Genesis 9:26

And he said, Blessed be the Lord, the God of Shem, whose work is righteous; and therefore shall Kenaan be servant unto him.

BLESSED BE THE ETERNAL G-D OF SHEM, AND MAY CANAAN BE SERVANT TO THEM. Rabbi Abraham ibn Ezra explained that to them means that Canaan be servant to G-d and to Shem since Shem will compel him to worship G-d. And the second time [this expression is repeated — in Verse 27: May G-d enlarge Japheth, and may He dwell in the tents of Shem, and may Canaan be servant to them — Ibn Ezra] explained that Canaan would be a servant to Japheth and Shem. But if this be so, Noah came to curse his enemies, and behold he blessed Canaan that he be a servant to G-d!
But Rashi wrote: “Blessed be the Eternal G-d of Shem, Who will in days to come carry out His promise to the descendants of Shem to give them the land of Canaan, and may Canaan pay them tribute. This is repeated again [in Verse 27, as explained above], in order to state that even when the children of Shem will be in exile, the children of Canaan will be sold to them as slaves.” [Thus Rashi interprets to them as referring to the descendants of Shem.]
The correct interpretation appears to me to be that at first he [Noah] cursed him that he be a servant of servants to the entire world, and whosoever will find him will enslave him, for the meaning of unto his brethren is “unto all men,” just as in the verse, For I will set all men every one against his neighbor, and as is the sense of the expression, Every man his fellow. It may that unto his brethren refers to Shem and Japheth for his father’s brothers are called “his brothers,” just as in the expression, that his brother was taken captive, [which refers to Lot who was a son of Abraham’s brother]. And some say — as found in Ibn Ezra — that unto his brethren means his father’s children [namely, Cush, Mitzraim and Phut, who are his father’s children]. Thus, after being made a servant to his father’s children and to Shem and Japheth, he was a servant to the whole world. Now Noah first blessed the G-d of Shem, thereby letting it be known that Shem will be a servant of G-d while Canaan will be subject to him. And to them alludes to the seed of Shem who were many. It is possible that to them reverts also to his brothers already mentioned. Then he blessed Japheth with an enlargement of the boundary, he blessed Shem with the dwelling of G-d in his tents, and finally said that Canaan be a servant to them, meaning to the two of them. He made Canaan subservient to Shem twice, [in Verses 26 and 27, as explained above], thus hinting that the seed of Shem will inherit his land and all that he has, for that which a slave acquires belongs to his master.
This section was written in Scripture in order to make known that it was on account of his sin that Canaan became a servant forever and that Abraham was favored with his land. The subject of the wine’s effect on Noah was written because it contains a greater warning against drunkeness than that of the section on the Nazirite: even the perfectly righteous man — whose righteousness saved the whole world — even he sinned on account of wine, and it brought him to disgrace and the cursing of his seed.

ויהי כנען, his offspring [seeing that the word ויהי is in the future tense; Ed.]

עבד למו, to the G’d as well as to the offspring of Shem. The formulation is parallel to Joshua 9,27 where the Gibeonites are condemned to be “hewers of wood and carriers of water” for the Israelites (having duped them into thinking that they were not Canaanites)

ויאמר ברוך ה' אלוקי שם, Noach said this as a prophecy. He used the most holy attribute of G’d in conjunction with the regularly mentioned attribute of G’d when blessing in His name. The reason he did this was that he foresaw in his vision that the descendants of Shem would serve G’d in His capacity as the “Lord, the Eternal,” i.e. as Hashem. When we recite our major prayers we always combine mention of these two attributes of G’d; Noach foresaw this already. We encounter this combination in connection with the Jewish people, the descendants of Shem for the first time in Exodus 3,6. G’d has described Himself as being especially אלוקי ישראל, the G’d of Israel. (Exodus 5,1)

ויהי כנען עבד למו, Canaan is to be a servant to the descendants of Shem.