib/base64: Add support for multiple variants

[David Laight <david.laight.linux@gmail.com>]

On Fri, 14 Nov 2025 14:00:45 +0800
Guan-Chun Wu <409411716@gms.tku.edu.tw> wrote:

> From: Kuan-Wei Chiu <visitorckw@gmail.com>
> 
> Extend the base64 API to support multiple variants (standard, URL-safe,
> and IMAP) as defined in RFC 4648 and RFC 3501. The API now takes a
> variant parameter and an option to control padding. Update NVMe auth
> code to use the new interface with BASE64_STD.
> 
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> Co-developed-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>
> Signed-off-by: Guan-Chun Wu <409411716@gms.tku.edu.tw>

Reviewed-by: David Laight <david.laight.linux@gmail.com>

> ---
>  drivers/nvme/common/auth.c |  4 +--
>  include/linux/base64.h     | 10 ++++--
>  lib/base64.c               | 62 ++++++++++++++++++++++----------------
>  3 files changed, 46 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/nvme/common/auth.c b/drivers/nvme/common/auth.c
> index 1f51fbebd9fa..e07e7d4bf8b6 100644
> --- a/drivers/nvme/common/auth.c
> +++ b/drivers/nvme/common/auth.c
> @@ -178,7 +178,7 @@ struct nvme_dhchap_key *nvme_auth_extract_key(unsigned char *secret,
>  	if (!key)
>  		return ERR_PTR(-ENOMEM);
>  
> -	key_len = base64_decode(secret, allocated_len, key->key);
> +	key_len = base64_decode(secret, allocated_len, key->key, true, BASE64_STD);
>  	if (key_len < 0) {
>  		pr_debug("base64 key decoding error %d\n",
>  			 key_len);
> @@ -663,7 +663,7 @@ int nvme_auth_generate_digest(u8 hmac_id, u8 *psk, size_t psk_len,
>  	if (ret)
>  		goto out_free_digest;
>  
> -	ret = base64_encode(digest, digest_len, enc);
> +	ret = base64_encode(digest, digest_len, enc, true, BASE64_STD);
>  	if (ret < hmac_len) {
>  		ret = -ENOKEY;
>  		goto out_free_digest;
> diff --git a/include/linux/base64.h b/include/linux/base64.h
> index 660d4cb1ef31..a2c6c9222da3 100644
> --- a/include/linux/base64.h
> +++ b/include/linux/base64.h
> @@ -8,9 +8,15 @@
>  
>  #include <linux/types.h>
>  
> +enum base64_variant {
> +	BASE64_STD,       /* RFC 4648 (standard) */
> +	BASE64_URLSAFE,   /* RFC 4648 (base64url) */
> +	BASE64_IMAP,      /* RFC 3501 */
> +};
> +
>  #define BASE64_CHARS(nbytes)   DIV_ROUND_UP((nbytes) * 4, 3)
>  
> -int base64_encode(const u8 *src, int len, char *dst);
> -int base64_decode(const char *src, int len, u8 *dst);
> +int base64_encode(const u8 *src, int len, char *dst, bool padding, enum base64_variant variant);
> +int base64_decode(const char *src, int len, u8 *dst, bool padding, enum base64_variant variant);
>  
>  #endif /* _LINUX_BASE64_H */
> diff --git a/lib/base64.c b/lib/base64.c
> index b736a7a431c5..a7c20a8e8e98 100644
> --- a/lib/base64.c
> +++ b/lib/base64.c
> @@ -1,12 +1,12 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
> - * base64.c - RFC4648-compliant base64 encoding
> + * base64.c - Base64 with support for multiple variants
>   *
>   * Copyright (c) 2020 Hannes Reinecke, SUSE
>   *
>   * Based on the base64url routines from fs/crypto/fname.c
> - * (which are using the URL-safe base64 encoding),
> - * modified to use the standard coding table from RFC4648 section 4.
> + * (which are using the URL-safe Base64 encoding),
> + * modified to support multiple Base64 variants.
>   */
>  
>  #include <linux/kernel.h>
> @@ -15,26 +15,31 @@
>  #include <linux/string.h>
>  #include <linux/base64.h>
>  
> -static const char base64_table[65] =
> -	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
> +static const char base64_tables[][65] = {
> +	[BASE64_STD] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
> +	[BASE64_URLSAFE] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_",
> +	[BASE64_IMAP] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,",
> +};
>  
>  /**
> - * base64_encode() - base64-encode some binary data
> + * base64_encode() - Base64-encode some binary data
>   * @src: the binary data to encode
>   * @srclen: the length of @src in bytes
> - * @dst: (output) the base64-encoded string.  Not NUL-terminated.
> + * @dst: (output) the Base64-encoded string.  Not NUL-terminated.
> + * @padding: whether to append '=' padding characters
> + * @variant: which base64 variant to use
>   *
> - * Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
> - * by RFC 4648, including the  '='-padding.
> + * Encodes data using the selected Base64 variant.
>   *
> - * Return: the length of the resulting base64-encoded string in bytes.
> + * Return: the length of the resulting Base64-encoded string in bytes.
>   */
> -int base64_encode(const u8 *src, int srclen, char *dst)
> +int base64_encode(const u8 *src, int srclen, char *dst, bool padding, enum base64_variant variant)
>  {
>  	u32 ac = 0;
>  	int bits = 0;
>  	int i;
>  	char *cp = dst;
> +	const char *base64_table = base64_tables[variant];
>  
>  	for (i = 0; i < srclen; i++) {
>  		ac = (ac << 8) | src[i];
> @@ -48,44 +53,49 @@ int base64_encode(const u8 *src, int srclen, char *dst)
>  		*cp++ = base64_table[(ac << (6 - bits)) & 0x3f];
>  		bits -= 6;
>  	}
> -	while (bits < 0) {
> -		*cp++ = '=';
> -		bits += 2;
> +	if (padding) {
> +		while (bits < 0) {
> +			*cp++ = '=';
> +			bits += 2;
> +		}
>  	}
>  	return cp - dst;
>  }
>  EXPORT_SYMBOL_GPL(base64_encode);
>  
>  /**
> - * base64_decode() - base64-decode a string
> + * base64_decode() - Base64-decode a string
>   * @src: the string to decode.  Doesn't need to be NUL-terminated.
>   * @srclen: the length of @src in bytes
>   * @dst: (output) the decoded binary data
> + * @padding: whether to append '=' padding characters
> + * @variant: which base64 variant to use
>   *
> - * Decodes a string using base64 encoding, i.e. the "Base 64 Encoding"
> - * specified by RFC 4648, including the  '='-padding.
> + * Decodes a string using the selected Base64 variant.
>   *
>   * This implementation hasn't been optimized for performance.
>   *
>   * Return: the length of the resulting decoded binary data in bytes,
> - *	   or -1 if the string isn't a valid base64 string.
> + *	   or -1 if the string isn't a valid Base64 string.
>   */
> -int base64_decode(const char *src, int srclen, u8 *dst)
> +int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base64_variant variant)
>  {
>  	u32 ac = 0;
>  	int bits = 0;
>  	int i;
>  	u8 *bp = dst;
> +	const char *base64_table = base64_tables[variant];
>  
>  	for (i = 0; i < srclen; i++) {
>  		const char *p = strchr(base64_table, src[i]);
> -
> -		if (src[i] == '=') {
> -			ac = (ac << 6);
> -			bits += 6;
> -			if (bits >= 8)
> -				bits -= 8;
> -			continue;
> +		if (padding) {
> +			if (src[i] == '=') {
> +				ac = (ac << 6);
> +				bits += 6;
> +				if (bits >= 8)
> +					bits -= 8;
> +				continue;
> +			}
>  		}
>  		if (p == NULL || src[i] == 0)
>  			return -1;